「Science of Hybrid Quantum Systems」

Project Period
2014FY～ 2019FY

Table of contents
１

Preface・・・・・・・・・・・・・・・・・・・・・・・・・・

1

２

Organization and members・・・・・・・・・・・・・・・・・・・

3

３

Purpose and outline of the project・・・・・・・・・・・・・・・・・

9

４Main research results・・・・・・・・・・・・・・・

12

4-1 Best magnetic-field sensitivities with single NV centres
at room temperature

14

4-2 Room Temperature Electrically Detected Nuclear Spin Coherence of NV Centres in Diamond15

4-3 Highly Sensitive AC Magnetic Field Sensing using Nitrogen-vacancy Centers in Diamond

16

4-4 Microwave Imaging in Micrometer Resolution－Precision measurement of microwave field-distribution using Rabi oscillations－17

4-5 Probing thermal magnon current via nitrogen-vacancy centers in diamond－Coupling of quantum spin state with thermal magnon current－
4-6 Operando Analysis of Electron Devices Using Nanodiamond Thin Films Containing Nitrogen-Vacancy Centers

18
19

4-7 Successful quantum teleportation transfer— Preserving the quantum state of photons in diamond: a new development in quantum communication —20

4-8 Development of the world’s first error-tolerant qubit— Quantum memory and quantum sensor devices that use geometric echoes to self-stabilize —21

4-9 Demonstration of a new principle of optical spin control that paves the way for quantum integrated memory— Facilitates high-speed quantum computing and quantum communication —22

4-10 Ultra-low noise microwave amplification by spin maser －Back to the basic for quantum technologies－23

4-11 Ultralong relaxation times in bistable hybrid quantum systems

24

4-12 Superradiance from diamond25

4-13 Relaxation to negative temperatures and reservoir-assisted quantum entanglement in hybrid quantum systems

26

4-14 Quantum Metrology beyond the Classical Limit under the Effect of Dephasing

27

4-15 Designing measurement with hybrid quantum systems

28

4-16 Robust control of two-qubit Hamiltonian dynamics

29

4-17 Reversing Unknown Quantum Transformations: Universal Quantum Circuits for Inverting General Unitary Operations 30
4-18 Exploring Protocols for Control of Quantum Transport31

4-19 Control of Quantum Many-body State by Observation－Realization of Stabilizing Insulator state by Strong Dissipation－32

4-20 Development of New Method for Observing Single Atoms in an Optical Lattice33

4-21 Photonic quantum interfaces with atoms

34

4-22 Realization of low-loss, all-fiber system for strong and efficient coupling between distant atoms- A step closer to realizing distributed quantum computers -35

4-23 Cavity dark mode in a coupled cavity quantum electrodynamics system- Observation of remote exchange of energy between atom and light 4-24 Experimental all-photonic quantum repeaters

36
37

4-25 Tuning Radiative Lifetime of Circularly Polarized Light by a Three-Dimensional Semiconductor-Based
Chiral Photonic Crystal
4-26 Demonstration of a topological nanocavity laser

3839

4-27 Optical Aharonov-Bohm Effect in Single Quantum Ring －Observation of Wigner molecule among excitons－

40

4-28 Novel phenomena in optical microresonators－Demonstration of anomalous group delays and high-Q mechanical resonators－

41

4-29 Optical coherent transients in 167Er3+ －Coherent manipulation of 4f orbital electrons at telecom-band wavelength－424-30 Coherent Coupling between Ensemble Superconducting Qubits and a Superconducting Resonator43

4-31 Experimental test of macroscopic realism using a superconducting flux qubit

44

4-32 Electron Spin Resonance Spectroscopy Using a Superconducting Qubit－Sensitive detection of electron spins in microscale area－45

4-33 Josephson junction with a topological insulator

46

4-34 Large magnetoresistance in magnetic topological insulator －Switching of non-dissipative topological current－

47

4-35 A new insulating state in topological insulator－Realization of the materials platform for topological magnetoelectric effect－4-36 Current-induced breakdown of quantum anomalous Hall effect48
49

4-37 Resistively-Detected NMR in InSb Quantum Hall Systems－Reciprocity of nuclear polarization in a quantum Hall ferromagnet－
4-38 Electron evaporative cooling using asymmetric double barrier semiconductor heterostructure

50
51

4-39 1-bit quantum simulation with silicon transistor－Single spin qubit reproduce a well-known phenomenon in magnetic resonance－

52

4-40 Detection of the Kondo screening cloud53

4-41 Hybrid structure of quantum-dot and quantum-well superlattice grown by molecular beam epitaxy

54

4-42 Dicke Effect in Photocurrent through Quantum Dot Array －Sensitive detector of THz light－

55

4-43 Ge/Si nanowire double quantum dots coupled with a microwave resonator

56

4-44 Helical channel formation in Ge/Si core-shell nanowires

57

4-45 Microscopic NMR in Quantum Point Contact

58

4-46 Dynamical nuclear spins and disorder potential effect in quantum point contacts

59

4-47 Theory of carbon nanotubes in hybrid systems －Topological states and their quantum property－

60

4-48 Flexible Carbon Nanotube Electrochemical Sensors

61

4-49 Modulation of Phonon in Carbon Nanotubes by Defect Formation

62

4-50 Thermal Conductivity Measurements of Chirality Assigned Single-Walled Carbon Nanotubes

63

4-51 Observation of band-like transport from defect-repaired graphene oxide film
-Towards scalable production of highly crystalline graphene thin film-

64

4-52 Monte Carlo Simulation of Mobility Enhancement in Graphene

654-53 Isotope control in graphene phononic crystal –Towards phonon transport control in graphene–

66

4-54 Controlling phonon propagation of monolayer graphene by structural defects–Phonon control for enhancing thermoelectric device performance–

67

4-55 Directional heat flux and heat focusing

68

4-56 Thermal conduction enhancement by surface phonon polaritons69

4-57 Heat conduction control based on the wave nature of phonons

70

4-58 Ultrasonic pulse compression in a phononic crystal waveguide71

4-59 Topological localized state of elastic wave in one-dimensional phononic crystal

72

4-60 Control of Spin-Phonon Interaction and Photon Excitation in Asymmetric Artificial Lattices

73

4-61 Highly sensitive motion detection in a mechanical resonator using a gate-controlled quantum dot74

4-62 Nuclear spin control by a mechanical oscillator

75

4-63 Mechanical engineering of excitons in semiconductor－Demonstration of strain-mediated coupling between dark and bright states－

76

4-64 Ising spin coupling in electromechanical resonators

77

4-65 Fast and Sensitive Bolometric Terahertz Detection at Room Temperature through Thermomechanical Transduction

78

4-66 Focusing Terahertz Radiation on a Single Molecule by Nanogap Electrodes and Observationof Enormous Terahertz Field Enhancement Effect79

4-67 Observation of Ultrafast Motion of a Single Molecule by Terahertz Spectroscopy

80

4-68 THz-field-induced Macroscopic Ionic Flow in a Superionic Conductor Na+ β-Alumina

81

4-69 Terahertz Spectroscopy of a Single Carbon Nanotube

82

4-70 Phase-controlled THz-field-driven Scanning Tunneling Microscopy－Ultrafast electron manipulation with tailor-made single-cycle THz near fields－

83

4-71 Probing microscopic property of topological protection

84

4-72 Scanning Nuclear Resonance Microscope －Microscopic MRI of spin state in quantum structure－85

５

Achievements・・・・・・・・・・・・・・・・・・・・・・・・

86

5-1 Publications86

5-2 Major invited talks97

1. Preface
The Grant-in-Aid for Scientific Research on Innovative Areas "Science of Hybrid Quantum Systems"(HQS project) pursues the basic science of hybrid quantum systems. It is intended to establish a quantum
coupling between different physical quantities, such as charge, Cooper pair, spin, nuclear spin, photons,
and phonons, leading to various high-sensitivity sensors, highly-sensitive measurements of physicalproperties, and the development of new physics. By exploring so-called Quantum Enabled Technology thatmakes the best use of the functions of a hybrid quantum system, we discuss impact on a wide range of fields
from science and engineering to medicine. The exploration of quantum entangled physics for various
materials and physical quantities is a run-up to the quantum network.
The HQS project started in July 2015 to promote the above mentioned research fields. The main streamsof quantum science and quantum technology at that time were quantum information processing, such as
quantum cryptography, qubits on the basis of superconductivity, electron spin, atom and ion traps, and tointegrate them toward quantum computers. The project began with the finding that there was a different
approach from integrating the same type of qubits, and much of the interest in quantum science went insuch a direction. Even with a small number of qubits, we have achieved unprecedented sensitivity of sensors.
By developing quantum transducers with different physical quantities, we can exchange quantum
information on different scales such as energy and distance. An attempt at developing a new quantum
technology has started.
The planned research areas of this project were divided into four groups, A01-A04. The A01groupstudied the control of quantum coupling of charge (including Cooper pair), spin, and nuclear spin, andextended this to the coupling with photons and phonons. The A02 group pursued the establishment ofadvanced control technology for photons and the quantum coupling between photons and other physicalquantities, and A03 pursued the establishment of advanced control technology for phonons and the quantum
coupling between phonons and other physical quantities. The A04 group promoted the theoreticalframework for advancing hybrid quantum science. This group not only theoretically supported theinterpretation of various experimental results obtained from A01 to A03, especially new hybrid phenomena,
but also played an important role in bundling the entire field and showing the heart of hybrid quantum
systems.
A unique feature of the Grant-in-Aid for Scientific Research on Innovative Areas is the existence of open
research proposals. In open research proposals, researchers who were working on coherent control ofvarious physical systems, those who were researching classical systems but wanted to expand their researchin the quantum direction by using their technologies, or those who wanted to break new ground incollaboration with researchers already participating in the HQS project conducted many wonderful studies.
I was first worried that it would be difficult to collect open research proposals due to the characteristics ofthe research areas of the HQS project, but partly due to the relatively large budget, there were many
interesting applications. We were able to adopt such high-quality research. In fact, there were many open
research proposals that obtained excellent results comparable to planned research. The joint research withplanned research group was also actively conducted. The headquarter management actively supporting theequipment sharing and the travel expenses required for joint research also worked in a positive direction. I
believe that the all areas were united, and we were able to open up a new horizon of quantum hybridization,although it is still not enough.
Since the physical quantities are different, when researchers who have been conducting research on1

electric charge, electron spin, nuclear spin, photons, and phonons gathered, there was a concern that it was
just a random mixture. When the HQS project started, this was the case in certain instances. However, thecollaborations within the different areas have steadily progressed, and this “random” impression has faded
year by year. As a representative of the HQS project, I am very pleased with this change.
As a number of joint studies progressed, some interesting directions came about. In spite of thecollaboration regarding state-of-the-art technologies for the control of charge, spin, photons, and phonons
toward quantum coupling, quantum control is not easy, so we could not reach “hybrid quantum” in somecases. Even in such a situation, some classical hybridizations not reaching quantum showed wonderful
functions that had not existed. Just as hybrid vehicles have hybridized gasoline and electric vehicles,"hybrid quantum" has emerged as having a different meaning from quantum transducers, hybridizingclassical and quantum systems in the areas of charge, spin, photons, and phonons. There may be various
opinions, but I have abandoned the idea that the HQS project must be 100% quantum, and managed toactively support interesting initiatives that have emerged through hybridization regardless of “classical” or“quantum”. Many of the research areas of the HQS project involve pure basic researches, and it is difficult
to directly apply such research to applications, but I believe that some of these results have attracted theinterests of companies.
More importantly, through the interaction of planned research group on charge/spin, photons, phonons,
theory, and open research proposals, different views on how to proceed with research and how to measure
the characteristics were exchanged. I hope that we can promote hybridization as researchers and even as
people by interacting with many others beyond the existing boundaries. When considering the current world
situation, it is important as a researcher and as a person to maintain a hybrid sense in various aspects.
This booklet is intended to introduce the activities of the HQS project over the past five years and theresearch results. First, it introduces the organizations and participants of our project, and the purpose andoutline of the research areas. In particular, it was glad to see that young researchers played the importantroles in this project. After briefly introducing the degree of achievement of research objectives in the project,
this booklet introduces 72 examples of the main results from the project’s activities. The final report is inJapanese, although both Japanese and English versions are posted for the main results. Here, we plan toprovide an English version on the Web focusing on the important parts. Finally, I will list achievements,
such as publications, invited talks, and awards. Please forgive us not completely covering all, because manymembers have participated and the project lasted for 5 years. I hope that this web booklet will help you
understand the project, Grant-in-Aid for Scientific Research on Innovative Areas "Science of Hybrid
Quantum Systems" (HQS project) and serve as a reference for your future research.

Project Leader, Grant-in-Aid for Scientific Researchon Innovative Area "Science of Hybrid Quantum Systems"
Professor, Tohoku University
Yoshiro Hirayama22

Organization and members＊The research institute / department shown here is for the period of the project.

Steering Group
Title

Principal

Department, Institution

Research period
2015 - 2019FY

Investigator
Project Leader,

YoshiroGraduate School of Science,

International Research

Hirayama

Tohoku University

Koji Ishibashi

Device Laboratory, RIKEN

2015 - 2019FY

Photon Group Leader,

Kazuhiko

Institute of Industrial Science,

2015 - 2019FYInternational Research

Hirakawa

The University of Tokyo

Phonon Group Leader,

HiroshiNanostructure Technology ResearchInternational Research

YamaguchiGroup, NTT Basic Research

Support Project,
Project Leader
Charge & Spin Group Leader,International Research
Support Project,
Group Leader

Support Project,
Group Leader

Support Project,

2015 - 2019FY

Laboratories

Group Leader
Theory Group Leader,International Research

Kae Nemoto

Principles of Informatics Research2015 - 2019FY

Division, National Institute of Informatics

Support Project,
Group Leader
Charge & Spin Group
Name

Department, Institution

Research period

Koji Ishibashi,

Device Laboratory, RIKEN

2015 -2019FY

Yutaka Ono,

Future Electronics, Institute of Materials and Systems for2015 -2019FY

Co-Investigator (kenkyu-

Sustainability, Nagoya University

Group Leader

buntansha)
Yoshiro Hirayama,

Graduate School of Science, Tohoku University

2015 -2019FY

Akinobu Kanda,

Faculty of Pure and Applied Sciences,

2015 -2019FY

Co-Investigator (kenkyu-

University of Tsukuba

Co-Investigator (kenkyubuntansha)

buntansha)

3Yoshihiro Kobayashi,

Graduate School of Engineering, Osaka University

2015 -2019FY

Center for Emergent Matter Science, RIKEN

2015 -2019FY

Takaaki Koga,

Faculty of Information Science and Technology,

2016 -2017FY

Open Research Proposals

Hokkaido University

Shinji Kuroda,

Faculty of Pure and Applied Sciences,

Open Research Proposals

University of Tsukuba

Yoshiro Takahashi,

Graduate School of Science,

Open Research Proposals

Kyoto University

Michihisa Yamamoto,

School of Engineering,

Open Research Proposals

The University of Tokyo

Hiroshi Shimada,

School of Informatics and Engineering,

Open Research Proposals

The University of Electro-Communications

An Toshu,Japan Advanced Institute of Science andOpen Research Proposals

Technology(JAIST)

Shinichiro Mouri,

College of Science and Engineering,

Open Research Proposals

Ritsumeikan University

Yuimaru Kubo,

Okinawa Institute of Science and Technology Graduate

Open Research Proposals

University (OIST)Keiji Ono,

RIKEN

2015 -2019FY

NTT Basic Research Laboratories

2015 -2019FY

NTT Basic Research Laboratories

2015 -2019FY

Kyushu Institute of Technology

2015 -2019FY

Ryota Negishi,

Graduate School of Engineering,2015 -2019FY

Co-Investigators (renkei-

Osaka University

Co-Investigator (kenkyubuntansha)
Minoru Kawamura,
Co-Investigator (kenkyubuntansha)

2016 -2017FY

2016 -2017FY
2018 -2019FY
2018 -2019FY
2018 -2019FY
2018 -2019FY
2018 -2019FY

Co-Investigators (renkeikenkyusha)
Kosuke Kakuyanagi,
Co-Investigators (renkeikenkyusha)
Shiro Saito,
Co-Investigators (renkeikenkyusha)
Hirofumi Tanaka,
Co-Investigators (renkeikenkyusha)

kenkyusha)4Photon Group
Kazuhiko Hirakawa,

Institute of Industrial Science,Group Leader

The University of Tokyo

Norikazu Mizuochi,

Institute for Chemical Research,

Co-Investigator (kenkyu-

Kyoto University

2015 -2019FY

2015 -2019FY

buntansha)
Satoshi Iwamoto,

Institute of Industrial Science,

Co-Investigator (kenkyu-

The University of Tokyo

2015 -2019FY

buntansha)
Jyunko Hayase,

Faculty of Science and Technology,

Co-Investigator (kenkyu-

Keio University

2015 -2019FY

buntansha)
Kouichi Akahane,

National Institute of Information and Communications

2015 -2017,

Co-Investigator (kenkyu-

Technology(NICT)

2019FY

Faculty of Engineering, Yokohama Nationl University

2016 -2017FY

Faculty of Science and Engineering, Waseda University

2016 -2019FY

NTT Basic Research Laboratories

2016 -2017FY

Shintaro Nomura, OpenFaculty of Pure and Applied Sciences,

2018 -2019FY

Research Proposals

University of Tsukuba

Jun Takeda, Open Research

Faculty of Engineering, Yokohama Nationl University

2018 -2019FY

College of Science and Technology, Nihon University

2018 -2019FY

Hiroshi Yamguchi,

Nanostructure Technology Research Group,2015 -2019FY

Group Leader

NTT Basic Research Laboratories

Yoshikazu Homma,

Faculty of Science Division I,

Co-Investigator (kenkyu-

Tokyo University of Sciencebuntansha)
Hideo Kosaka, Open
Research Proposals
Takao Aoki, Open Research
Proposals
Takehiko Tawara, Open
Research Proposals

Proposals
Shuichiro Inoue,
Open Research Proposals
Phonon Group2015 -2019FY

buntansha)
Masahiro Nomura,Institute of Industrial Science,

Co-Investigator (kenkyu-

The University of Tokyo

2015 -2019FY

buntansha)
Takayuki Arie,

Graduate School of Engineering,

Co-Investigator (kenkyu-

Osaka Prefecture University

buntansha)
52015 -2019FY

Hitoshi Tabata,

Graduate School of Engineering,

2016 -2019FY

Open Research Proposals

The University of Tokyo

Takashi Yamamaoto,

Graduate School of Engineering Science,

Open Research Proposals

Osaka University

Imran Mahboob ,NTT Basic Research Laboratories

2015 -2019FY

Reo Kometani,

Graduate School of Engineering,2015 -2019FY

Co-Investigators (renkei-

The University of Tokyo

2016 -2019FY

Co-Investigators (renkeikenkyusha)

kenkyusha)
Maki Shimizu,

Tokyo University of Science

2015 -2019FY

NTT Basic Research Laboratories

2015 -2019FY

Seiji Akita,

Graduate School of Engineering,

2016 -2019FY

Co-Investigators (renkei-

Osaka Prefecture University

Co-Investigators (renkeikenkyusha)
Daiki Hatanaka,
Co-Investigators (renkeikenkyusha)

kenkyusha)
Hajime Okamoto,

NTT Basic Research Laboratories

2016 -2019FY

Takahiro Yamamoto,

Faculty of Engineering,

2016 -2019FY

Co-Investigators (renkei-

Tokyo University of Science

Co-Investigators (renkeikenkyusha)

kenkyusha)
Theory Group
Kae Nemoto,Principles of Informatics Research Division,

Group Leader

National Institute of Informatics

Mikio Eto,

Faculty of Science and Technology,

Co-Investigator (kenkyu-

Keio University

2015 -2019FY
2015 -2019FY

buntansha)
Yuichiro Matsuzaki,

National Institute of Advanced Industrial Science and

Co-Investigator (kenkyu-

Technology(AIST)2015 -2019FY

buntansha)
Nobuya Mori,

Graduate School of Engineering,

Co-Investigator (kenkyu-

Osaka University

2015 -2019FY

buntansha)
Wataru Izumida,

Graduate School of Science,

Open Research Proposals

Tohoku University

Tomosuke Aono,

College of Engineering,

Open Research Proposals

Ibaraki University
62016 -2019FY
2016 -2017FY

Mio Murao,

Graduate School of Science,

Open Research Proposals

The University of Tokyo

Chikako Uchiyama,

Graduate Faculty of Interdisciplinary Research Faculty ofOpen Research Proposals

Engineering, University of Yamanashi

Masahiko Hayashi,

Faculty of Education and Human Studies,

Co-Investigators (renkei-

Akita University

2016 -2019FY
2018 -2019FY
2015 -2019FY

kenkyusha)
Advisory Boad
Domestic Adviser
Masakazu Aono

Director, International Center for Materials Nanoarchitectonics,
National Institute for Materials Science

Motoko Kotani

Principal Investigator of AIMR and Professor of Tohoku University

Hiroyuki Sakaki

President, Toyota Technological Institute(TTI)

Naoki Yokoyama

Honorary Fellow, Fujitsu Laboratories Ltd.

International Adviser
Gerald Bastard

Professor, École Normale Supérieure, France

Ian Walmsley

Professor, University of Oxford, UK

Jörg Peter Kotthaus

Professor, Ludwig-Maximilians-Universität München, Germany

Robert Westervelt

Professor, Harvard University, USA

Hongqi Xu

Professor, Peking University, China, and Lund University, Sweden

Adviser from Company
Kazufumi Azuma

Shimadzu Corporation

Akihiro Odagawa

Panasonic Corporation

Tetsufumi Tanamoto

Toshiba Corporation

Eiji Fujii

Panasonic Corporation

Tatsuro Watahiki

Mitsubishi Electric Corporation

Young Researchers Committee
Maki Shimizu

Tokyo University of Science

Toru Tomimatsu

Tohoku University

Shojun Nakayama

National Institute of Informatics

Ryota Negishi

Osaka University

Daiki Hatanaka

NTT Basic Research Laboratories

Yusuke Hama

National Institute of Informatics

Masanori Fujiwara

Kyoto University

Yuishiro Matsuzaki

NTT Basic Research Laboratories, National Institute of Advanced Industrial Scienceand Technology(AIST)

7

Secretariat
Toru Tomimatsu

Tohoku University

Yoshiko Takahashi

Tohoku University

8

３

Purpose and outline of the project

１．BackgroundResearch on quantum coherent manipulation of charge, spin, and nuclear spin in quantum nanostructures wereactively studied worldwide with the aim of quantum computation, thus having a significant impact as a new quantum
manipulation of physical quantities. The development of quantum operation appeared from other viewpoint, which
was different from the direction toward large-scale quantum computation. The D-Wave machine, which executed
quantum simulations in a much simpler manner than ordinary quantum computation, had gained considerable
attention. Within such research stream, as a more familiar direction, Quantum Enabled Technology (science andtechnology made possible by the control of quantum coherence) has made rapid progress worldwide, for example,
for quantum high-sensitivity measurement based on quantum coupling. Such measurement is the basis of science andtechnology and is expected to be applied in a wide range of fields from science and engineering to medicine. Theinternal and external research activities promoted toward this direction revealed that the method of transferring
quantum entanglement between different physical systems has played an essential role. That is, to achieve thisQuantum Enabled Technology, a small-scale quantum-transducer function of various physical quantities is
indispensable. In particular, photons and phonons are important for transporting quantum information to different
locations and placing them on the measurement system. Photons have been widely recognized as a medium forconnecting quantum systems, but the importance of phonons has recently attracted; thus, research on phononic
crystals as well as photonic crystals has been conducted.

Fig. 1
Schematic diagram of our project

Taking these situations into consideration, a group of researchers active in the charge (including Cooper pair),spin, nuclear-spin, photon, and phonon research fields gathered to investigate a small but innovative hybrid quantum
system between different physical quantities. They proposed establishing a project on the basis of Quantum EnabledTechnology. Figure 1 illustrates a simple concept at the time of establishing the HQS project. This project wascomposed of researchers who were studying in the fields of charge (including Cooper pair), spin, nuclear spin,
photons, and phonons. In particular, photons and phonons are indispensable for transferring signals over long
distances and combining different quanta separating a long distance in the medium. Therefore, we strengthened
photon- and phonon-related studies by setting independent planned research groups (A02 and A03). In addition,
researchers of nanomaterials and nanostructures were involved because establishment of quantum coupling of various
physical quantities asked new materials and innovative structures. Since the fusion of theory and experiment is
indispensable in hybrid quantum science, in addition to A01 planned research (charge / spin), A02, and A03, theworld's leading theoretical researchers in hybrid quantum science were assigned to A04 planned research (theory).
There were only four planned research groups and no sub-groups were inside the planned research groups. This wasa strategy to avoid subdividing for the sake of mutual collaboration. Various hybridizations are the most important
initiatives in this project, we aimed to promote the fusion within planned research and between planned researchgroups by not subdividing. Furthermore, we actively adopted open research proposals that span each planned research
9groups, and endeavored to further promote the integration of the entire project.
2. Importance of HQS project from the perspective of improving and strengthening Japan’s academic
standards
There are four important roles of the HQS project from the perspective of improving and strengthening Japanese
academic standards. The first role, through the HQS project, it was possible to develop in the direction of further
using the superior research possessed by the participating members and contribute to the improving Japan's academic
standards in each area. The A01 planned research group leaded the world in controlling charge (including Cooperpair) and electron spin, coupling between electron-spin and nuclear-spin systems, and metrology based on nuclear
spins. By adding new directions to these research directions, their respective academic standards have beenstrengthened. The same can be said for A02 and A03. The A02 group developed world-leading research on opticalcontrol using photonic crystals, the coupling between THz and quantum structures, and the coupling between NV
centers in diamonds and electromagnetic waves. The A03 group developed a phononic crystal by giving a periodic
structure to an elastic body and made a world-leading contribution to the electrical control of phonon propagation.
By adding new directions to these research activities, their respective academic standards have also been strengthened.
The A04 planned research group had many world-class active members advocating Quantum Enabled Technology.
In this group, the level of research raised by pursuing issues while discussing with experimental groups. Furthermore,
the level of each research was further improved by collaborating with excellent open research proposals.
The second important role, and most importantly, the world-leading research groups in each quantum system havecome together to collaborate with front-line theoretical research, achieving exciting hybridization in this project.
Through their innovative and creative achievements described later, we can contribute to the strengthening ofJapanese academic standards in the field of quantum hybridization, which is becoming increasingly importantworldwide. By pushing integrated research straddling planned research in the entire project including open research
proposals, innovative studies that would not have been possible without this project have launched. Some of theresults are very important and will play a major role in improving and strengthening the academic standards of Japan.
The third important role is of the world-leading groups in nanotechnology participating in the project because newnanomaterials and nanostructures are indispensable for conducting highly-sensitive quantum measurements invarious fields. Japan has a strong background in nanotech materials and nanostructure fabrication technology.
However, many groups have focused on classical devices. By presenting a new research direction of hybrid quantum
systems to these groups, it is expected that high-level technologies and expertise find a new direction and contributeto the further development of nanotechnology in Japan. The involvement of the nanotechnology groups was usefulfor the entire project in that new materials and structures could be seamlessly introduced into a quantum hybrid
system.
The fourth important role is involving a wide variety of fields in hybrid quantum systems. We can broaden thebase of researchers in quantum science, especially for young researchers. Our project is useful in solving the problem
of not enough quantum researchers at Japanese universities. Since the research activities in this project do not aim
for large-scale quantum integration, each group was able to work on quantum science at their own base, which helped
to expand the groups researching quantum science in Japan. In particular, the Young Committee in the projectcontributed significantly to this. Considering the importance of quantum technology field in the future, raising thelevel of quantum science at universities is important from the viewpoint of improving and strengthening the academic
standards of Japan.
3. Development and completion of the project studies, expectation for the future
While research on quantum transducer functions in various physical systems has progressed through theachievements of the entire project, the meaning of “hybrid quantum” has expanded. There are various stages in a
hybrid quantum system, from 100% classical to 100% quantum. It is noteworthy that we can show the attractivefunctions even if they are not 100% quantum. They are also important for expanding hybrid quantum system to the10industrial world.
Each planned research group has conducted research on topological insulators and topological Josephson
junctions, high-sensitivity measurements using the correlation between electron-spin and nuclear-spin systems,
quantum correlation of double-spin systems, and various quantum technologies based on theory. A representative
example of theoretical success is demonstrating the possibility of and proposing a quantum measurement method for
obtaining quantum gain even under realistic noise. We succeeded in showing the theoretical framework of hybrid
quantum science of various physical systems in the energy domain spanning several digits. The fusion in this project
was used to apply these theoretical findings to an experimental system.
Regarding the sophistication of photon and phonon control in this project, we developed circularly-polarized lightemission from quantum dots controlled by chiral photonic crystals, development of the topological photonics field
where the concept of topology is applied to photonic crystals, demonstration of optical waveguides without backscattering, ultra-sensitive and local measurement based on the NV center in diamonds, and the pioneeringdevelopment of phononic crystals with various unique functions. Mechanical oscillators are a typical example of a"macroscopic" physical system, and can form "entangled states" with electrons, spins, and photons, which are
representative of "microscopic" physical systems. It is an important platform that can challenge the fundamental
proposition of how the macroscopic routine world and the microscopic system dominated by quantum mechanics arecontinuously connected. This direction of research naturally has high academic impact for the future.
Furthermore, as an innovative and creative part of this project, the hybridization of charge, spin, photons, andphonons has progressed beyond planned research groups and open research proposals. One impactful outcome forthe future is the hybridization between charge, phonons, and THz photons by a single molecule trapped in a metal
nanogap. This opens the door to a new discipline called "THz nanoscience" and shows the possibility of quantum
coupling of charge, spin, phonons (molecular vibrations), and THz photons. In the hybridization of mechanicalvibration and THz electromagnetic waves in a mechanical resonator structure, THz detection performance exceedingthat of current devices was demonstrated before going to quantum coupling.
The researchers successfully demonstrated quantum coupling between spin and superconducting quantum
systems. Nanofiber resonator quantum electrodynamics (QED) systems connected by optical fibers were also
constructed. They are the basis of an original quantum network in which many resonator QED systems are coherently
coupled via photons and phonons. Research has also progressed on superconducting qubits, electron/nuclear spinsinteractions expected as quantum memories, and novel mechanical systems as interfaces for different physicalsystems and photons that propagate quantum states over long distances. It is widely recognized that these may be thekey to future quantum networks.

11

4. Main research results
Charge / spin planned research (A01) and related open proposals
This group pursued single and collective manipulation of electrons, Cooper pairs, electron spins, and nuclear
spins as quantum information carriers, elucidating their background physics. This group also pursued quantum
transducer function between them and photons and/or phonons. Since it is necessary to hybridize materials tohybridize quantum systems, the group expanded their research to new material systems such as carbon nanomaterials
and topological insulators in addition to traditional semiconductor nanostructures. To meet the above goals, they
established quantum control of electron spins and nuclear spins in novel systems consisting of silicon and compound
semiconductor micro/nanostructures, and conducted highly-sensitive measurements on the basis of nuclear-spins.
They also succeeded in enabling quantum control of excitons in carbon nanotubes. Furthermore, they clarified themechanism of interaction between spin systems and microwave photons or phonons toward the hybridization ofdifferent physical systems. These results are expected to develop into hybridization of heterogeneous quanta inquantum information processing and quantum measurement. As a unique material system, this group was able toobtain a foothold in the physics of quantum states with magnetic topological insulators based on laminated and thinfilms, and hybrid structures of topological insulators and superconductors.
Photon planned research (A02) and related open research proposals
This group promoted research toward the quantum-transducer function based on the basis of photons andsophisticated photon control necessary for its development. To this end, they developed ultra-sensitive/local quantum
measurement technology using NV centers in diamonds and had significant achievements such as achieving theworld's longest T2 time at room temperature for solid-state electron spin, world's first electrical detection of nuclearspin-coherence, and world's highest magnetic field sensitivity by a single NV center. With the advancement in
nanophotonics, the group succeeded in controlling circular polarization emission from quantum dots embedded inthree-dimensional chiral photonic crystals. In addition, innovative developments such as orbital momentum controlof light and topological photonics, which were not envisioned at the time of planning, were achieved. Attempts tocoherently couple a nanofiber cavity-QED system of a resonator by an optical fiber network have also madesignificant progress. Moreover, using a metal nanogap electrode operating as a THz antenna, a single molecule wastrapped and the effect of molecular vibration on electron transport was clarified. This result opened up the field of
THz spectroscopy and laid the foundation for quantum hybridization of charges, phonons, and THz photons basedon a molecule. It is also noteworthy that a novel high-performance THz detector was demonstrated using mechanicalresonance characteristics.
Phonon planned research (A03) and related open research proposals
This group promoted research with the goal of improving the quantum-transducer function based on the basis ofphonons and sophistication of phonon control toward its practical application. To this end, phononic crystal
fabrication technology and quantum hybrid structure fabrication for quantum dot mechanical resonators have madesignificant progress, and completely new nanostructure fabrication technologies, such as isotope control of graphene
growth, have been established. Regarding functional operation using quantum properties, the group developed ultrasensitive vibration sensors using quantum dots and a technology toward quantum entanglement state generation
between nuclear spins and phonons. They also demonstrated an opto-electromechanical hybrid system through thefusion of bottle-type optical resonators and semiconductor electromechanical resonators. The acquired basic
technologies will be a milestone for future quantum transducers. They also proposed and demonstrated phonon
conduction control focusing on the quantum nature of phonons. These achievements have created sufficient academic
value and new technologies, and their objectives have been achieved at a high level.
Theoretical planned research (A04) and related open research proposals
The group proceeded with research aimed at creating a systematic theoretical study for hybrid quantum science,design guidelines and proposals for the development of Quantum Enabled Technology, and theoretical understandingof hybrid quantum systems in various physical systems. To achieve this goal, the phenomena of various physicalsystems, such as charge, spin, photons, and phonons in various fields such as quantum optics, superconductivity,
12

semiconductor condensed matter physics, and nanostructured physics are fused, reaching universal physics andconcepts through hybridization. Specific examples include several orders of magnitude expansion in the energy
region of super-radiance phenomena in hybrid quantum systems. In addition, the properties of carbon nanotubes as
topological insulators were clarified as well as the effect of phonons on the behavior of hybrid quantum systems.
They also developed a quantum measurement method for demonstrating quantum superiority even under realistic
noise through the use of new resources made possible by hybrid quantum systems and hybridization with quantum
protocols such as quantum teleportation. By understanding the quantum transducer universally, the features andproblems commonly found in the design of various combinations were clarified as design knowledge.
During the period of this project, we published many high-impact papers, including 1 in Nature, 1 in Nature
Physics, 2 in Nature Photonics, 3 in Nature Nanotechnology, 16 in Nature Communications, 3 in Communications
Physics, 4 in Science Advances, and 17 in Physical Review Letters. Reflecting a high level of research achievement,
paper publication was active throughout the entire project.
The following is an overview of 72 examples from the main results. As mentioned above, hybridization has been
actively promoted in this project, and there are many results that span planned research groups and open research
proposals. Therefore, individual achievements will be posted in the form of summarizing the achievements of related
fields regardless of the planned research groups from A01 to A04.

13

Best magnetic-field sensitivities with single NV
centres at room temperature
1

2

1

1

2

2

E. D. Herbschleb1 , H. Kato , Y.
Maruyama , 1T. Danjo , T. Makino, S. Yamasaki,
1
1
1
I. Ohki , K. Hayashi , H. Morishita , M. Fujiwara , N. Mizuochi

1Institute for Chemical Research, Kyoto University, Gokasho, Uji-city, Kyoto 611-0011, Japan
2National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki, Japan
Solid-state spins are a leading contender inquantum technology. Enhancing the inhomogeneous
spin-dephasing time (T2*) and the Hahn-echo spincoherence time (T2) is a central issue. The electron spinplays a signiﬁcant role for quantum sensing and forcoherent connectivity with other qubits such as
photons, nuclear spins, and superconducting qubit.
Therefore, the coherence times define the physicalbehavior of the quantum device, and their improvement
allows new perspectives for quantum applications.
From the viewpoint of material science,enhancements of T2* and T2 have been realized by
Figure 1. Results of Hahn-echo signal. The
development of growth techniques. Althoughexponential-decay fit with line, T2 = 2.43 ms.
enrichment of the spin-zero 12C and 28Si isotopes
greatly reduces spin-bath decoherence in diamond and silicon, the solid-state environment provides
undesired interactions between the electron spin and the remaining spins of its surrounding. Here wedemonstrate, contrary to widespread belief, that an impurity-doped (phosphorus) n-type single-crystal
diamond realizes remarkably long spin-coherence times. Single electron spins show the longest
inhomogeneous spin-dephasing time (T2* ≈ 1.5 ms) and Hahn-echo spin-coherence time (T2 ≈ 2.4 ms) everobserved in room-temperature solid-state systems, leading to the best sensitivities. The AC magnetic fieldsensitivity, estimated to be 9.1 nT/(Hz)1/2, is improved by almost a factor of two compared to previous
results. The reasons for this improvement are the longer T2, the larger Rabi contrast and the slightly higher
photon count due to n-type diamond.
That the doping of phosphorus extends the spin-coherence times and gives better magnetic fieldsensitivities is against intuition, because phosphorus is paramagnetic at room temperature in diamond.
During the CVD growth, it is known that many vacancies are generated, which causes generation ofthermally stable impurity-vacancy and multi-vacancy complexes. However, their generation can besuppressed by Coulomb repulsion of charged vacancies in n-type diamond. We discuss the origin of noises
by measuring noise spectroscopy and T1 measurement.
Our research opens a new avenue for further
extension of coherence times of NV centres using newsynthesis techniques of quantum-grade diamond.
Moreover, the elongation of coherence times in n-typesemiconductor diamond paves the way to the development and application of diamond-based quantumFigure 2. Result of FID measurement (datainformation, sensing and spintronics devices.
with crosses, sinusoidal exponential-decay fit
with line, T2* = 1.54 ms).

Reference： E. D. Herbschleb, H. Kato, Y. Maruyama,
T. Danjo, T. Makino, S. Yamasaki, I. Ohki, K. Hayashi, H. Morishita, M. Fujiwara, N. Mizuochi, “Ultralong coherence times amongst room-temperature solid-state spins”, Nature Communications, 10, 3766(2019)., DOI : https://doi.org/10.1038/s41467-019-11776-8

14

Room Temperature Electrically Detected Nuclear Spin
Coherence of NV Centres in Diamond
H. Morishita,1 S. Kobayashi,1 M. Fujiwara,1 H. Kato,2 T. Makino,2 S. Yamasaki,2 N. Mizuochi1
1Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan
2
National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki, Japan
Nuclear spins have a long coherence time (T2)
due to the good isolation from environmental noise.
Therefore, they are candidates for quantum memories
in quantum-information devices and quantum
sensors. Using nuclear spin, diamond for quantum
memories, highly sensitive magnetic sensors,quantum repeaters, quantum registers, have been
demonstrated at room temperature. Previously, we
proposed theoretically that hybrid quantum magneticfield sensor with an electron spin and a nuclear spincan enhance a sensitivity.[1] In these demonstrations,the detection of nuclear spin coherence is essential.
So far, NV electron spins have been detected by
optical techniques and electrical techniques. The
Figure 1. Pulse sequence (top) and the result
electrical technique is an important technology for(bottom) of an electrically detected nuclear
developing and integrating quantum devices.
Rabi oscillation. ±x indicate the phase of MW
Furthermore, a theoretical model predicts that its
pulse. (Inset) Rabi frequencies as a function of
detection sensitivity is approximately three times
the square root of RF power.
higher than that of the optical technique. While thephotoelectrical detection of the electron spin coherence of an ensemble of NV centres and photoelectricalcoherent spin-state readout of single NV centres at room temperature has been demonstrated, the directelectrical detection of nuclear spin coherence remains challenging.
Here, we demonstrate electrical detection of the 14N nuclear spin coherence of NV centres in diamondat room temperature. We used a pulsed electrically detected electron-nuclear double resonance technique
to measure the Rabi oscillations (Fig. 1) and coherence time (T2) of 14N nuclear spins in NV centres. We
observed T2 ≈ 0.9 ms at room temperature (Fig. 2). To the best of our knowledge, this is the first
demonstrations of room-temperature electrical detection of nuclear spin coherence in diamond or any othermaterials. Our results will pave the way for the development of novel electron- and nuclear-spin-based
diamond quantum devices.
Reference：[1] Y. Matsuzaki, T. Shimo-Oka, H. Tanaka, Y.
Tokura, K. Semba, N. Mizuochi, "Hybrid
quantum magnetic field sensor with anelectron spin and a nuclear spin in diamond",
Physical Review A, 94, 52330 (2016).
[2] H. Morishita, S. Kobayashi, M. Fujiwara, H.
Kato, T. Makino, S. Yamasaki, N. Mizuochi,“Room Temperature Electrically Detected
Nuclear Spin Coherence of NV centers inDiamond”, Scientific Reports, 10, 792 (2020).
DOI ： https://doi.org/10.1038/s41598-02057569-8

2τ (ms)Figure 2. Pulse sequence (top) and the result(bottom) of an electrically detected spin coherence
measurement of the 14N nuclear spins in NV centres.
±x indicate the phase of MW pulse.

15

Highly Sensitive AC Magnetic Field Sensing
using Nitrogen-vacancy Centers in Diamond
Junko Ishi-Hayase1, Yuichiro Matsuzaki2, Hideyuki Watanabe2, Norikazu Mizuochi3, Shiro Saito4
1School of Fundamental Science and Technology, Keio University,
2
National Institute of Advanced Industrial Science and Technology (AIST),
3
Institute for Chemical Research, Kyoto University, 4NTT Basic Research Laboratories, NTT Corporation
Negatively-charged nitrogen-vacancy (NV) centers in diamond are promising for highly-sensitive
nanoscale quantum sensor. It is because that spin-triplet electric ground states of NV centers can becoherently manipulated using microwave field and optically initialized/read out with long coherence timeat room temperature. In this study, we propose and demonstrate two quantum protocols for highly-sensitive
AC magnetic field sensing using NV center ensemble in diamond.
One of the proposed protocols is effective to improve the sensitivity for vector magnetic field sensing by
multi-frequency control of electric spins of NV centers. The key idea is that four types of NV centers withdifferent axes are simultaneously controlled by multi-frequency microwave pulses [1]. We demonstrate
vector magnetic field sensing with an ensemble of NV centers in diamond via such multi-frequency control
with pulsed-type measurements. We find that the sensitivity of the vector field sensing with multi-frequency
control is better than that with single-frequency control for every vector component of a magnetic field [2].
Another protocol enables us to detect high-frequency (MHz range) AC magnetic field with continuous
application of microwave and laser [3]. This method utilizes double resonance excitation of electron spinsof NV centers. Unlike conventional methods, the proposed method does not require a pulse sequence; thisgreatly simplifies the procedure and apparatus needed for implementation.
Our results pave a way to implement AC magnetic sensors with high performances based on the electricspin manipulation of NV centers in diamond.
Reference：[1] S. Kitazawa, Y. Matsuzaki, S. Saijo, K. Kakuyanagi, S. Saito, and J. Ishi-Hayase，“Vector-magneticfield sensing via multifrequency control of nitrogen-vacancy centers in diamond”，Physical Review A 96,
042115/1-7 (2017).
[2] K. Yahata, Y. Matsuzaki, S. Saito, H. Watanabe and J. Ishi-Hayase, “Demonstration of simultaneous
vector magnetic field sensing with nitrogen-vacancy centers in diamond via multifrequency control ofmicrowave pulses”, Applied Physics Letters, 114, 022404/1-5 (2019).
[3] S. Saijo, Y. Matsuzaki, S. Saito, T. Yamaguchi, I. Hanano, H. Watanabe, N. Mizuochi and J. Ishi-Hayase，“AC magnetic field sensing using continuous-wave optically detected magnetic resonance of nitrogenvacancy centers in diamond”，Applied Physics Letters, 113, 082405/1-5 (2018).
(a)
(a)

(b)
( π 2) x( π 2) x( π 2) x( π 2) x

τ

τ

2

2

τ

πx

2

τ

2
πx

2

τ

τ

τ
2

πx

2

τ
2

πx

( π 2) y

0.02
0.01
0.00

( π 2) − y-0.01( π 2) − y-0.02( π 2) y

-0.03

-5

0

5

Fig. 1 (a) Microwave pulse sequence for multifrequency control
of NV centers. (b) Spin echo signals vs. applied AC magnetic
field amplitude using standard single-frequency control and ourmulti-frequency control method. Multifrequency control leads
to the enhancement of the signal.

16

Fig. 2 (a) Energy levels of the NV
centers with applied magnetic fields
perpendicular to one of the four
possible crystallographic axes. (b)CW-ODMR for different frequenciesof the applied MW and RF fields.

Microwave Imaging in Micrometer Resolution－Precision measurement of microwave field-distribution using Rabi oscillations－
Shuhei Nomoto1, Giacomo Mariani1, Satoshi Kashiwaya2, and Shintaro Nomura1
Division of Physics, University of Tsukuba, 2Department of Applied Physics, Nagoya University.

1

Nondestructive imaging is widely used in material characterization, medical examination, border security,and so on. The most commonly used nondestructive imaging system utilizes X-rays for applications suchas medical imaging. The spatial resolution of X-ray imaging is high due to the short wavelength of less than
10 nm. However, regulatory dose limits restrict application areas of X-ray imaging. Microwave imaging
may be used in areas where X-ray exposure should be avoided, and may extend the application areas ofnondestructive imaging further. Antenna array has often been used for microwave imaging, but complex
analysis is required by taking mutual inductance into account. Moreover, there are challenges in absolute
quantification of the microwave amplitude and the spatial resolution limited by the wavelength.
Here, we have succeeded in developing a microwave imaging system in micrometer resolution by using
a quantum sensor based on nitrogen-vacancy (NV) centers in diamond, which has recently been attracting
considerable interests as a platform for quantum information and quantum sensing. We have successfully
obtained microwave field images quantitatively at the spatial resolution of a micrometer. In our newly
developed microwave image microscope, the frequency of the microwave to be detected is selected bytuning the resonance frequency of NV centers by the external magnetic field. We have measured the Rabi
frequency of the electron spin in NV centers, and obtained image mappings of the microwave amplitude byusing the proportionality relation between the Rabi frequency and the microwave amplitude at ambient
temperature.
We demonstrate to image microwave distribution around microwave resonators (Fig. 1) with a straightwire and a tapered wire. The width of the tapered wire was modulated to spatially control the amplitude of
the microwave field. The obtained microwave images in the vicinity of the straight and the tapered wires
are shown in Figs. 2(a) and (c), respectively. The obtained images agree well with the simulated results byfinite-difference time-domain (FDTD) analysis (Figs. 2(b) and (d)). We have obtained 22-fold enhancement
the microwave amplitude, or 460-fold enhancement of microwave power by the microwave resonator.
The results of this research provide a new method for precision measurement of microwave field
distribution in micrometer resolution. Our method is expected to find applications in areas such as
characterizations of microwave devices or metamaterial elements, and visualization analysis of biologicalactivities, and promotes research in quantum sensing using quantum spins.
Reference： Giacomo Mariani, Shuhei Nomoto, Satoshi Kashiwaya, and Shintaro Nomura, “System for the
remote control and imaging of mw fields for spin manipulation in NV centers in diamond”, Sci. Rep. 10,4813 (2020). DOI: 10.1038/s41598-020-61669-w

Fig. 1 Schematics of microwave resonatorswith a straight wire (left) and a tapered wire(right) wire.

Fig. 2 Results of the microwave imaging and
FDTD simulation for the resonators with (a, b) a
straight wire and (c, d) a tapered wire.

17

Probing thermal magnon current via nitrogen-vacancy
centers in diamond－Coupling of quantum spin state with thermal magnon current－

Dwi Prananto1, Yuta Kainuma1, Kunitaka Hayashi1, Norikazu Mizuochi2, Ken-ichi Uchida3, and Toshu An1
１
School of Materials Science, Japan Advanced Institute of Science and Technology、2Institute for Chemical Research, Kyoto University、3National Institute for Materials Science
Thermally excited magnon current is being intensively investigated owing to their potential applicationin spin caloritronics and magnon spintronics. Conventionally, the thermal magnon current is detected byspin Seebeck effect where injected spin current is converted to electro motive force via inverse spin Hall
effect. For this, large size of spin detector such as platinum thin film electrode more than micrometer isneeded for signal detection. Meanwhile, the quantum sensors based on the electron spins associated withnitrogen-vacancy (NV) centers in diamond has been regarded as high-resolution (nanometer scale) andhigh-sensitivity sensors. Recently, it has been demonstrated that the NV center can sense AC magnetic field
produced by spin waves (coherent magnon). Because the spin waves are known to be modulated by thermal
magnon current exerting thermal spin transfer torque, thermal magnon current can be detected by NV center.
We report the detection of thermal magnon current mediated by coherent spin waves propagating in amagnetic insulator yttrium iron garnet (YIG) under a temperature gradient using the NV centers in diamond(Fig. 1). The NV spins hosted in a beam-shaped bulk diamond and a nanodiamond were prepared, andfingerprint of the thermal magnon current is observed via the spin waves (magnetostatic surface spin wave,
MSSW) in the form of modified Rabi oscillation frequencies as a function of temperature difference formedin the lateral direction of the YIG sample (Fig. 2) as well as spin relaxation rates.
This demonstration of local probing of thermal magnon current provides a basis for creating a new
device platform hybridizing spin caloritronics and spin qubits.
Reference： D. Prananto, Y. Kainuma, K. Hayashi, N. Mizuochi, K. Uchida, and T. An, “Probing thermal
magnon current via nitrogen-vacancy centers in diamond”, arXiv:2007.13433

Fig. 1 Schematic of detection of thermal magnons current

Fig.

mediated by coherent spin waves via NV centers in diamond.

oscillation2

Modification

of

Rabi

frequenciesofNV

centers by thermal magnon current.

18

Operando Analysis of Electron Devices Using NanodiamondThin Films Containing Nitrogen-Vacancy Centers
Haruki Uchiyama1, Soya Saijo2, Shigeru Kishimoto1, Junko Ishi-Hayase2, and Yutaka Ohno1
Department of Electronics, Nagoya University, 2School of Fundamental Science and Technology, Keio
University

1

Operando analysis of electron devices provides key information regarding their performanceenhancement, reliability, thermal management, etc. For versatile operando analysis of device, the nitrogenvacancy (NV) centers in diamonds are potentially useful media owing to their excellent sensitivity tomultiple physical parameters. However, in single-crystal diamond substrates often used for sensing
applications, placing NV centers in contiguity with the active channel is difficult. This study proposes anoperando analysis method using a nanodiamond thin film that can be directly formed onto various electron
devices by a simple solution-based process.
We started this study from improving the detectivity of the optically-detected magnetic resonance(ODMR) of nanodiamonds. Results of the detailed noise analysis show that ODMR measurements withhigh SNR could be achieved in the shot-noise region, excluding the large 1/f noise and spike-like noises
attributable to the NV centers of the nanodiamond. The SNR using lock-in detection in the shot-noise region
was improved by a factor of 36 compared with the SNR using the photon counting method.
The magnetic field formed by the current and increase in temperature owing to Joule heating could be
evaluated for the metal microwire fabricated on a silicon wafer under bias from the differential ODMR
measurement. The spatial mapping data showed similar profile the calculated magnetic field distribution.
Because a nanodiamond thin film can be easily formed at room temperature by a solution-based
process directly onto the device surface without disturbing the device property, the proposed method
presents the possibility of operando analysis of various types of electron devices.
Reference: H. Uchiyama, S. Saijo, S. Kishimoto, J. Ishi-Hayase, and Y. Ohno, "Operando Analysis ofElectron Devices Using Nanodiamond Thin Films Containing Nitrogen-vacancy Centers", ACS Omega 4,7459-7466 (2019). doi:10.1021/acsomega.9b00344

Fig. 1 Test device for operando analysis using Fig. 2 Spatial distributions of the magnetic field
nanodiamond thin film.
strength in the vicinity of the metal wire.

19

Successful quantum teleportation transfer— Preserving the quantum state of photons in diamond: a new development inquantum communication —Hideo Kosaka
Yokohama National University
Professor Hideo Kosaka of the Graduate School of Engineering at Yokohama National University and agroup at the University of Stuttgart in Germany have become the first in the world to successfully
demonstrate a new principle whereby photons used in quantum communication can be transferred using
the principle of quantum teleportation in diamond used as a quantum memory.
This success is a ground-breaking discovery showing that it is possible to transfer the quantum state of aphoton to a nucleon that does not act directly, and to store this state for a prolonged period, simply byabsorbing the photon with an electron in a quantum entangled state with the nucleon.
The results of this study suggest that quantum teleportation, which is the basic principle of a quantum
repeater, can be achieved based on an extremely simple principle, and that the quantum state of a photon
can be reliably reproduced at high speed and stored for a long time at a remote location that is not directly
reachable. It is therefore expected to pave the way to dramatic improvements in the range and reliability ofquantum communication networks whose absolute secrecy is guaranteed by the laws of physics.
To achieve quantum teleportation, a quantum entanglement state must first be prepared in an atom. Thisis achieved by using the quantum entanglement inherent in matter. The spins of an atom’s constituent
electrons and nucleons are connected by a force called hyperfine interaction that leads to quantum
entanglement. We started by using microwaves and radio waves to purify this quantum entanglement. Next,
by using this entanglement as a seed, we succeeded in transferring the quantum state of a photon to a carbon
nucleon by applying a technique for quantum entanglement detection by absorption that was demonstrated
previous paper (Hideo Kosaka, et. al., Phys. Rev. Lett., 114, 053603 (2015)).
The figure illustrates the operating principle of using quantum teleportation to transfer a quantum statefrom a photon to a carbon nucleon, which was successfully demonstrated in this study. Quantum entangled
electron and nucleon are prepared in advance. In this experiment, we achieved this by irradiating withmicrowaves and radio waves. After that, in incoming photon is absorbed by the electron. When it is detectedthat the photon and electron are in a specific entangled state, the quantum state of the photon is transferredto the nucleon.
Reference: Sen Yang, Ya Wang, Thai Hien Tran, S. Ali Momenzadeh, M. Markham, D. J. Twitchen, Rainer
Stohr, Philipp Neumann, Hideo Kosaka, and Joerg Wrachtrup, “High ﬁdelity transfer and storage of photon
states in a single nuclear spin", Nature Photonics (2016). DOI:10.1038/nphoton.2016.103

Fig. 1 Quantum teleportation using quantum entanglement in diamond. A quantum-entangled electron (e)and carbon nucleon (13C) are prepared in advance. When an incoming photon excites the electron into a
specific orbit, the quantum state of the photon is instantly transferred to the carbon nucleon.

20Development of the world’s first error-tolerant qubit— Quantum memory and quantum sensor devices that use geometric echoes
to self-stabilize —Hideo Kosaka, Yokohama National University
For the first time ever, we have succeeded in demonstrating a new method for constructing error-tolerant
qubits, which are used in quantum communication, quantum computing, and quantum measurement, and a
new principle for the self-stabilization of these devices. We achieved this result by proposing an errortolerant qubit structure that uses the electron spin of a single defect in a diamond, which is a promisingform of qubit. This is a revolutionary discovery that demonstrates the possibility of self-stabilization
through a technique based on a new principle called geometric spin echo, which differs completely fromthe conventional dynamic echo technique. We have shown that environmental noise and control errors thatcause qubit destruction can be autonomously eliminated in a non-magnetic environment where the magnetic
field has been completely eliminated. This is expected to result in quantum memory devices that require noerror correction, and quantum sensors with the ultimate level of sensitivity.
Quantum information science has opened up a new era of information science where the traditional
concept of information units (“classical” bits) is extended to quantum-dynamic information units (called
quantum bits, or “qubits”). By allowing quantum effects to work on the inputs and outputs of information
processing, it is possible to implement quantum computers with unprecedented computing power andfundamentally unbreakable quantum cryptography. It is also expected to be applicable to quantum
measurement techniques that provide ultra-sensitive sensors. To realize these technologies, it is essential tobe able to manipulate qubits accurately and store them stably. However, the qubits proposed so far havebeen prone to operational errors, and it has turned out to be difficult to store them reliably.
In our study, we focused on electron spin pairs at nitrogen-vacancy centers (NV centers) in diamond, andbecame the first in the world to demonstrate a method for constructing error-tolerant qubits and a newprinciple for autonomously stabilizing these qubits. An NV center consists of a nitrogen impurity pairedwith an adjacent carbon vacancy in a diamond, which forms a stable quantum medium resembling an
isolated atom in a vacuum. It is expected that electron spin pairs localized in vacancies of this type can beused as qubits. Conventional qubits operate by using two quantum states, but our new qubits have an errortolerant configuration resulting from the use of an auxiliary third quantum state. We have shown that astabilization technique called geometric spin echo can be used to autonomously stabilize this qubit in anenvironment that is completely free of magnetic fields. This behavior is completely different from the
dynamic spin echo exhibited by conventional qubits. This results in a quantum coherence time of 83 µs,
which is about 140 times longer than the 0.6 µs of conventional quantum states. This shows thatenvironmental noise and control errors that lead to qubit destruction can be autonomously eliminated in a
non-magnetic environment where the magnetic field has been completely eliminated.
Reference: Yuhei Sekiguchi, Yusuke Komura, Shota Mishima, Touta Tanaka, Naeko Niikura and Hideo
Kosaka*, Nature Communications, 7, 11668 (2016). DOI:10.1038/ncomms11668

Fig. 1 Schematic diagram of NV center and spin bus arrangement (left) and magnetic field dependence ofcoherence time T2 (right). The electron spin localized in the NV center creates a magnetic dipole fieldaround it (shown by the gray arrow on the left). By applying geometric spin echo in a zero magnetic field,
the dynamics of the noise-generating spin bus (13C) can be effectively suppressed, resulting in a much
longer coherence time T2.

21

Demonstration of a new principle of optical spin control thatpaves the way for quantum integrated memory— Facilitates high-speed quantum computing and quantum communication —Hideo Kosaka
Yokohama National University
With the advent of next-generation quantum information technology based on the quantum mechanicallaws of quantum computing and quantum communication, we can expect the development of computersthat outperform conventional technology, and communication systems with perfect security. Various
material systems with quantum properties have been proposed as the basis for realizing these technologies.
In particular, methods that treat electron spins in a diamond as units of information (qubits) are known tohave excellent performance in terms of information retention and integration potential. To exercise
quantum-level control over the spin states of an integrated array of electrons in diamond, a technique isneeded in order to control each spin individually, arbitrary and accurately. Although electron spins can beselectively controlled by using the local electric field of laser light (Fig. 1), the control methods that havebeen proposed and demonstrated so far only have limited control capabilities, and lack high-fidelity
performance.
We have succeeded in demonstrating a technique that can use laser light to accurately control the spin ofa single electron at a nitrogen vacancy (NV) center in diamond. Until now, an important consideration has
been the magnitude of the energy difference imparted to the physical system by applying a magnetic field.
In our research, however, we devised a method whereby the energy difference of the physical system isintentionally eliminated by strictly eliminating the magnetic field so as to make skillful use of the degreeof freedom of the space that appears as a result, and we also demonstrated this method experimentally. By
adopting a contrary approach to conventional methods, this technique makes it possible to perform quick
non-adiabatic operations instead of time-consuming adiabatic operations. As a result, we became the firstin the world to achieve highly precise and completely free control with a fidelity of over 90% at nanosecond(10−9 s) timescales. This is about a hundred times faster than conventional technology, but achieves threetimes more fidelity while using a small light power of the order of microwatts (10−6 W). This showed thepossibility of using light to simultaneously control 108 NV spin states. We have also conducted theoreticalsimulations showing that the spin control mechanism shifts from dynamic phase rotation with low noise
immunity to geometric phase rotation with high noise immunity. According to this result, it should bepossible to perform all the operations required for quantum computing at a practical scale, which is expectedto accelerate the pace of future quantum computing experiments.
With this result, we were able to use laser beam technology to complete each of the three basic elemental
technologies required for quantum computing: writing, gate control, and reading. With a view toimplementing quantum information networks, we will continue to use these technologies and will apply
them to demonstrations of advanced quantum information technologies such as quantum teleportationtransfer and quantum entanglement measurements. These quantum technologies have also opened the way
to applications such as ultra-sensitive electromagnetic field sensing and bioimaging for handling delicate
physical quantities.
Reference: Yuhei Sekiguchi, Naeko Niikura, Ryota Kuroiwa, Hiroki Kano and Hideo Kosaka*, “Opticalholonomic single quantum gates with a geometric spin under a zero field”, Nature Photonics.
DOI:10.1038/nphoton.2017.40
Fig. 1 Schematic diagram of a nitrogen vacancy
center (NV center) in diamond and the use of a laser
beam for controlling electron spin. An NV center
consists of a nitrogen atom occupying a carbon site
in a diamond lattice, with an adjacent vacancy. The
electron spin is localized in the vacancy. Since thelaser beam can be focused, it is possible to selectively
control the spin of a single target electron.

22Ultra-low noise microwave amplification by spin maser－Back to the basic for quantum technologies－

Jason Ball1, Petr Moroshkin1, and Yuimaru Kubo1,2
Quantum Dynamics Unit, Okinawa Institute of Science and Technology Graduate University

１

Current quantum information technologies at microwave frequencies require ultra-low temperature
operations, typically at 10 – 100 millikelvin, because of microwave photons' tiny energy. One of the key
technologies is an ultra-low noise amplification of microwave signals at the millikelvin environments.
This ultra-low noise amplification has only been realized by superconducting Josephson parametricamplifiers (JPA) based on superconducting circuits. However, JPAs have suffered from smaller saturation
power. The state-of-the-art JPA has a maximum input power of about -100 dBm (0.1 picowatts). Moreover,
JPAs do not properly work under strong magnetic fields due to the superconductivity.
One of the other principles for amplifying microwave signals is maser, an acronym of "microwave
amplification by stimulated emission of radiation" with spins in solid crystals. Although maser has been
intensively studied in the late 1950s and early 1960s, it has been forgotten behind because of the rise andrapid progress of semiconductor technologies.
We demonstrate that this "maser amplifier" is indeed very interesting and promising for microwave
quantum information and technology applications at millikelvin temperatures, where nobody has tried tooperate a spin maser. Using P1 centers in diamond, we realized a cavity-maser amplifier with a gain of
about 36 dB and a saturation power of at least -70 dBm, three orders of magnitude larger than that of thebest-reported JPAs. Such an amplifier may be promising for quantum computers or magnetic resonanceimaging applications.

Figure: Maser amplifier demonstrated in this work. (a) P1 (nitrogen) center in diamond. (b) Experimental
setup. A strong pump microwave tone generates a population inversion on one of the P1 center electron
spin resonance transitions. The maser amplifier then amplifies a weak probe tone. (c) 36 dB gain has beenobtained with a noise temperature TN of about 0.5 K. Note that the power of the input probe tone of 100 fW
is the saturation power of the best reported JPAs.

23

Ultralong relaxation times in bistable hybrid quantum
systems
Andreas Angerer 1, Stefan Putz1, Dmitry O. Krimer1, Thomas Astner1, Matthias Zens1, Ralph Glattauer1,
Kirill Streltsov1, W. J. Munro2,3, Kae Nemoto3, Stefan Rotter1, Jorg Schmiedmayer1, and Johannes Majer1
Technische Universität Wien、2NTT Basic Research Laboratories、3National Institute of Informatics

１

Nonlinearities are one of the most important sources of complexity that a systems dynamic may exhibit.
In classical dynamics, it is a source of rich behavior with bistability, chaos & solitons illustrative examples.
It is often deeply related to critical phenomena. Nonlinear phenomena are not only scientifically interesting,but are important in the design of many technologies; bistability is a typical example used in opticalswitches. On the other hand, in quantum mechanics it has been known that nonlinear behavior differsfrom its classical counter parts. Superradiance is a nonlinear quantum behavior that appears counterintuitive
compared to classical nonlinearities. In this work, using a hybrid system of an ensemble of diamond NV
centers coupled to a microwave cavity (see Fig 1), we have explored the dynamics of amplitude bistability
that naturally arises.
Usually the cavity quantum electrodynamics (cQED) involved atoms or trapped ions coupled with opticallight. In such cases it is difficult for atoms to have long enough coherence times so that we can explire
the amplitude bistability dynamics. In our work, we instead used negatively charged nitrogen-vacancy(NV−) centers in diamond at millikelvin temperature as artificial atoms. The low temperatures extended thelife time of the artificial atoms enabling us to investigate the observe bistability in cQED and the dynamics
associated with it. In the experiment, our hybrid system exhibits the amplitude bistability in new regimesof cQED with unusual decay rates for the spin system. A critical slowing down of the decay of the cavity
population on the order of 11 hours was observed. This time scale is several orders of magnitude longer
than that observed previously for this effect and many orders of magnitude longer than other time scales
associated with our system. Further our experiment provides a useful foundation for the exploration of
additional nonlinear phenomena in hybrid quantum systems and future quantum technologies that may arise
from it. It paves the way for high-sensitivity magnetic field sensing & quantum metrology as well
microwave isolators and diodes.
Reference： Andreas Angerer, Stefan Putz, Dmitry O. Krimer, Thomas Astner, Matthias Zens, Ralph
Glattauer, Kirill Streltsov, William J. Munro, Kae Nemoto, Stefan Rotter, Jörg Schmiedmayer and Johannes
Majer“, Ultralong relaxation times in bistable hybrid quantum systems”, Science Advances Vol. 3, no. 12,e1701626 (2017).

Fig.1 A schematic illustration showing our
hybrid quantum system composed of an
ensemble of diamond NV centers and themicrowave resonator.

24

Superradiance from diamond
Andreas Angerer 1、Kirill Streltsov1, Thomas Astner1, Stefan Putz1, Hitoshi Sumiya2, Shinobu Onoda2,
Junichi Isoya2, W. J. Munro3,4, Kae Nemoto4, Jorg Schmiedmayer1, and Johannes Majer1
１
Technische Universität Wien 2Tsukuba University 3 NTT Basic Research Laboratories
4
National Institute of Informatics“Superradiance” looks like a flash of light from a material. What is the source of this strong short-lived
emission of light? When an atom changes from one energy state to another, the difference of the energyof these two states can be emitted as light. What color of light will be emitted is dependent on the energy
difference, and it can be visible or could be microwave. Superradiance can be observed then when many
atoms emit light in a very short period of time. Because of the short time period associated with thisbehaviour, superradiance looks like a flash of light.
This phenomenon, superradiance, was predicted decades ago, however it has been regarded as difficult
to realize. This is simply because the requirements for such phenomena to occur were difficult to achieve;
many atoms need to be very close together to couple with the same light field (a task already difficult in areal system). In addition to this, coupling between the atoms themselves needs to be negligible, which initself seems to be impossible due to the closest of atoms to realize superradiance.
In this work, we used a diamond nitrogen-vacancy (NV) center as an artificial atom which has a
microwave energy transition. As microwaves has a much longer wave length than visible light, it ispossible to pack a high density of NV centers within the few cm microwave wave-length while minimizing
the interaction between NV centers. The superradiance demonstration however requires a special diamondsample, an ultra-pure one possessing a high concentration of NV centers.
The key for demonstration of superradiance is the experimental observation of the emission nonlinearity
to the number of NV centers involved. It is almost impossible to count them all in the real sample, so we
exploited the nature of the diamond crystal. There are four directions in how a NV center can form, andhence we could change the number of NV centers contributing to the superradiance through directional
magnetic fields from an unknown number N to 4N. By measuring not only the characteristics of the
microwave light emission but also the spin polarization in the sample we demonstrated superradiance inthis hybrid system. This result forms the basis for the future development of microwave masers andvarious quantum technologies.
Reference： Andreas Angerer, Kirill Streltsov, Thomas Astner, Stefan Putz, Hitoshi Sumiya, Shinobu
Onoda, Junichi Isoya, W. J. Munro, Kae Nemoto, Jorg Schmiedmayer, and Johannes Majer, Nature Physics
14,1168-1172 (2018).

Fig.1 Photograph of the 3D microwave
cavity used in the experiment. The
microwave mode of the cavity couples
with the ensemble of NV centers in the
diamond sample placed inside thecavity.

Fig.2 Plot showing the spin dynamics (blue)
and microwave light emission (red). The
rapid decay in the spin polarization as well
as a burst of microwave photons indicates thesuperradiance. The decay time without
superradiance is the order of 4×104 s.

25

Relaxation to negative temperatures and reservoir-assisted
quantum entanglement in hybrid quantum systems
Yusuke Hama1, Emi Yukawa1, W. J. Munro3,1, Kae Nemoto1
2
3
National Institute of Informatics
RIKEN.
NTT Basic Research Laboratories

１“Relaxation” is one of the fundamental behaviors in physics and occurs when a system is coupled to an
environment. In this situation the system will relax to the thermal state associated with the temperature of
the environment. However, in quantum mechanics, even with a simplest model, there are dynamics
unique to those quantum mechanical systems which may affect such relaxation. Superradiance is one
notable example and occurs when the system composed of many atoms/spins etc is coherently coupled to
the reservoir. When the system, which consists of two-level atoms, such as spins, interacts with a bosonicreservoir, we normally expect the relaxation process to occur with an exponential decay rate. However,when the spins in the system are collectively coupled with the reservoir, super-exponential decay is
expected to emerge. Due to the time scales involved it is often quite difficult to observe such phenomena,
however recently we have experimentally demonstrated in the microwave regime (also see “superradiancefrom diamond” in this report) .
In this work, we have investigated collective decay processes in hybrid quantum systems and observedcounterintuitive relaxation, that is relaxation to negative temperatures. Our simple model consists of two
domains of a spin ensemble coupled to a single bosonic reservoir. Assuming all those spins couple equallyto the reservoir, the spin ensemble would be expected to exhibit superradiance decay. However, the twodomain structure in the ensemble allows us choose initial states with different symmetries from those
associated with the systems dynamics. When this happens, the domain relaxation does not necessarily
reach the thermal state, and in principle it could heat up to give thermal populations beyond the hightemperature limit, i.e. one may reach the negative temperature (See Fig 1). When the size is vastly
imbalanced between the two domains, the small domain can become almost fully excited, even when it was
initially in its ground state.
To deepen our understanding of this relaxation dynamics, we also explored the degree of entanglement
between two domains (Fig 2). As there is no direct or indirect coupling between the spin domains, wewould usually not expect to see any mechanism for entanglement generation emerge. However, in thisrelaxation process, the system symmetry restricts the relaxation passage meaning our system can generateentanglement between the two domains.
These results suggest that when the system has multiple symmetries, the dynamics could be restrictedwith them, and even when the system is coupled with the reservoir, it can exhibit non-trivial dynamics.
Having the initial state and the lifetime of the conservation quantities controllable, we could design uniquerelaxation paths that can be applied to realize new quantum technologies including quantum batteries.
Reference： Yusuke Hama, W. J. Munro, and Kae Nemoto, Phys. Rev. Lett. 120, 060403 (2018)
Yusuke Hama, Emi Yukawa, W. J. Munro and Kae Nemoto, Phys. Rev. A 98, 052133 (2018)

Fig.1 Illustration showing the decay processes for domain 1(red), domain 2 (blue) and the total system (green). (a) depicts
the N=2 case where N is the number of the spins in domain 1
while (b) shows the N=5 case. For both situations, thenumber of spins in domain 2 is one.

26

Fig. 2 Plot showing the generationof entanglement by the relaxation
between domain 1 with N spins anddomain 2 with 1 spin.

Quantum Metrology beyond the Classical Limit
under the Effect of Dephasing
Yuichiro Matsuzaki1, Simon Benjamin2, Shojun Nakayama3, Shiro Saito1, and William J. Munro1
1
NTT Basic Research Laboratories, 2University of Oxford, 3National Institute of Informatics
Magnetic field sensing is an important technique, and this is widely used in many practical areas such as
materials science and biology. One of the measures to quantify the performance of the magnetic field sensor
is an uncertainty of the estimation described as δB. The inverse of the uncertainty is defined as a sensitivity.
The suppression of the uncertainty is important for the practical purposes. When we use conventionalclassical sensors, for a given total measurement time T, the uncertainty of the estimation is known to bescaled as δB∝T-0.5, and we call this a classical scaling.
Many efforts have been devoted to realizing a sensitive quantum sensor that utilizes quantum properties
such as superposition. Especially, a magnetic field sensor with qubits is considered as one of the mostpromising applications of quantum sensing. By using a superposition of a qubit, it is in principle possible
to have a better sensitivity than a classical sensor if we assume an ideal case. For a quantum sensing without
any noise, the uncertainty δB decreases by T-1 for a given total measurement time T, and we call this aquantum scaling. However, it is known that quantum states are fragile against noise, and the noise typicallydecreases the sensitivity of quantum sensing. Especially, under the effect of dephasing, which is one of themost common noise for the quantum magnetic field sensors, the uncertainty δB decreases just by ∝T-1/2
even with a quantum senor in a conventional scheme, and this is the same scaling as the classical scaling.
Here, we propose a new quantum magnetic field sensor that is robust against dephasing. Even underthe effect of dephasing, we can achieve a quantum scaling of δB∝T-1, and so our proposed quantum
sensor beats the classical sensor in scaling. The key idea is to use quantum teleportation between qubits.
Although quantum teleportation has been used in the area of quantum computation and quantum
communication, we focus on the use of the quantum teleportation to suppress the dephasing. While thequbits are interacting with the target magnetic fields, we implement frequent quantum teleportation between
the qubits. We show that the effect of the dephasing can be drastically suppressed while the information of
the magnetic fields is encoded in the qubits in our scheme. Our results pave the way for practical quantum
magnetic field sensing that would be useful for the area of materials science and biology.
Reference： Y. Matsuzaki, S. Benjamin, S. Nakayama, S. Saito, and W. J. Munro, Phys. Rev. Lett. 120,
140501 (2018).

Fig. 1 Performance of our proposed new quantum sensor to measure magnetic fields where δB denotes
the uncertainty of the estimation and T denotes the total measurement time. The sensitivity of the sensor
corresponds to the inverse of the estimation uncertainty. As the total measurement time increases, theuncertainty of the estimation decreases, and so the scaling between them is important to realize moresensitive magnetic fields sensors. Our proposed quantum sensor can beat the classical sensor in scalingeven under the effect of dephasing that is one of the most common noise for the quantum magnetic fieldsensors.

27

Designing measurement with hybrid quantum systems
Shane Dooley1, Michael Hanks2,1, Shojun Nakayama1, William J. Munro3,1, and Kae Nemoto1,2
１2
National Institute of Informatics
Graduate University for Advanced Studies
3
NTT Basic Research Laboratories
Measurement is the fundamental basis for science and technology, and physics provides us not only theability but also the limitation to measure physical quantities. When we hit the limitation in our
measurement, our science and technology cannot go beyond the precision the measurement gives.
Nanotechnology for example has rapidly developed in the last decade allowing us to measure andmanipulate devices on the scale of nano-meters, but we are already seeing further improvements limited byour measurement resolution. This limitation arises from the fundamental principle of quantum mechanics
and is called the quantum standard limit (shot noise limit). Such quantum noise is fundamental and cannot
be eliminated by cooling or stabilizing the system. Quantum measurements (and quantum sensing) areable to challenge this fundamental limitation by applying the principle of quantum mechanics to design
better measurements.
It is known that when we design measurements based on quantum mechanics, it is possible to break thequantum standard limit and reach the ultimate Heisenberg limit (the best quantum mechanics will allow).
In these quantum measurements we prepare the probe to be in a quantum state with maximum sensitivity
to the quantity we want to measure. This in principle allows us to reach the Heisenberg limit, howeverrealistic measurement also involve noise around the measurement apparatus. Hence, the current problem
is to circumvent these effects keeping the sensitivity the quantum measurements offers. This is achallenging problem as it is often nontrivial to distinguish the signal from the noise. In our work, we
address this problem by designing the probe state to be resilient to the noise. To achieve that effect, we
focus on the interaction between spins in a quantum probe. We have found that when the spin-spin
interaction is strong enough, we can establish a quantum probe robust against heat noise. Fig.1 shows
how the measurement scheme and how the energy spectrum can be engineered using spin-spin coupling.
This energy spectrum engineering gives us the stability of the quantum probe. For instance, when J>ω,the information of ω is stored in the relative phase in the two ground states. As shown in Fig.2, the strong
spin-spin interaction allows us to achieve higher sensitivity measurements.
Reference： Shane Dooley, Michael Hanks, Shojun Nakayama, William J. Munro, and Kae Nemoto,"Robust quantum sensing with strongly interacting probe systems", npj Quantum Information 4, 24 (2018)

Fig.1 (Top) Schematic illustration of themeasurement scheme. (Bottom) This illustrates
how the energy spectrum of the probe can be
manipulated by the spin-spin coupling.

28

Fig. 2 Plot showing the sensitivity
possible with these measurement
schemes.

Robust control of two-qubit Hamiltonian dynamics
Ryosuke Sakai1, Akihito Soeda1, Mio Murao1, and Daniel Burgarth2
１
Graduate School of Science, The University of Tokyo,
2
Department of Physics and Astronomy, Macquarie University
We showed that it is possible to achieve robust control of Hamiltonian dynamics to implement anarbitrary target quantum gate for two-qubit Hamiltonian systems, including an unknown parameter byadding a single-qubit control Hamiltonian. To perform the same task with conventional feedback control,
we first need to perform quantum measurements and estimate the value of the unknown parameter, thenderive and design the control Hamiltonian based on the estimated value. In robust control, a control
Hamiltonian is used to implement the target quantum gate for all values in the range of the parameters;
therefore, estimation of the value is not necessary. Such robust controllability of quantum dynamics had
only been shown for single-qubit systems before.
We first analytically proved the robust controllability of a class of two-qubit Hamiltonian dynamics
based on group theory. However, we found that the running time required for the robust control using thecontrol Hamiltonian derived by the analytical method can be very long and might not be practical. We
considered a numerical method to derive the control Hamiltonian by discretization of the unknown
parameters. We regarded all the discretized values within the unknown parameter range to correspond todifferent modes, and numerically optimize the pulse sequence for the control Hamiltonian to achieve thesame target quantum gate (unitary gate) for all modes for a particular target time by using the GREPE
algorithm. We analyzed the quantum gate's accuracy implemented by the optimized pulse sequence for thecontinuous unknown parameters. We showed that robust control of two-qubit Hamiltonian dynamics is
possible with high accuracy for continuous unknown parameters even for some cases where robust
controllability is not analytically proven if the parameter's discretization is fine enough.
These results suggest that it is possible to implement arbitrary quantum gates without finely calibrating
the unknown parameters of the Hamiltonian by using optimized pulse sequences for some Hamiltoniansystems. Calibration of parameters for running a quantum computer requires a lot of work and is very costly.
The idea of robust control of Hamiltonian dynamics that allows fully controlling quantum systems without
knowing all the system parameters may help realize quantum computers.
Reference ： R. Sakai, A. Soeda, M. Murao and D. Burgarth, Phys. Rev. A 100, 042305 (2019).
DOI:https://doi.org/10.1103/PhysRevA.100.042305

Figure: An example of a robust-controllable two-qubit Hamiltonian system and the control pulse. The
error of the implemented gate is within 10-3 irrespective to the unknown parameter .

29

Reversing Unknown Quantum Transformations: Universal
Quantum Circuits for Inverting General Unitary Operations
Marco T. Quintino１, Qingxiuxiong Dong１, Atsushi Shimbo１, Akihito Soeda１ and Mio Murao１
１
Graduate School of Science, The University of Tokyo,
Reversible operations in quantum mechanics are described by unitary operators. Consider the following
problem: a quantum physicist receives a physical apparatus that is guaranteed to perform some unitary
operation given by a black box. Apart from its dimension, no additional information about this unitary
operation is provided. We may consider that the black box is a quantum system evolving by an unknown
Hamiltonian. We sometimes want to remove the effect of the unitary dynamics of the original Hamiltonian
to run a desired quantum program by applying quantum gates. To remove the effect of a unitary operation,
the simplest way is to apply the inverse unitary operation on the system. If we know the description of theunitary operation, we can simply apply the inverse unitary operation. However, if the unitary operation is
given by a black box in this setting, is it possible to implement the action of the inverse operation without
initially knowing the matrix description of the unitary? A simple strategy to solve this problem is to perform
process tomography, obtain a matrix representation, find the inverse matrix that represents the inverse
unitary operation and then decompose the inverse matrix in terms of elementary quantum gates. This
tomographic approach suffers from a major problem: it requires infinitely many uses of the black box inquestion and can never be done exactly with finite uses. Is there a universal way for performing theinverse with finite uses of the black box without any errors?
In this work, we focus on exact protocols, that is, with unit fidelity, that may fail with some probability,
but when successful signal their success. Based on the newly developed idea of higher order quantum
operations, we present a quantum circuit whose failure probability decays exponentially in the number ofthe use of the black box. The circuit represents an adaptive protocol and assumes the use of the black box
should be bigger than d-1 where d is the dimension of the black box unitary operation, both conditions
proven necessary for exponential performance. We then present a numerical method to generate a finite setof linear algebraic constraints and formulate the problem of finding the optimal quantum circuit in terms of
semidefinite programming (SDP). With this SDP approach we show that some quantum circuits withindefinite causal order have an advantage over all conventionally ordered circuits.
Reference： M. T. Quintino, Q. Dong, A. Shimbo, A. Soe da and M. Murao, Phys. Rev. Lett. 123, 210502(2019). DOI: 10.1103/PhysRevLett.123.210502

30

Exploring Protocols for Control of Quantum Transport
Chikako Uchiyama1,2
Graduate School of Interdisciplinary Research, Univ. of Yamanashi,

１

National Institute of Informatics

2

According to quick developments of experimental techniques, various kinds of implementation ofquantum information processing such as quantum computing and quantum cryptography have been
proposed and attracting considerable attentions. To extend the field further, it would be necessary to
explore protocols to control exchange of quantum information between different kind of quantum devices,for example, between quantum processing units and quantum memory devices. For this purpose, we needto control transport of quantum entities which carry quantum information. However, such quantum entities
easily suffer inevitable effects from their surroundings to decrease the efficiency and accuracy of quantum
transport.
In this study, we found a new way to control quantum transport by utilizing the environmental effects
with referring to a model to explain an adaptation strategy of photosynthetic bacteria. The bacteria canharvest even a few photons and transport the excitations to the center of photosynthetic reaction, whichenables them to live in dark circumstances as a bottom of deep lake. We referred a model to explain thelight harvesting mechanism in a pigment-protein complex where transport of excitation energy throughpigments can be accelerated by thermal fluctuation of surrounding protein molecules. While conventional
studies on this topic have been mainly focusing on the elucidation of feature of environmental noise of thebacteria and mimicking them, we found that the controllability of quantum transport can be considerably
raised by applying artificial noise on quantum systems. We found that the spatial-temporal correlation ofenvironmental noise is essential to assist and suppress of transport of excitation energy[1,2].
In addition to the above energy transport, we also explore a protocol to control polarization of spin current.
For a quantum dot under a rotating magnetic field and interaction with a lead, we found that control theamount of spin current is possible by changing the frequency of magnetic field[3]. We also evaluated thelower bound of energy to eliminate the quantum information[4].
We believe that the above studies would be basis on such as quantum switching devices and spintransistor to promote the field of quantum information processing.
Reference：[1] C. Uchiyama, W. J. Munro, and K. Nemoto, “Environmental engineering for quantum
energy transport”, npj Quantum Information, 4, 33 (2018). DOI:10.1038/s41534-018-0079-x [2] C.
Uchiyama, W. J. Munro, and K. Nemoto, in preparation. [3]K. Hashimoto, G. Tatara and C. Uchiyama,“Spin backflow: A non-Markovian effect on spin pumping”, Phys. Rev. B. 99, 205304 (2019).
DOI:10.1103/PhysRevB.99.205304 [4]K. Hashimoto, B. Vacchini, and C. Uchiyama, “Lower bounds forthe mean dissipated heat in an open quantum system”, Phys. Rev. A 101, 052114 (2020).
DOI:10.1103/PhysRevA.101.052114

Fig. 1 Our schematic model for quantum
transport(left）, Dependence of averagetrapping time on spatial correlation ofnoise（right）[1].

Fig.2 Our schematic model for generationof spin current (left), Dependence ofamount of spin current on frequency ofrotating magnetic field（right）[2].

31Control of Quantum Many-body State by Observation－Realization of Stabilizing Insulator state by Strong Dissipation－
Yoshiro Takahashi
Graduate School of Science, Kyoto University
A quantum mechanical system changes its state by the influence of the dissipation. For the deeper
understanding of the physical phenomena in real materials and the development of quantum mechanicaldevices, it is, therefore, important to clarify how the dissipation influences the quantum many-body system.
The change of the quantum state by dissipation is closely related with the “observation” which is an
important concept in quantum theory. It is expected that novel phenomena related with quantum-mechanicalmeasurements can emerge in the dissipative quantum many-body system.
In this work, we investigated a quantum many-body system realized by ultracold ytterbium atoms in an
optical lattice by introducing the dissipation with a laser beam at a specific wavelength. In particular, we
focus on the “Mott insulator – superfluid quantum phase transition” observed for Bose atoms in an opticallattice. When the optical lattice potential is deep enough, the atoms form “Mott insulator state” with fixed
number of particles in each lattice site to minimize the on-site interaction energy due to the repulseinteratomic interaction on the one hand. On the other hand, the atoms form “superfluid state” where atoms
make frequent hopping between lattice sites when the optical lattice potential becomes shallow. In thisexperiment, starting from the Mott insulator initial state, we slowly decreased the optical lattice depth while
we apply a photo-association laser beam to induce dissipation. As a result, we find that the growth of thesuperfluidity is delayed due to the strong dissipation (see Fig. 1). This can be explained by a quantum Zeno
effect which is a purely quantum-mechanical phenomenon.
This result broadens the range of the experimental research explored by cold atom quantum simulator into
an open, dissipative quantum many-body system. Since real materials suffer from dissipation by someextent, the present work is an important step to deeper understanding of the quantum many-bodyphenomena in real systems as well as the development of quantum mechanical devices.
Reference： T. Tomita, S. Nakajima, I. Danshita, Y. Takasu, and Y. Takahashi, “Observation of the Mott
insulator to superfluid crossover of a driven-dissipative Bose-Hubbard system”, Science Advances, 3,e1701513. (2017). DOI: 10.1126/sciadv.1701513.

Fig. 1 False-color images of momentum distributions of atoms with various strengths of dissipation
𝛾𝛾. The matter-wave interference peaks representing the atomic superfluidity is suppressed by strong
dissipation.

32

Development of New Method for Observing Single Atoms in
an Optical Lattice
Yoshiro Takahashi
Graduate School of Science, Kyoto University
Recently, a quantum gas microscope technique, which is a method for observing single atoms in an
optical lattice with single-site spatial resolution, has been developed. Owing to the high controllability, we
can expect realization of ultimate quantum simulator using this technique. In fact, the observation of an
antiferromagnetically ordered phase is reported for two-component fermions of alkali-metal atoms loaded
into a two-dimensional optical lattice.
In this work, we developed a new kind of method in quantum gas microscopy for ultracold two-electron
atoms of ytterbium, which is expected to have unique applications different from alkali atoms. In theconventional quantum gas microscope technique, the fluorescent photons emitted from single atoms in an
optical lattice due to the irradiated resonant probe light are detected with high sensitivity camera. Different
from this conventional method, our new method is based on the dispersive interaction between atoms andprobe light off-resonantly applied with linear polarization. This dispersive interaction results in a rotationof polarization of the probe light (Faraday rotation) which is detected in this new Faraday quantum gas
microscope (See Fig. 1). We successfully achieved 10 degrees rotation angle at the largest for the single
atom. The inherent advantage of this method is the expected smaller heating effect during the measurementof atoms. We also clarify the classical theoretical limit for the heating effect of Faraday quantum gas
microscopy using coherent state of probe light. In addition, we theoretically reveal the possible scheme ofquantum non-destructive detection scheme of single atoms in an optical lattice by using squeezed vacuum.
This result demonstrates the important possibility of minimally destructive detection of single atoms in an
optical lattice, opens the door for the study of dynamics of quantum many-body system.
Reference： R. Yamamoto, J. Kobayashi, K. Kato, T. Kuno, Y. Sakura, and Y. Takahashi, "Site-resolved
imaging of single atoms with a Faraday quantum gas microscope", Phys. Rev. A 96, 033610 (2017). DOI:
https://doi.org/10.1103/PhysRevA.96.033610.

Fig. 1 Images of single atoms in an optical lattice with dispersive methods. (left)Faraday image basedon the polarization rotation (Faraday rotation) angle. (right) Dark-field Faraday image based on thepolarization-rotated scattering light with no incident probe light.

33

Photonic quantum interfaces with atoms
Takashi Yamamoto1,2
Graduate School of Engineering Science, Osaka University、2QIQB, OTRI, Osaka University

１

The quantum internet including quantum interconnect is possible by connecting the hybrid quantum
system which consists of light and matter systems. Especially, quantum interfaces with the long-distancefiber communication technology is important not only from the viewpoint of the long-distance quantum
communication but also from the viewpoint of the quantum state operation by the high-performance
communication technology. In this study, some progress has been made in the quantum interface between
light and communication technology between neutral atoms or trapped ions.
First, we realized a high-efficiency and low-noise quantum frequency converter that translates photons of
866 nm, the resonance wavelength of calcium ions, into the 1550 nm band, the optical fiber communication
wavelength. As a result, a quantum interface that fills the wavelength gap, which has been a problem in thepast, has become possible, and it has become possible to read and write photons of the communication
wavelength for calcium ions. By incorporating this quantum frequency converter into a calcium ion trap
coupled to an optical resonator at the University of Sussex in UK, we succeeded in an experiment to convert
a single photon from calcium ion to a communication wavelength band (1550 nm band). At 866 nm, only
1/1000 of the photons remain after traveling 10 km, whereas half of the photons remain at about 15 km in
the 1550 nm band. By reducing the loss through this wavelength conversion, we realized 10 km singlephoton fiber communication, which was the world record for trapped ions at that time. Even when theconversion efficiency is added, the efficiency sufficiently exceeds the direct transmission of a single photonof 866 nm, which clearly indicates the superiority of the wavelength converter.
Next, we realized a polarization-independent quantum frequency converter that converts the wavelength
to the communication wavelength band without changing the polarization state of the photon, and realized
the cold atom (Rb) quantum memory and the quantum interface of the communication wavelength photon.
By incorporating the newly developed polarization-independent quantum frequency converter, thegenerated short-wavelength photons (780 nm) were converted into optical fiber communication wavelength
bands (1522 nm). Furthermore, by entangling the cold atom (Rb) quantum memory and short-wavelength
photons (780 nm) and converting them, it was confirmed that the quantum states of the cold atom (Rb)quantum memory and the optical fiber communication wavelength photons were entangled. As a result, we,for the first time, succeeded in generating entanglement of the cold atom (Rb) quantum memory andcommunication wavelength photon using a polarization-independent quantum frequency converter.

Reference： T. Walker et al., "Long-Distance Single Photon Transmission from a Trapped Ion via Quantum
Frequency Conversion" Phys. Rev. Lett. 120, 203601, 2018. R. Ikuta et al., "Polarization insensitivefrequency conversion for an atom-photon entanglement distribution via a telecom network" Nature
Communications, 9, 1997, 2018.

Fig. 1 10-km fiber transmission by a single photon quantum frequency converter from trapped ions34

Realization of low-loss, all-fiber system for strong andefficient coupling between distant atoms- A step closer to realizing distributed quantum computers -S. Kato1,2, N. Német3, K. Senga1, S. Mizukami1, X. Huang1, S. Parkins3, and T. Aoki1
１
Waseda University, 2PRESTO, JST, 3University of Auckland
A cavity-QED system is a system in which photons – elementary quanta of light – and atoms are confinedwithin an optical resonator and interact with each other in a quantum-mechanical manner. This system has
been a prototypical experimental platform for helping scientists to better understand and manipulate thequantum properties of photons and atoms, as highlighted by the award of the Nobel Prize in 2012 tophysicist Serge Haroche for his ‘groundbreaking experimental methods that enable measuring andmanipulation of individual quantum systems.’ Consequently, the expectation for cavity-QED systems torealize quantum information science technology has increased.
In order to realize such technology, integrating multiple cavity-QED systems with coherent, reversible
coupling between each system was necessary, but obtaining such coupling with high enough efficiency has
made this very challenging. We approached this problem by demonstrating a system consisting of two
nanofiber cavity-QED systems connected to each other in an all-fiber fashion.
In each cavity, an ensemble of several tens of atoms interacts with the cavity field through the evanescentfield of a nanofiber, both ends of which are connected to standard optical fibers through tapered regions
and sandwiched by a pair of fiber-Bragg-grating mirrors. Multiple resonators can be connected withminimal losses using additional, standard optical fiber, making the coherent, coupled dynamics of the two
nanofiber cavity QED systems possible.
Our achievement is an important step towards the physical implementation of cavity QED-based
distributed quantum computation and a quantum network, where a large number of cavity QED systems
are coherently connected by low-loss fiber channels. In such systems, quantum entanglement over thewhole network can be created deterministically, instead of probabilistically.
Reference： S. Kato, N. Német, K. Senga, S. Mizukami, X. Huang, S. Parkins, and T. Aoki, “Observationof dressed states of distant atoms with delocalized photons in coupled-cavities quantum electrodynamics”,
Nature Communications, 10, 1160 (2019).

Fig. Experimental device for an all-fiber,
coupled cavities-QED system

35

Cavity dark mode in a coupled cavity quantum
electrodynamics system- Observation of remote exchange of energy between atom and light D. White1, S. Kato1,2, N. Német3, S. Parkins3, and T. Aoki1
Waseda University, 2PRESTO, JST, 3University of Auckland

１

We report the first observation of "cavity dark mode", a dark mode that exists in a coupled-cavities
quantum electrodynamics system. The cavity dark mode is a superposition state of remote atoms andphotons, and it has no photonic excitations at the atom locations, such that the atoms are not locally exposed
to light fields. With the absence of local photons, we demonstrate nonlocal excitation and saturation of
atoms. Such phenomena have never been observed in any kind of systems.
A dark mode is a class of normal modes in which one or more oscillators does not exhibit excitation due
to destructive interference. An example of such a mode is a dark atomic state, which is prevented fromabsorbing a photon due to coupling induced by control fields. In addition to the widely used application ofelectromagnetically-induced transparency, the dark mode of a coupled system has for example been used
to suppress mechanical dissipation in an optomechanical resonator. We recently demonstrated a coupledcavity QED system, in which two nanofiber cavity QED systems are connected by an intermediate linkfiber cavity. Here we observe a novel type of dark normal mode in this system (Fig. 1), in which the photonic
excitations at the atom locations are dark, such that the atoms are not locally exposed to light fields. This`cavity dark mode' is robust and does not depend on cavity symmetry. With the absence of local photons,
we demonstrate nonlocal excitation and saturation of atoms.
We emphasize that this is a truly macroscopic network: the cavities are each of order 1 meter long. Our
observation of all normal modes of a macroscopically large quantum network (Fig. 2), observed
simultaneously at two points of the network, lays the foundation for extension to larger networks of multiple
atom-cavity systems for quantum information processing purposes.
Reference： D. White, S. Kato, N. Német, S. Parkins, and T. Aoki, “Cavity dark mode of distant coupledatom-cavity systems”, Phys. Rev. Lett., 122, 253603 (2019).

Fig. 1 Observed cavity-dark mode in a coupled cavity QED system

Fig. 2 Five eigenmodes of a coupled cavity QED system

36

Experimental all-photonic quantum repeaters
Takashi Yamamoto1,2
Graduate School of Engineering Science, Osaka University、2QIQB, OTRI, Osaka University

１

Quantum repeaters in future quantum internet, which enable hybrid quantum systems to be efficiently
connected by photons, can be implemented by the mainstream processes (1) A large number of quantum
memories that store quantum information are arranged at relay points, and when photons are "arrived" thequantum information is stored. (2) Process (1) is carried out in parallel by a plurality of communication
paths, and when photons are "arrived", two quantum memories are selected, and then Bell measurement iscarried out (We call this Adaptive Bell measurement.). As a result, quantum teleportation in which quantum
information is transferred to an adjacent relay point is realized, and the photon loss is suppressed. Recently,
unlike this quantum memory scheme, the NTT group has theoretically proposed a all-photonic quantum
repeater that realizes quantum repeaters using only optical devices [1]. This all-photonic quantum repeater
had the same effect as Adaptive Bell measurement by reversing the order of operations (1) and (2) using
entanglement properties " Time Reversal".
Together with the NTT group, we organized this all-photonic quantum repeater so that it can be graduallyextended from a small optical device to a large one, and proposed a Time-Reversed Adaptive Bell
(TRABell) measurement as a core of it, and built a new optical system to realize this TRABell measurement.
As shown in the figure, a photonic entangled state called a graph state is generated in a plurality of sites at
a relay point. Photons passing through each channel are sent to each site, and measured by a Type II Fusion
Gate together with photons in a graph state. At this time, if the photon is arrived, this measurement teleports
the quantum state of the photon to the remaining photons in the graph state, but if no photon, the remaining
photons are kept in the graph state "can be used for another channel". This allows TRABell measurements
in which photons perform Bell measurements on any two communication paths the photon has arrived, andthe quantum information is teleported from A to B. In order to realize this TRABell measurement, wecreated the simplest experimental system that generates a graph state of three photons and inputs photons
into two communication channels, and conducted the experiment. From the experimental results, it was
confirmed that the quantum information was teleported to the remaining photons in the graph state when
the photons were arrived for both communication paths, and it was verified that the travel measurement
was operated for the first time. At the same time, it was the first demonstration of the basic operating
principles of quantum repeaters.
Reference ： Y. Hasegawa, et al.,"Experimental
time-reversed
adaptive Bell measurement towards
all-photonic quantum repeaters"
Nature Communications, 10, 378,
2019.
[1] K. Azuma, et al., "All-photonic
quantum
repeaters"
NatureCommunications 6, 6787 (2015).
Fig. 1 Quantum entanglement isgenerated between A and B bymeasuring the graph state ofphotons generated at the relay
point and traveling with arriving
photons.

37

Tuning Radiative Lifetime of Circularly Polarized Lightby a Three-Dimensional Semiconductor-Based
Chiral Photonic Crystal
Shun Takahashi1, 2, Yasutomo Ota1, Takeyoshi Tajiri3, Jun Tatebayashi1,
Satoshi Iwamoto1, 3, 4, and Yasuhiko Arakawa1, 3
１
INQIE, The University of Tokyo, 2Kyoto Institute of Technology,
3
IIS, The University of Tokyo, 4RCAST, The University of Tokyo
Circularly polarized light is currently used for three-dimensional (3D) displays or biochemical sensingof chiral molecules, as well as spintronics or quantum information technology through spin angularmomentum transfer (spin-photon interface) with electrons/holes in solid states. Currently, such circularly
polarized light is generated by using a combination of a polarizer and a waveplate or an external magnetic
field. However, these methods are not suit for the future miniaturization of the integrated optical circuits,
and a semiconductor-based optical device directly emitting circularly polarized light is expected. Whencircularly polarized light propagates, the electric/magnetic field traces a helix having a period of its
wavelength scale. From the view point of the symmetry, a similar helical/chiral structure with a 3D period
can tune such circularly polarized light efficiently. In this study, we prepared a semiconductor-based chiralphotonic crystal (PC) having a 3D sub-micron periodicity. Since this chiral PC modifies the vacuum field
connecting to circularly polarized light, we experimentally observed that the radiative lifetime for circularly
polarized light emitted from semiconductor quantum dots (QDs) inside the chiral PC was tuned by thechiral structure, and therefore the direct emission of circularly polarized light was successfully obtained.
The studied structure was composed of GaAs thin layers having a stripe pattern with a 500 nm periodicity.
These thin layers were stacked one-by-one with an in-plane rotation of 60° by a micro-manipulation
technique, as schematically shown in Fig. 1. This left-handed chiral PC forms a circular polarization
bandgap where the density of states for left-handed circularly polarized (LCP) light is suppressed and theradiative lifetime of LCP light extends. For InAs QDs in this chiral PC, we performed a time-resolved
photoluminescence measurement. At 1200 nm emission wavelength in the polarization bandgap, theradiative lifetime of LCP light was found to be 10 % longer than that of right-handed circularly polarized(RCP) light, as shown in Fig. 2. By this control of the radiative lifetime of CP light, as large as 75% of theemitted light from the QDs were polarized in RCP. This result is applicable to photonics as a CP microlaser, as well as to spintronics as a highly sensitive spin sensor by hybridization of spins and circularly
polarized photons.
Reference： S. Takahashi, Y. Ota, T. Tajiri, J. Tatebayashi, S. Iwamoto, and Y. Arakawa, “Circularly
polarized vacuum field in three-dimensional chiral photonic crystals probed by quantum dot emission,”
Physical Review B 96, 195404 (2017). DOI：10.1103/PhysRevB.96.195404

Fig. 2 Time decay of the QD emission intensity
for each circular polarization component at
1200 nm wavelength.

Fig. 1 Schematic diagram of the studied
3D semiconductor-based chiral PhC.

38

Demonstration of a topological nanocavity laser
Yasutomo Ota1, Yasuhiko Arakawa1, and Satoshi Iwamoto1,2,3
１
Nanoquine, 2RCAST, 3IIS, The University of Tokyo
Topology is a field of mathematics, which is famously employed for classifying the structures of objects
from a large perspective – a well-known example is distinguishing a doughnut and a ball. Another notableapplication of topology is providing a brand new point of view in condensed matter physics, which wasawarded by Nobel prize in physics in 2016. Currently, topology has been penetrated in various fields ofphysics including photonics. Topological photonics mostly concerns the optical bands of periodical patternsof permittivity. The engineering and understanding of the band topologies in momentum space have so far
led to a bunch of novel pathways for controlling the flow of light. At the beginning of the research, most of
the concern on topological photonics was theoretical, and proof-of-principle experiments were mainly
performed using centimeter scale structures operating at the microwave frequencies. More recently, there
is a sharply-growing interest in topological photonic devices that consist of nanophotonic structures andthus can operate in the optical regime. Indeed, some important photonic structures, such as opticalwaveguides and microring resonators, have been demonstrated on topological photonics platforms.
In this work, we design a topological photonic crystal nanocavity and demonstrate a topologicalnanocavity laser. Figure 1 shows a schematic of the investigated nanocavity. The device is composed of
two one-dimensional photonic crystals interfaced at the center. The two photonic crystals are topologicallydistinct, which results in the deterministic emergence of a topological edge mode trapped at the interface.
This is a consequence of the bulk-edge correspondence, a well-known principle in topological physics.
Figure 1 also shows a computed field distribution of the edge mode, which exhibits tight localization at theinterface – a prerequisite for utilizing as a nanocavity. The topological origin of the mode guarantees the
singlemodedness, which is advantageous for many photonic applications. In experiments, we patterned thedesigned structure into a GaAs slab embedding InAs quantum dots as active media. Figure 2 showsemission spectra from a fabricated device under optical pumping. By increasing pump power, we succeededin the observation of single mode lasing from the device.
The results discussed here cast new light on topological photonics. In another project, we also found ananocavity design in a two-dimensional topological photonic crystal. These findings are important
additions to topological photonics and may eventually revolutionize the technology of integrated photonics
Reference： Y. Ota, R. Katsumi, K. Watanabe, S. Iwamoto, and Y. Arakawa, "Topological photonic crystal
nanocavity laser", Commun. Phys. 1, 86 (2018). DOI: 10.1038/s42005-018-0083-7

P = 150 μW

x

𝜃𝜃𝑍𝑍𝑍𝑍𝑍𝑍 = 𝜋

Intensity (a. u.)yz𝜃𝜃𝑍𝑍𝑍𝑍𝑍𝑍 = 0

Interface

Cavitymode

P = 5 μW

X=0

W

Fig. 1 Schematic of the investigated topologicalnanocavity (Top). Computed field distribution of theedge mode (Bottom). Zak phase, 𝜃𝜃𝑍𝑍𝑍𝑍𝑍𝑍 , is a topologicalinvariant of the photonic crystal.

39

l

th (

)

Fig. 2 Measured emission spectraof a fabiricated nanocavity taken
under optical pumping.

Optical Aharonov-Bohm Effect in Single Quantum Ring
－Observation of Wigner molecule among excitons－

Rin Okuyama1, Mikio Eto2
Faculty of Science of Technology, Meiji University, 2Faculty of Science of Technology, Keio University

１

When a magnetic flux is applied inside a mesoscopic ring, the interference pattern for electrons changes
by the Aharonov-Bohm (AB) effect. The AB effect is usually observed by a “double-slit interference
experiment” in the measurement of electric current. In an isolated ring, on the other hand, thephotoluminescence spectrum shows the AB oscillation when an exciton is created by the light irradiation.
This is called optical AB effect. We experimentally and theoretically study the optical AB effect in a single
quantum ring in collaboration with Prof. K. Kyhm, Pusan National University, South Korea.
In our experiment, we examine a quantum ring fabricated on GaAs/AlGaAs. The quantum ring is created
when a GaAs layer is grown on AlGaAs substrate in a specific condition. Figure (a) schematically depicts
an exciton in the ring by the optical excitation of a pair of electron and hole. They are strongly bound toeach other by the Coulomb interaction. Reflecting the different effective mass, the orbital radius is different
for electron and hole. In consequence the exciton shows the AB oscillation in spite of its electrical neutrality.
Figures (c)-(e) show the photoluminescence from the exciton, as a function of magnetic field B, withchanging the strength of excitation light. The observed AB oscillation is in good agreement with ourtheoretical results (solid line). The stronger excitation light creates more extra-charges surrounding thequantum ring, which influences the exciton wavefunction in the ring through an effective electric field.
Figure (b) shows the schematic view of biexciton in the ring while Figs. (f)-(h) present thephotoluminescence from it as a function of B. In our system, a biexciton is made of two excitons in which
an electron and a hole is strongly bound. The two excitons are apart from each other by the Coulombinteraction, forming a “Winger molecule.” As a result, the period of the AB oscillation for the biexciton isnearly half of that for a single exciton. Remarkably the photoluminescence from the biexciton becomes
discontinuous at some values of B. This is due to the change of angular momentum of the biexciton withan increase in B. The exciton in the final state has the same angular momentum as the biexciton in the initialstate after the photon emission. Consequently the final state changes when the angular momentum of thebiexciton changes with B, which results in the discontinuous change in the photon energy. The agreementwith the theoretical results (solid line) strongly suggests the Wigner molecule formation among the excitons.
Reference： H. Kim, S. Park, R. Okuyama, K. Kyhm, M. Eto, R. A. Taylor, G. Nogues, L. S. Dang, M.
Potemski, K. Je, J. Kim, J. Kyhm, and J. Song, “Light Controlled Optical Aharhonov-Bohm Oscillations ina Single Quantum Ring,” NANO Lett. 18, 6188 (2018). DOI：10.1021/acs.nanolett.8b02131

Figure (a), (b): Schematic viewsfor exciton and biexciton in single
quantum ring.
Figure (c)-(e): Photoluminescencefrom an exciton as a function ofmagnetic field B. The strength of
excitation light P changes to fivetimes and ten times larger. The
theoretical result is shown bysolid line.
Figure (f)-(h): Photoluminescencefrom a biexciton as a function ofmagnetic field B.

40

Novel phenomena in optical microresonators－Demonstration of anomalous group delays and high-Q mechanical resonators－
Motoki Asano1 and Takashi Yamamoto2,3
NTT Basic Research Laboratories, 2Graduate School of Engineering Science, Osaka University、
3
QIQB, OTRI, Osaka University

１

Whispering-gallery-mode (WGM) optical microresonators have attracted large interests as quantum
photonic interfaces thanks to the strong enhancement of light-matter interactions with strongly-confinedcavity photons. In this study, we aim to develop novel functionalities in this microresonators via two kindsof experiments: observing anomalous large group delays by precisely controlling waveguide-resonator
coupling and demonstrating photon-phonon coupling in bottle microresonators.
The waveguide-resonator coupling is controllable in WGM microresonator system by finely adjusting
the gap between a microresonator and a tapered fiber. This controllability has been applied to manipulategroup delays in optical pulses with respect to its coupling strength. So far, the amount of group delays has
been considered as equivalent to the time constant of the microresonator (i.e., the inverse of resonancelinewidth). We observed anomalous large group delays around a singular point in the two-dimensionalparameter space spanned by the coupling strength and laser detuning (Fig. 1) [1]. Such an anomalous large
shift has been observed in only two- and three-dimensional optical systems by analogy of quantum weakmeasurement. We unveiled that the anomalous shift with this framework also appears in one-dimensional
system with finite dissipation, and succeeded a principle-of-proof experiment with a microtoroid.
WGM microresonators are possible to strongly confine not only optical modes but also mechanical(acoustic) modes. Because the optical and mechanical (acoustic) modes are confined in the same structure,cavity optomechanical coupling via radiation pressure (optical strain effect) becomes available. We firstobserved cavity-enahnced coupling to both mechanical modes (~30 MHz) and acoustic modes (~11 GHz)in the microbottles [2, 3]. A resolved-sideband regime, where the optical cavity dissipation rate is smaller
than the mechanical frequency, was obtained by using an ultrahigh-Q resonance with Q facot of 107 (Fig.
2). In this regime, laser cooling of mechanical motion to the phononic ground state and photon-phonon
entanglement generation would be available. Moreover, to develop novel functionalities in cavity
optomechanics with micrbottles, we attempted to optimize the microbottle geometry, and demonstrated
near-field cavity optomechanics with optical evanescent fields from the bottle microresonators [4].
Reference：[1] M. Asano et al., Nat. Commun. 7, 1 (2016) [2] M. Asano et al., Laser & Photon. Rev. 10, 603 (2016).
[3] M. Asano et al. Opt. Express 24, 12082 (2016). [4] M. Asano et al., Appl. Phys. Rev. 112, 201103(2018).

Fig. 1 Conceptual illustration of group delay control
with a waveguide-resonator system (up) and groupdelays with respect to coupling strengths in our
experiment (bottom). The time constant of the
microtoroid is shown by black-dotted lines.

41

Fig. 2 Optical transmission spectra withsidebands generated via optomechanicalcoupling in the resolved sideband regime. The
inset describes an conceptual illustration of
optomechanical coupling in a microbottle.

Optical coherent transients in 167Er3+－Coherent manipulation of 4f orbital electrons at telecom-band wavelength－
Takehiko Tawara
NTT Basic Research Laboratories, NTT Corporation
Optical coherent manipulation of the quantum superposition states in solid-state materials is one of theelemental technologies essential for the realization of quantum information networks. Since the coherencetime T2 of the optically accessible quantum 2 level system in the material determines the performance of
this quantum manipulation, extending T2 is one of the important issues. The main cause of decoherence isthe fluctuation of the spin magnetic moment that exists around the quantum two-level system. We arefocusing on the 4f orbital electrons of the erbium (Er), which has a two-level system accessible by telecomband wavelength (1.53µm). By dilutely doping isotope-purified Er3+ to the solid crystal, we tried to suppress
the fluctuation of the spin magnetic moment, extend T2, and coherently manipulate the Er 4f orbital electron
by telecom-band light.
First, Y2SiO5 crystals doped with 0.001% of only 167Er3+, which has the only nuclear spin among theisotopes, were grown by CZ method. For this sample, the homogeneous width Γh of the 167Er3+ hyperfine
level was investigated by spectral hole burning (SHB), and T2 was estimated from the relation of Γh = 1 /(πT2). As a result, the magnetic fluctuations produced by the Er isotopes themselves other than 167Er3+ were
suppressed, and we succeeded in extending T2 by about 4 times (Fig. 1). We also demonstrated the coherent
transient phenomenon among the Λ-like 3 levels formed by this hyperfine structure, that is, the Rabi
oscillation and the photon echo (Fig. 2). Rabi oscillation is measured by the pump pulse width dependenceof photoluminescence (PL) integrated intensity, and the π and π / 2 pulse area conditions are obtained fromthe oscillation period. When the 2-pulse photon echo was measured using this pulse condition, lightconservation and regeneration with T2 = 12 µs was observed. Until now, optical coherent manipulation with
Er3+ has not been realized, and this time, by realizing a longer T2 by purifying Er isotopes, we succeeded incoherent manipulation of 4f orbital electrons with telecom-band light for the first time.
These results show that 167Er3+-doped crystals are promising as a solid material platform for quantum
nodes, which are indispensable for long-distance quantum information communication. Currently, we areproceeding with isotope purification of host crystals for 167Er3+ doping, and fusion of them with photonic
nanostructures.
References：
T. Tawara, G. Mariani, K. Shimizu, H. Omi, S. Adachi, and H. Gotoh, “Effect of isotopic purification on
spectral-hole narrowing in 167Er3+ hyperfine transitions”, Applied Physics Express, 10, 042801 (2017).
DOI： 10.7567/APEX.10.042801
M. Hiraishi, M. IJspeert, T. Tawara, S. Adachi, R. Kaji, H. Omi, and H. Gotoh, “Optical coherent transientsin 167Er3+ at telecom-band wavelength”, Optics Letters, 44, 4933 (2019). DOI： 10.1364/OL.44.004933

Fig. 1 SHB spectra of non-purified Er3+
(blue) and purified 167Er3+ (red).

Fig. 2 (a) Rabi oscillation of PL intensity, (b, c) pulse
sequence and echo signal of 2 pulse photon echo.

42Coherent Coupling between Ensemble Superconducting
Qubits and a Superconducting Resonator
Kosuke Kakuyanagi1, Yuichiro Matsuzaki1, Corentin Deprez1, Hiraku Toida1,
Kouichi Semba2, Hiroshi Yamaguchi1, William J. Munro1 and Shiro Saito1
1
NTT Basic Research Laboratories, 2NICT

Driving Frequency ω/2π (GHz)

Materials formed by an ensemble of atoms exhibit various physical properties; however, it is difficult
to freely control the interactions between the atoms. On the other hand, interactions between
superconducting qubits in artificial atom clusters can be freely designed, which could lead to thedevelopment of multibody quantum simulators or quantum metamaterials with properties not found realmaterials.
In particular, hybridization of a superconducting resonator and ensembles of two-level systems has
potential to realize quantum technologies. Conventional approaches have used natural systems
comprising atoms and molecules to build ensembles, but the properties of such "atoms" are difficult totailor to the properties of the device [l].
Our approach is to create an ensemble from superconducting qubits and couple them to a resonator.
The properties of superconducting qubits are not intrinsic; they can be largely changed even after
fabrication. Moreover, due to their large size, we can in principle achieve individual controllability. Thisapproach has been used in previous work, but only a small number of superconducting qubits (eight intotal and not an ensemble) were collectively coupled to a resonator [2].
Here, we fabricated a hybrid device composed of 4,300 superconducting flux qubits embedded in asuperconducting resonator [3]. We observed a large dispersive frequency shift of 250 MHz in the
spectrum as shown in Fig. 1. Our theoretical analysis showed that this frequency shift is evidence ofcoherent coupling between the resonator and thousands of flux qubits. Although the strength of thecoupling between a single flux qubit and the resonator was much smaller than the inhomogeneous widthof the ensemble, the coupling can be enhanced by collective effects, which will provides us with ameasurable signal for experiments.
Our results represent the largest number of coupled superconducting qubits realized so far. Futureissues to address include how to further increase the coupling strength between collective qubits and aresonator and uniformize the characteristics of the collective qubits.
[1] Z. L. Xiang, et al., Rev. Mod. Phys. 85, 623 (2013).
[2] P. Macha, et al., Nature Commun. 5, 5146 (2014).
[3] K. Kakuyanagi, et al., Phys. Rev. Lett. 117, 210503 (2015).

Experiment
実験

Simulation
シミュレーション

5.6
5.5
5.4
5.3
5.2
10

5

0

ΔΦ/mΦ0

5

10

10

5

0

ΔΦ/mΦ05

10

Fig. 1. Energy spectrum of a superconducting microwave resonator coupled to an ensemble of flux
qubits. (Left) Experimental results. (Right) Theoretical analysis.

43Experimental test of macroscopic realism
using a superconducting flux qubit
George C. Knee1, Kosuke Kakuyanagi1, Mao-Chuang Yeh2,
Yuichiro Matsuzaki1, Hiraku Toida1, Hiroshi Yamaguchi1, Shiro Saito1,
Anthony J. Leggett2 and William J. Munro1
1
NTT Basic Research Laboratories, 2University of Illinois
Realism is the idea that an object’s state is determined before its observation. Although this idea iswidely believed to hold in our lives, it has been shown that “realism” is broken in the microscopic world.
The microscopic world is governed by the principles of quantum mechanics, which allows a state to havea superposition. For a superposed state, measurable values cannot be determined until they are observed.
Since the macroscopic world is composed of microscopic objects, quantum mechanics could be valid
even in this world, or there could be limitations to applying quantum mechanics to it. Currently, there is
still no consensus about which is likely to be true.
Here, we aim to address this issue. A superconducting flux qubit is a circuit composed of several
Josephson junctions and a superconducting loop. Due to the non-linearity of the Josephson junctions, thisdevice provides a two-level system with clockwise and anti-clockwise current states. These two states
contain 1012 electrons flowing around the circuit each second. We tested whether or not realism is broken
with this macroscopic device.
In our normal world, it is accepted that we can measure macroscopic objects without disturbing them(noninvasiveness). If realism is true, any noninvasively measured result on this device should satisfy theLeggett-Garg inequality. However, if quantum mechanics is true, we could observe a violation of theinequality using noninvasive measurements.
We show that the Leggett-Garg inequality is mathematically equivalent to an experimental test to checkif the noninvasive measurements affect the state of the device. Interestingly, even if the measurement isdesigned to be noninvasive, observation by it induces a projection according to quantum mechanics. Thiscan change the state of the device.
In our test, we performed two experiments. First, we checked the noninvasiveness of the measurementsby evaluating the classical disturbance our measurement device has on the flux qubit. Second, we
compared the measured state of the flux qubit with its unmeasured state. From these experiments, wefound that there is a large difference in these measured results, which cannot be explained by the classicaldisturbance [Fig. 1(a)]. This is a manifestation of quantum superposition. Our results conclusively
demonstrate that “realism” is broken even for a macroscopic device such as a superconducting qubit [Fig.
1(b)] [1].
[1] G. C. Knee, K. Kakuyanagi, M-C. Yeh, Y. Matsuzaki, H. Toida, H. Yamaguchi, S. Saito, A. J.
Leggett, and W. J. Munro, Nature Commun. 7, 13253 (2016).
(a)Difference by imperfection of observation
Experimental result

MR impossible
-0.10

-0.08

-0.06

de

dg

dρ

-0.04

ψ =

MR possible
-0.02

0.00

0.02

(b)

0.04

2µm

|+1⟩

2µm

+

State difference by existence of observation

Fig. 1. (a) Differences by observation; (b) quantum superposition of current states

44

|−1⟩

Electron Spin Resonance Spectroscopy Using a
Superconducting Qubit－Sensitive detection of electron spins in microscale area－
Hiraku Toida1, Yuichiro Matsuzaki1, Kosuke Kakuyanagi1, Xiaobo Zhu1,
William J. Munro1, Hiroshi Yamaguchi1, and Shiro Saito1
１
NTT Basic Research Laboratories, NTT Corporation
Superconducting qubits are an important research focus for the realization of quantum computers due totheir controllability and scalability. The technology for superconducting qubits has matured to the extent
that small systems are readily available within the community. Such technology however can be applied toother quantum tasks. Here we apply it to the field of quantum metrology. We demonstrate an electron spinresonance (ESR) spectrometer using a superconducting flux qubit with excellent sensitivity.
First ESR is an essential tool used to obtain information about unpaired electrons in materials which isextremely useful in many distinct fields. A conventional ESR spectrometer uses a microwave cavity todetect the ESR signal. However, due to the weak coupling between the cavity and sample, the required
number of electron spins in the sample is large, of the order of ~1013. In this method, the applied microwave
frequency is limited near the cavity resonance meaning the magnetic field is only the parameter one cansweep. On the other hand, our method directly measures the magnetization of the sample without a cavity.
This feature enables us to sweep two parameters: the spin excitation frequency and the magnetic field.
Furthermore, the spatial resolution is determined by the loop size of the flux qubit, which leads to muchhigher spatial resolution. In our current experimental setup, we realize the sensitivity of 400 spins/√Hz witha detection volume of 0.05 pl.
Fig. 1 shows a schematic diagram of our ESR spectrometer. Here the quantum state of the flux qubit ismeasured by using a superconducting quantum interference device (SQUID). That measured state reflects
the magnetization of the sample. We sweep both the microwave frequency and magnetic field to obtain thedetailed ESR spectrum. The ESR spectrum of nitrogen-vacancy (NV) centers in diamond is shown in Fig.
2 which allows us to reproduce the g-factor and zero-field splitting reported in the literature. A number ofsolid-state materials show complicated ESR spectrums in the low-field and low-frequency regime. Ourdemonstrated ESR spectrum proves that our spectrometer is useful to evaluate such materials. We havefurther proposed a flux qubit array could be used to obtain a spatial image of the ESR spectrum. Our method
can be applied to the measurement of biomaterials or used for pathological diagnosis.
Reference： Hiraku Toida, Yuichiro Matsuzaki, Kosuke Kakuyanagi, Xiaobo Zhu, William J. Munro,
Hiroshi Yamaguchi, and Shiro Saito, “Electron paramagnetic resonance spectroscopy using a single
artificial atom”, Communications Physics, 2, 33. (2019). DOI：10.1038/s42005-019-0133-9

Fig. 1 Schematic diagram of the ESR spectrometer.

Fig. 2 ESR spectrum of NV centers in diamond.

45

Josephson junction with a topological insulator
Russell S. Deacon1,2 and Koji Ishibashi1,2Advanced Device Laboratory, RIKEN、2RIKEN Center for Emergent Matter Science (CEMS)

１

Topological insulator (TI)/superconductor hybrid structures are interesting in terms of predictedemergence of Majorana particles. The Majorana particle or Majorana zero mode is also attractive for a
possible application to a topological qubit that is thought to be robust to decoherence. Until now, thedirect confirmation of it has not been made though there are some experimental signatures that support its
existence. It is theoretically predicted that Josephson junctions made of the topological insulator should
show a 4π periodic current-phase relationship instead of the ordinary 2π periodic relationship due to theexistence of the Majorana zero mode. To test this, we have carried out measurements of thecurrent-voltage relationship under the microwave irradiation and microwave emission from thevoltage-biased junctions. Based on the predicted 4π periodic current-phase relationship, the missing of the
odd steps are expected in the Shapiro steps in the former measurement, and the microwave emission withhalf the ordinary Josephson frequency is expected in the latter measurement.
The HgTe quantum well was used as a 2-dimensional or 3-dimensional topological insulator, and Al
was deposited to form the Josephson junction (Fig.1). The gate metal was deposited on top of the HgTe
normal region to change the Fermi energy which should be set in the bulk bandgap. In the 2DTI, thehelical edge states are formed and the supercurrent could flow through them. This was suggested
experimentally by the observed SQUID-like pattern of the supercurrent in magnetic fields, rather than the
Fraunhofer pattern that was expected when the supercurrent flowed uniformly in the junction. Figure 2
shows the Shapiro step measurements, where the missing odd steps are observed for the lower
frequencies as expected. Figure 3 shows the microwave emission intensity mapping as functions ofvoltage and frequency. In addition to the ordinary Josephson frequency (fJ), half the frequency is also
observed in some regions. Details have not been understood yet, but the experimental results strongly
suggest the predicted 4π periodic current-phase relationship due to the Majorana zero modes.
The work has been done in collaboration with Prof. L. Molenkamp’s group in Univ. Wurzburg.
References
1. J. Wiedenmann, E. Bocquillon, R.S. Deacon, S. Hartinger, O. Herrmann, T.M. Klapwijk, L. Maier,
C. Ames, C. Bru¨ne, C. Gould, A. Oiwa, K. Ishibashi, S. Tarucha, H. Buhmann & L.W. Molenkamp,
Nature Communications. 7, 10303 (2016)
2. Erwann Bocquillon, Russell Deacon, Jonas Wiedenmann, Philipp Leubner, Teun M. Klapwijk,
Christoph Brüne, Koji Ishibashi, H. Buhmann, Laurens W. Molenkamp, Nature Nanotechnology, 12,
137 (2017)
3. Russell Deacon, Jonas Wiedenmann, Erwann Bocquillon, Teun M. Klapwijk, Philipp Leubner,
Christoph Brüne, Seigo Tarucha, Koji Ishibashi, Hartmut Buhmann, Laurens W. Molenkamp, Phys.
Rev. X7, 021011 (2017)

Fig 1. SEM image ofthe sample structure

Fig 2. Shapiro stepmeasurements

46

Fig 3. Emission
intensity plotLarge magnetoresistance in magnetic topological insulator－Switching of non-dissipative topological current－

M. Mogi1, M. Kawamura2, R. Yoshimi2, A. Tsukazaki3, K. S. Takahashi2, M. Kawasaki1,2, Y. Tokura1,2,4
１
The Univ. of Tokyo, 2RIKEN CEMS, 3IMR, Tohoku university, 4Tokyo college, the Univ. of Tokyo
Topological current can flow without energy loss in a topological material whose electronic state in thematerial is characterized by its topology. These topological currents may be available at room temperature
and are being actively studied around the world. The anomalous quantum Hall effect is a typical exampleof causing a topological current. In this state, edge current, which is a kind of topological current, can flow
along the edge and domain wall of the magnetic thin film sample. If the edge current can be freely controlled
by a small external stimulus, it will greatly expand the range of applications of topological current. We used
the molecular beam epitaxy method, and added the magnetic elements V (vanadium) and Cr (chromium)to the topological insulator (Bi1-ySby) 2Te3. By selectively adding magnetic elements V and Cr to the upperand lower parts of the thin film, a three-layer structure of magnetic / non-magnetic / magnetic is formed(Fig. 1A). When the electrical resistance of this heterostructured thin film was measured under a strong
external magnetic field (~ -2 T), and the magnetization directions of the V-added layer and the Cr-added
layer were aligned to produce the quantum anomalous Hall state (Fig. 1B). When the direction of theexternal magnetic field is reversed and gradually strengthened, the magnetization of the Cr-added layer
with a small coercive force is reversed by a magnetic field of a certain magnitude (~ 0.2T), and themagnetization directions of the Cr layer and V layer become opposite (anti-parallel). When the two-terminal
resistance between the current terminals was measured in this magnetization configuration, the resistancevalue exceeds 2 GΩ, which is 100,000 times larger than the 25.8 kΩ of the quantum anomalous Hall effect(Fig. 1C). Converting this to the magnetoresistance ratio, it exceeds 10,000,000 %.
This result indicates that by controlling the magnetization direction with an external magnetic field, thetopology of the quantum anomalous Hall effect was changed, and the edge current could be turned on andoff. In other words, our observation means the establishment of the switching principle of non-dissipative
current. Furthermore, this high resistance state is called an "axion insulator" where the manifestation ofquantized magnetoelectric effect is theoretically predicted. By developing a Cr and V three-layer structure,a more stable axion insulator has been realized compared to the earlier studies.
Reference: M. Mogi, M. Kawamura, A. Tsukazaki, R. Yoshimi, K. S. Takahashi, M. Kawasaki and Y.
Tokura, "Tailoring tricolor structure of magnetic topological insulator for robust axion insulator", Science
Advances 3, eaao1669 (2017), DOI: 10.1126/sciadv.aao1669.
C
(c)

B
(b)

Resistance (Ω)

Hall conductivity (e2/h)

(a)

-1.0

-0.5

0.0

0.5

磁場 (T)
Magnetic
field (T)

1.0

Magnetic field (T)Figure 1： (a) Layered structure of the developed tricolor heterostructure film. (b) Magnetic fielddependence of Hall conductivity. Quantized Hall conductivity is observed. (c) Magnetic fielddependence of the two-terminal resistance. The huge enhancement of the resistance is observed.

47

A new insulating state in topological insulator－Realization of the materials platform for topological magnetoelectric effect－
M. Mogi1, M. Kawamura2, R. Yoshimi2, A. Tsukazaki3, K. S. Takahashi2, M. Kawasaki1,2, Y. Tokura1,2,4
１
The Univ. of Tokyo, 2RIKEN CEMS, 3IMR, Tohoku university, 4Tokyo college, the Univ. of Tokyo
A topological insulator is a new kind of material which have an insulating bulk and metallic surface
because of the topological nature of the electronic state. When a magnetic impurity is added to a topologicalinsulator, the interaction between the magnetic moments and electrons on the surface states causes thequantum anomalous Hall effect in which an electric current flows only at the edge of the sample [Fig. 1(a)].
Besides that, it is theoretically predicted that the magnetic topological insulator exhibits an exotic
electromagnetic response termed as the topological magnetoelectric effect where magnetization is induced
by applying an electric field and conversely, electric polarization is induced by applying magnetic field [Fig.
1(b)]. Surprisingly, the coefficients of the topological magnetoelectric effect are determined only by thefundamental physical constants regardless of the materials parameters. To measure the topologicalmagnetoelectric effect, it is necessary to insulate the surface state of the magnetic topological insulator.
Theoretically, it is predicted that if the magnetization is aligned outward from all surfaces, the metallic
surface states of the topological insulator are gapped and a perfect insulator appears. However, it has beendifficult to freely control the magnetization direction with conventional magnetic topological insulators.
Therefore, aimed to control the magnetization direction, we created a heterostructure film of magnetic
topological insulators. We made a magnetic/non-magnetic/magnetic three-layer structure thin film that waslayered on top of each other. By adding a coercive force difference between the two magnetic layers, it ispossible to control the magnetization direction of each layer independently. When the magnetizations of
the two magnetic layers become antiparallel, it was observed that the thin film sample becomes insulating.
This indicates that by controlling the direction of magnetization, the transport property on the surface ofthe topological insulator could be changed, and the quantum anomalous Hall effect could be transformed
into an insulator state where the topological magnetoelectric effect is expected. This result establishes amaterial basis for observing the topological magnetoelectric effects in a magnetic topological insulator.
Reference： M. Mogi, M. Kawamura, R. Yoshimi, A. Tsukazaki, Y. Kozuka, N. shirakawa, K.S. Takahashi,
M. Kawasaki, and Y. Tokura, “A magnetic heterostructure of topological insulators as a candidate for anaxion insulator”, Nature Materials 6, 516 (2017). DOI: 10.1038/nmat4855(a) Quantum anomalous Hall effect(b) Topological magnetoelectric effectmagnetic field

Figure 1: Schematic of the quantum anomalous Hall effect and the electromagnetic effect in a
topological insulator heterostructure film. (a) When the magnetic moments (red arrow) are aligned in
one direction, the current flows only at the edge of the sample (green arrow), and the quantum anomaly
Hall effect appears. (b) When the magnetic moments are antiparallel, no current flows to the edge ofthe sample, and a perfect insulator is realized. In this insulator state, the topological magnetoelectriceffect is expected: when an external magnetic field is applied, electric polarization occurs in the same
direction (large pink arrow).

48

Current-induced breakdown of quantum anomalous Hall
effect1

M. Kawamura1, R. Yoshimi1, A. Tsukazaki2, K. S. Takahashi1, M. Kawasaki1,3, Y. Tokura1,3,4
RIKEN CEMS, 2IMR, Tohoku university, 3The Univ. of Tokyo, 4Tokyo college, the Univ. of Tokyo

Topological insulators are materials which have an insulating bulk state and a metallic Dirac surface
state. When a magnetic element is introduced into a topological insulator to make it in a ferromagnetic state,a quantum anomalous Hall effect appears where the Hall resistance value is quantized to the von Klitzing
constant h/e2. In order to observe the anomalous quantum Hall effect, it is necessary to cool the sample toa low temperature below 100 mK. When the current flowing through the magnetic topological insulator
sample is increased, it is expected that the quantum anomalous Hall effect will be broken down when acertain threshold current is exceeded, and the Hall resistance value will begin to deviate from the quantizedvalue. The threshold current that causes the quantum anomalous Hall effect breakdown is one of theimportant indicators showing the stability of the quantum anomalous Hall effect. Therefore, in this study,
we conducted a systematic experiment to investigate the threshold current.
A magnetic topological insulator Crx(Bi1-ySby)2-xTe3 thin film sample was prepared using the molecularbeam epitaxy, and the quantum anomalous Hall effect was observed by cooling the sample to a temperatureof 30 mK using a dilution refrigerator. We observed the breakdown of the quantum anomalous Hall effect,
where the Hall resistance becomes smaller than the quantized resistance value when a certain thresholdcurrent is exceeded. The breakdown of the quantum anomalous Hall effect was measured using multiple
samples of different sizes. We found that the current value at which the quantum anomalous Hall effectbreaks down increases in proportion to the width of the sample. This suggests that the Hall electric field
generated in the sample due to the application of current causes the breakdown. Furthermore, from thetemperature dependence of the resistance in the quantum anomalous Hall state, it was found that the
hopping mechanism via the localized state due to impurities predominates in the electrical conduction at
low temperatures. This indicates that the impurity concentration affects the threshold current for thequantum anomalous Hall effect breakdown. From the results of this study, it was found that it is necessary
to reduce the impurities contained in the sample in order to observe the more stable quantum anomalous
Hall effect.
Reference: M. Kawamura, R. Yoshimi A. Tsukazaki, K. S. Takahashi, M. Kawasaki, and Y. Tokura“Current-driven instability of quantum anomalous Hall effect in ferromagnetic topological insulator thinfilms”, Physical Review Letters 119, 016803 (2017). DOI: 10.1103/PhysRevLett.119.016803
(b)

(a)

Figure 1: (a) Gate voltage dependence of the longitudinal resistance and the Hall resistance undervarious measurement currents. The Hall resistance deviates from the quantum resistance above 30 nA.
(b) Current-voltage characteristic curve for three samples with different width. The critical current
increases with increasing the sample width.

49

Resistively-Detected NMR in InSb Quantum Hall Systems－Reciprocity of nuclear polarization in a quantum Hall ferromagnet－
Yoshiro Hirayama
Graduate School of Science, CSIS, CSRN,

Tohoku University

Extremely large g-factor of InSb two-dimensional system allows us a crossing of down spin of ground
Landau-level (LL) and up spin of the first LL at ν = 2 in a tilted magnetic field, resulting in a formation of
the quantum Hall ferromagnet (QHF) at ν = 2 with spin domain structures. The dynamic nuclear
polarization and resistively-detected (RD) NMR have been successfully demonstrated in this InSb QHF [1].
This is the simplest QHF and provides us a chance to study the fundamental feature of dynamic nuclear
polarization in QHF.
We fabricated both Corbino and Hall-bar structures based on InSb 2D system. It is well-known that theHall-bar has chiral edge channel running one-direction; however, there is no edge channel for Corbino disk.
For both structures, we can see RDNMR response at ν = 2 QHF realized in a tilted magnetic field. The
RDNMR signal is symmetric for current flow direction and disappears at 2 K for the Corbino disk. On theother hand, RDNMR signal is asymmetric for current flow direction and remains up to 6 K for the Hall-bar
structure. This result clearly indicates an important role of the chiral edge channel for dynamic nuclear
polarization [2]. When we set the Hall-bar structure at 3 K, where bulk (edge) dominated nuclear
polarization disappears (remains), we confirm clear reciprocity of the RDNMR response reflecting thecharacteristics of the chiral edge channel in the QHF [2].
The above-mentioned RDNMR is combined with gate-controlled InSb two-dimensional structure,
resulting in successful pump-probe nuclear relaxation experiment. In contrast to a long T1 of quantum Hall
states around ν = 1 that possesses a Korringa-type temperature dependence, the temperature-independent
short T1 of the ν = 2 QHF suggests the presence of low energy collective spin excitations in the domain
wall of the QHF [3].
Reference： [1] H. W. Liu, K. F. Yang, T. D. Mishima, M. B. Santos, and Y. Hirayama, Phys. Rev. B 82(RC),241304, doi.org/10.1103/PhysRevB.82.241304 (2010) [Editor’s suggestion] [2] K. Yang, K. Nagase, Y.
Hirayama, T. D. Mishima, M. B. Santos, and H. Liu, Nature Comm. 8: 15084, doi: 10.1038/ncomms15084(2017). [3] K. F. Yang, M. M. Uddin, K. Nagase, T. D. Mishima, M. B. Santos, Y. Hirayama, Z. N. Yang
and H. W. Liu, New Journal of Physics 21, 083004 doi.org/10.1088/1367-2630/ab34ce (2019).

Fig. 1 Reciprocity characteristics of the
RDNMR response in a Hall bar with ν = 2
QHF.

50

Electron evaporative cooling using asymmetric double barrier
semiconductor heterostructure
Marc Bescond1,2, Aymen Yangui1,2, Naomi Nagai1, and Kazuhiko Hirakawa1,2,3
Institute of Industrial Science, University of Tokyo, 2LIMMS-CNRS, 3INQIE, University of Tokyo

１

Rapid progress in high-speed, densely packed electronic/photonic devices has brought unprecedented
benefits to our society. However, this technology trend has in reverse led to a tremendous increase in heatdissipation, which degrades device performance and lifetimes. The scientific and technological challenge
henceforth lies in efficient cooling of such high-performance devices.
We have focused ourselves on the thermionic cooling technology, which can achieve higher coolingefficiency by properly designing the semiconductor heterostructures. Electrons thermionically emitted fromthe cathode transfer their kinetic energies to the anode and give rise to refrigeration in the cathode.
The aim of the present work is to demonstrate that a significant electron cooling as much as ~50 K is
possible in a semiconductor heterostructure operating at room temperature. The studied AlGaAs/GaAs
asymmetric double barrier heterostructure, which combines resonant tunneling and thermionic emission,
was originally proposed by Chao et al. (Appl. Phys. Lett. 87, 022103 (2005)) as a lattice cooler. The electron
temperature, Te, in the QW as well as Te in the electrodes are determined from photoluminescencemeasurements. At 300 K, Te in the QW is remarkably reduced by as much as 50 K as the bias voltage isincreased up to the maximum resonant tunneling condition. This behavior is qualitatively explained in termsof the evaporative cooling process. Evaporative cooling is known in the field of the cold atom physics. In
this work, we have implemented the concept of the evaporative cooling in a solid-state system, i.e., thesemiconductor heterostructures, and observed a significant electron cooling as much as ~50 K at 300 K.
The observed cooling behavior is quantitatively confirmed by quantum transport calculations that selfconsistently couples the non-equilibrium Green's function (NEGF) formalism for electrons with the heat
equation.
These results make our heterostructure device promising for a comprehensive heat management in
nanodevices.
Reference: Aymen Yangui, Marc Bescond, Tifei Yan, Naomi Nagai, and Kazuhiko Hirakawa: “Evaporativeelectron cooling in asymmetric double barrier semiconductor heterostructures”, Nature Communications,10, 4504 (2019), DOI: https://doi.org/10.1038/s41467-019-12488-9

Fig. 1 (a) GaAs/AlGaAs heterojunction asymmetric double-barrier thermionic emission structure, (b)electron temperature evaluated by photoluminescence; green: electron in GaAs electrode, red: electron inquantum well, blue: Electrons in quantum wells (theory)51

1-bit quantum simulation with silicon transistor－Single spin qubit reproduce a well-known phenomenon in magnetic resonance－
K. Ono1、S. N. Shevchenko2、T. Mori3、S. Moriyama4、and F. Nori1
1
RIKEN, 2B. Verkin Institute, 3AIST, ４NIMS
Motional narrowing (averaging) is a phenomenon that has been known for a long time in the field ofmagnetic resonance. Particles placed in a non-uniform magnetic environment move around quickly toequalize the effective environment, resulting in a narrowing of resonance line width. Normally, many spinsare involved in magnetic resonance, and it was not possible to freely control a non-uniform environment.
By using spin qubits we have succeeded in simulating this phenomenon experimentally with a single
spin and in a more controlled magnetic environment. The qubit is based on a silicon tunnel field-effecttransistor, and a deep impurity introduced into this transistor function as a spin qubit. The time ensemble
average of the spin state is read as the source/drain current ISD of the transistor. The device was cooled to atemperature of 1.6 K and applied a static magnetic field and an AC magnetic field with microwave
frequency f to cause magnetic resonance. When the gate voltage VG of the device is changed whilesatisfying this condition, the g-factor of spin changes due to Stark effect, and the resonance frequencychanges through the change of Zeeman energy. The high-speed modulation of the resonance frequency by
VG has made the experiment described later possible.
Figure 1 (b-d) shows the results when square wave modulation (Fig. 1 (a)) is applied to the gate voltage.
If the square modulation frequency is much smaller than the reciprocal of the coherence time (4 MHz), twopeaks will appear (Fig. 1(d)), reflecting the resonant frequency at each stage of the modulation (i.e. highand low stage of the square wave). This is because the time constant of ISD measurement is as slow as 1
second. As the modulation frequency of this square wave is increased, these two trivial peaks go through acomplex interference pattern (Fig. 1 (c)) and eventually a single peak at a high modulation frequency (>>4 MHz) is appeared (Fig. 1 (b)). This indicates that the spin that modulated faster than the coherence time
feel the average value of the modulated external field, which can be understood as the motional averaging.
Furthermore, in the result obtained in the same way when the shape of the square wave is asymmetric (Fig.
1 (e)), the spin is found to feel the external field of the weighted average value (Fig. 1 (f-h)). This result
can also be regarded as an analog calculation of the weighted average value using a single qubit. These
results show that useful findings can be obtained even with 1-qubit simulation, and indicate one possible
direction for qubit applications with relatively low technical difficulty.
Reference： K. Ono, S. N. Shevchenko, T. Mori, S. Moriyama, F. Nori, Quantum interferometry with a gfactor-tunable
spin
qubit,
Phys.
Rev.
Lett.
122,
207703(2019).
DOI ：https://doi.org/10.1103/PhysRevLett.122.207703
Fig.１(a) Symmetrical modulationsof VG. The high/low ratio of thesquare wave is fixed at 1:1. (b)Magnetic resonance spectrum at a
modulation frequency of 50 MHz.
Modulation
frequency(c)dependence of magnetic resonancesignal. The derivative of ISD withrespect to f was plotted toemphasize the peak position. (d)Spectrumatamodulation
frequency of 0.5 MHz. (e)Asymmetrical modulations of VG.
The high/low ratio is fixed at 4:1. (fh) A plot similar to (b-d) for
asymmetric modulation.

52

Detection of the Kondo screening cloudIvan V. Borzenets1, Jeongmin Shim2, Jason C. H. Chen3, Arne Ludwig4、Andreas D. Wieck4, Seigo Tarucha5, Heung-Sun Sim2, and Michihisa Yamamoto5
１
Department of Physics, City University of Hong Kong, 2Department of Physics, KAIST,
3
Department of Applied Physics, University of Tokyo, 4Chair of Applied Solid State Physics, Faculty ofPhysics and Astronomy, Ruhr-University Bochum, 5Center for Emergent Matter Science, RIKEN
When a magnetic impurity is placed in a metal, the conducting electrons become entangled with themagnetic impurity and effectively screen it. This is called the Kondo effect after the Japanese theoreticalphysicist Jun Kondo who first revealed the role of this effect in the mid-1960s, and its strength is known as
the Kondo temperature.
The cloud size is another important parameter for materials that contain more than one magnetic impurity
because the spins in the cloud couple with one another and mediate the coupling between magnetic
impurities when the clouds overlap. Although the Kondo effect for a single magnetic impurity is coveredin textbooks on many-body physics, the Kondo cloud had not been directly detected until now despite many
attempts over the past five decades. It was known to exist, but its spatial extension had never been observed,
creating a controversy over whether such an extension actually existed.
In the present study, we observed a Kondo screening cloud formed by an impurity defined as a localized
electron spin in a quantum dot coupled to quasi-one-dimensional conducting electrons, and then used aninterferometer to measure changes in the Kondo temperature, allowing us to investigate the presence of acloud at the interferometer end (Fig. 1). Essentially, we slightly perturbed the conducting electrons at alocation away from the quantum dot using an electrostatic gate. The wave of conducting electrons scatteredby this perturbation returned back to the quantum dot and interfered with itself. The Kondo cloud is aquantum mechanical object which acts to preserve the wave nature of electrons inside the cloud. Even
though there is no direct electrostatic influence of the perturbation on the quantum dot, this interference
modifies the Kondo signature measured by electron conductance through the quantum dot if theperturbation is present inside the cloud. We found that the length as well as the shape of the cloud isuniversally scaled by the inverse of the Kondo temperature, and that the cloud’s size and shape were ingood agreement with theoretical calculations (Fig. 2).
The size of the Kondo cloud in semiconductors was found to be much larger than the typical size ofsemiconductor devices. The cloud can therefore mediate interactions between distant spins confined inquantum dots, which is a necessary protocol for semiconductor spin-based quantum information processing.
This spin-spin interaction mediated by the Kondo cloud is unique since both its strength and sign (two spinsfavor either parallel or anti-parallel configuration) are electrically tunable, while conventional schemes
cannot reverse the sign. This opens up a novel way to engineer spin screening and entanglement.
Reference： I. V. Borzenets, J. Shim, J. C. H. Chen, A. Ludwig, A. D. Wieck, S. Tarucha, H.-S. Sim, M.
Yamamoto, “Observation of the Kondo screening cloud”, Nature 579, 210-213 (2020). DOI ：10.1038/s41586-020-2058-6

Fig. 2 Shape of the Kondo cloud plotted as afunction the distance from the localized spin
normalized by the cloud size.

Fig. 1 Schematic illustration of the device used
to observe the Kondo cloud.

53

Hybrid structure of quantum-dot and quantum-wellsuperlattice grown by molecular beam epitaxy
Kouichi Akahane
National Institute of Information and Communications Technology
Research on quantum dots (QDs) has attracted considerable attention because of their applications inhigh-performance optical devices such as semiconductor lasers [1]. Self-assembled InAs QDs grown on
InP substrates have advantages for use in optical devices for fiber optic communication systems operatingin the 1.55-µm wavelength region. InGaAlAs barrier material can be used to embed InAs, enabling the
bandgap to be tailored by changing the composition of the barrier. However, compositional control of
InGaAlAs is not easy because the exchange of Ga and Al atoms is insensitive to changes to the lattice
constant. To overcome this problem, we developed a new growth method for embedding InAs QDs on an
InP substrate. This method utilizes lattice-matched InGaAs and InAlAs superlattices (SLs) to embed theInAs QDs using the so-called digital embedding method [2]. The emission wavelength of InAs QDs could
be effectively controlled by changing the SL period or ratio of the thickness of the InGaAs to that of the
InAlAs.
In this study, all samples were grown by conventional solid-source molecular beam epitaxy. We
fabricated six-layer QD and InGaAs/InAlAs stacked structures on an InP(311)B substrate. After the
InGaAs/InAlAs SL was grown, 5 ML of InAs QDs were grown. Then, InAs QDs were embedded by
InGaAs/InAlAs SL. A reference sample that had In0.52Ga0.24Al0.24As embedding layers was also grown. A
transmission electron microscope (TEM) was used to observe the cross-section of the sample. In addition,
photoluminescence (PL) measurements were conducted at room temperature. Figure 1 shows a crosssectional TEM image of the sample with 2-ML SL. The image confirms that the InAs QDs weresuccessfully embedded in the InGaAs/InAlAs SL. Because the structure of the SL was nearly perfect, theminiband of the SL could act as a barrier for the QDs. Figure 2 shows the PL spectra measured at room
temperature for the reference sample (black), the sample with 2-ML SL (red), and the sample with 16-ML
SL (blue). The peak wavelengths of the digital embedding samples were shorter than that of the reference
sample and were shifted to shorter wavelengths with increasing thicknesses of the InGaAs and InAlAs.
Therefore, this technique provides a simple method of precisely controlling the emission wavelengths of
QDs. In addition, carrier dynamics can be controlled by changing the thickness of SL which leads to changeof PL decay time (Fig. 3). Therefore, the interaction between the QD and SL states can be used for efficient
injection and/or correction of carriers around the QD if these energy states can be controlled accurately.
Reference：[1] Kouichi Akahane et. al., J. Cryst. Growth, 432, 15 (2015).

Intensity (arb. units)(a) S_2/2(b) S_16/16(c) S_ref

0

2

4

6

8

10

Time (ns)Fig. 1 Cross-sectional TEM
image of sample with 2-ML SL.

Fig. 2 PL spectra of reference
sample (black), sample with 2ML SL (red), and sample with
16-ML SL (blue).

54

Fig. 3 PL decay of reference
sample (black), sample with 2ML SL (red), and sample with
16-ML SL (blue).

Dicke Effect in Photocurrent through Quantum Dot Array－Sensitive detector of THz light－

Mikio Eto1, Rin Okuyama2
Faculty of Science of Technology, Keio University, 2Faculty of Science of Technology, Meiji University

１

Photocurrent through a quantum dot was reported by irradiating the terahertz (THz) light [1]. In a selfassembled InAs quantum dot, discrete energy levels are separated by an energy of THz light. In the
Coulomb blockade regime of a single electron transistor, the light irradiation excites an electron from anenergy level below the Fermi level (EF), |𝑔𝑔⟩, to that above EF, |𝑒𝑒⟩, which results in an electric current
without applying a bias voltage between the source and drain leads [Fig. (a)]. The direction of thephotocurrent is determined by an asymmetry of the tunnel couplings of the associated energy levels, Γ𝑔𝑔𝐿𝐿 ,Γ𝑔𝑔𝑅𝑅 , Γ𝑒𝑒𝐿𝐿 ,and Γ𝑒𝑒𝑅𝑅 , and no current flows in the case of Γ𝑔𝑔𝐿𝐿 �Γ𝑔𝑔𝑅𝑅 ≠ Γ𝑒𝑒𝐿𝐿 ⁄Γ𝑒𝑒𝑅𝑅 . This system could be applied to asensitive THz detector.
We theoretically study the photocurrent through an array of N quantum dots in parallel, to investigate apossibility for more sensitive THz detector by the quantum effect. The quantum dots are connected tocommon source and drain leads without tunnel coupling to one another. The fundamental idea is thesuperradiance or Dicke effect when the distance among the quantum dots is smaller than the wavelength ofthe light. The absorption or emission of photon makes the entangled states of N quantum dots: e.g., for N=2,
the ground state |𝑔𝑔𝑔𝑔⟩ changes to an entangle state, |B⟩ = (|𝑒𝑒𝑒𝑒⟩ + |𝑔𝑔𝑔𝑔⟩)⁄√2, whose transition rate to|𝑔𝑔𝑔𝑔⟩ or |𝑒𝑒𝑒𝑒⟩ is twice as large as that of |𝑒𝑒𝑒𝑒⟩ or |𝑔𝑔𝑔𝑔⟩, as shown in Fig. (b). No transition takes place toanother entangled state, |D⟩ = (|𝑒𝑒𝑒𝑒⟩ − |𝑔𝑔𝑔𝑔⟩)⁄√2 (dark state).
First, we formulate the photocurrent through a single quantum dot in Fig. (a) using the density matrix
method. It is given by
𝑔𝑔2 Γ1
Γ𝑒𝑒𝑅𝑅 − Γ𝑒𝑒𝐿𝐿 Γ𝑔𝑔𝑅𝑅 − Γ𝑔𝑔𝐿𝐿−
�𝐼𝐼 ⁄𝑒𝑒 = � 𝑅𝑅
Γ𝑒𝑒 + Γ𝑒𝑒𝐿𝐿 Γ𝑔𝑔𝑅𝑅 + Γ𝑔𝑔𝐿𝐿 (ℏ𝜔𝜔 − ∆)2 + (ℏΓ2 ⁄2)2

where 𝑔𝑔 is the coupling constant between electron and light and ∆ is the energy level spacing between|𝑔𝑔⟩ and|𝑒𝑒⟩ . Γ1 and Γ2 are constants determined by Γ𝑒𝑒𝑅𝑅 + Γ𝑒𝑒𝐿𝐿 , Γ𝑔𝑔𝑅𝑅 + Γ𝑔𝑔𝐿𝐿 , and 𝑔𝑔 . The photocurrent ismaximal when the photon energy ℏ𝜔𝜔 matches ∆ and proportional to the asymmetric factor in the bracket.
Next, we examine the photocurrent through an array of N equivalent quantum dots in parallel. (i) If N
quantum dots are connected to N pairs of source and drain leads separately, the entangled states aredestroyed by the observation of the current. Then the photocurrent is simply N times of that through a single
quantum dot. (ii) When the quantum dots are connected to a common pair of leads with single conduction
channel by identical tunnel couplings, the current is enhanced by a factor of (N+2)/3 if the tunneling rate ismuch smaller than the photon-induced transition rate. (iii) The photocurrent is generally smaller than thatin case (ii) in the presence of multiple channels in the leads.

[1] Y. Zhang, K. Shibata, N. Nagai, C. Ndebeka-Bandou, G. Bastard, and K. Hirakawa, Nano. Lett. 15,1166 (2015); Phys. Rev. B 91, 241301(R) (2015); ibid. 93, 235313 (2016).

55

Ge/Si nanowire double quantum dots coupled with amicrowave resonator
Rui Wang1 , Russell S. Deacon1,2, Jian Sun1 and Koji Ishibashi1,2Advanced Device Laboratory, RIKEN, 2Center for Emergent Matter Science (CEMS), RIKEN

１

Ge/Si core-shell nanowires, where holes are accumulated in a Ge core covered by a thin Si shell, havea small diameter of ~10nm and are attractive for studying physics and for spintronics applications,associated with a large spin-orbit interaction (SOI). The electron spin would be an excellent candidate fora quantum bit because of an long coherence in group four material such as Si and Ge where nuclear spinsare minority. Quantum information can be exchanged between the spin and a photon when a strong coupling
between them are realized. This is useful because the quantum information stored in the distant spin qubits
could be exchanged through a photon in a resonator. However, an interaction between the spin and thephoton (magnetic interaction) is generally weak, compared with that between a charge and a photon(electric interaction). SOI can be helpful to mediate the interaction between the spin and the photon. In real
devices, decoherence exists, for example, due to the photon loss in a resonator and the qubit relaxation. To
realize the coherent interaction between them, the coupling has to be larger than the decoherence rate
(strong coupling). In this work, we have studied a charge coupling between the double quantum dot as acharge qubit and a photon in a resonator.
Figure 1shows the images of the sample structures. The nanowire is located on the finger gates with a
hBN insulating layer in between. By applying positive gate voltages on the suitable finger gates, double
quantum dots are formed with a tunable center barrier that separates the nanowire. The sample was set in adilution refrigerator. The charge stability diagram of the double dots (Fig.2 (left)) was obtained bymeasuring the phase shift of the transmitted microwave as functions of the gates voltages that change apotential of each dot. The detuning between the two dot levels can be changed by sweeping the gate voltages
along the arrow in Fig.2 (left). At the position where the arrow crosses the boundary of the two charge states,
the molecular states should be formed as a result of the maximal coupling between the two dots. Figure 2(right) shows the resonant frequency change of the resonator as the detuning is changed along the arrow.
The behavior can be simulated by considering an interaction between the double dots and a photon with apossible decoherence. From that, we concluded the strong coupling was not realized due to the qubit
decoherence larger than the coupling strength.
Reference：
Rui Wang, Russell S. Deacon, Jian Sun, Jun Yao, Charles M. Lieber, Koji Ishibashi, Nano Lett. 19, 1052–
1060 (2019)

Fig.1: SEM image of the sample
structures. The nanowire is locatedat the position where the electricfield strength is maximum

Fig.2: (left) Charge stability diagram of the double dot obtainedby measuring the phase change of the transmitted microwave).
(right) A change of the resonant frequency as the gate voltage(detuning) is changed along the allow in the left Fig.

56

Helical channel formation in Ge/Si core-shell nanowires
Jian Sun1, Russell S. Deacon1,2, Rui Wang1 and Koji Ishibashi1,2Advanced Device Laboratory, RIKEN、2Center for Emergent Matter Science (CEMS), RIKEN

１

Ge/Si core-shell nanowires, where holes are accumulated in a Ge core covered by a thin Si shell, have asmall diameter of ~10nm and are attractive for studying physics and for spintronics applications, associatedwith a large spin-orbit interaction (SOI). SOI is also important to form a helical state where spin is lockedwith momentum. The helical channel is essential to realize a one-dimensional topological superconductor
when superconductivity is induced in the semiconductor nanowires with a large SOI under an external
magnetic field. Majorana zero-modes are expected to emerge in it, and that can constitute a topologicalquantum bit (qubit) which is considered to have a long coherence, an essential requirement for the quantum
computer. Experimentally, it is important to demonstrate the formation of the helical state. In this work, we
did it by measuring conductance of the Ge/Si nanowire in magnetic fields as the gate voltage and a magnetic
field direction are changed.
Figure 2 shows an expected energy dispersion of the one-dimensional nanowire when the helical stateis formed. Due to the SOI, the two bands for spin up and down states shift and the “helical gap” opens at
k=0 due to the external magnetic field. Generally, the conductance of the ballistic nanowire is quantizedwith the number of occupied subbands. The formation of the helical gap reflects on the behavior of the
conductance quantization as a reentrant quantized step with a dip when the gate voltage (Fermi energy) is
swept. Figure 1 show the false color image of a typical fabricated sample. A metal gate is formed on athermally oxidized Si substrate and a nanowire is located on top of it with a hBN insulating layer between
the gate metal and the nanowire. Multiple metal contacts are deposited to flow a current. Fermi level canbe changed by changing the gate voltage.
Figure 2 (right) shows the conductance near the first step as a function of the gate voltage with andwithout magnetic fields. The expected conductance “dip” or the reentrant behavior, indicated by an arrow,is observed on the step. The dip is also observed in no magnetic field, the reason of which is not known.
The width of the helical gap should depend on the direction of the external magnetic field with respect tothat of the effective magnetic field (BSO) associated with the SOI, and become zero when the two fields arealigned. This expectation was confirmed by measuring the width of the dip when the external magnetic
field direction was changed.
Reference：
1. Rui Wang, Russell Deacon, Jun Yao, Charles Lieber, and Koji Ishibashi, Semicon. Sci. Technol., 32,094002 (2017)
2. Jian Sun, Russell Deacon, Rui Wang, Jun Yao, Charles M. Lieber, Koji Ishibashi, Nano Lett. 18, 61446149 (2018)

Fig.2 (left): Dispersion
relation in a 1D wireunder
anexternal
magnetic field. The
helical gap is formed.
Fig.1: False color SEM image ofthe typical sample.

Fig.2 (right): Conductance as a function of the gate
voltage with and without magnetic fields at 7.5K

57

Microscopic NMR in Quantum Point Contact
M. H. Fauzi* and Y. Hirayama
Graduate School of Science, CSIS, CSRN, Tohoku University
Resistively-detected NMR (RDNMR) measurement has been applied to a GaAs-based quantum point
contact (QPC) and interesting characteristics are obtained in the quantum Hall regime, where spin-flip interedge-channel scattering occurs near the QPC. The RDNMR signal appears when filling of the both side of
the QPC (νb) is even and that of the inside of the QPC (νQPC) is νb-2< νQPC< νb -1. First, νb is set to 2 (theground Landau level). The successful RDNMR detection is confirmed down to B = 1.25 T as shown in Fig.
1. All the RDNMR signals exhibit a threefold spectra attributed to electric quadrupole interaction.
Interestingly, the central NMR linewidths, which are not affected by the strain distribution discussed later,increases in proportion with field up to B = 3 T and saturate. This saturation suggests the contribution of
Coulomb interaction [1].
Furthermore, RDNMR can be achieved up to the fifth Landau level, where νb =10 and 8 < νQPC < 9. In
such situation, the magnetic field can be lower than 1 T. We are able to retain the RDNMR signals in acondition where the spin degeneracy of the first one-dimensional (1D) subband is still preserved.
Furthermore, the effects of orbital motion on the first 1D subband can be made smaller than those due toelectrostatic confinement. This developed RDNMR technique is a promising means to study electronic
states in a quantum point contact near zero magnetic field [2].
Gate patterning on semiconductors is routinely used to electrostatically confine electrons into reduced
dimensions. At cryogenic temperatures, differential thermal contraction between the patterned gate and thesemiconductor often lead to an appreciable strain modulation. The impact of such modulated strain to the
conductive channel buried in a semiconductor has long been recognized, but measuring its magnitude andvariation are rather challenging. Here, thanks to the quadrupolar splitting in the RDNMR signal, the strain
felt by the electrons flowing in the quasi one-dimensional channel is precisely detected as shown in Fig. 2.
The detected strain magnitude on the order of 10−4 varies spatially in the nanometer scale. This result
provides us an important hint for studying the effects of strain on semiconductor quantum devices. [3].
Reference： [1] A. Noorhidayati, M. H. Fauzi, M. F. Sahdan, S. Maeda, K. Sato, K. Nagase, and Y.
Hirayama, Phys. Rev. B101, 035425, doi.org/10.1103/PhysRevB.101.035425 (2020). [2] M. H. Fauzi, A.
Noorhidayati, M. F. Sahdan, K. Sato, K. Nagase, and Y. Hirayama, Phys. Rev. B97 (RC), 201412
doi.org/10.1103/PhysRevB.97.201412 (2018). [3] M. H. Fauzi, M. F. Sahdan, M. Takahashi, A. Basak, K.
Sato, K. Nagase, B. Muralidharan, and Y. Hirayama, Phys. Rev. B100 (RC), 241301, DOI:
10.1103/PhysRevB.100.241301 (2019).
*present address: Research Center for Physics, Indonesian Institute of Sciences, Indonesia

Fig. 1 Magnetic field dependence of
RDNMR signals measured at νb =2
and νQPC< 1

Fig. 2 (a) Diagonal magnetotransport trace as a function of
VSG1 with VSG2 = −1.65 V and VCG = −0.45 V. The inset
shows schematic diagram of the QPC device and variationof the channel position by VSG1. (b) Quadrupole splitting ∆Qfrom the RDNMR spectra measured along the red line in(a). The inset shows a typical spectrum.

58

Dynamical nuclear spins and disorder potential effect inquantum point contacts
Tomosuke Aono1
Faculty of Engineering, Ibaraki University

１

Spin polarization can be easily achieved using a magnetic field for electron spins, but not for nuclear
spins. The dynamical nuclear spin polarization (DNP) uses a spin flip-flop between the electron and nuclear
spin to achieve nuclear spin polarization. Recently, a method called resistivity-detecting NMR, which
detects NMR signals as a change in electrical resistance, has been developed, making it possible to observe
DNP formation in semiconductor nanostructures.
The DNP using quantum point contacts (QPCs) and the DNP detection by resistance-detecting NMR are
considered. When a finite bias voltage is applied to the QPC at a conductance G = e2/h, a dipole-type DNP
is generated. The DNP orientation is reversed between the source and drain electrodes, as shown in Fig. 1.
This dipolar-type DNP has qualitatively different response characteristics from the homogeneous nuclear
spin polarization when detected by resistance-detection NMR. This works is done in collaboration with Dr.
Kawamura, and Dr. Stano from RIKEN, and Prof. Komine from Ibaraki Univ.
The gate voltage dependence of QPC conductance reflects the QPC's potential structure; when the QPC
potential is parabolic, the slope of the gate voltage dependence of the conductance gives the potential
curvature. In recent experiments, the relationship between the potential curvature and the split gate length
has been investigated by measuring the gate voltage characteristics of about 100 QPCs. As the split-gate
length increases, one would expect the QPC curvature to decrease; however, contrary to this expectation,
the curvature remains almost unchanged with the gate length. Furthermore, the results suggest that thebackground disorder potential causes this property.
We investigate the QPC conductance under disordered potentials using 1D and 2D tight-binding models.
As shown in Fig. 2 (left), we consider the disorder potential is added to the parabolic potential energy. The
disorder potential has a Gaussian correlation function in space. Given the disorder potential strength andthe spatial correlation length, the effective QPC length is obtained by taking the sample average of the gate
voltage dependence. As shown in Fig. 2 (right), the effective QPC length is insensitive to the QPC length.
Moreover, the results even exhibit the opposite trend, where the effective QPC length weakly decreases as
the QPC length increases. This work is done in collaboration with Prof. Hirayama’s group.
Reference： [1] P. Stano, T. Aono, M. Kawamura, “Dipolelike dynamical nuclear spin polarization arounda quantum point contact” Phys. Rev. B 97, 075440 (2018). DOI: 10.1103/PhysRevB.97.075440 [2] T.
Aono, M. Takahashi, M. Fauzi, Y. Hirayama, “Quantum point contact potential curvature under correlateddisorder potentials” Phys. Rev. B 102, 045305 (2020). DOI: 10.1103/physrevb.102.045305

Fig. １ : Current through QPC anddipole-type DNP

Fig. ２: (left)QPC potential (black curves) and Gaussian disorder
potential (right)QPC length and effective QPC length59

Theory of carbon nanotubes in hybrid systems－Topological states and their quantum property－
Wataru Izumida
Graduate School of Science, Tohoku University
Carbon nanotubes have been extensively studied as ideal one-dimensional conductors in nanoscale.
Hybrid structures, in which individual ultraclean single-wall carbon nanotubes are embedded insemiconductor devices, have been fabricated in the last two decades. Quantum transport measurements
have revealed that there exist fine structures. The basic electronic property of the nanotubes can beunderstood from that of the graphene by employing the boundary condition in the circumference direction.
However, the observed fine structures cannot be captured by this simple picture. They exhibit the uniquequantum effects of the nanotubes. We have focused on these phenomena and investigated them theoretically.
The bound state spectrum arises due to the finiteness of the nanotube length. There exist two valleys in
the energy bands. The valley has been widely treated as a good quantum number on the bound states.
However, there have been unclear points regarding the role on the bound state. To explore this problem, we
have been carried out the construction of microscopic theory.
As shown in the figure, we have constructed one-dimensional models by utilizing the rotational
symmetry of the system. This model enables us the study on the bound state including the evanescent modes
near the boundary. The theory has been expanded to the edge states lying in the bulk band gap. An exact
relation between the edge states and a
topological invariant has been found. This hasrevealed the topological nature of thenanotubes [1,2,3].
Furthermore, international research projects
have been carried out. Formation of end spinson the topological edge states and theirantiferro-, ferro-magnetic interaction under theelectron correlation have been demonstrated[4]. For the hybrid system of a nanotube
proximity coupled to a superconductor,
emergence of the topological states localized at
the
edges
includingthe
Majorana
Figure Construction of 1D models for thequasiparticles has been investigated [5,6,7].
nanotubes.
References：[1] W. Izumida, R. Okuyama, A. Yamakage, R. Saito, "Angular momentum and topology in semiconducting
single-wall carbon nanotubes", Physical Review B, 93, 195442 (2016).
[2] R. Okuyama, W. Izumida, M. Eto, "Topological Phase Transition in Metallic Single-Wall Carbon
Nanotube", Journal of the Physical Society of Japan, 86, 013702 (2017).
[3] R. Okuyama, W. Izumida, M. Eto, "Topological classification of single-wall carbon nanotube", PhysicalReview B, 99, 115409 (2019).
[4] C. P. Moca, W. Izumida, B. Dóra, Ö. Legeza, J. K. Asbóth, G. Zaránd, "Topologically Protected
Correlated End Spin Formation in Carbon Nanotubes", Physical Review Letters, 125, 056401 (2020).
[5] W. Izumida, L. Milz, M. Marganska, M. Grifoni, "Topology and zero energy edge states in carbon
nanotubes with superconducting pairing", Physical Review B, 96, 125414 (2017).
[6] M. Marganska, L. Milz, W. Izumida, C. Strunk, M. Grifoni, "Majorana quasiparticles in semiconducting
carbon nanotubes", Physical Review B, 97, 075141 (2018).
[7] L. Milz, W. Izumida, M. Grifoni, M. Marganska, "Transverse profile and three-dimensional spin cantingof a Majorana state in carbon nanotubes", Physical Review B, 100, 155417 (2019).

60

Flexible Carbon Nanotube Electrochemical Sensors
Nguyen Xuan Viet, Keita Nishimura, Takuya Ushiyama, Shigeru Kishimoto, and Yutaka Ohno
Department of Electronics, Nagoya University
Electrochemical sensors based on carbon nanotubes (CNTs) have great potential for use in wearable or
implantable biomedical sensor applications because of their excellent mechanical flexibility andbiocompatibility. However, the electrochemical activity of such materials is not yet fully understood. In
addition, the main challenge associated with applications of CNT-based sensors is their uniform andreproducible fabrication on flexible plastic film. In this study, we focused on understanding the origin of
the electrochemical activity of single-walled CNTs (SWNT). We also elaborated to establish a highly
reliable technique to fabricate uniform flexible CNT microelectrodes on a plastic film.
We fabricated electrochemical sensors with high-quality and clean SWNT film formed by the floatingcatalyst CVD technique; however so-fabricated SWNT electrodes exhibited a low electron transfer rate.
Electrochemical functionalization with an H2SO4 solution successfully enhanced the electrochemical
activity of the SWNT electrode. This method is gentle and controllable, but also effective at increasing theelectron transfer rate without either degrading the potential window. We found out that there was acorrelation between the electron transfer rate and the amount of defects evaluated from Raman scattering
spectroscopy. XPS analysis showed that the functionalization process introduced C–O and C=O species,
suggesting that these species constituted active sites for inner sphere probes.
We also realized a highly reliable technique to fabricate flexible CNT microelectrodes. In addition tousing the clean CNT thin film, an oxide protection layer, which is used to cover the CNT thin film during
the fabrication process, minimizes contamination of the surface. The fabricated flexible CNT
microelectrodes show almost ideal electrochemical characteristics for microelectrodes with the averagevalue of the quartile potentials, ∆E = |E3/4 − E1/4|, was 60.4 ± 2.9 mV for the 28 electrodes after theelectrochemical functionalization. The CNT microelectrodes also showed the enhanced resistance tosurface fouling during dopamine oxidation in comparison to carbon fiber and gold microelectrodes. The
high-sensitivity detection of dopamine is also demonstrated with differential-pulse voltammetry, with aresulting limit of detection of ~50 nM. The reliability, uniformity, and sensitivity of the present CNT
microelectrodes provide a platform for flexible electrochemical sensors.
Reference:
1. K. Nishimura, T. Ushiyama, N. X. Viet, M. Inaba, S. Kishimoto, and Y. Ohno, "Enhancement of theelectron transfer rate in carbon nanotube flexible electrochemical sensors by surface functionalization",
Electrochimica Acta 295, 157-163 (2019). doi:10.1016/j.electacta.2018.10.147
2. N. X. Viet, S. Kishimoto, and Y. Ohno, "Highly Uniform, Flexible Microelectrodes Based on Clean
Single-walled Carbon Nanotube Thin Film with High Electrochemical Activity", ACS App. Mater.
Interfaces 11, 6389-6395 (2019). doi:10.1021/acsami.8b19252

Fig.
1
Highly-uniform
flexible
CNT Fig. 2 High-sensitivity detection of dopamine withelectrochemical sensors fabricated on PEN film.
activated CNT microelectrode.

61Modulation of Phonon in Carbon Nanotubes by DefectFormation
Takumi Inaba and Yoshikazu Homma
Department of Physics, Tokyo University of Science
A single-walled carbon nanotube (SWCNT) is a hybrid system of electrons, photon, and phonons.
Phonons in SWCNTs are sensitively accessed with Raman scattering spectroscopy resonant to the quasi 1Delectronic states. Together with the robust exitonic states, the resonant Raman transitions in SWCNTs are
attractive as a quantum hybrid control. However, technological applications of phonons in SWCNTs remain
unexplored. We need to investigate deeply the intrinsic properties of phonons in SWCNTs and theirinteractions with photons and electrons.
We have investigated modifications of SWCNT phonons by means of molecular adsorption,
encapsulation, and defect formation to SWCNTs. Here, we report the intensity modification of theintermediate frequency mode (IFM), which is attributed to K-momentum phonons. The IFM is interesting
because photons with nearly-zero momentum can couple with acoustic nonzero-momentum phonons.
The Raman spectra of IFM in the frequency range from 300 to 500 cm−1 were investigated using
individually suspended SWCNTs, together with photoluminescence (PL) spectra which is sensitive to thedefect density. Owing to the introduction of defects due to the use of an intense excitation laser, Ramanpeaks originating from K-momentum phonons (IFM and D-mode peaks) were enhanced, while Γmomentum phonons (radial breathing mode: RBM, out-of-plane transverse optical mode (oTO), and Gmode peaks) were decreased. The intensities of each Raman peak from a (11, 3) SWCNT are plotted against
the PL intensity in Fig. 1(c). The intensities of Γ-momentum phonons, RBM, oTO and G-mode, decreaselinearly correlating with the PL intensity. By contrast, the IFM and D-mode intensities increase inverselycorrelates with the PL intensity. For K-momentum phonons, presence of defects is essential because Kmomentum phonons need to be elastically scattered by disorder or defect of the graphene lattice. Therefore,
the K-momentum phonon intensity can be modulated by introducing defects. In other words, the photonphonon coupling can be enhanced by defects.
The application of those phononic properties of SWCNTs to quantum information technologies is stillchallenging, but the understanding them deeply will hopefully bring a breakthrough in this field.
Reference： T. Inaba, Y. Tanaka, S. Konabe, and Y. Homma, “Effects of Chirality and Defect Density on
the Intermediate Frequency Raman Modes of Individually Suspended Single-Walled Carbon Nanotubes”,
J. Phys. Chem. C 122, 9184 (2018). DOI：10.1021/acs.jpcc.8b01017*https://www.researchgate.net/publication/337706741_IFM_Animation
Fig. 1 (a) Raman spectrumof suspended (11,3)
SWCNT.
(b) Illustration of atomic
deformation vectors for
IFM of (11,3) SWCNT.*(c) Relationship between
Raman and PL intensities.

62

Thermal Conductivity Measurements of Chirality Assigned
Single-Walled Carbon Nanotubes
Yoshikazu Homma
Department of Physics, Tokyo University of Science
Single-walled carbon nanotubes (SWCNTs) are expected to have high thermal conductivity along thetube axis. Although many experimental measurements of the thermal conductivity have been reported, the
SWCNT structure was not characterized sufficiently. In particular, the chirality was not assigned, and it was
not confirmed whether the SWCNT was isolated or not.
Here, we measured the thermal conductivity of chirality assigned SWCNTs, which were individuallysuspended, by using photoluminescence (PL) imaging spectroscopy. The crystallinity of SWCNTs were
evaluated by Raman spectroscopy. The temperature distribution along the tube axis was obtained, and thetemperature dependence of the thermal conductivity was measured in a wide-temperature range (from 350
to 1000 K). For (9, 8) SWCNTs with 10−12 μm in length, the thermal conductivity was 1166 ± 243 W/(m·K)
at 400 K.
The proposed PL imaging spectroscopy enables to measure the thermal conductivity of SWCNTs withhigh precision and without any contacts. The method is based on the combination of single suspended
SWCNT formation technology and high-sensitivity resonance spectroscopy and enables non-contact
measurement of thermal conductivity with high precision. SWCNTs provide a hybrid system of electrons,
photon, and phonon, and understanding the basic physical properties of phonons such as thermal
conductivity contributes to the development of hybrid quantum technology.

Reference： K. Yoshino, T. Kato, Y. Saito, J. Shitaba, T. Hanashima, K. Nagano, S. Chiashi, and Y. Homma,“Temperature Distribution and Thermal Conductivity Measurements of Chirality-Assigned Single-Walled
Carbon Nanotubes by Photoluminescence Imaging Spectroscopy”, ACS Omega, 3, 4352 (2018). DOI：
10.1021/acsomega.8b00607

Fig. 1 Temperature distribution along the tube axis was measured by spectroscopic imaging of asuspended (9, 8) SWCNT under laser irradiation with different powers. The temperature dependenceof the thermal conductivity was obtained from the temperature distributions for (9, 8) SWCNTs withdifferent lengths (L)63

Observation of band-like transport fromdefect-repaired graphene oxide film
-Towards scalable production of highly crystalline graphene thin filmRyota Negishi and Yoshihiro Kobayashi
Department of Applied Physics, Graduate School of Engineering, Osaka University
Graphene oxide (GO) is a nanocarbon material which can be produced in a scalable manner from bulk
graphite. In this work, the crystallinity is successfully improved by thermal treatment at high temperature
above 1100°C in a reactive atmosphere. The improved crystallinity unveils the original electrical propertiesof graphene from the reduced GO films, resulting in observation of band-like transport for the first time [1].
GO is attracting attention as a starting material for mass synthesis of graphene, which can be formed by
the reduction of GO. However, defects formed during synthesis remain even after usual reduction processes
by chemical treatment or heating. The carrier transport properties of the graphene thin film produced bysuch methods are not the band-like conduction caused by excellent physical properties of graphene, butreflect variable-range hopping (VRH) conduction in which electrons were localized due to defects.
Therefore, the carrier mobility is limited to several cm2/Vs at most, and it has been an issue to improve thecrystallinity and approach the properties of high-quality graphene.
Recently, our research group has been investigating the process to produce graphene by heating andreducing GO thin films at high temperatures in an ethanol atmosphere. Raman and TEM study confirmedthat the defects are drastically repaired by the thermal treatment above 1100°C. The remarkable
improvement in crystallinity results in very high carrier mobility (~ 210cm2 / Vs) which is top-level data
observed from reduced GO (rGO) thin films. Furthermore, we analyzed the temperature dependence ofconductance in the high-mobility rGO thin film and found that the conductance exhibits a non-linear change
in the range from room temperature to 40K, indicating a change of transport mechanism from hopping toband-like conduction. This behavior reflects the original electronic structure of graphene and is the firstcase to be observed from a graphene thin film derived from GO. As for the rGO obtained by the lower
temperature process at ~ 900C, a lot of defects remain as reported and the VRH conduction was observed.
These behaviors of the transport measurements indicate that the improvement in crystallinity reduces todisconnect the electronic band structure and causes the change from hopping to band-like conduction. The
band-like conduction was also supported by the electronic structure analysis of X-ray absorption finestructure spectroscopy and photoelectron spectroscopy.
The result shown here has opened up the possibility of scalable production of highly crystalline graphene
thin films, enabling various applications such as electronic devices and sensors using graphene.
Furthermore, various progress based on this work is expected as future research, such as nuclear spin control
by introducing 13C into the graphene lattice using the defect repair process, the modulation of local
electronic structure by intentionally formed defects, and their application to quantum devices.
[1] R. Negishi, M. Akabori, T. Ito, Y. Watanabe and Y. Kobayashi, “Band-like transport in highly crystalline
graphene films from defective graphene oxides”, Sci. Rep. 6, 28936(2016). DOI：10.1038/srep28936

Fig. 1 TEM images andcarrier transportcharacteristics (conductance
σ vs temperature T)
observed from rGO film
formed by thermal
processes at 900 and
1100°C.

64

Monte Carlo Simulation of Mobility Enhancement inGraphene
N. Mori1, S. A. Mojtahedzadeh1, L. Turyanska2, O. Makarovsky2, L. Eaves2, and A. Patanè2
１
Graduate School of Engineering, Osaka University
2
School of Physics and Astronomy, The University of Nottingham
To date, the high room-temperature carrier mobility of the exfoliated graphene is not reproduced in single
layer graphene (SLG) grown by scalable large area methods. This mobility reduction is usually attributed
to the presence of crystalline defects and scattering of free carriers by charged impurities on the substrate.
Understanding the processes that control and limit the carrier mobility of graphene is a challenging research
field that has potential to accelerate the technological readiness of large area SLG. We demonstrate
theoretically and experimentally that the spatial correlation of charges in surface-functionalized graphene
can provide a means to control the carrier mobility of SLG.
We performed Monte Carlo simulation of carrier dynamics in SLG decorated with a surface layer ofcolloidal PbS quantum dots (see Fig. 1). The spatial correlation between the charged impurities on thesubstrate and the localized charges in a capping layer is modeled with a correlation length 𝑟𝑟max . Strong
spatial correlation (small 𝑟𝑟max ) smooth out the electrostatic potential (Fig. 2), thus enhancing carrier
mobility. The Monte Carlo simulations are in good agreement with experiments (Fig. 3). The control of
the carrier mobility could prove to be a useful tool for fundamental studies of charge correlation phenomena
and for application of graphene in devices requiring a high mobility.
[1] L. Turyanska, O. Makarovsky, L. Eaves, A. Patanè, and N. Mori, "Mobility enhancement of CVD
graphene by spatially correlated charges," 2D Materials, Vol. 4, 025026 (1-6), 2017, DOI:
10.1088/2053-1583/aa55b4[2] O. Makarovsky, L. Turyanska, N. Mori, M. Greenaway, L. Eaves, A. Patanè, M. Fromhold, S. LaraAvila, S. Kubatkin, and R. Yakimova, "Enhancing optoelectronic properties of SiC-grown graphene
by a surface layer of colloidal quantum dots," 2D Materials, Vol. 4, 031001 (1-7), 2017, DOI:
10.1088/2053-1583/aa76bb
Fig. 1 Illustration of a single-layer graphene
decorated with a surface layer of colloidal PbS
quantum dots (QDs) which act as electron
donors. Impurities are located on the substrate.

Fig. 2 [left, center] Simulated potential profiles for different correlation lengths, 𝑟𝑟max .
Fig. 3 [right] Mobility as a function of carrier density. Open circles are data points for measured devices
with QDs with different capping molecules (QD1, QD2, and QD3) and a device without QDs (Pristine).
Closed circles correspond to Monte Carlo simulations with different 𝑟𝑟max .

65

Isotope control in graphene phononic crystal–Towards phonon transport control in graphene–
Takayuki Arie and Seiji Akita
Osaka Prefecture University
Graphene is a potential candidate for next generation electronic devices due to its unique electronic andmechanical properties. Since the main heat carrier in graphene is phonon, we aimed to control the phonontransport properties in graphene by introducing the interface of graphene composed of 12C (12C-graphene)and 13C (13C-graphene). This enables us to control the thermal conductivity of graphene, resulting in thehigher thermoelectric performance of graphene devices.
Graphene was grown by chemical vapor deposition (CVD) using CH4 as a source gas and Cu foils as acatalyst. As a top-down process, graphene isotopic heterostructures, 12C-graphene and 13C graphene, weresynthesized by CVD and O2 plasma etching. As a bottom-up process, on the other hand, we synthesizedgraphene heterostructures by continuously switching 12CH4 and 13CH4 repeatedly during CVD process toform isotopic superlattices in graphene hexagonal single crystals.
The isotopic interface grown by the top-down process (Fig. 1) shows significant increase in the thermal
resistance, possibly due to the phonon frequency mismatch between 12C-graphene and 13C-graphene. Forgraphene grown by a bottom-up process, on the other hand, Raman spectral mapping from single-crystal
graphene shows that each graphene has Raman peaks corresponding to 12C-graphene or 13C-graphene,
indicating that the heterointerfaces were repeatedly fabricated. The apparent thermal resistance of thedevices with respect to the interface number indicates that the resistance increases linearly as the interface
number less than 4. The interfacial thermal resistance was estimated as 125 μm2K/W. In the device with 4interfaces, however, the resistance increases more significantly. As the distance between interfaces isapproximately 600 nm in this device, which is shorter than the reported mean free path of phonon ingraphene at room temperature, the heat transport in the device more likely changes from diffusive to quasiballistic regime, leading to a dramatic increase in the interfacial thermal resistance.
References： Y. Anno, K. Takei, S. Akita, T. Arie, “Artificiallycontrolled synthesis of graphene intramolecular heterojunctions
for phonon engineering” Phys. Status Solidi RRL 8, 692 (2014)/DOI 10.1002/pssr.201409210.

Figure 1 Isotopic heterostructures(top) and Raman spectra from eachposition in graphene (bottom).

Figure 2 (a) Isotopic superlattice in single-crystal graphene andRaman spectral mapping of 12C (red) and 13C (green). (b)Thermal resistance of graphene isotopic heterostructures withrespect to the interface number.

66

Controlling phonon propagation of monolayer graphene bystructural defects–Phonon control for enhancing thermoelectric device performance–
Takayuki Arie and Seiji Akita
Osaka Prefecture University
Graphene is one of the potential candidates for thermal management devices. Since phonon is the mainhear carrier in graphene, the thermal conductivity can be controlled by the structural modifications into
graphene networks. In particular, reducing the thermal conductivity of graphene without changing its
electrical conductivity leads to the application as high efficient thermoelectric devices. We have been
investigating the control of phonon transport by introducing isotope atoms in graphene. The phonon scattersat the interface between graphene composed of 12C and 13C due to the phonon frequency mismatch, resulting
in the significant reduction in the thermal conductivity. Here, we investigate the change in thermal andthermoelectric properties of graphene by controlling defect densities.
The defects introduced into graphene by O2 plasma are classified into 2 stages; sp3-type defects at thelower defect density (stage 1) and vacancy-type defects at the higher defect density (stage 2). Raman spectrafrom graphene with each defect density show that D’ band originating from defects begins to appear at thestage 2 (Fig. 1(a)). From Ioffe’s semiclassical approximation of the thermoelectric properties, we foundthat at the stage 1 phonons are pre-dominant source of carrier scattering, while the scattering is mainly
caused by charged impurities at the stage 2 (Fig. 1(b)). This corresponds to a transition in defect populationfrom sp3-type (stage 1) to vacancy-type defects (stage 2).
We also measured the thermal conductivity of graphene with various amounts of defects. Increase in thedefect density were evaluated by the ratio between Raman D band and G band intensities (ID/IG). When
ID/IG≈2.4, the thermal conductivity was dramatically reduced (150 W/mk) compared to that of as-preparedgraphene (2,670 W/mK). At this stage, the density of defects was estimated to be 0.1%. This suggests thatsuch a small amount of defect effectively modifies the phonon transport, leading to the great reduction ingraphene thermal conductivity. Thus, the thermoelectric device performance can be enhanced by precisely
controlling the stage of defects that are introduced into graphene.
References： Y. Anno, Y. Imakita, K. Takei, S. Akita, T. Arie, “Enhancement of graphene thermoelectricperformance through defect engineering” 2D Mater. 4, 025019 (2017) /DOI 10.1088/2053-1583/aa57fc.
Y. Anno, M. Takeuchi, M. Matsuoka, K. Takei, S. Akita, T. Arie, “Effect of defect-induced carrier scatteringon the thermoelectric power of graphene” Appl. Phys. Lett. 110, 263501 (2017) /DOI 10.1063/1.4989820.

Figure 1 (a) Raman spectra with respect to the defect density. The
defect stage is the stage 1 (ID/IG≤0.76) and stage 2 (ID/IG>2.61). (b)The carrier scattering derived from the thermoelectric measurement.

67

Figure 2 Thermal conductivity
as a function of the defectdensity.

Directional heat flux and heat focusing
Roman Anufriev, Aymeric Ramiere, Jeremie Maire, and Masahiro Nomura
Institute of Industrial Science, The University of Tokyo

In the past few years, ballistic heat transport has been demonstrated experimentally inthe bulk, thin-films and various nanostructures. Yet, practical use of this phenomenon
remains challenging, because thermal phonons tend to travel in almost random directions.
We used µTDTR experiments and Monte-Carlo simulations to show the in-plane ballistic
heat transport in silicon phononic crystals and a possibility to use them for directional
thermal emission and heat focusing.
First, our simulations demonstrated that aligned lattices of holes in a thin plate or
periodic corrugations in a nanowire (Fig. 1) could form directional phonon fluxes frominitially random phonon gas. In a series of µTDTR experiments, we demonstrated that
membranes with an aligned lattice of holes have higher thermal conductivity thanmembranes with staggered lattice, indicating that aligned lattices indeed has directional
heat fluxes between the holes.
Such phononic structures can act as sources of directional heat rays emitted in thedesired directions. Thus, this phenomenon opens various possibilities of heatmanipulations based on the ballistic transport of phonons, in contrast to traditional
phononic manipulations based on wave interference of phonons.
To illustrate a practical application of this effect, we proposed a thermal lens structurethat can focus the thermal energy in a spot. Using Monte Carlo simulations, wedemonstrated the formation of a hot spot of 115 nm in a thermal lense structure (Fig. 1).
Moreover, our µTDTR experiments showed experimental evidence of the heat focusing
effect. These results motivate the concept of ray-like heat manipulations at the nanoscale
and form a new paradigm of heat manipulations that we call ray phononics.
Reference： R. Anufriev, A. Ramiere, J. Maire, and M. Nomura, "Heat guiding and focusing using ballistic
phonon transport in phononic nanostructures," Nat. Commun. 8, 15505 (2017). DOI：
10.1038/ncomms15505 (2017).
R. Anufriev, S. Gluchko, S. Volz, and M. Nomura, "Quasi-ballistic heat conduction due to levy phonon
flights in silicon nanowires," ACS Nano 12, 11928 (2018). DOI： 10.1021/acsnano.8b07597.

Fig. 1.

(Left) Directionality predicted by Monte Carlo simulations in a corrugated nanowire. (Right) Heat

focusing effect in a thermal lense structure predicted by Monte Carlo simulations.

68

Thermal conduction enhancement by surface phonon polaritons
1

Yunhui Wu1, Roman Anufriev1, Sebastian Volz1,2, and Masahiro Nomura1,2
Institute of Industrial Science, The University of Tokyo、2 LIMMS-IIS UT, CNRSAs the semiconductor devices scale down into thin film structure, phonons frequently scattered by thesurface of the film into random directions to hinder the heat transport, resulting in a significant decrease inthermal conductivity. In addition, phonons scatter more often as the temperature of devices rises, leading
the thermal conductivity further decreases. Modern semiconductor devices are highly integrated and large
amount of electrical power is localized. Thus, intensive heat generation and reduction in thermal
conductivity make heat dissipation difficult.
In this study, we experimentally investigated the heat conduction of surface phonon polaritons (SPhP).
We observed that the heat conductivity increases as the temperature rises in dielectric thin film and thethinner the films have greater the effect of SPhP to enhance heat conductivity. The heat conduction wasmeasured in four thin film samples: 30, 50, 100 and 200 nm at temperature between room temperature and
500 degree Celsius. In general, thermal conductivity decreases as the temperature of a substance increases,
which is observed in 100 and 200 nm thin film (green and blue dots). The 200 nm thin film diminished withthe square of the temperature, indicating that acoustic phonons, as well as sufficiently thick materials, areprimarily responsible for heat conduction. However, it was observed that the decreasing tendency
diminished in the thin film with a thickness of 100 nm, the thermal conductivity increased in the thin films
with the thickness of 30 and 50 nm (black and red dots). This is a clear sign that SPhP is an important carrierof heat conduction in thin films. It was also found that the SPhP has the mean free path in millimeter range.
This is because phonons form a mixed state with light, resulting a faster and less lossy propagation. It was
found that thin films with thickness of 30 and 50 nm are equivalently double the phonons heat conduction.
The results of this research show that SPhP contribute significantly to heat conduction in a thin film
structure, which can be the main heat dissipation mechanism. In addition to conduction, convection, andradiation, it paves the way as a fourth heat dissipation mechanism by phonons with the help of light. We
expect to overcome the heat dissipation problem in semiconductor devices that have become highly
integrated and miniaturized, furthermore, to be applied widely in the semiconductor field. It is expectedthat heat will be dissipated by using heat conduction of surface phonon polaritons to conduct the localized
and intensive heat, which will contribute to further improve the performance of the devices.
Reference： Y. Wu, J. Ordonez-Miranda, S. Gluchko, R. Anufriev, D. De Sousa Meneses, L. Del Campo,
S. Volz, and M. Nomura, "Enhanced thermal conduction by surface phonon-polaritons," Sci. Adv. 6,
eabb4461 (2020). DOI: 10.1126/sciadv.abb4461

Fig. 1. Surface phonon polaritons in a semiconductor thin film can be a heat dissipation
mechanism besides conduction, radiation, and convection. The temperature dependence ofthermal conductivities is normalized with the ones at room temperature (300 K).

69

Heat conduction control based on the wave nature of phonons
Jeremie Maire,Roman Anufriev, and Masahiro Nomura
Institute of Industrial Science, The University of Tokyo
Heat conduction control using nanostructures attracts much attention since 1990’s. Phononic crystal(PnC) is one of the most attracting structure due to not only the ballistic phonon transport but also its
possibility of band engineering by the periodic structure. A single-crystalline Si is often used for theplayground due to its long phonon mean free path. We fabricated 145-nm-thick single-crystalline Si porous
membranes by conventional top-down approach using electron beam lithography and measured thermal
conduction in the nanostructures by a custom-built micro-time-domain thermoreflectance system. We
compared heat dissipation time through various nanostructures of interest between 4 K and 295 K toinvestigate that heat conduction can be tuned by wave nature of phonons via heat wave interference.
We demonstrate that thermal conduction can be tuned by controlling the short-range order in PnC
nanostructures at low temperature. Thermal decay rates were compared with a perfect PnC with aperiodicity of 300 nm and disordered phononic structures [Fig. 1(a)]. The disorder was added to the spatial
position of holes from the perfect periodic position. Thermal conduction is decreased as the structure
approaches to the perfect crystal at 4 K. This result can be attributed to the group velocity reduction causedby the band-folding effect induced by the periodicity. However, this trend disappears around 15 K due tomore incoherent phonon scattering process at higher temperature. The temperature limit to observe thiscoherent tuning can be increased by downsizing the phononic crystal structures, but too much downsizing
will be suffered from the surface roughness of the holes. We also simulated thermal conduction in the
diffusive regime and Monte-Carlo method, but the experimentally observed behavior shows opposite trend.
Then, we constructed a simple model to explain the thermal decay rate reduction as the short-range orderapproaches to the perfect crystal. We adopted a cut-off frequency to distinguish the coherent and incoherent
regimes. We assumed that the contribution of thermal phonons in the coherent regime is negligible due tothe strong group velocity reduction and incoherent thermal phonons mainly contribute to the thermal
conduction. The surface roughness play an important role in the coherent heat conduction. The simulation
curve with a surface roughness of 1.5 nm reproduces experimental data points, and the roughness value
shows a good agreement with the obtained value by a high-resolution scanning electron microscope.
Reference： J. Maire, R. Anufriev, A. Ramiere, R. Yanagisawa, S. Volz, and M. Nomura, “Heat conduction
tuning by wave nature of phonons,” Sci. Adv. 3, e1700027 (2017). DOI：10.1126/sciadv.1700027

Fig. 1. (a) SEM images of suspended Si phononic structures (period: 300 nm). Position of holes are shiftedin random directions for disordered structures. (b) Disorder dependence of thermal decay time at 3.7 and
295 K. The heat conduction can be controlled by the disorder in the phononic crystals at low temperature.

70

Ultrasonic pulse compression in a phononic crystal waveguide
Megumi Kurosu1,2, Daiki Hatanaka1, and Hiroshi Yamaguchi1,2
NTT Basic Research Laboratories, 2 Graduate School of Science, Tohoku University,

１

When a bell is hit, it resonates at a specific frequency which depends on its shape and size. A structurethat has resonance with respect to mechanical vibration is called a mechanical resonator. A tinymechanical resonator created using cutting-edge nano-fabrication technology has high resonancefrequency in ultrasonic regime since resonance frequency inversely depends on its size. Latest smart
phones can send and receive information through surface acoustic filters and oscillation devices which
utilize high-frequency mechanical oscillations.
NTT research group has developed an acoustic artificial crystal, called a phononic crystal, which isfabricated by using nano-fabrication techniques and proceeded with the research of ultrasonic wave
manipulation by using this phoninic crystal. The phononic crystal has thin and long membrane structure,
called a waveguide, which transfers small mechanical oscillation as shown in Fig 1. The ultrasonicmechanical oscillation is generated by applying pulsed AC voltage at the metal electrode located at one
end of the waveguide because this device is composed of piezoelectric GaAs/AlGaAs heterostructure.
The ultrasonic mechanical pulses travel along the waveguide and are detected optically by Doppler
interferometer at another end of the waveguide. In this way we have investigated the frequency
dependence of ultrasonic pulses in a phononic crystal waveguide, i.e. group velocity dispersion (GDV).
In general, pulse shape broadens during propagation since a pulse contains different frequencies and adifferent-frequency wave travels at different velocity due to GVD. This effect is unfavorable for efficient
wave guiding. However, we have utilized this disadvantage to demonstrate temporal focusing of theultrasonic pulse. Instead of using unchirped pulses, chirped pulses are injected to cancel out the effect of
GVD. As a result, the traveling pulses are temporally focused and the peak amplitude was amplified (Fig.
2). This pulse manipulation technique enables the timing and location of focusing to be controlled bychanging the excitation frequency, input pulse width and chirp parameters, which pave the way to achieve
the miniaturization and high integration of communication devices.
In this research, we have realized the temporal and spatial focusing of ultrasonic elastic waves in aphononoic crystal waveguide. Furthermore, this device is composed of GaAs/AlGaAs heterostructures,
which is expected to be applied to hybrid structure with electron, spin and photon systems.
References M. Kurosu, D. Hatanaka, K. Onomitsu, and H. Yamaguchi, “On-chip temporal focusing ofelastic waves in a phononic crystal waveguide ” , Nature Communications 9, 1331 (2018). DOI:
10.1038/s41467-018-03726-7

1 mm

Fig. 1: A schematic of a phononic crystal
waveguide.

71

Fig. 2: Temporal evolution ofultrasonic waves.

Topological localized state of elastic wave
in one-dimensional phononic crystal
Ingi Kim1,2, Yasuhiko Arakawa3, and Satoshi Iwamoto1-3
1
RCAST, 2IIS, 3Nanoquine, The University of Tokyo
Topology is an important concept in modern condensed matter physics. The concept of band topology alsooffers an intriguing route for controlling the flow of classical waves such as light, sound, and elastic wave.
Generating topological states for such waves is the first step towards innovative devices based on topology.
In this study, we realized a topological state of elastic wave in a continuous medium having a complete
phnonic bandgap for the first time.
In a continuous medium, longitudinal-, transversal-waves as well as their mixed wave co-exist. This makes
it difficult to obtain a topological state isolated within a complete phononic bandgap in general. We designed
a quasi-one-dimensional phononic crystal (PnC) that have a complete phononic bandgap.The unit structureof the PnC is composed of two cuboids with different sizes. We found two types of structures possessing acommon bandgap with different topology by tuning the area and thickness of each cuboid. A topologicallocalized state for elastic wave is formed at the boundary between these two topologically distinct structures(Fig. 1). The presence of such a state is deterministically predicted from the bulk-edge correspondence. We
fabricated the connected structure with quartz glass (Fig. 1) and experimentally verified the presence of the
topological state by measuring the transmission of elastic wave through the structure. The measured
transmission spectrum is shown in Fig. 2 (blue curve). The result shows good agreement with thecalculation (black curve in Fig. 2). A sharp transmission peak at around 200 kHz with a Q-factor of ~5,700
is originated from the topological localization mode. We also succeeded in visualizing the spatial
distribution of the topological state by photoelastic imaging, confirming the strong confinement of elastic
wave at the boundary. The frequency of the topological elastic state can be increased simply by scaling thesize of the structure. Such high-frequency topological elastic states can be applied to high-speed acoustic
devices for signal processing and opto-mechanical devices, which can function as quantum transducers
between photons and phonons.
The paper reporting the results was selected as one of the 2018 Spotlight papers in Appl. Phys. Express.
Reference ： I. Kim, S. Iwamoto, and Y. Arakawa, “Topologically protected elastic waves in onedimensional phononic crystals of continuous media”, Appl. Phys. Express 11, 017201 (2018). DOI:
10.7567/APEX.11.01720

Fig. 1 One-dimensional phononic crystal
made of quartz (bottom) and calculated
distribution of displacement field of the
topological localized stateFig. 2 Measured (blue) and calculated(black) transmission spectra of elastic
wave

72

Control of Spin-Phonon Interaction and Photon Excitation in
Asymmetric Artificial Lattices
Hiroyasu Yamahara1, Md Sarker Shamim1, Munetoshi Seki1 and Hitoshi Tabata1
１
Graduate School of Engineering, The University of Tokyo
Rare-earth iron garnets (RIGs) are ferrimagnetic insulators whose chemical formula is R3Fe5O12 (R : rareearth elements). They have been industrially available for optical devices such as optical isolators since
they show large magneto-optical effect. On the other hand, they are unlikely to show remnant dielectric
polarization in bulk, because their crystal structures are centrosymmetric cubic. If remnant magnetizationand dielectric polarization co-exist in RIGs, simultaneous ordering of dipole and spin are expected inaddition to the magneto-electric correlation (ME-effect), which is promising material for future application
on spintronics devices. In this research, we demonstrate the coexistence of remnant magnetization anddielectric polarization in Sm3Fe5O12 (SmIG) films grown on Gd3Ga5O12 (GGG) substrates. The latticemismatch between film and substrate is −1.17%, so that the critical thickness where misfit dislocation
occurs is estimated to be 60 nm. SmIG films grown on GGG show tetragonal, strain-gradient, and cubic
structures from the interface to the surface due to the epitaxial strain and the lattice relaxation. In the straingradient region, the inhomogeneous strain can generate flexoelectric polarization, P=μ(∂u/∂x), where μ and(∂u/∂x) are flexoelectric tensor and strain-gradient, respectively. The presence of dielectric polarization in
the strain-gradient region is confirmed by a scanning nonlinear dielectric microscopy. Negatively polarized
local domains, whose size is 30 nm corresponding to the density of stacking-fault, exist in strain-gradientphase. We conclude that remnant magnetization and dielectric polarization co-exist in strain-gradient SmIG
film. Moreover, we fabricate spin wave devices using an ultra-low damping Y3Fe5O12 thin films anddemonstrate a dynamic spin wave modulation using electric current. An additional Pt stripe connected to
dc current source was integrated between a pair of coplanar waveguides to demonstrate the spin wave
resonance frequency and amplitude modulations. Electric current applied through the Pt stripe generates
local joule heating that modifies magnetic properties of the Y3Fe5O12 film, which modulates the frequency
and the amplitude of the spin wave spectra. This study presents a more convenient technique using simple
DC current, which can be extended to thermal mapping for more complex spin wave devices.
Reference：Md S. Sarker, H. Yamahara, H. Tabata, “Current-controlled magnon propagation in Pt/Y3Fe5O12
heterostructure”, Appl. Phys. Lett. Accepted. Md S. Sarker, H. Yamahara, H. Tabata, “Spin wave modulation
by topographical perturbation in Y3Fe5O12 thin films”, AIP Adv., 10, 015015 (2020).
(a)(b) t = 40 nm

SmIG

Pt

(b)
Real S21 (dB)(c) t = 60 nm

VNA
Port 2dc current source

μ0HextVNA
Port 1

Jdc

YIG

z
x

y

30µ0Hext = 40 mT
20
10
0

S12 (Reference device)
S21 (Reference device)-10 S21 (Pt striped device (Jdc = 0 A/m2))
2.1

S21 (Pt striped device (Jdc = 12 × 109 A/m2))

2.2
2.3
Frequency (GHz)

2.4

Fig. 2 (a) Schematic image of spin wave device.
(b) S21 spectra of the reference device (black),and Pt/YIG bilayer device without (blue) andwith (red) DC current through the Pt layer.

Fig. 1 (a) STEM image of strain-gradient
SmIG film. (b,c) SNDM image for tetragonal(c) and strain-gradient (b) SmIG films. Brightcolor indicates negative polarization.

73

Highly sensitive motion detection in a mechanical resonatorusing a gate-controlled quantum dot
Y. Okazaki, I. Mahboob, K. Onomitsu, S. Sasaki and H. Yamaguchi
NTT Basic Research Laboratories, Nippon Telegraph and Telephone Corporation
A mechanical resonator built into a GaAs/AlGaAs heterostructures is a promising hybrid quantum system,
which can open new avenues for coherent coupling between macroscopic mechanical motion and wide
variety of electron states formed in semiconductor quantum structures. The critical element in such ademonstration is an interface between the tiny mechanical motion of the resonator and the electronic
degrees of freedom in the quantum structure. A semiconductor quantum dot (QD) is a potential candidate
for this purpose, but the experimental realization of such systems is still in its infancy. Here we demonstrate
highly sensitive displacement transduction of a doubly clamped mechanical resonator using a QD.
In our device ( Fig.(a) ), the QD is formed at one of the clamping points of the resonator using
negatively-biased top gates ( Fig. (b) ). The motion of the fundamental flexural mode of our resonator is
detected through power spectral measurements of the QD’s current. By analyzing the temperaturedependence of thermally-driven mechanical vibrations, the minimum detectable displacement of the QD
transducer at a temperature of 80 mK is determined to be 63 fm/Hz1/2. From the results, the position
resolution is estimated to be 170 fm, which is about 70 times the zero-point quantum fluctuation for thisresonator. Furthermore, the single electron transport in the quantum dot induces a backaction onto themechanical motion, where the control of gate voltage enables the damping and even current-driven
amplification of the mechanical motion. The result takes the first step toward the coherent coupling between
mechanical resonator and electronic states, which pave the way to transfer the microscopic quantum
phenomena in low-dimensional electron systems into macroscopic mechanical objects.
Reference ： Y. Okazaki, I. Mahboob, K. Onomitsu, S. Sasaki and H. Yamaguchi, “Gate-controlled
electromechanical backaction induced by a quantum dot”, Nature Communications, 7, 11132 (2016). DOI：
10.1038/ncomms11132

Figs. (a) Optical and (b) electron micrograph of our device. A doubly-clamped mechanical resonatorof 50 µm length is fabricated from GaAs/AlGaAs heterostructure. QD are defined at the clamping
point of the resonator.

74

Nuclear spin control by a mechanical oscillator
Y. Okazaki1,2, I. Mahboob1, K. Onomitsu1, S. Sasaki1, S. Nakamura2, N. Kaneko2, and H. Yamaguchi1
1
NTT Basic Research Laboratories, Nippon Telegraph and Telephone Corporation
2
National Institute of Advanced Industrial Science and Technology
Nuclear spin is a kind of rotation of an atomic nucleus, and under a magnetic field, it shows aprecession. The precessional motion is widely detected as nuclear magnetic resonance (NMR) and isrecently promising to the application in various quantum technologies, such as highly sensitive magnetic
field sensors and quantum memory. We developed a novel architecture using a compound-semiconductor
nanostructure device to manipulate nuclear spins with a micromechanical oscillator.
The mechanical oscillator consists of a doubly clamped beam structure and is fabricated using a
piezoelectric GaAs/AlGaAs heterostructure. The piezoelectric transduction electrically actuate themechanical vibration. The motion generates periodic strain at the clamping point and the strain modifies
the quadrupole interaction between nuclear spins in the strained region. In the experiments, we observed
strain-induced NMR frequency shift as well as the sideband resonances, where the resonance was detected
at two sideband frequencies. The numerical calculation showed a good agreement with the experimental
results, indicating that the phenomenon is induced by the effect of mechanical oscillation.
Reference： Y. Okazaki, I. Mahboob, K. Onomitsu, S. Sasaki, S. Nakamura, N. Kaneko, and H. Yamaguchi,“Dynamical coupling between a nuclear spin ensemble and electromechanical phonons”, Nature Commun.
9, 2993 (2018). DOI：10.1038/s41467-018-05463-3

Fig. 1 A mechanical resonator used for controlling nuclear spins.

75Mechanical engineering of excitons in semiconductor－Demonstration of strain-mediated coupling between dark and bright states－
Ryuichi Ohta, Hajime Okamoto, Takehiko Tawara, Hideki Gotoh, and Hiroshi Yamaguchi
NTT Basic Research Laboratories, NTT Corporation,
Electron-hole pairs (excitons) in semiconductor efficiently convert electrons to photons and thus havebeen applied to various opto-electro devices, such as light sources, detectors, modulators and amplifiers.
The optical properties of excitons obey the selection rule based on their spin configurations, which resultsin the two different states. One is called as the bright state which is allowed to be optically addressed, andthe other is called as the dark state which is not available to be optically addressed. Although the dark stateis of great interest owing to its long-lived nature indicating the potential for quantum information andspintronic applications, its optical inaccessibility limits its practical usage. Magnetic field enables thecoupling between dark and bright states and has been used to allow the optical access to dark state via brightstate. However, dynamic control of their coupling is technically challenging by magnetic field because
strong magnetic field does not rapidly change. Here, we demonstrate a new scheme to couple the dark state
to bright state allowing the optical addressing the dark state by means of time-varying strain of a
micromechanical resonator. The uniaxial strain induced by the mechanical motion breaks the symmetry of
the crystal field and mixes dark and bright excitons via deformation potential. In contrast to the magnetic
approach, this scheme has an advantage of high-speed switching of the coupling, which will lead to thememory and logic applications based on the dark excitons.
We fabricated a mechanical resonator from GaAs/AlGaAs heterostructures containing excitons (Fig. 1).
To investigate the strain effect for excitons, we continuously drove the mechanical resonator and applied
pulse laser whose repetition synchronized to the driving frequency. By changing the relative phase of pulse,
we could obtain the spectra at arbitral timing of the mechanical motion. As shown in Fig. 2(a), themechanical strain modulated the exciton energies, and caused avoided-crossing between dark and brightstates, which is sign of the coupling between them. The photoluminescence from the dark state wasoriginally zero, but was enhanced by the strain-mediated coupling to the bright state. It indicates that the
optical access to the dark state became possible via the bright state. This experimental result was well
reproduced by numerical analysis based on semiconductor band modes (Fig. 2(b)).
Reference： R. Ohta, H. Okamoto, T. Tawara, H. Gotoh, and H. Yamaguchi, “Dynamic control of thecoupling between dark and bright excitons with vibrational strain”, Physical Review Letters, 120, 267401.
(2018). DOI：10.1103

Fig.1 Scanning electron microsopy image ofthe mechanical resonator based on the
GaAs/AlGaAs heterostructure.

Fig.2(a) Experimental andstroboscopic photoluminescencemechanical motion.

76(b) numerical
spectra with

Ising spin coupling in electromechanical resonators
I. Mahboob, H. Okamoto, and H. Yamaguchi
NTT Basic Research Laboratories, Nippon Telegraph and Telephone Corporation
A parametric oscillator is the harmonic resonator in which the oscillations are driven bymodulating the force constant at the frequency that differs from the resonance. One of the simplest examples
is the child swing and nowadays they are used in many experiments such like microwave amplifier andoptical wavelength convertors. In degenerate parametric oscillators, the force constant modulation is madeat twice the resonance frequency and two different phase states appear in the oscillation reflecting thebroken half-period time translational symmetry. The bistability can be assigned to a classical spin-1/2
system and it is proposed to use a mutually coupled resonator network for numerial calculation. This
coupled resonator system is called as “Ising machine”, and used for efficiently obtaining the solution of
optimization problems.
In this work, we demonstrated the Ising coupling between two electromechanical parametricoscillation modes. We fabricated a coupled GaAs/AlGaAs piezoelectric beam resonators and investigatedthe correlation of phase states between two flexural vibration modes. Fig. 1(a) shows the schematic
illustration of experimental setup. Two alternate voltages at 2ωS and 2ωA are applied to excite parametricoscillation in two modes. The pump voltage at ωp is applied to induce the coupling. Fig. 1(b) shows thecorrelation coefficient for phase states between two modes. By changing the phase of pump voltage, thephase of coupling can be continuously controlled from antiferromagnetic to ferromagnetic.
Reference： I. Mahboob, H. Okamoto, and H. Yamaguchi, “An electromechanical Ising Hamiltonian”, Sci.
Adv. 2 : e1600236 (2016). DOI：10.1126/sciadv.1600236.

Fig. 1 (a) A schematic illustration of experimental setup. The symmetric and antisymmetric vibration
modes are both parametrically excited by VS(2ωS) and VA(2ωA) and the pump voltage VP(ωP) is also
applied for their coupling. (b) The correlation coefficient measured between two modes as a functionof the phase of pump voltage.

77

Fast and Sensitive Bolometric Terahertz Detection at Room
Temperature through Thermomechanical Transduction
Ya Zhang1, Yasuyuki Watanabe1, Suguru Hosono1, Boqi Qiu1, Tianye Niu1, Ryoka Kondo1, Naomi Nagai1,
and Kazuhiko Hirakawa1,2１Institute of Industrial Science, University of Tokyo, 2INQIE, University of Tokyo
Terahertz (THz) electromagnetic waves interact with various substances and are suitable forinvestigating their structures and functions. In general, broadband THz detectors use detection elements
which once convert THz radiation into heat and then read out the temperature rise of the detection element
as a signal (bolometers). However, in order to obtain high sensitivities, bolometers are often cooled down
to extremely low temperatures. Therefore, for wider applications of THz technologies, the development of
uncooled, high-sensitivity, and high-speed THz detectors is necessary.
Microelectromechanical system (MEMS)-based resonators are very attractive for sensing applications.
High quality (Q)-factors of the MEMS resonators even at room temperature are advantageous for detecting
small changes in resonance frequency. It has been demonstrated that shifts in resonance frequencies can beused to detect mass, charge, spin orientation, temperature, and infrared radiation.
In this work, we have proposed and demonstrated a very sensitive, room temperature thermistor thatconsists of a doubly clamped GaAs MEMS beam resonator. It detects a temperature change by measuring
a shift in its resonance frequency induced by thermal expansion of the beam. The MEMS thermistor senses
a temperature change by measuring a shift in the mechanical resonance frequency and can detect atemperature change as small as ~1 μK (noise equivalent temperature difference ~1 μK/√Hz) even at room
temperature. This unprecedented temperature sensitivity of the MEMS resonator is advantageous not only
for realizing high sensitivity but also achieving high-detection speed in the order of several kHz, which ismore than 100 times faster than other uncooled THz thermal sensors. We have achieved an electrical noise
equivalent power (NEP) as low as ~90 pW/√Hz, which is close to the fundamental limit set by the thermal
fluctuation noise. Furthermore, we note that the dynamic range of the present MEMS bolometer is greaterthan 107. The present MEMS bolometers are fabricated by the standard semiconductor fabrication process
and are well suited for making detector arrays for fast THz imaging.
Reference： Ya Zhang, Suguru Hosono, Naomi Nagai, Sang-Hun Song, and Kazuhiko Hirakawa, “Fast andsensitive bolometric terahertz detection at room temperature through thermomechanical transduction”,
Journal of Applied Physics 125, 151602 (2019); https://doi.org/10.1063/1.5045256, etc.

Fig. 1 (a) MEMS double-sided beam structure manufactured using a GaAs / AlGaAs semiconductor
heterostructure, (b) shift of resonance frequency with respect to input power to the MEMS beam, and (c)phase-locked loop (PLL). Signal readout circuit

78

Focusing Terahertz Radiation on a Single Molecule by
Nanogap Electrodes and Observation of Enormous Terahertz
Field Enhancement EffectKenji Yoshida1, Kenji Shibata1, and Kazuhiko Hirakawa1,2Institute of Industrial Science, University of Tokyo, 2INQIE, University of Tokyo１

The use of molecules to electronic devices has great potential. We have fabricated extremely smalltransistors (Fig. 1(a)) with a single molecule as an active region and investigated how electrons aretransferred through such a single molecule. In particular, we have been working on the elucidation andcontrol of the electron dynamics using terahertz (THz) radiation.
Since the wavelength of THz radiation is typically as long as 100 µm, we have a problem that theinteraction between the THz radiation and a single molecule is extremely small. By using the source/drainelectrode of the single molecule transistor structure as an antenna, we have successfully focused the THz
radiation on a single C60 fullerene molecule, exceeding the diffraction limit by 100,000 times.
Figure 1(b) shows a color map of the conductivity of a C60 single molecule transistor. When the sample
was illuminated with a THz laser light with a wavelength of 119 µm, we observed that, in addition to thetunnel conduction through an ordinary molecular orbital, equally spaced new conduction channels areformed above and below it by integer multiples of the THz photon energy (10 meV). When the quantum
level in the molecule is shaken by a strong THz electric field, the level is split into equally spaced photonside bands, forming new conduction channels (photon-assisted tunneling). Furthermore, the formation ofphoton sidebands means that the single C60 molecule sandwiched between the nanogap electrodes feels avery intense THz electric field in the order of hundreds of kV/cm. In this experiment, the THz electric fieldoutside the sample is only about several V/cm, which means that the THz electric field is enhanced by
100,000 times by the nanogap electrode.
In this study, we have shown that nanogap electrodes are suitable for clarifying the THz dynamics of nmscale nanostructures and that they can create a huge electric field enhancement effect in the order of 100,000
times. Nanogap electrodes provide a valuable opportunity to explore new physics in atomic-scale systems.
Reference ： K. Yoshida, K. Shibata, and K. Hirakawa, Phys. Rev. Lett. 115, 138302 (2015); DOI:
https://doi.org/10.1103/PhysRevLett.115.138302

Fig. 1 (a) Schematic illustration of a single molecule transistor structure, (b) Coulomb stability diagram ofa single C60 molecule transistor when terahertz radiation is off (left) and on (right)

79

Observation of Ultrafast Motion of a Single Molecule byTerahertz Spectroscopy
Shaoqing Du1, Kenji Yoshida1, Ya Zhang1, and Kazuhiko Hirakawa1,2Institute of Industrial Science, University of Tokyo, 2INQIE, University of Tokyo

１

Terahertz (THz) spectroscopy has been developed as a powerful tool for clarifying vibrational dynamics
of various kinds of molecules. Because of the long-wavelength nature of the THz electromagnetic waves(typically, ~100 µm), however, spectral information was obtained only for an ensemble average of a huge
number of molecules. It has been a formidable challenge to by far exceed the diffraction limit and focus theTHz radiation on single molecules. Furthermore, the number of mobile charges that can absorb THz
radiation in a single molecule is very few, which makes THz absorption extremely small.
Here, we report on the THz spectroscopy of single molecules by using the single molecule transistor(SMT) geometry. The SMT is a structure in which a single molecule is captured in a sub-nm gap createdbetween the source and drain metal electrodes fabricated on a field plate. Using the source and drainelectrodes separated by a sub-nm gap as a THz antenna, we focus THz radiation onto a single fullerene
molecule trapped in the nanogap electrodes. Furthermore, we can detect a very small absorption bymeasuring the THz-induced photocurrent by the same electrodes.
We have studied the dynamics of a single C60 (fullerene) molecule with a THz radiation using this SMT
structure. We could detect ultrafast motion of a single molecule on a time scale of about psec. Such THz
measurements have become possible only when both atomic-level ultrafine fabrication technology andultrahigh-speed time-domain terahertz measurement technology become available. Furthermore, we havefound that the observed THz peaks are finely split into two, reflecting the difference in the van der Waals
potential profile experienced by the C60 molecule on the metal surface when the number of electron on themolecule fluctuates between N and N+1 during the single electron tunnelling process. Such an ultrahighsensitivity to the electronic/vibronic structures of a single molecule upon charging/discharging a single
electron has been achieved by using metal source-drain electrodes separated by a sub-nm gap as a THz
antenna and detecting the THz-induced photocurrent. This novel scheme provides a new opportunity forinvestigating ultrafast THz dynamics of sub-nm scale systems.
Reference： S.Q. Du, K. Yoshida, Y. Zhang, I. Hamada, and K. Hirakawa, “Terahertz dynamics of electronvibron coupling in single molecules with tunable electrostatic potential”, Nature Photonics, 12, 608–612(2018), https://doi.org/10.1038/s41566-018-0241-1

Fig. 1 (a) Single molecule terahertz spectrum system using nanogap electrode and femtosecond laser pulse,(b) Molecular vibration spectrum in which C60 molecule moves its center of gravity on a gold electrode80

THz-field-induced Macroscopic Ionic Flow in a Superionic
Conductor Na+ β-Alumina
Jun Takeda
Graduate School of Engineering Science, Yokohama National University
Recent advances in terahertz (THz) technology have provided possibilities for novel nonperturbativeand nonlinear processes in solids with ultimate spatiotemporal resolutions. However, most of theseprocesses are dominated by the ultrafast electron dynamics, and the nonlinear responses of ions haverarely been investigated because of the greater mass of ions compared to that of electrons.
In the present study, we show that a field-driven ionic motion is induced by applying single-cycle
intense THz fields, generating a macroscopic current that depends on the polarity of the applied THz
fields. We used stoichiometric crystalline Na+ β-alumina, which is a superionic conductor wherein Na+
ions move in the two-dimensional space between the spinel layers perpendicular to the c axis (Fig. 1). The
ionic conductivity of Na+ β-alumina is as large as 1 S/m at room temperature.
By applying single-cycle THz pulses with a peak field strength ranging from 15 to 300 kV/cm, we
could observe the THz-induced macroscopic direct current using a conventional ammeter at high electricfield strengths, indicating that the motion of Na+ ions transfers from the vibration mode to the conduction
mode (Fig. 2). We believe that our finding — macroscopic current flow in a superionic conductor driven
by single-cycle THz pulses — may pave the way for future ultrafast ionics.
Reference： Y. Minami, B. Ofori-Okai, P. Sivarajah, I. Katayama, J. Takeda, K. A. Nelson, and T.
Suemoto, Physical Review Letters, 124, 147401 (2020). DOI: 10.1103/PhysRevLett.124.147401

Fig. 1 Setup used for measuring theTHz-field-induced ionic current using anammeter.

Fig. 2 (a) THz intensity dependence of the ioniccurrent measured using an ammeter. (b)Configuration of the ion and local potential inreal space for Na+ β-alumina at room temperature.
The intense THz electric field leads to the ionicconfiguration from the vibration mode to the
conduction mode.

81

Terahertz Spectroscopy of a Single Carbon Nanotube
Takuma Tsurugaya1, Kenji Yoshida1, Maki Shimizu2, Yoshikazu Homma2, and Kazuhiko Hirakawa1,3
１Institute of Industrial Science, University of Tokyo, 2Tokyo University of Science,
3
INQIE, University of Tokyo
Carbon nanotubes (CNTs) are unique electronic materials of one-dimensional character and have been
extensively studied as promising materials for optoelectronic devices. When potential barriers at two
locations are introduced, they behave as quantum dots. We formed source and drain electrodes with a 100
nm-gap on a single metallic carbon nanotube grown from a catalyst and fabricated a single carbon nanotube
quantum dot (QD) transistor (Fig. 1(a)). Figure 1(b) is the color-coded differential conductivity of thissample as a function of the gate voltage and the source-drain voltage. From the observed diamond-shaped
patterns called Coulomb diamonds, we can tell that this sample works as a single electron transistor.
This sample is illuminated with terahertz radiation and the photocurrent spectra induced by the THz
radiation are shown in Fig. 1(c). By using this method, we have successfully detected THz spectral signals
from individual CNTs.
We have found that sharp resonant peaks appear in the THz spectra and their energies are quantitatively
in agreement with the sublevel energy spacing expected from the linear band dispersion in metallic CNTs,
which indicates that the observed peaks originate from the intersublevel transitions between two
neighboring quantized orbitals in the CNT-QDs. The linewidth of the photocurrent peaks is as narrow as
0.3 meV, which is consistent with the tunnel escape time from the CNT-QDs to the electrodes. The
linewidth of the photocurrent peaks is governed by the tunnel coupling with the electrodes, suggesting thatelectrons in the CNT QD have a scattering time comparable to or longer than 10 ps. The observation of a
sharp absorption peak at the bare quantization energy was not consistent with the Tomonaga-Luttinger
liquid theory.
Reference: Takuma Tsurugaya, Kenji Yoshida, Fumiaki Yajima, Maki Shimizu, Yoshikazu Homma, andKazuhiko Hirakawa, “Terahertz Spectroscopy of Individual Carbon Nanotube Quantum Dots”, Nano
Letters, 19, 242–246 (2019), https://doi.org/10.1021/acs.nanolett.8b03801

Fig. 1 (a) AFM image of a sample in which nanogap electrodes are formed on metallic single carbon
nanotubes, (b) color mapping of conductivity of single carbon nanotube transistors, (c) measured terahertz
excitation light. Current spectrum

82

Phase-controlled THz-field-driven Scanning TunnelingMicroscopy－Ultrafast electron manipulation with tailor-made single-cycle THz near fields－
Jun Takeda
Graduate School of Engineering Science, Yokohama National University
Light-field-driven processes occurring under conditions far beyond the diffraction limit of the light canbe manipulated by harnessing spatiotemporally tunable near fields. A tailor-made carrier envelope phase(CEP) in a tunnel junction formed between nanogap electrodes allows to precisely manipulate theseprocesses. Here, we demonstrate that desirable phase-controlled near fields can be produced in a tunnel
junction via terahertz scanning tunneling microscopy (THz-STM) with a broadband THz phase shifter(Fig. 1). Measurements of the phase-resolved sub-cycle electron tunneling dynamics revealed an
unexpected large CEP shift between far-field and near-field single-cycle THz waveforms, which stems
from the wavelength-scale feature of the tip-sample configuration. By using a dual-phase double-pulse
scheme (Fig. 2), the electron tunneling was coherently manipulated over the femtosecond timescale. Our
new prescription — in situ tailoring of single-cycle THz near fields in a tunnel junction — will offer
unprecedented control of electrons for ultrafast atomic-scale electronics and metrology.
Reference： K. Yoshioka, I. Katayama, Y. Arashida, A. Ban, Y. Kawada, K. Konishi, H. Takahashi, and J.
Takeda, Nano Letters, 18, 5198-5204 (2018). DOI: 10.1021/acs.nanolett.8b02161

Fig. 1 Schematic of phase-controlled THz-STM with a broadband THz phase shifter composed by three
optical elements: quarter wave plate, half wave plate and wire grid polarizer. By rotating the half-wave
plate, the CEP of THz near fields can be precisely tuned from 0 to 2π.
Fig. 2 Schematic of ultrafast electron manipulation with CEP- and delay-controlled double THz pulses.
By using sinusoidal THz near fields, the bidirectional tunnel current can be flowed on the femotosecond
timescale.

83Probing microscopic property of topological protection
Katsushi Hashimoto1,2, Toru Tomimatsu1, and Yoshiro Hirayama1,2
Graduate School of Science, Tohoku University、2CSIS, CSRN, Tohoku University

１

Topological materials, which are expected as materials for next-generation information processing
devices, have the property that information carried by electrons is less to be disturbed by impurities thanconventional materials. We succeeded in visualizing the special insulating region by disturbing the quantum
Hall state, which is one of the topologically protected electronic states, with an excess current and observing
with a scanning gate microscope. As shown in FIG. 1 (a), the quantum Hall insulating region (white andbright region) appears along the left-side the Hall bar edge, and moves to the interior of the Hall bar withbringing the electron filling factor ν closer to an integer value. By comparing the filling factor dependenceof the position of this insulating region with the theoretical calculation (Fig. 1 (b)), it is demonstrated thatthe topologically protected microscopic state is maintained even under disturbance such as excess current.
On the other hand, when a larger current is applied, the observed filling factor dependence (Fig. 2 (a) (b))
disappears (Fig. 2 (c) (d)) due to breakdown of the quantum Hall state.
These results provide a new method for exploring the microscopic state created by topologicaluniversality, and is expected to be applied to various topological quantum state observations in the future.
It can contribute to the search for information processing device materials, which are more robust against
disturbance.
Reference ： K. Hashimoto, T. Tomimatsu, S. Taninaka, S. Nomura, and Y. Hirayama, “Probing the
breakdown of topological protection: Filling-factor-dependent evolution of robust quantum Hall
incompressible
phases”,
PhysicalReview
Research,
2,
013128.
(2020).
DOI ：https://doi.org/10.1103/PhysRevResearch.2.013128

Fig. 1 (a) The electron filling factor dependence ofthe quantum Hall insulating region (bright white
region) appearing at the hole bar edge (broken line).
(B) Comparison of the center position (point) andwidth (horizontal line) of the insulating region withthe one deduced by theoretical calculation。

84

Fig. 2The electron filling factor dependence (a)(b) of the quantum Hall insulating region
observed by the current under the excess
current (0.5-1.0 µA) disappears under thelarger excess current (2.3-2.5 µA) (c) (d).

Scanning Nuclear Resonance Microscope－Microscopic MRI of spin state in quantum structure－
Katsushi Hashimoto1,2, Toru Tomimatsu1, and Yoshiro Hirayama1,2
Graduate School of Science, Tohoku University、2CSIS, CSRN, Tohoku University

１

MRI (Magnetic Resonance Imaging) has been widely used for diagnostic imaging of diseases in
the medical field. To detect a small disease, it is necessary to display MRI with fine pixels, but it is currently
difficult to perform high-resolution diagnosis in which the pixel spacing is tens of micrometers or less,which is smaller than that of hair. Even in semiconductor devices with quantum structures, nuclear spinresonance, which is the core technology of MRI, is used as a powerful tool for investigating the spin stateof quantum structures. However, when using MRI for nano- to micron-scale confined structures such as
semiconductor devices, in addition to the resolution problem described above, the question is how to extract
nuclear spin resonance signals from quantum structures embedded in semiconductors.
In this work, we developed a scanning probe incorporated with a resistively detected nuclear
resonance technique and succeeded in microscopically probing the nuclear resonance signal from asemiconductor quantum device. This was demonstrated using the quantum Hall state that emerges in thetwo-dimensional electron system confined in the semiconductor quantum structure with a strong magnetic
field. From the nuclear spin resonance signal obtained at each point, we extracted not only the signal
intensity, but also the shift of the resonance frequency called the Knight shift, which indicates the electron
polarization around the nuclear spin to obtain spin information for both the nucleus and the electron. By
mapping these signal strength and resonance frequency shifts, we succeeded in clearly observing the
distribution of nuclear spin polarization that occurs in a semiconductor quantum structure with a thicknessof several tens of nanometers (Fig. 1) and the spatial changes of electron spin polarization at a few microns
range (Fig. 2). Figure 1 shows that the region where the nuclear spins are polarized changes significantly
from one end of the hole bar sample to the center with changing the quantum Hall state. In addition, in theelectron spin polarization distribution in Fig. 2, it was found that the spatial change in electron spinpolarization became more severe as the current increased.
The results of this research provide a new technology that clearly reflects the distribution ofelectron and nuclear spins in quantum structures, and are expected to be applied to the spin states of various
quantum structures and MRI diagnosis of quantum devices in the future.
Reference： K. Hashimoto, T. Tomimatsu, K. Sato, and Y. Hirayama, “Scanning nuclear resonance imaging
of a hyperfine-coupled quantum Hall system”, Nature Communications, 9, 2215. (2018). DOI ：10.1038/s41467-018-04612-y

Fig. 2 Color scale images of electron spinpolarization Pe obtained at different electric
currents (indicated above the images) flowing
through the sample.

Fig. 1 Image of nuclear spin resonance signal
intensity (right) in different quantum Hall
states (shown below) obtained in the Hall-bar
sample (left).

85

５ Achievements
5-1 Publications

2015
1. A. Kaskela, K. Mustonen, P. Laiho, Y. Ohno, and E. I. Kauppinen, Toward the Limits of Uniformity of Mixed Metallicity SWCNT TFT Arrayswith Spark-Synthesized and Surface-Density-Controlled Nanotube Networks, ACS Appl. Mater. Interfaces, 7, 2015, 28134, DOI:
10.1021/acsami.5b10439.
2. Y. Anno, K. Takei, S. Akita, T. Arie, Enhancing the Thermoelectric Device Performance of Graphene Using Isotopes and Isotopic
Heterojunctions, Adv. Electron. Mater., 1, 2015, 1500175, DOI: 10.1002/aelm.201500175.
3. S. Baba, J. Sailer, R. S. Deacon, A. Oiwa, K. Shibata, K. Hirakawa, and S. Tarucha, Superconducting transport in single and parallel double InAs
quantum dot Josephson junctions with Nb-based superconducting electrodes, Applied Physics Letters, 107, 2015, 222602, DOI:
10.1063/1.4936888.
4. Y. Zhang, K. Shibata, N. Nagai, C. Ndebeka-Bandou, G. Bastard, and K. Hirakawa, Gate-controlled terahertz single electron photovoltaic effectin self-assembled InAs quantum dots, Applied Physics Letters, 107, 2015, 103103, DOI: 10.1063/1.4930023.
5. H. Wang, C. Yamada, J. Liu, B. Liu, X. Tu, M. Zheng, C. Zhou, and Y. Homma, Re-growth of single-walled carbon nanotube by hot-wall andcold-wall chemical vapor deposition, Carbon, 95, 2015, 497, DOI: 10.1016/j.carbon.2015.08.039.
6. H. Shirae, D. Y. Kim, K. Hasegawa, T. Takenobu, Y. Ohno, and S. Noda, Overcoming the quality–quantity tradeoff in dispersion and printingof carbon nanotubes by a repetitive dispersion–extraction process, Carbon, 91, 2015, 20, DOI: 10.1016/j.carbon.2015.04.033.
7. Z. Han, K. Kohno, H. Fujita, K. Hirakawa, and H. Toshiyoshi, Tunable terahertz filter and modulator based on electrostatic MEMS reconfigurable
SRR array, IEEE Journal of Selected Topics in Quantum Electronics, 21, no. 4, 2015, 1, DOI: 10.1109/JSTQE.2014.2378591.
8. H. Tanaka, Y. Ohno, and Y. Tadokoro, Angular Sensitivity of VHF-Band CNT Antenna, IEEE Trans. Nanotechnol., 14, 2015, 1112, DOI:
10.1109/TNANO.2015.2477813.
9. Hiroshi Tomizawa, Tomohiro Yamaguchi, Seiji Akita, Koji Ishibashi, Fabrication and characterization of tunnel barriers in a multi-walled carbon
nanotube formed by Argon atom beam irradiation, J. Appl. Phys., 118, 2015, 44306, DOI: 10.1063/1.4927615.
10. M. Ito, Y. Ito, D. Nii, H. Kato, K. Umemura, and Y. Homma, The Effect of DNA Adsorption on Optical Transitions in Single Walled Carbon
Nanotubes, J. Phys. Chem. C., 119, 2015, 21141, DOI: 10.1021/acs.jpcc.5b05087.
11. Y. Matsuzaki, and H. Tanaka, Quantum Zeno Effect in an Unstable System with NMR, J. Phys. Soc. Jpn, 48, 2015, 103001, DOI:
10.7566/JPSJ.85.014001.
12. N. Mori, R. J. A. Hill, A. Patanè, and L. Eaves, Monte Carlo study on anomalous carrier diffusion in inhomogeneous semiconductors, Journalof Physics: Conference Series, 647, 2015, 12059, DOI: 10.1088/1742.
13. Y. Kobayashi, T. Ishida, Y. Miyata and Y. Shinoda, Highly crystalline graphene formation from graphene oxides by ultrahigh temperatureprocess using solar furnace, MRS Proceedings, 1786, 2015, 31, DOI: 10.1557/opl.2015.765.
14. R.S. Deacon, A. Oiwa, J. Sailer, S. Baba, Y. Kanai, K. Shibata, K.Hirakawa, S. Tarucha, Cooper pair splitting in parallel quantum dot Josephson
junctions, Nature Communications, 6, article no. 7446, 2015, 1, DOI: 10.1038/ncomms8446.
15. S. Souma, A. Sawada, H. Chen, Y. Sekine, M. Eto, and T. Koga, Spin Blocker Using the Interband Rashba Effect in Symmetric Double Quantum
Wells, Physical Review Applied, 4, 2015, 34010, DOI: 10.1103/PhysRevApplied.4.034010.
16. T. Tanaka*, P. Knott*, Y. Matsuzaki*, S. Dooley, H. Yamaguchi, W. J. Munro, and S. Saito (*equally contribution), Proposed Robust
Entanglement-Based Magnetic Field Sensor Beyond the Standard Quantum Limit, Physical Review Applied, 115, 2015, 170801, DOI:
10.1103/PhysRevLett.115.170801.
17. Y. Zhang, K. Shibata, N. Nagai, C. Ndebeka, Probing many-body quantum states in single InAs quantum dots: Terahertz and tunnelingspectroscopy, Physical Review B, 91, 2015, 241301(R), DOI: 10.1103/PhysRevB.91.241301.
18. K. Yoshida, K. Shibata, and K. Hirakawa, Terahertz Field Enhancement and Photon-Assisted Tunneling in Single-Molecule Transistors,
Physical Review Letters, 115, 2015, 138302, DOI: 10.1103/PhysRevLett.115.138302.
19. S. Ishida, Y. Anno, M. Takeuchi, M. Matsuoka, K. Takei, T. Arie, S. Akita, Highly photosensitive graphene field-effect transistor with opticalmemory function, Sci. Rep., 5, 2015, 15491, DOI: 10.1038/srep15491.
20. H. Tanaka, R. Arima, M. Fukumori, D. Tanaka, R. Negishi, Y. Kobayashi, S. Kasai, T. Yamada, T. Ogawa, Method for Controlling Electrical
Properties of Single-Layer Graphene Nanoribbons via Adsorbed Planar Molecular Nanoparticles, Scientific Reports, 5, 2015, 12341, DOI:
10.1038/srep12341.
21. Z. Han, K. Kohno, H. Fujita, K. Hirakawa, H. Toshiyoshi, Terahertz devices with reconfigurable metamaterials by surface micromachining
technique, 電気学会論文誌 E（センサ・マイクロマシン部門誌）, 135, no.11, 2015, 450, DOI: 10.1541/ieejsmas.135.450.
2016
22. K. Hashimoto, T. Tomimatsu, S. Shirai, S. Taninaka, K. Nagase, K. Sato, and Y. Hirayama, Scanning nuclear electric resonance microscopyusing quantum-Hall-effect breakdown, AIP Advances, 6, 2016, 75024, DOI: 10.1063/1.4960430.
23. Akira Hida, Takayuki Suzuki, and Koji Ishibashi, Detecting the formation of single-walled carbon nanotube rings by photoabsorption
spectroscopy, Appl. Phys. Express, 9, 2016, 85102, DOI: 10.7567/APEX.9.085102.
24. M. Villiers, I. Mahboob, K. Nishiguchi, D. Hatanaka, A. Fujiwara, and H. Yamaguchi, An electromechanical displacement transducer, Appl.
Phys. Express, 9, 2016, 86701, DOI: 10.7567/APEX.9.086701.
25. M. Nomura, J. Nakagawa, K. Sawano, J. Maire, and S. Volz, Thermal conduction in Si and SiGe phononic crystals explained by phonon mean
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5-2 Major invited talks
International conference2015
1. J. Hirotani, R. Matsui, S. Kishimoto and Y. Ohno, Large-scale characterization of carbon nanotube thin-film transistors, NT15 Satellite Symposia(Third Carbon Nanotube Thin Film Electronics and Applications Satellite), 2015
2. J. Ishi-Hayase, Orientation and Position-controlled Nitrogen-Vacancy Centers in CVD Diamond grown on Micropatterned (001) Sybstrate,
Diamond Quantum Sensing Workshop 2015, 2015
3. J. Ishi-Hayase, H. Watanabe, K. M. Itoh, Control of position and orientation of nitrogen-vacancy centers in CVD-grown diamond thin film, 28th
International Conference on Defects in Semiconductors (ICDS 2015), 2015
4. J. Ishi-Hayase, H. Watanabe, K. M. Itoh, Engineered nitrogen vacancy centers in diamond for quantum sensing, EMN Meeting on Vacuum
Electronics, 2015
5. J. Ishi-Hayase, H. Watanabe, K. M. Itoh, Spatially selective creation of nitrogen-vacancy centers with preferential orientation in an isotopicallypurified diamond thin film, XIV International Conference on Quantum Optics and Quantum Information (ICQOQ'2015), 2015
6. K. Akiba, S. Kanasugi, T. Yuge, K. Nagase, and Y. Hirayama, Optically induced nuclear spin polarization in the quantum Hall regime,
International Workshop : Quantum Nanostructures and Electron-Nuclear Spin Interactions , 2015
7. Y. Ohno, Carbon nanotube thin films for flexible and formable electronics, 4th International Conference and Exhibition on Materials Scienceand Engineering, 2015
8. Y. Ohno, Carbon nanotube flexible devices for wearable healthcare electronics, 5th International Conference on Nanotek & Expo, 2015
9. Y. Ohno, Electronic and optoelectronic device applications of carbon nanotube thin films, Nanotechnology-2015, 2015
10. Y. Ohno, Wafer-scale investigation of electrical characteristics of carbon nanotube thin-film transistors, Pre-NT15 Workshop of Carbon
Nanotubes and Graphene at U Tokyo, 2015
11. Y. Ohno, Carbon nanotube thin film-based transistors and biosensors for flexible healthcare devices, The 6th A3 Symposium on Emerging
Materials Nanomaterials for Electronics, Energy, and Environment, 201512. Y. Ohno, Bio-electronics applications of carbon nanotube thin film, The International Chemical Congress of Pacific Basin Societies,
PACIFICHEM, 2015
13. Y. Ohno, Flexible bio-electronics applications of carbon nanotube thin films, The International Conference on Small Science, 2015
14. Yoshiro Hirayama, Highly-sensitive Resistively-Detected Nuclear–Magnetic -Resonance in Compound Semiconductor Quantum Systems, 1stInternational conference on “Physics for sustainable development and Technology” (ICPSDT-2015) , 201515. Yoshiro Hirayama, Nuclear spin polarization and manipulation in semiconductor quantum systems, EMH HongKong Meeting, 2015
16. Yoshiro Hirayama, Nuclear spin polarization and detection in quantum Hall systems, Sweden-Japan QNANO Workshop, 201517. Yoshiro Hirayama, Nuclear spin polarization and manipulation in quantum Hall systems, The 2015 Gordon Godfrey Workshop on Spins andStrongcorrelations, 2015

97

2016
18. Akihito Soeda, Universal controllization--its no-go and remedy for projective measurement of energy, Quantum Information Science Workshop,
2016
19. Daiki Hatanaka, Imran Mahboob, Koji Onomitsu, Hiroshi Yamaguchi, Electromechanical Phononic Crystal, 20th International Vacuum
Congress (IVC-20), 201620. H. Yamaguchi, I. Mahboob, H. Okamoto, Two-mode nonlinear electromechanics, Opto- and Electro-mechanical Technologies 2016
(OET2016), 201621. Hiroshi Yamaguchi, Daiki Hatanaka, Yuma Okazaki, and Imran Mahboob1, Piezoelectric phonon manipulation in electromechanical resonators
and waveguides, SPICE Workshop Quantum Acoustics, 201622. Jun Kobayashi , An ytterbium quantum gas microscope with narrow-line laser cooling, CEMS Topical Meeting on Cold Atoms, 2016
23. K. Hashimoto, T. Tomimatsu, S. Shirai, S. Taninaka, K. Nagase, K. Sato, and Y. Hirayama, Scanning nuclear electric resonance microscopy ina quantum Hall system, 33rd International Conference on the Physics of Semiconductors (ICPS2016), 2016
24. K. Hirakawa, Room temperature, very sensitive bolometer using doubly clamped microelectromechanical resonators, 5th Russia-Japan-USAEurope Symposium on Fundamental & Applied Problems of Terahertz Devices & Technologies (RJUSE TeraTech-2016), 2016
25. K. Hirakawa, Terahertz spectroscopy of quantum nanostructures far beyond the diffraction limit, TERAMETANANO 2016, 2016
26. K. Hirakawa, S. Du, K. Yoshida, and Y. Zhang, Seeing single molecules with long wavelength terahertz radiation, Workshop University ofTokyo/ENS, 201627. Satoshi Iwamoto, Shun Takahashi, Ingi Kim, Takeyoshi Tajiri, Yasutomo Ota, and Yasuhiko Arakawa, Control of Light Polarization using
Photonic and Phononic Crystals, Asia Communications and Photonics Conference (ACP) ACP2016, 201628. Satoshi Iwamoto, Shun Takahashi, Takeyoshi Tajiri, Yasutomo Ota, and Yasuhiko Arakawa, Control of Quantum Dot Light Emission by Chiral
Photonic Crystal Structures , The 37th Progress in Electromagnetics Research Symposium (PIERS), 201629. Satoshi Iwamoto, Yasutomo Ota, Shun Takahashi, Takeyoshi Tajiri, Kazuhiro Kuruma, Masahiro Kakuda, and Yasuhiko Arakawa, QuantumDot Cavity Quantum Electrodynamics using 2D and 3D Photonic Crystal Structures, The 12th International Symposium on Photonic andElectromagnetic Crystal structures (PECS-XII), 201630. Satoshi Iwamoto, Yasutomo Ota, Shun Takahashi, Takeyoshi Tajiri, Kazuhiro Kuruma, Masahito Kakuda and Yasuhiko Arakawa, QuantumDot Cavity Quantum Electrodynamics using Photonic Crystals, German-Japanese Meeting on the Science of Hybrid Quantum Systems, 2016
31. T. Ushiyama, N. X. Viet, S. Kishimoto and Y. Ohno, Bio-electronics applications of carbon nanotube thin film, The Seventeenth International
Conference on the Science and Applications of Nanotubes and Low-dimensional Materials, 2016
32. Takaaki Koga, Electric spin generation using a double quantum well based on the interband Rashba effect, EMN Quantum Meeting 2016, 2016
33. Takaaki Koga, Quantitative determination of the Rashba parameters in the InGaAs/InAlAs quantum wells and the proposal to use the double
quantum wells to enhance the Edelstein effect, International Conference on Semiconductor Nanostructures for Optoelectronics and Biosensors(IC SeNOB), 2016
34. Takaaki Koga, Spin Blocking Device Using the Inter-Band Rashba Effect in Double Quantum Well, The 6th Annual World Congress of Nano
Science and Technology-2016 (Nano S&T-2016), 201635. Y. Ohno, Bio-electronics applications of carbon nanotube thin film, The Fifith International Workshop on Nanocarbon Photonics andOptoelectronics, 201636. Yoshiro Hirayama, Resistively-detected nuclear based measurements in semiconductor quantum systems, China-Japan International Workshop
on Quantum Technologies (QTech 2016) , 201637. Yoshiro Hirayama, Quantum Transport and Nuclear Related Phenomena in GaAs and InSb Systems, Recent Development in 2D Systems(RD2DS) , 201638. Yoshiro Takahashi, A quantum gas microscope for ytterbium atoms, 47th Annual Meeting of the APS Division of Atomic, Molecular and Optical
Physics, 201639. Yoshiro Takahashi, Quantum simulation using ultracold atoms in an optical lattice, International Symposium on New Horizons in Condensed
Matter Physics, 201640. Yosuke Takasu, Study of Non-Equilibrium Dynamics of Isolated Quantum Systems Using Ultracold Ytterbium Atoms in an Optical Lattice,
NCTS Annual Theory Meeting 2016:Quantum Simulations and Numerical studies in Many-Boday Physics, 201641. 高橋義朗, トポロジカルポンピング現象の冷却原子を用いた新展開, 第 2 回「トポロジーが紡ぐ物質科学のフロンティア」領域研究会, 20162017
42. Akinobu Kanda, Search for unusual Andreev reflection in a graphene/superconductor interface, Collaborative Conference on Material Science(CCMR 2017), 201743. D. Hatanaka, M. Kurosu, and H. Yamaguchi, Dynamic phonon propagation control in GaAs/AlGaAs phononic crystal wave guides, 6thInternational Workshop "Epitaxial Growth and Fundamental Properties of Semiconductor Nanostructures", 201744. D. Hatanaka, M. Kurosu, and H. Yamaguchi, GaAs/AlGaAs phononic crystal waveguide, Asia Pacific Society for Materials Reseach 2017 Annual
Meeting (APSMR2017), 201745. D. Hatanaka, M. Kurosu, and H. Yamaguchi, GaAs/AlGaAs electromechanical phononic crystal waveguide, Physics and Applications of
Nanoelectronic and Nanomechanical Systems, 201746. H. Tabata, Noble functionalities created by Yuragi/Fluctuation in strongly correlated electron compounds, 2017 Asia-Pacific Workshop on
Fundamentals and Applications of Advanced Semiconductor Devices (AWAD 2017), 201747. H. Tabata, New electronic devices for low power consumption by learning from bio system, The 14th International Symposium on Sputteringand Plasma Processes (ISSP2017), 2017
48. H. Tabata, Oxide Electronics and Ferroelectrics – Their History and Relations –, The 34th Meeting on Ferroelectric Materials and Their
Applications(FMA34), 201749. H. Tabata, Ferrite Oxide Engineering for Solar Energy Harvesting and Spin-based Electronics, The Core-to-Core Workshop, 2017
50. H. Tabata, M. Adachi, H. Yamahara, M. Seki, Spin Fluctuated Garnet Ferrites for Brain Mimetic Memory Devices, IUMRS-ICM 2017(the 15th
International Conference on Advanced Materials), 2017
51. H. Yamaguchi, Electromechanical semiconductor quantum structures, SPIE Optics & Photonics annual meeting 2017, 2017
52. H. Yamaguchi, I. Mahboob, H. Okamoto, and D. Hatanaka, Parametric coupling and correlated fluctuation in multimode electromechanicalresonators, Frontiers of Nanomechanical Systems 2017 (FNS2017), 2017
53. H. Yamaguchi, M. Kurosu, and D. Hatanaka, Acoustic phonon manipulation in GaAs/AlGaAs electromechanical systems, US-Japan Joint
Seminar on Nanoscale Transport Phenomena, 2017
54. H. Yamaguchi, M. Kurosu, D. Hatanaka, GaAs/AlGaAs phononic crystal waveguide, International Workshop on Quantum Technologies(QTech2017), 2017
55. Hitoshi Tabata, Phonon and Magnon Properties of Gradient Strain Introduced Garnet Ferrite Oxide Thin Films, 18th US-Japan Seminar onDielectric and Piezoelectric Ceramics, 201798

56. Hitoshi Tabata, THz-TDS Combined with Metamaterials for Detecting Hydration State of Bio Related System, MTSA 2017&TeraNano-8,
2017
57. J. Ishi Hayase, Improvement of photon-echo generation efficiency by adiabatic rapid passages with a pair of chirped pulses in an inhomogeneousquantum dot ensemble, XV International Conference on Quantum Optics and Quantum Information（ICQOQI’2017）, 2017
58. K, Hirakawa, S. Du, K. Yoshida, and Y. Zhang, Terahertz spectroscopy of single molecules and single atoms far beyond the diffraction limit,
Russia-Japan-USA-Europe Symposium on Fundamental & Applied Problems of Terahertz Devices & Technologies (RJUSE TeraTech 2017),
2017
59. K, Hirakawa, S. Du, K. Yoshida, C.Tang, and Y. Zhang, Terahertz spectroscopy of single molecules and single atoms, 4th International
Symposium on Microwave/Terahertz Science and Applications (MTSA 2017), 2017
60. K. Hashimoto, Scanning-probe imagning of nuclear/electron spin polarization in a quantum Hall system, The Collaborative Conference on
Materials Research (CCMR) 2017, 2017
61. K. Hirakawa, Uncooled, sensitive, high-speed bolometers using doubly clamped microelectromechanical resonators, 2017 Sweden-Japan
International workshop on quantum nanophysics and nanoelectronics, 2017
62. K. Hirakawa, Uncooled, sensitive, high-speed bolometers using doubly clamped microelectromechanical resonators, 2017 Sweden-Japan
International workshop on quantum nanophysics and nanoelectronics, 2017
63. K. Hirakawa, Ultrafast nanomechanical oscillation of single C60 molecules investigated byterahertz spectroscopy, Japan-China International
Workshop on Quantum Technologies (QTech 2017), 2017
64. Kae Nemoto, A Universal Quantum Module For Quantum Computation And Communication, 2017 CLEO Pacific Rim Conference, 2017
65. Kouichi Akahane, Carrier dynamics of InAs quantum dot with digital embedding method grown on InP(311)B substrate, 6th International
Workshop Epitaxial Growth and Fundamental Properties of Semiconductor Nanostructures (SemiconNano2017), 2017
66. M. Nomura, Thin Si thermoelectric material by phonon engineering, IUMRS-ICA2017, 201767. M. Nomura, Heat transfer control by Si phononic nanostructures, PHONONICS2017, 201768. M. Nomura, Physics of Nanoscale Heat Transfer and Applications, The 9th International Electronics Cooling Technology Workshop, 201769. M. Nomura, Phononic Crystal Nanopatterning in Si and SiGe Thin Films for Thermoelectric A pplication, TMS2017, 201770. M. Nomura, Thermophononic crystals, Wave Phenomena and Phonon Thermal Transport Sientific School, 201771. Michael Hanks, Nicolò Lo Piparo, Michael Trupke, Jörg Schmiedmayer, William J. Munro, Kae Nemoto, A universal quantum module forquantum communication, computation, and metrology, SPIE. Optics+Photonics, 201772. Mio Murao, Higher order quantum operations of unitaries and their implications, The 17th Asian Quantum Information Science Conference,
2017
73. R. S. Deacon, E. Bocquillon, J. Wiedenmann, F. Dominguez, T. Klapwijk, K. Ishibash, and L. W. Molenkamp, Topological States of Matter ,The 20th International Conference on Electron Dynamics in Semiconductors, Optoelectronics and Nanostructures (EDISON20), 2017
74. Ryota Negishi and Yoshihiro Kobayashi, Bandlike-tranport in highly crystalline graphene films from defective graphene oxide, Collaborative
Conference on Materials Research, 201775. S. Du, Y. Zhang, K. Yoshida, and K. Hirakawa, Terahertz spectroscopy of a single atom in a fullerene cage, 42 International Conference on
Infrared, Millimeter and Terahertz Waves (IRMMW-THz 2017), 2017
76. T. Tomita, S. Nakajima, I. Danshita, Y. Takasu, Y. Takahashi, Controlling quantum many-body states and dynamics of strongly correlatedbosons with an engineered dissipation, The 2nd Tokyo-Beijing Workshop on Ultracold Atoms, 2017
77. Takao Aoki, Nanofiber resonator for a cavity QED network, The 3rd Australia New Zealand Conference on Optics and Photonics (ANZCOP),
2017
78. Takashi Yamamoto, Motoki Asano, Sahin Kaya Ozdemir, Controlling group delay with passive and active microresonators, SPIE Photonic West2017, 201779. Y. Homma and S. Chiashi, Measurements of Thermodynamic Properties on Nano-Scale by Single Carbon Nanotube Spectroscopy, 2017
International Conference on Functional Carbons (ICFC), 2017
80. Y. Ohno, Flexible devices based on carbon nanotube thin films, 固体物理, 201781. Y. Ohno, Flexible thin-film transistors and biosensors based on carbon nanotubes for wearable health monitoring devices, International
Symposium on Nanocarbon Materials, 201782. Y. Ohno, Carbon nanotube thin film devices for wearable electronics, Japan-India Joint Seminar, 2017
83. Y. Ohno, Flexible voltage generator based on movement of electrolyte droplet on carbon nanotube thin film, JSAP-KPS Joint Symposium, 201784. Y. Ohno, Flexible bio-electronics based on carbon nanotube thin films, Nano and Giga Challenges in Electronics, Photonics and Renewable
Energy, 201785. Y. Ohno, Carbon nanotube-based flexible electronics: TFTs, ICs, and biosensors, Nanomaterials for biomedical applications: Magnetic
nanoparticles and carbon nanotubes as enhancers for targeted RNA delivery in vivo, 201786. Y. Ohno, Highly-sensitive, flexible electrochemical biosensor based on carbon nanotube thin film, The 12th Asian Conference on Chemical
Sensors, 201787. Y. Ohno, Carbon Nanotube-based Flexible/Stretchable Devices on Polymer Films for Wearable Electronics, The 25th Annual World Forum on
Advanced Materials (POLYCHAR 25), 2017
88. Y. Ohno, Carbon Nanotubes for Wearable Electronics: Transistors, Circuits, Sensors, and Energy Harvesting Devices, The 8th A3 Symposiumon Emerging Materials, 201789. Y. Zhang and K. Hirakawa, Novel bolometric THz detection by MEMS resonators, 14th International Conference on Intersubband Transitionsin Quantum Wells (ITQW2017), 2017
90. Y. Zhang, S. Hosono, N. Nagai, and K. Hirakawa, Room temperature, sensitive, high-speed bolometers using doubly clamped
microelectromechanical resonators, International Conference on Terahertz Emission, Metamaterials and Nanophotonics (Terametanano-2),
2017
91. Y. Zhang, S. Hosono, N. Nagai, and K. Hirakawa, Uncooled, sensitive, high-speed bolometers using doubly clamped microelectromechanicalresonators, Optical Terahertz Science and Technology (OTST 2017), 2017
92. Y.Takahashi, Non-equilibrium dynamics of ultracold ytterbium atoms in optical lattices, Quantum Optics Ⅸ, 2017
93. Yoshiro Hirayama, Resistively-detected NMR in semiconductor quantum systems, Frontiers in Quantum Materials and Devices Workshop
2017, 2017
94. Yoshiro Hirayama, New Directions of Physics Studies in Semiconductor Quantum Systems, Joint Workshop“World Leading Research for Future
10 Years -For International Industry-University Collaboration based on Cooperation between NCTU and Tohoku Univ.-, 201795. Yoshiro Hirayama, Nuclear Spin Related Measurements for Semiconductor Quantum Systems, Nano and Giga Challenges in Electronics,
Photonics, and Renewable Energy (NGC2017), 201796. Yoshiro Takahashi, Novel phenomena of ultracold atoms in an optical super-lattice, Fudan University Physics Department Colloquium, 201797. Yoshiro Takahashi, Topological physics of ultracold atoms in an optical lattice, International Workshop on Topological Structures in Quantum
Matter, 201799

98. Yoshiro Takahashi, Topological Thouless pumping of ultracold fermions, YIPQS long-term and Nishinomiya-Yukawa memorial workshop
Novel Quantum States in Condensed Matter 2017, 20172018
99. Satoshi Iwamoto, Advances in quantum dot cavity quantum electrodynamics using photonic crystal nanocavities, CLEO-PRThe 13th Pacific
Rim Conference on Lasers and Electro-Optics, 2018100. D. Hatanaka, M. Kurosu, and H. Yamaguchi, Propagation control of acoustic waves in compound semiconductor phononic crystal waveguides,
IEEE International Conference on Emerging Electronics (IEEE-ICEE) 2018, 2018
101. H. Tabata, Functional Oxide Engineering for Solar Energy Harvesting and Neuromorphic Devices based on Spintronics & Magnonics, The
2nd Electron Devices Technology and Manufacturing (EDTM) Conference 2018, 2018
102. H. Tabata, IR and THz characterization of bio related materials and analysis by machine learning, the 43rd International Conference on
Infrared, Millimeter, and Terahertz Waves (IRMMW-THz), 2018
103. H. Tabata, Y. Kuranaga, H. Matsui, Strong light confinements coupled with surface plasmons in the hetero layers of Ga2O3-ZnO thin films,
4th E-MRS & MRS-J Bilateral Symposium, 2018
104. H. Yamaguchi, GaAs/AlGaAs heterostructures for micro- and nano-electromechanics, 2-days workshop "MBE technology of hetero-structureswith a high-mobility Two-Dimensional Electron Gas (2DEG)", 2018
105. H. Yamaguchi, Electron-Photon-Phonon hybrid systems based on compound semiconductor mechanical resonators, 65th Annual American
Vacuum Society International Symposium and Exhibition (65th AVS), 2018106. H. Yamaguchi, D. Hatanaka, and M. Kurosu, Propagation control of acoustic waves in GaAs-based phononic crystal waveguide, 34th
International Conference on the Physics of Semiconductors (ICPS2018), 2018107. H. Yamaguchi, R. Ohta, and H. Okamoto, Carrier mediated optomechanical coupling in a GaAs/AlGaAs heterostructure cantilever, SPIE
Optics + Photonics 2018, 2018108. H. Yamaguchi, R. Ohta, and H. Okamoto, Carrier mediated optomechanics, France-Japan Bilateral Workshop on Hybrid Quantum Systems,
2018109. H.Tabata, Ultra-high sensitive skin gas sensing by quantum nano-devices -Application for wearable fat metabolism monitoring-, the Third
Chile-Japan Academic Forum, 2018110. Hayata Yamasaki and Mio Murao, Partial quantum information and two-way classical communication, post-AQIS18, 2018111. Hideo Kosaka, Holonomic quantum manipulation of diamond qubits, The 2nd CEMS International Symposium on Dynamics in Artificial
Quantum Systems(DAQS2018), 2018112. I. Katayama, Y. Minami, Y. Arashida, O. S. Handegard, T. Nagao, M. Kitajima, and J. Takeda, Nonlinear Terahertz Dynamics of Dirac
Electrons in Bi Thin Films, SPIE Optics + Photonics 2018, 2018113. J. Ishi-Hayase, AC magnetic field sensing using NV centers in diamond, 14th International Conference on Atomically Controlled Surfaces,
Interfaces and Nanostructures (ACSIN-14), 2018114. J. Ishi-Hayase, Highly-sensitive Quantum Sensor based on Electric Spin Manipulation in Diamond, The 13th Japan-US Joint Seminar on
Quantum Electronics and Laser Spectoscopy (US-Japan QELS-13), 2018
115. J. Takeda, K. Yoshioka, Y. Arashida, and I. Katayama, Nanoscale Electron Manipulation Using Phase-controlled THz Near-fields, The
Conference on Lasers and Electro-Optics (CLEO 2018), 2018116. J. Takeda, K. Yoshioka, Y. Minami, Y. Arashida, and I. Katayama, THz-Field-Driven Electron Tunneling On The Nanoscale, 43rd International
Conference on Infrared, Millimeter, and Thertz Waves (IRMMW-THz 2018), 2018
117. K. Hashimoto, T. Tomimatsua, and Y. Hirayama, Nuclear Resonance Spectroscopic Imaging of Hyperfine-Coupled Quantum Hall System,
Reimei/GPSpin/ICC-IMR Workshop on New Excitations in Spintronics, 2018118. K. Hirakawa, Room temperature, fast, and sensitive bolometric terahertz detection by using MEMS resonators, The 6th Workshop on Physics
between École Normale Supérieure and University of Tokyo, École Normale Supérieure, Paris, France, 2018
119. K. Hirakawa (keynote), High-sensitivity and fast terahertz bolometric detection by MEMS resonators, The 9th International Symposium on
Ultrafast Phenomena and Terahertz Waves (ISUPTW 2018), Changsha, China, 2018120. K. Hirakawa, Y. Zhang, B. Qiu, N. Nagai, Giant enhancement in thermomechanical terahertz detection sensitivity of GaAs MEMS resonators
through coherent internal mode coupling, the 34th International Conference on the Physics of Semiconductors 2018 (ICPS2018), 2018121. K. Hirakawa, Y. Zhang, N. Nagai, S. Hosono (invited), Fast and sensitive terahertz detection at room temperature by GaAs doubly clamped
MEMS beam resonators, SPIE Nanoscience + Engineering, 2018122. K. Ishibashi, Nanoscale Quantum Effect Devices with Nanotubes and Nanowires, Nanotech Malaysia 2018, 2018123. K. Ishibashi, Single-wall carbon nanotubes for quantum-dot devices, The 3rd International Conference on Emerging Advanced Nanomaterials(ICEAN2018), 2018124. Kae Nemoto, Superradiance and thermalization in hybrid quantum systems, AIP Congress 2018, 2018125. Kae Nemoto, Scalability of quantum networks from a qubit to tomorrows quantum internet, The Quantum Internet; Charting the CriticalPath, 2018126. Kae Nemoto, Michael Hanks, Nicolò Lo Piparo, and William J. Munro, Universal Optical Modules for Quantum Network, Summer Topicals
Meeting Series 2018, 2018
127. M. Bescond, A. Yangui, T.F. Yan, F. Michelini, N. Nagai, N. Cavassilas, M. Lannoo, K. Hirakawa (invited), Evaporative cooling effect in
AlGaAs/GaAs Heterostructures, GDRe Meeting on "Thermal Nanosciences and NanoEngineering", 2018
128. M. Kurosu, D. Hatanaka, and H. Yamaguchi, Nonlinear dynamics and four-wave mixing in MEMS waveguides, The 15th NanomechanicalSensing Workshop (NMC2018), 2018129. M. Nomura, Heat conduction control in Si membrane by phononic nanostructures, IEEE Nano 2018, 2018130. M. Nomura, Advanced heat transfer control in Si membrane by phononic nanostructures, The 5th Micro & Nanoscale Heat Transfer andEnergy Workshop, 8-2, Taipei, Taiwan, 2018131. M. Nomura, Nanostructured Si film thermoelectrics, European Advanced Materials Congress, B41-42 21-EM-1, Stockholm, Sweden , 2018132. M. Nomura, Advanced heat conduction engineering by phonon engineering and thermoelectric application, NAMIS Marathon Workshop,
Taiwan , 2018133. M. Nomura, Phononics learn from photonics: thermal phonon engineering by phononic crystal, Optics & Photonics Japan, 31aCJ4, Tokyo,
Japan, 2018134. Michihisa Yamamoto, A localized spin in an electron wave cavity: measurement on the Kondo cloud length, Quantum Science Symposium
Europe-2018, 2018135. Minoru Kawamura, Quantum phase transition in magnetic topological insulator studied by transport measurement, China-Japan International
Workshop on Quantum Technologies, 2018
136. Minoru Kawamura, Topology: a new knob for electric switch, France-Japan Bilateral Workshop on Hybrid Quantum Systems, 2018
137. Minoru Kawamura, Metal-insulator transition in magnetic topological insulator, The 34th international conference on physics of100

semiconductors (ICPS2018), 2018138. Mio Murao, Higher order quantum operations of unitaries, 4th Seefeld workshop on Quantum Information (2018), 2018139. Mio Murao, Higher order quantum operations of unitaries, Hong Kong - Shen Zhen Workshop on Quantum Information Science, 2018
140. Mio Murao, Using quantum computers for analyzing quantum physics, Internaitonal Conference on Challenges in Quantum Information
Science (CQIS 2018), 2018141. Mio Murao, Using quantum computers for manipulating and analysing quantum systems, The Bristol Quantum Information Technologies
Workshop (BQIT2018), 2018142. N. Mori, G. Mil'nikov, J. Iwata, and A. Oshiyama, Quantum transport device simulation based on real-space density functional theory andnon-equilibrium Green's function method, International Union of Materials Research Societies - International Conference on Electronic
Materials 2018, 2018
143. Qingxiuxiong Dong, Marco Tulio Quintino, Akihito Soeda and Mio Murao, Implementing positive maps with multiple copies of an input state,
post-AQIS18, 2018
144. R. Anufriev, R. Yanagisawa, and M. Nomura, Surface engineering of nanobeams and nanomembranes for silicon-based thermoelectrics,
Collaboratie Conference on Materials Research, 2018145. R. Negishi and Y. Kobayashi, Restoration and layer-by-layer growth of graphene structures by controlling partial pressure of ethanol vapor
through high process temperature , Nanotech Malaysia （Kuala Lumpur, Malaysia）, 2018
146. Russell S. Deacon, Fractional ac-Josephson effect as a signature of topological superconductivity, France-Japan Bilateral Workshop on Hybrid
Quantum Systems, 2018
147. S. Du, Y. Zhang, K. Yoshida, and K. Hirakawa, Terahertz spectroscopy at the atomic-scale level, CLEO Pacific Rim 2018, 2018148. S. Iwamoto, Topological localized states in quasi-1D photonic and phononic crystals, International workshop ”Variety and universality of bulkedge correspondence in topological phases: From solid state physics to transdisciplinary concepts” (BEC2018), 2018
149. S. Iwamoto, Photonic crystal nanocavities by topological concept, International workshop ”Variety and universality of bulk-edgecorrespondence in topological phases: From solid state physics to transdisciplinary concepts” (BEC2018X), 2018150. S. Mouri, Y. Nanishi, and T. Araki, Van der Waals Epitaxy of Nitride Semiconductor Towards Energy Conversion Devices, The 9thInternational Symposium of Advanced Energy Science, 2018
151. Satoshi Iwamoto, Takeyoshi Tajiri, Shun Takahashi, Yasutomo Ota and Yasuhiko Arakawa, Three-dimensional functional photonic crystals
made by micromanipulation, Physics@Veldhoven, FT5.1, 2018
152. Satoshi Iwamoto, Yasutomo Ota, Ryota Katsumi, Katsuyuki Watanabe, Yasuhiko Arakawa, Topological Localized State in Photonic Crystal
Nanobeam, 2018 Progress In Electromagnetics Research Symposium, 2018
153. Satoshi Iwamoto, Yasutomo Ota, Takuto Yamaguchi, and Yasuhiko Arakawa, Topological edge states in semiconductor-based photonic crystals,
China-Japan International Workshop on Quantum Technologies, 2018
154. Shintaro Nomura, Generation of vector-shaped light pulses and its application to spin control of semiconductor two-dimensional electron
system, Global Research Efforts on Energy and Nanomaterials 2018, 2018155. Takashi Yamamoto, Quantum network with photons, atoms, and optomechanics, France-Japan Bilateral Workshop on Hybrid Quantum
Systems, 2018
156. William J. Munro, Nicolò Lo Piparo, and Kae Nemoto, Quantum Multiplexing as a Resource Saver in Quantum Networks, Summer Topicals
Meeting Series 2018, 2018
157. Y. Kuranaga, H. Matsui, A. Ikehata, Y.-L. Ho, J.-J. Delaunay, and H. Tabata, Surface Plasmon Excitation on Hybrid Structures of Oxide
Semiconductors of (Ga2O3)/ZnO:Ga in Near-infrared Range, Progress In Electromagnetics Research Symposium (PIERS) 2018, 2018158. Y. Ohno, Carbon nanotube TFTs, ICs, energy harversters for wearable sensor devices: Device modeling, circuit design tools, and fabrication,
19th International Conference on the Science and Application of Nanotubes and Low-dimensional Materials, 2018159. Y. Ohno, Carbon nanotube-based flexible electronics for wearable devices, 2018 International Forum on Graphene, 2018160. Y. Ohno, Carbon Nanotube-Based Flexible Devices for Wearable Sensor System, 9th A3 Symposium on Emerging Materials: Nanomaterials
for Electronics, Energy, and Environment, 2018
161. Y. Ohno, Carbon Nanotube-Based Flexible Devices for Wearable Sensor System, AsiaNano 2018, 2018162. Y. Ohno, Carbon Nanotube-Based Flexible Electronics: Transistors, Integrated Circuits, Biosensors, and Energy harvesters for Wearable
Devices, International Conference on Innovative Research in Science, Technology and Management, 2018
163. Y. Ohno, Carbon nanotube-based analog circuits for wearable sensor applications: Device modeling, circuit desing and fabrication,
International Workshop on Nanocarbon Photonics and Optoelectronics, 2018164. Y. Ohno, Flexible Carbon Nanotube ICs for Wearable Electronics: Transistor technologies, Circuit Design Tools, and Analog IC design andFabrication, MRS Fall Meeting, 2018
165. Y. Ohno, Flexible and transparent energy harvesters with carbon nanotube thin films, The 55th Fullerenes-Nanotubes-Graphene General
Symposium, 2018
166. Y. Zhang, S. Hosono, N. Nagai, and K. Hirakawa, Novel bolometric THz detection by MEMS resonators, 2018 43rd International Conferenceon Infrared, Millimeter, and Terahertz Waves (IRMMW-THz 2018), Nagoya Congress Center, Aichi, Japan, 2018167. Yoshikazu Homma and Shohei Chiashi, Single SWNT Spectroscopy for Nano-metrology, 7th Workshop on Nanotube Optics andNanospectroscopy WONTON 2018, 2018
168. Yoshiro Hirayama, Transport and resistively-detected NMR characteristics of III-V quantum structures, 2018 Tohoku-Harvard Workshop,
2018
169. Yoshiro Hirayama, Resistively-detected nuclear resonance and its imaging, China-Japan International Workshop on Quantum Technologies(QTech2018), 2018170. Yoshiro Hirayama, Microscopic Characterizations Based on Nuclear Resonance, France-Japan Bilateral Workshop on HQS, 2018171. Yoshiro Hirayama, Microscopic Nuclear-Spin-Resonance in Semiconductor Quantum Systems, Frontiers in Quantum Materials & Devices
Workshp (FQMD) 2018, 2018172. Yoshiro Hirayama, Resistively‐Detected Nuclear‐Magnetic‐Resonance in Microscopic Scale, International Symposium on Quantum Hall
Effects and Related Topics, 2018173. Yoshiro Hirayama, Nuclear Spin Resonance in Semiconductor Quantum Systems, Kick-off Symposium for World Leading Research CentersMaterials Science and Spintronics –, 2018174. Yoshiro Takahashi, Topological physics explored by ultracold ytterbium atoms, International workshop "Variety and universality of bulk-edgecorrespondence in topological phases: From solid state physics to transdisciplinary concepts" (BEC2018), 20182019
175. S. Iwamoto, Semiconductor topological photonic crystal nanocavities, International Workshop on New Trends in Topological Insulators 2019
& Variety and Universality of Bulk-edge Correspondence in Topological Phases (NTTI2019 and BEC2019), 2019176. C. Uchiyama, Non-Markovian Effect on Quantum Transport, Quantum Information Processing in Non-Markovian Quantum Complex

101

Systems(QIPQC2019), 2019177. D. Hatanaka, M. Kurosu and H. Yamaguchi, Dispersive and nonlinear dynamics of acoustic wave propagation in a phononic crystal waveguide,FQMD2019, 2019178. D. Hatanaka, M. Kurosu, and H. Yamaguchi, Control of acoustic waves in an electromechanical phononic crystal, Frontier of Nanomechanical
Systems (FNS2019), 2019179. H. Tabata, Magnetic, Dielectric and Optical Anomaly in Nano Structural Controlled Strain Gradient Garnet Ferrite Films, IUMRS-ICA-2019,2019180. H. Tabata, Biooptics and bioelectronics, The 4th UTokyo-NTU Joint Conference, 2019
181. H. Tabata, Near IR Plasmonics based on Nano Patterned Metallic Antennas and Oxide Semiconductors for Bio-Medical Sensing, Workshop
on information optics 2019(WIO2019), 2019182. H. Tabata, H. Yamahara, S. Shamim, A. Katogi and M. Seki, Magnetic, dielectric and optic anomaly in strain gradient garnet films, The 8th
Indo-Japan Seminar Designing Emergent Materials, 2019183. H. Yamaguchi, Strain-mediated mechanical control of spin systems in semiconductor heterostructures, Physics and Applications in
Nanoelectronics and Nanomechanics, 2019184. Hitoshi Tabata, Design and Demonstration of Low Power Consumption Devices Based on Stochastic Resonance Learning from Fluctuationof Bio-system, The 2nd Symposium for World Leading Research Centers, 2019185. J. Ishi-Hayase, Quantum Protocols for AC Magnetic Field Sensing using Nitrogen-vacancy Centers in Diamond, Canada-Japan Workshop on
Hybrid Quantum Systems, 2019
186. J. Ishi-Hayase, Highly-sensitive AC Magnetic Field Sensing based on Electric Spin Manipulation of Nitrogen-vacancy Centers in Diamond,
XVI International Conference on Quantum Optics and Quantum Information（ICQOQI’2019）, 2019187. J. Takeda, K. Yoshioka, Y. Arashida, and I. Katayama, Ultrafast Electron Manipulation Using THz Scanning Tunneling Microscopy With
Tailor-Made Near Fields, International Photonics and OptoElectronics Meetings (POEM 2019), 2019188. Jason ball, Petr Moroshkin, Denis Konstantinov, Yuimaru Kubo, Towards a quantum transducer with spins in diamond, International
Workshop on Hybrid Quatum Systems, 2019189. K. Hirakawa, Terahertz Spectroscopy of Electron-vibron Coupling in single Molecules by Using Nanogap Electrodes, International School andSymposium on Nanoscale Transport and phoTonics 2019 (ISNTT2019), 2019190. K. Hirakawa, Evaporative electron cooling in asymmetric double barrier semiconductor heterostructures, LIMMS-Next PV Joint EnergyWorkshop, 2019
191. K. Hirakawa, Room-temperature, fast and sensitive terahertz detection using MEMS resonators, Partners for International Business (PIB)
Event Nanotechnology Japan, 2019
192. K. Hirakawa, Terahertz Spectroscopy of Electron–vibron Coupling in Single Molecules, The 7th Workshop on Physics between Ecole Normale
Superieure and University of Tokyo, 2019
193. K. Ishibashi, Quantum structures with carbon nanotubes, 700. WE-Heraeus-Seminar on One-Dimensional Systems for Quantum Technology,
2019
194. Kae Nemoto, New approaches to quantum computation, Japan-Netherlands Quantum Conference, 2019195. Kae Nemoto, DISTRIBUTED QUANTUM INFORMATION PROCESSING, SPIE. Optics + Photonics 2019, 2019196. Kae Nemoto, Quantum Complex Networks, Workshop on Selected Topics in Quantum Computation and Quantum Information, 2019
197. Kazuhiko Hirakawa, Fast And Sensitive Bolometric Terahertz Detection At Room Temperature Through Thermomechanical Transduction,
44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz 2019), 2019
198. Kazuhiko Hirakawa, Terahertz dynamics of electron-vibron coupling in single molecules with tunable electrostatic potential, Hybrid Quantum
Systems Workshop in Ottawa, 2019199. Kazuhiko Hirakawa, Terahertz Dynamics of Single Molecules and Single Atoms Studied by Using Nanogap Electrodes, The 21st International
Conference on Electron Dynamics in Semiconductors, Optoelectronics and Nanostructures (EDISON 21), 2019200. Koji Ishibashi, Topological insulator-superconductor Josephson junction -Search for Majorana fermion-, 2019 RIKEN-NCHU Joint
Symposium, 2019201. Kouichi Akahane, Atsushi Matsumoto, Toshimasa Umezawa, and Naokatsu Yamamoto, Hybrid structure of quantum-dot and quantum-wellsuperlattice grown by molecular beam epitaxy, Energy, Materials, and Nanotechnoglogy Meeting on Epitaxy (EMN Epitaxy 2019), 2019202. M. Bescond, A. Yangui, C. C. Tang, T. F. Yan, N. Nagai, and K. Hirakawa, Electron cooling in asymmetric double-barrier heterostructure: theevaporative approach, The 21st International Conference on Electron Dynamics in Semiconductors, Optoelectronics and Nanostructures(EDISON 21), 2019
203. M. Bescond, A. Yangui, T. Yan, N. Nagai, and K. Hirakawa, Evaporative electron cooling in asymmetric double barrier semiconductor
heterostructures, International Workshop on Computational Nanotechnology (IWCN), 2019
204. M. Nomura, Phonon Engineering Learns Photonics for Heat Condution Control, International Symposium on Numerical Methods in Heatand Mass Transfer, Plenary Talk 3, Hangzhou, China, 2019
205. M. Nomura, Directional Heat Flux in Phononic Crystals, Q04.12.01, MRS Spring Meeting and Exhibit, Phoenix, USA, 2019206. M. Nomura, Phononics learns photonics for heat transport control, Wed-3, Conference on Nanophononics, Bridging Statistical Physics,
Molecular Modeling and Experiments, Trieste, Italy, 2019
207. M. Nomura, Phononics learns photonics, JSIV-1.2, CLEO/EUROPE-EQEC 2019, Munich, Germany, 2019
208. M. Nomura, Advanced heat flux control by phononic nanostructures, LIMMS-Next PV Joint Energy Workshop, 2019
209. M. Nomura and R. Yanagisawa, Thermoelectric Si thin film with nanostructures, Asian Advanced Materials Congress, 2019
210. M. Nomura and R. Yanagisawa, Power enhancement of planar-type Si thermoelectric devices by nanostructuring, The 13th Pacific Rim
Conference of Ceramic Societies, 2019211. Magdalena Marganska, Lars Milz, Wataru Izumida, Christoph Strunk, Milena Grifoni, Majorana states in carbon nanotubes, DPG Spring
Meeting, 2019
212. Marco Túlio Quintino, Qingxiuxiong Dong, Atsushi Shimbo, Akihito Soeda and Mio Murao, Reversing unknown quantum transformations:
A universal quantum circuit for inverting general unitary operations, Quantum Information Structure of Spacetime HKU workshop (QISSHKU 2020), 2019213. Michael Hanks, The Many Faces of Quantum Device Design, AQIS 2019 Satellite Meeting, 2019214. Michihisa Yamamoto, Measurement of the Kondo cloud length, Canada-Japan Workshop on Hybrid Quantum Systems, 2019
215. Michihisa Yamamoto, Measurement of the Kondo cloud length, Frontiers in Quantum Information Physics and Technology, 2019
216. Michihisa Yamamoto, Measurement of the Kondo cloud length, Frontiers in Quantum Materials & Devices Workshop, 2019
217. Michihisa Yamamoto, Manipulation of electron waves and solid-state flying qubits, RIKEN-Berkeley Workshop on Quantum Information
Science, 2019
218. Michihisa Yamamoto, Observation of the Kondo Screening Cloud, The 11th International Conference on Advanced Materials and Devices(ICAMD2019), 2019102

219. Mikio Eto, Kondo effect and phase measurement in quantum dot embedded in mesoscopic ring, 14th Asia Pacific Physics Conference, 2019220. Mikio Eto, Kondo effect in quantum dot interferometer in multiterminal geometry, 5th EMN Meeting on Quantum (Barcelona, Spain), 2019221. Mikio Eto, Physics in double quantum dot in parallel, Canada-Japan Workshop on Hybrid Quantum Systems (Ottawa, Canada), 2019222. Minoru Kawamura, Topological quantum phase transition in magnetic topological insulator, 2019 RIKEN-NCHU Joint Symposium, 2019
223. Minoru Kawamura, Quantum anomalous Hall effect in magnetic-proximity-coupled topological insulator, APW2019 and Tsinghua-RIKENKITS Joint workshop, 2019
224. Mio Murao, Higher order quatum oeprations of blackbox unitareis, 57th Annual Allerton Conference 2019, 2019
225. Mio Murao, Higher order quatum oeprations of blackbox unitareis, Quantum Information Processing in Non-Markovian Quantum Complex
Systems (QIPQC 2019), 2019
226. Mio Murao, Higher order quatum oeprations of blackbox unitareis, Xith International Sumposium on Quantum Theory and Symetreis(QTS2019), 2019227. Mio Murao, Using quantum computers for processing quantum systems, Young Researchers Forum on Quantum Information Science, 2019
228. N. Namekata, D. Wu, S. Ohnuki, D. Fukuda, and S. Inoue, Quantum walk in a plasmonic waveguide lattice structure, International Conferenceon Emerging Quantum Technology, 2019229. Nemoto Kae, Quantum device design with noise, Quantum Information Processing in Non-Markovian Quantum Complex Systems(QIPQC2019), 2019230. R. Anufriev and M. Nomura, Ballistic thermal transport in silicon nanowires, Nanowire week, 2019
231. R. Anufriev and M. Nomura, Time-Domain Thermoreflectance for Thermal Characterization of Nanostructures, 20th International
Conference on Photoacoustic and Photothermal Phenomena, Moscow, 2019232. R. Ohta, H. Okamoto, T. Tawara, H. Gotoh, H. Yamaguchi, Mechanical control of bound excitons: strain-induced coupling of dark and brightstates, Frontier of Nanomechanical Systems (FNS2019), 2019233. R. Ohta, H. Okamoto, T. Tawara, H. Gotoh, H. Yamaguchi, Mechanical control of localized excitons: strained coupling between dark andbright states and mechanical control of exciton lifetime, HQS2019, Ottawa, 2019234. S. Iwamoto, Confinement of light in semiconductor using topological concept, Canada-Japan Workshop on Hybrid Quantum Systems, 2019
235. S. Iwamoto, Semiconductor topological photonic crystal nanocavities, International Workshop on New Trends in Topological Insulators 2019
& Variety and Universality of Bulk-edge Correspondence in Topological Phases (NTTI2019 and BEC2019), 2019236. S. Iwamoto, Topological Localized States in Semiconductor Photonic Crystals, International Workshop TOPOLOGY, 2019237. Satoshi Iwamoto, Generation of Structured Light Using Spin-orbit Interaction of Light in Photonic Nanostructures, Optomagnonics 2019
Cambridge, 2019
238. Satoshi Iwamoto, Topological photonics using semiconductor photonic crystals, The 4th A3 Metamaterials Forum 2019, 2019239. Shintaro Nomura, Wide-field imaging of microwave with nitrogen-vacancy center ensembles in diamond, Canada-Japan Workshop on Hybrid
Quantum Systems, 2019240. Shintaro Nomura, Wide-field quantum sensing using nitrogen-vacancy center ensembles in diamond, NCTU–Seminar, 2019241. Shohei Chiashi, Yoshikazu Homma, Water Adsorption and Desorption on Single and Suspended Single‐walled Carbon Nanotubes bySpectroscopy, International Conference on the Science and Application of Nanotubes and Low-Dimensional Materials, NT19, 2019242. Takashi Yamamoto, Quantum Network with atoms and photons, International Workshop for Young Researchers on the Future of Quantum
Science and Technology (FQST2020), 2019
243. Takashi Yamamoto, Quantum network with photons and diverse media, International Workshop on Hybrid Quantum Systems, 2019244. Takashi Yamamoto, Quantum repeaters with photons, Okinawa School in Physics 2019: Coherent Quantum Dynamics (CQD 2019), 2019245. Takashi Yamamoto, Experimental all-photonic quantum repeaters, SPIE Optics + Photonics 2019, 2019
246. Takashi Yamamoto, Optomechanical properties in a microbottle resonator, Progress In Electromagnetics Research Symposium PIERS 2019,2019247. Toshu An, Daisuke Kikuchi, Dwi Prananto, Yuta Kainuma, Kunitaka Hayashi, Long-distance excitation of NV centers in diamond via spinwaves, the Joint 5th International Symposium on Frontiers in Materials Science & 3rd Nano-materials, Technology and Applications (FMS2019 & NANOMATA 2019), 2019248. X. Li, K. Yoshioka, Q. Zhang, F. Katsutani, W. Gao, N. Marquez, G. T. Noe, J. Watson, M. Manfra, I. Katayama, J. Takeda, and J. Kono,
Observation of Narrow-Band Terahertz Gain in Two-Dimensional Magnetoexcitons, The Conference on Lasers and Electro-Optics (CLEO2019), 2019249. X. Li, K. Yoshioka, Q. Zhang, F. Katsutani, W. Gao, N. Marquez, T. Noe, J. Watson, M. Manfra, I. Katayama, J. Takeda, and J. Kono,
Observation of Narrow-Band Terahertz Gain in Two-Dimensional Magnetoexcitons, The Conference on Lasers and Electro-Optics (CLEO2019), 2019250. Y. Ohno, Carbon nanotube thin films for wearable electronics application, 1&2DM, 2019251. Y. Ohno, Carbon nanotubes for wearable electronics applications, 14th International Conference on Advanced Carbon Nano Structures, 2019252. Y. Ohno, Low-voltage operable, ultra-stretchable carbon nanotube thin film transistors and integrated circuits, 2019 International Meetingon Information Display, 2019253. Y. Ohno, Carbon Nanotube-Based Stretchable Devices for Wearable Electronics, International Conference on the Science and Application of
Nanotubes and Low-Dimensional Materials, 2019254. Yoshikazu Homma, Shohei Chiashi, Characterization of Phase of Water Confined in Nanospace, 12th International Symposium on Atomic
Level Characterizations for New Materials and Devices '19 (ALC' 19), 2019255. Yoshiro Hirayama, Hyperfine interaction and resistively-detected NMR in semiconductor quantum systems, Frontiers in Quantum
Information Physics and Technology, 2019
256. Yoshiro Hirayama, Electron Spin Characteristics Unveiled by Resistively-detected NMR, Rocky Mountain Conference： 42nd Int. EPR
Symposium, 2019257. Yoshiro Hirayama, Resistively-detected NMR and nuclear resonance imaging, Spintronics Workshop II, 2019258. Yoshiro Hirayama, Microscopic characterization and resistively-detected NMR of semiconductor quantum systems, Workshop Spintronic
Tohoku-Mainz-Lorraine 2019, 2019259. 安東秀, 菊池大介, Dwi Prananto, 貝沼雄太, 林都隆, Long-distance excitation of NV centers in diamond via spin waves, the Joint 5thInternational Symposium on Frontiers in Materials Science & 3rd Nano-materials, Technology and Applications (FMS 2019 & NANOMATA
2019), 20192020
260. C. Uchiyama, Non-Markovian Effect Quantum Transport, The 6th International Workshop on Statistical Physics and Mathematics forComplex Systems, 2020
261. Jason ball, Shota Norimoto, Petr Moroshkin, Denis Konstantinov, Yuimaru Kubo, Quantum information technologies with maser,
International Workshop for Young Researchers on the Future of Quantum Science and Technology, 2020103

262. Jason ball, Shota Norimoto, Petr Moroshkin, Denis Konstantinov, Yuimaru Kubo, Quantum information technologies with maser,
International Workshop for Young Researchers on the Future of Quantum Science and Technology, 2020
263. K. Hirakawa, Terahertz Spectroscopy of Electron-Vibron Coupling in Single-Molecule Transistors, Colloquium "Terahertz Nanoscience",
2020
264. N. Lo Piparo, M. Hanks, C. Gravel, W. J. Munro and K. Nemoto, Quantum multiplexing for error correction codes, Workshop on Quantum
Networks and Quantum Information, 2020
265. N. Mori, G. Mil'nikov, J. Iwata, and A. Oshiyama, RSDFT-NEGF quantum transport simulation of ultra-small field-effect transistors, The 4thIEEE Electron Devices Technology and Manufacturing, 2020266. R. Ohta, Micromechanical engineering of light-matter interaction in solid-state two-level system, FQST2020, 2020
267. Rui Wang, Jian Sun, Russell S. Deacon, Koji Ishibashi, Spin-Orbit Interaction in a Hole Nanowire and its Applications for Hybrid Quantum
Systems, 2020 International Conference on Solid State Devices and Materials (SSDM2020), 2020
268. S. Iwamoto, Yasutomo Ota, Takuto Yamaguchi, Hironobu Yoshimi, and Yasuhiko Arakawa, Topological waveguides and nanoacvities using
semiconductor photonic crystals, Photonics West 2020, 2020
269. Satoshi Iwamoto, Light Propagation in Semiconductor Valley Photonic Crystals, International workshop"Variety and universality of bulk-edgecorrespondence in topological phases:From solid state physics to transdisciplinary concepts“, 2020104