01

Message from the Director

We at NTT Basic Research Laboratories (BRL) are extremely gratefulfor your interest and support with respect to our research activities.
BRL’s core mission is to promote progress in science along with
innovations in cutting-edge technology to advance NTT’s business.
Researchers in physics, chemistry, biology, mathematics, electronics,
informatics, and medicine have been undertaking groundbreaking
research within the material, physical, optical, and quantum sciences
fields. In 2020, we renewed our research structure to establish theMaterials Design & Science, Advanced Applied Physical Science, andQuantum Science & Technology Laboratories to better reflect thecurrent nature of BRL and its mission. This new structure brings all of
our key themes together in the same place.
Our management principle has cultivated the tradition of an “opendoor” policy at BRL. We are collaborating with many universities
and research institutes all over the world as well as within NTT.
Further, we have organized a number of workshops and international
symposiums (ISNTT and NTT-BRL School are two well known
examples) at the Atsugi R&D Center, where we share our research
results and efforts and host open discussions with people of various
background and interests. Our meeting style has changed somewhat
over the last year due to the COVID-19 pandemic, and under thesecircumstances, our management recognizes that the “open door”
has never been more important to BRL. We are currently planning
to organize a new style of workshops and symposiums that will
be facilitated on the Internet. We will never change our coremanagement principle.
These activities enable us to pursue our missions with respect to thepromotion of advances in science and the innovation of leading-edge
technology for NTT’s business. Your continued support in this is
greatly appreciated.

Front image:

Perovskite oxides
Complex oxides, which include
two or more cations in a unit
cell, especially those with theperovskite-related structures offer
a rich variety of functionalitiess u c h a s s u p e r c o n d u c t i v i t y,magnetism, and dielectricity.
They have been extensively
investigated from both scientificand technological viewpoints.
Researchers of NTT Basic
Re se a rch La b o rator ies havesucceeded in preparing theworld’
s best-quality thin filmsof such materials, including
trailblazing superconductors
and magnetic materials beyond
conventional concepts. Theyuse a unique oxide thin-film
growth technique that they havedeveloped over many years, withwhich atoms can be supplied ad
arbitrium in vacuum.

Activity Report

Advisor y Board
The aim of the Advisory Board is toprovide an objective evaluation of
our research plans and activities
that will enable us to utilize
strategic management in a timely
manner. At this meeting, BRL
researchers had lunch and a poster
session with the board members,
where they had the chances topresent their research to the board
in a casual atmosphere. The nextm e e t i n g , o u r 11 t h w i l l b e h e l donline in 2021.

Director of NTT Basic Research Laboratories

02

Activity Report

N T T- B R L S c h o o l
NTT-BRL School is designed to foster young researchers and topromote the international visibility of NTT. In 2019, with“Quantum
Hybrid Systems”as the theme, we had lectures by Prof. Göran
Johansson and Prof. Per Delsing (both from Chalmers Universityof Technology) and by Dr. Kouichi Semba (National Institute ofCommunications Technology). There were also laboratory tours
and a poster session.

ISNTTInternational School and Symposium on Nanoscale Transport and phoTonics

ISNTT, the international symposium and school hosted
biennially at NTT-BRL, brought together leading scientists,
researchers, and graduate students to share their latest
research and discoveries related to the physics andtechnology of nanoscale structures. We encouraged frankand open technical discussions on recent breakthroughs andadvances in related research. In 2019, we had 135 oral/
poster presentations, including a keynote talk by Prof. Klaus
von Klitzing (Max Planck Institute) and Prof. Yasunobu
Nakamura (University of Tokyo/Riken) and 19 invited talks.

LASOLV Seminar
To expand the application research fields of
optical oscillator-based computing, the LASOLV
seminar was held in February 2020. With a total of
80 attendees, the exciting power of LASOLV wasdemonstrated with the combinatorial optimization
problems. Moreover, Prof. Nozomu Togawa(Waseda University) made a special lecture on theemerging approaches around the world for solving
combinatorial optimization problems with the nonvon Neumann architecture.

03

Organization

NTT Basic Research Laboratories

Director

Hideki Gotoh

Research Planning Section

Multidisciplinary Materials Design and Science Laboratory

Advanced Applied Physical Science Laboratory

Quantum Science and Technology Laboratory

Executive Manager

Executive Manager

Executive Manager

Executive Manager

Kazuhide Kumakura

Hideki Yamamoto

P5●Nanodevices Research

Research Group●Low- Dimensional
Nanomaterials Research
Group●Molecular and Bio Science
Research GroupGroup●Nanomechanics ResearchGroup●Quantum Optical Physics
Research Group●Photonic Nano-Structure
Research Group●Researchers (Foreign Researchers)…９7（１3）●Research Associate/Specialist…１０●International Interns…7＊●Domestic Interns…9＊●Guest Researchers…1＊

P7●Thin-Film Materials

The population data of NTT-BRL members●Joint Researcher…7

Katsuya Oguri＊…Jan. to Dec. 2020 total

Hiroki Takesue

P9●Quantum Optical State

Control Research Group●Theoretical Quantum

Physics Research Group●Superconducting Quantum

Circuits Research Group●Quantum Solid State

Physics Research Group04
As of Dec. 31, 2020

Advisor y Board
Forschungszentrum Jülich, Germany

Prof. Andreas Offenhäusser
University of Twente, The Netherlands

Prof. Dave H.A. Blank

Chalmers University of Technology, Sweden

Prof. Per Delsing

Laboratoire Kastler Brossel, France
Sorbonne Université, Ecole Normale Supérieure, CNRS

Prof. Elisabeth Giacobino
CEA Saclay, France

Prof. Christian Glattli
Max-Planck-Institut für Festkörperforschung, Germany

10th Advisory Board Meeting (January 30, 2019)

Prof. Klaus von Klitzing

University of Illinois at Urbana-Champaign, U.S.A.

Prof. Sir Anthony J. Leggett

The University of Texas at Austin, U.S.A.

Prof. Allan H. MacDonald
Imperial College London, U.K.

Prof. Sir Peter Knight

Nanophotonics Center

Research Center for Theoretical Quantum Physics

Bio-Medical Informatics Research Center

Project Manager

Project Manager

Project Manager

Masaya Notomi

P11

William John Munro

P11

Hiroshi Nakashima

P11

Research Professors
Medical & Health Informatics Laboratories (MEI Lab),NTT Research, Inc.

Prof. Hitonobu Tomoike
Physics & Informatics Laboratories (PHI Lab),NTT Research, Inc.

Prof. Yoshihisa Yamamoto

05

Multidisciplinar y Materials Design and Science Laborator yGroup Introduction

Multidisciplinary Materials Design andScience Laboratory
Overview
T h e a i m of t h e M u lti d is c i p li n a r y M a te ri a l s D e s ig n a n d
Science Laboratory is to contribute to progress in materials
science a n d to revolutio nize informatio n commu nicatio ntechnolog y by creating novel materials with various
internal degrees of freedom (lattice, charge, spin, orbital,etc.) through materials design and synthesis beyond
c o nve n ti o n a l c o n c e p t s of c l a s s if i c a ti o n s , d i m e n s i o n s ,scales, and synthesis methods. The research groups that
constitute this laboratory are investigating a wide rangeof materials including semiconductors, superconductors,
m a g n e t i c m a t e ri a l s , t o p o l o g i c a l m a t e ri a l s , c o n d u c t i v epolymers, and biological soft materials. We are conducting
innovative materials research based on advanced thin-filmgrow th te ch n ologies , high - p re cisio n a n d high - resolutio nmeasurements of structures, properties along withtheoretical studies, and data science (informatics).

Multi-source molecular beam epitaxy apparatus:
an enabling technology for high-quality thin films
of complex oxides/nitrides, which is also exploited
as a synthesis method sui generis for novel
superconductors and magnetic materials.

Thin-Film Materials Research Group
Novel Semiconductor Devices

Creation of light- emitting devices over a wide range from
D U V to N I R , high - ef ficiency energ y conversion devices ,hig h - p owe r d evic e s , a n d n ovel m ultif u n ctio n al (o ptic al,
electric, and spintronic) devices

Low-Dimensional Nanomaterials ResearchGroup
2D atomic-layer Materials

Creation of ultimately thin functional atomic-layer materials
for next-generation electronics

Complex Oxide Thin Films

C re a tio n of t ra il b la zi n g s u p e rc o n d u cto r s a n d m a g n etic
materials beyond conventional concepts

Molecular and Bio Science Research Group
Biocompatible Electrode Materials

Development and application of bioelectrode materials formeasurement of deep biological information

Bio-devices
Creatio n of bio -fu n ctio nal mim etic d evices exploiting
biomolecules, cells, and soft materials

06

[Si]
low

106
104

high

102
100
1.0

1.5

2.0

2.5
-1

3.0

3.5

1000/T (K )[Si]: 1.21018 cm-3

1018
1017
1016

𝑛𝑛 𝑛𝑛 + 𝑁𝑁�
𝑁𝑁�
𝐸𝐸�
=
𝑒𝑒𝑒𝑒𝑒𝑒 −𝑁𝑁� − 𝑁𝑁� − 𝑛𝑛 𝑔𝑔�
𝑘𝑘� 𝑇𝑇

1014

Sr
Ru
O
Ti

ED : 0.19 eV
ND : 1.21018 cm-3
NA : 7.41017 cm-3

1015

0.5

1.0

1.5

2.0

2.5
-1

3.0

3.5

1000/T (K )

(a)

(b)

Experiment (Temp. 2 K)

100ǻıxx (kS/m)

10

1019

Conductance

Undoped[Si]:2.81017 cm-3
[Si]:1.21018 cm-3
[Si]:4.01018 cm-3
[Si]:1.51019 cm-3

8

Theoretical calculation

50
0
í50

0.10

0.15
1/B (Tí)

0.20

Magnetic field(a) Temperature dependence of resistivity for undoped and Si-doped c-BN (001) layers.
(b) Temperature dependence of carrier concentration for Si-doped c-BN (001) layer ([Si]= 1.2×10¹⁸ cm-³).

(Left) Crystal structure of SrRuO₃.
(Right) Quantum oscillations stemming from the Weyl semimetal states in SrRuO₃. The
experimental result (blue line) coincides well with the theoretical calculation (black line).

n-type Electrical-conductivity Control for Cubic
Boron Nitride (c-BN) Epitaxial Layers

Emergence of Magnetic Weyl Semimetal State in
Ultrahigh-quality SrRuO₃ Thin Films

Cubic BN (c-BN) is a widegap semiconductor with excellent
material properties such as large breakdown field and highthermal conductivity, etc. For c-BN, the Baliga figure-of-merit,which indicates the expected performance limit for powerswitching devices, is larger than those of AlN and diamond. For
electron device applications of c-BN, electrical conductivity
control by impurity doping is necessary. Recently, we achieved
control of the n-type conductivity of c-BN epitaxial layers with
Si doping: the resistivity decreases when the Si concentration
is increased. This result will open the door for new powerdevice applications of c-BN

SrRuO₃, a ferromagnetic metal, is an essential material foroxide electronics and spintronics. We observed quantum
transport phenomena peculiar to a unique electronic state
called“magnetic Weyl semimetal”in ultrahigh-quality SrRuO₃
thin films, which were achieved by a machine learning-assisted
thin film growth technique. This first experimental proof of themagnetic Weyl semimetal state in oxide materials will lead us
to innovative oxide materials and novel quantum devices in the
future.

K. Hirama, Y. Taniyasu, H. Yamamoto, and K. Kumakura, Appl. Phys. Lett. 116, 162104 (2020).

Y. K. Wakabayashi, et. al., APL Mater. 7, 101114 (2019).
K. Takiguchi, Y. K. Wakabayashi, et. al., Nat. Commun. 11, 4969 (2020).

Absorption
(a)

(c)
H2O

Light wavelength
0.8

532nm

0.6

785nm
1550nm0.4

Inﬁnite limit

0.2

H2O

(b)

T=400 s

12

5 µm
T=0 s

T=200 s

T=400 s(a) Schematic illustration of artificial freestanding membrane
expansion mechanism. (b) Fluorescence images of the change inartificial freestanding membrane shape induced by osmotic pressure
difference. (c) Time-lapse image of the lipid domain (white arrow) and

Lipid domain area (µm2)

1.0T=900 s

T=2500 s

10
8
6
4
2

the variation of the lipid domain area with time.

87

0

200

400

600

Number of graphene layer

800

0

1000

2000

3000

Time (s)

4000

5000

Calculated results

Universal layer number distinguishing
between graphene and graphite

Control of Lipid Domain Formationin Artificial Membranes

Graphene absorbs light in accordance with the fine-structure
c o ns t ant α ≅ 1/137: e .g ., a b o u t 2.3 % o f v is ib le lig h t i sabsorbed by graphene. The α value is universal in the sensethat it is not related to material parameters but rather is solely
related to the elementary charge, which is a fundamental
constant governing the coupling of light and matter. We foundin graphite a new universality governed only by α in which thereciprocal of α appears as a characteristic number of layers, 2 ⁄πα ≈ 87, in the light absorptance of an N-layer graphene.

The lipid domain in biological cell membranes plays a very
important role in signal transduction. We developed a method
to form a model structure of the lipid domain in an artificial
freestanding membrane formed on a microwell-patterned
substrate. We succeeded in forming a stable domain for morethan 1 hour by deforming the artificial freestanding membrane
through the osmotic pressure difference inside and outside thewell and moving the lipid and cholesterol necessary for domain
formation to the well part. Our accomplishment of forming
and controlling domain structures in artificial membranes
is expected to serve as a key technology for understanding
biological phenomena.

K. Sasaki and K. Hitachi, Commun. Phys. 3, 90 (2020).
K. Sasaki. J. Phys. Soc. Japan 89, 094706 (2020).

A. Oshima, H. Nakashima, and K. Sumitomo, Jpn. J. Appl. Phys. 59, 027001 (2020).

Multidisciplinary Materials Design and Science Laboratory

Resistivity (Wcm)

1010

Carrier concentration (cm-3)

Achievements in 2020

07

Advanced Applied Physical Science Laborator yGroup Introduction

Advanced Applied Physical Science
Laboratory
Overview
T he Advanced A pplied Physical Science L aboratory has
lau nched towa rds the creatio n of in novative informatio ncommunication technologies and future functional devices
that bring long-term value for the accelerating technologyd r i v e n s o c i e t y. L e a d i n g r e s e a r c h g r o u p s i n t h e f i e l d sof nanoelectronics, nanomechanics, nanophotonics,
spintronics, and quantum electronics are closelycollaborating for this exciting challenge. We will pioneer theforefront of the applied physical science field and discovernovel functionalities in solid-state quantum systems basedon our nanofabrication technology, advanced measurement
technology, and light-wave technology.

Nanodevice Research Group

Single-electron Devices for Ultimate Electronics
Highly accurate, highly sensitive, and low- power devices
based on single charge transfer and detection

Nanodevices with Novel Functions

Novel and high performance nanodevices based on silicon
and hybrid materials

Nanomechanics Research Group

Semiconductor Opto/electromechanics
Novel devices using mechanical functionality insemiconductor fine structures

Phonon Manipulation

P r o p a g a t i o n c o n t r o l o f a c o u s t i c w a ve s u s i n g a r t if i c i a l
structures

Quantum Optical Physics Research Group

Ma nip ulation of Ult rafast a n d Ult ra - st a ble L ase r
Field
Explore ultrafast physics and establish the standard opticalfrequency

Nano-scale Physics in Optically-active Materials

Characterize photons, excitons and spins in thesemiconductor nano-structures and rare-earth ions.

Photonic Nano-Structure Research Group
Integrated Nanophotonics Technologies

Ultra - compact and ultra -low power photonic devices andcircuits, novel photonic phenomena in nanostructures

Instrument to control optical dispersion andchirp for achieving ultrafast laser pulses inattosecond regime.

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Schematic illustrationof the device and themeasurement setupthat allows the chaos
generation (top) andthe experimental data(right).

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40

Optical Frequency Distribution Using Laser
Repeater Stations with Planar Lightwave Circuits

Demonstration of a Novel Scheme to Generate
Chaotic Signals Using a MEMS Oscillator

We have been conducting research on ultra-high-precision
optical frequency transfer via telecom fiber networks withthe aim of achieving time and frequency synchronization withaccuracy exceeding GNSS and observing relativistic effects
using optical clock networks. We have developed the world’sfirst ultra-low-noise laser repeater systems based on a planar
lightwave circuit in collaboration with NTT Device Technology
Laboratories. We installed the systems in a commercial
telecom fiber network of NTT East, which connects RIKEN,
the University of Tokyo (UTokyo), and NTT, and demonstrated
optical frequency transfer over a 200-km fiber with accuracy
exceeding that of optical lattice clocks.

Recently, there has been increasing interest in applying chaotic
signals in the field of information technologies, such as machinelearning and secure communications. With such applications, theefficient generation of chaotic signals using on-chip devices takes
on an added importance. Microelectromechanical systems (MEMS)
oscillators are one of the promising candidates that could meet suchrequirements, as they have advantages of high integration capability
and precise electrical control. We succeeded in generating chaotic
signals using a MEMS oscillator with lower voltage than typicallyreported in literature. This new method enables the integration ofchaos generators with standard MEMS devices and allows machinelearning of the output data from these devices directly on a common
semiconductor chip.

T. Akatsuka, T. Goh, H. Imai, K. Oguri, A. Ishizawa, I. Ushijima, N. Ohmae, M. Takamoto, H. Katori, T.
Hashimoto, H. Gotoh, and T. Sogawa, Opt. Express 28, 9186 (2020).

S. Houri, M. Asano, H. Yamaguchi, N. Yoshimura, Y. Koike, and L. Minati, Phys. Rev. Lett. 125, 174301(2020).


 

Silicon nanowire

60~50 nmNumber ofelectrons at 

Sensor current

Temperature (K)Sensor

1.53
1.52
1.51

Time

50

40

30




20

Probability

Sensor Power

Observation of Thermoelectric Effect in a
Silicon Nanowire MOSFET by Using Singleelectron Counting Statistics

Generation and Annihilation of TopologicallyProtected Bound States in the Continuum andCircularly Polarized States by Symmetry Breaking

We investigated nanometer-scale non-equilibrium phenomena insilicon single-electron devices by observing the Seebeck effectin a silicon nanowire using electron counting statistics. The
stochastic nature of the electron provides us with informationon the temperature difference between two points with tennanometer separation in a silicon nanowire.

Recently, the topological phenomena of photons in photonic
crystals have been extensively investigated. A bound statein the continuum (BIC), which is one of the topologicalsingularities in photonic crystals, is a unique topologicalstate of photons in photonic crystals. However, we must
carefully tune the structural parameters of photonic crystals
in order to generate nontrivial BICs. We have found a scheme
to deterministically generate nontrivial BICs by deforming aphotonic crystal and lowering its symmetry. This enables us tocontrol topological singularities dynamically and create novel
light-emitting devices with topological singularities.

K. Chida, A. Fujiwara, and K. Nishiguchi, 33rd International Microprocesses
and Nanotechnology Conference (MNC 2020).

T. Yoda and M. Notomi, Phys. Rev. Lett. 125, 053902 (2020).

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Achievements in 2020

09

Quantum Science and Technology Laborator yGroup Introduction

Quantum Science and Technology
Laboratory
Overview
T h e Q u a nt u m S cie n c e a n d Te c h n o l o g y L a b o ra to r y willcontribute to the exploration of the quantum science field
and the development of new technologies for overcomingth e co nve ntio nal info rmatio n p ro cessing limits withq u a n t u m - e n a b l e d d evi c e s a n d s y s te m s . W it h q u a n t u minformatio n theor y a nd our experimental research inphotonic, semiconductor, and superconducting systems asa basis, we aim to achieve new technologies in the areasof quantum communication , quantum sensing , opticaloscillator-based computing, and quantum computing basedon superconducting circuits and topological phenomena.

Q ua ntum Optical State Cont rol Resea rch
Group
Photonic Quantum Communication

Control of quantum state of light and its application to novelcommunication systems

No n -vo n Ne u m a n n Com p u t at io n Usi n g Q u a n t u m
OpticsNew computers based on coupled optical oscillators

Theoretical Q ua ntum Physics Resea rch
Group
Theoretical Quantum Information Science

Proposal and systematic design of quantum computation,communication, network and metrology schemes includingarchitectures.

Superconducting Quantum Circuits Research
Group
Superconducting Quantum Circuits

Manipulating quantum states using superconducting
devices

Ultimate Quantum Measurement and Sensing

Highly sensitive measurement technologies using quantum
mechanical effects

Quantum Solid State Physics Group

Quantum Transport in Hetero- and Nano-structures
based on Semiconductor and 2D Materials
Unconventional charge and spin transport phenomena inquantum devices

Fast Coherent Carrier Dynamics in Electronic Devices
Information processing with coherent electron motion3

He/4 He dilution refrigerator used to carryout low-temperature (below 100 milli-kelvins)
experiments for superconducting andsemiconductor quantum devices.

10

Achievements in 2020

Floquet theory:
2T-DTCC

B

Domain walls:

0 1 2 3 4 5 6 7Percolation rule:(A) Shows the 2T-DTC dynamics with no rotation error.
(B) Shows the effective Hamiltonian represented as a tight-binding matrix.
(C) After applying the percolation rule, the effective Hamiltonian is represented as a graph.

Controlled-phase Gate for Time-bin Qubits
Time-bin qubits, which encode the quantum information ona superposition of single photon states in two different timeslots, have been implemented in quantum communication overoptical fiber. However, two-qubit quantum gates for time-bin
qubits have not yet been achieved. We demonstrated the firstcontrolled-phase (CPhase) gate for time-bin qubits using a 2
× 2 optical switch as a beam splitter with a splitting ratio thatchanges depending on the temporal modes. This technology
will be useful for achieving advanced quantum information
processing over optical fiber networks.

H. P. Lo, T. Ikuta, N. Matsuda, T. Honjo, and H. Takesue, Appl. Phys. Express,11, 092801 (2018), (Spotlights 2018).
H. P. Lo, T. Ikuta, N. Matsuda, T. Honjo, W. J. Munro, and H. Takesue, Phys. Rev. Applied 13, 034013 (2020).

Simulating Complex Quantum Networks withTime Crystals
Crystals are widely present in everyday life in the form of solidmaterials with atoms arranged in regular patterns, such as
salt and diamonds. Crystalline structures also appear in timeand are known as discrete time crystals. By using common
tools in graph theory, we here introduce a method to describe
and characterize the physical phenomena related to discrete
time crystals. During their melting process, we show the
emergence of a preferential attachment mechanism that is
directly associated with the existence of scale-free networks.
Our work opens a new avenue of research and the possibility
to use discrete time crystals as quantum simulators of complex
quantum networks.

M. P. Estarellas, T. Osada, V. M. Bastidas, B. Renoust, K. Sanaka, W. J. Munro, and K. Nemoto,
Sci. Adv 6, eaay8892 (2020).

(a) Formation of plasmonic cavities by spatial control of graphene carrier density.
(b) Modulation of plasmon frequency in cavities defined by electrical boundaries.

Long-lived 3D Hybrid Flux Qubits
We developed a hybrid superconducting qubit that consistsof a 2D capacitively shunted flux qubit embedded in a 3D
microwave cavity. The hybrid qubit demonstrates excellent
relaxation times that are comparable to or exceed the values
reported for other types of flux qubits. Such long-lived fluxtunable qubits have potential applications in various quantum
technologies, including quantum sensing and quantum
computing. As one possible application, we demonstrated thata 3D hybrid flux qubit driven by a spin-locking pulse sequencecan be used for the detection of high-frequency solid-state
defects, which cause the qubit relaxation.

L. V. Abdurakhimov, I. Mahboob, H. Toida, K. Kakuyanagi, Y. Matsuzaki, and S. Saito, Phys.
Rev. B 102, 100502(R) (2020).

Active Spatial Control of Terahertz
Plasmons in Graphene
Plasmons, which are collective charge oscillations, are usefulfor developing nanophotonics and metamaterials. Graphene
plasmons have advantages over commonly used metal
surface plasmons in terms of their electrical tunability. In thiswork, we developed a way to control plasmon reflectivity atelectronic boundaries. This enables plasmons to be confined
to desired regions with controlled confinement strength. Our
device structure shows good potential for use as a platform for
implementing programmable plasmonic circuits.

N. H. Tu, K. Yoshioka, S. Sasaki, M. Takamura, K. Muraki, and N. Kumada, Commun. Mater. 1, 7 (2020).

Q u a n t u m S c i e n c e a n d Te c h n o l o g y L a b o r a t o r y

F

A

11

Nanophotonics Center

Nanophotonics Center

Nanophotonics Center

Overview
T h e N a n o p h oto nic s C e nte r was esta blis h e d in A p ril
2 012 a n d i s c o m p o s e d o f s e v e r a l g r o u p s i n v o l v e din nanophotonics research at NT T Basic Research
L a b o rato ries a n d N T T D evic e Te c h n olog y L a b o rato ries .
We are conducting studies of photonic crystals to reduce
the footprint and energy consumption of various photonic
d evices , such as o ptical switches , o ptical memories ,modulators , lasers , and photo - detectors . We are also
studying various photonic nanostructures to greatly enhancelight-matter interactions, and exploiting photonic integrated
circuits and devices for on-chip signal processing.
Extreme enhancement of light-matter interactions by using photonic
crystals and plasmonics
Integrable nanophotonic devices with extremely small energy
consumption● Nano-imprint, SPM lithography and manipulation● Integration of various high-performance devices on a silicon platform●●

Research Center for Theoretical Quantum Physics

R e s e a rc h C e n t e r f o r T h e o re t i c a l Q u a n t u m P h y s i c s

Research Center for Theoretical Quantum Physics

Overview
The twentieth century saw the discovery of quantum mechanics, a setof principles that explains the nature of matter and light at the atomic
level. These counter-intuitive principles have not only dramaticallychanged our understanding of the reality of our physical world but
also enabled a technological revolution. They are responsible forthe digital age in which we live. Naturally arising questions are whatfurther we can learn from these principles and what technologicaladvances could be enabled. The newly formed Center for Theoretical
Quantum Physics established in July 2017 brings together diverse
researchers (physicists, computer scientists, mathematicians andeven chemists) from across NTT to pursue cutting edge research in ahighly collaborative environment.
The foundation of quantum mechanics
Quantum matter (hybrid quantum systems, strongly correlated systems,
condensed matter and superconducting systems)● Quantum algorithms and complexity● Quantum communication, simulation and computation● Quantum metrology and sensing● Atomic, molecular and optical physics●●

Bio-Medical Informatics Research Center

B i o - M e d i c a l I n f o r m a t i c s R e s e a rc h C e n t e r

Bio-Medical Informatics Research Center

Overview
The Bio - M edical Informatics Research Center (B M C) wasestablished in J uly, 2019 as a research organization in which
five NTT laboratories collaborate with the goal of creating datadriven medicine using ICT. The BMC engages in basic and appliedresea rch o n A I a nalyses of medical a n d health data , genome
informatio n a n d b ehavior informatio n , real-time biomo nitoringin daily life, biomimetic na no d evices , a n d new biocom patible
materials . I n addition , it promotes innovations in medical andhealth fields in cooperation with partners at medical institutes
and Medical & Health Informatics Laboratories (MEI Lab), NT T
Research, Inc.
Personalized medicine by AI analysis of personal medical data (precision
medicine)●Long-term Holter ECG measurement and rehabilitation activity supported
by hitoe●Lifestyle-related disease management based on noninvasive blood glucose
sensing, core body temperature measurement, and AI risk analysis●Fabrication of implant materials and artificial neural networks thatcomplement biological functions●

12

Achievements in 2020

時間 (ナノ秒)

Demonstration of a High-performance Optical
Logic Gate for Ultralow-latency Processing

A

B

Output
2 μm

Different logic by tuning Bias intensity

B
AND
XNOR
NOR
0.5

Time (ns)1.0Linear Programs for Entanglement and Key
Distribution in the Quantum Internet
A quantum internet will enable the implementation of communication
tasks beyond the reach of conventional communication networks.
A pressing and necessary issue for the design of quantum network
protocols is the quantification of the rates at which these tasks
can be performed. In this work, we present a simple recipe thatyields efficiently computable lower and upper bounds on the
maximum achievable rates. This recipe is applied to protocols to
distribute secret key or maximal entanglement among clients in aquantum network. Our recipe reduces the computation to a linear
programming problem, and thus it can form the basis to rapidly
respond to requests from such clients.

S. Bäuml, K. Azuma, G. Kato, and D. Elkouss, Commun. Phys. 3, 55 (2020).

Wearable Acoustic Sensor Array System
Featuring Remote Transmission of Body Sounds
As a basic research toward providing a person with an enhanced
sense of well-being, such as early detection of diseases, wedeveloped a wearable acoustic sensor array system that can collectsounds from various parts of the human body and send the signals
remotely to a receiver terminal, which is equipped with many (e.g.,18) acoustic sensors inside an examination vest. When the systemcomes into practical use for medical care, a medical practitioner
will be able to listen to sounds from various locations on thepatient’s body without having to make direct physical contact withthe patient or use a traditional stethoscope, which will be usefulin online medical examinations. This system is expected to playa [key] role, potentially in combination with EEG signals, in the
research and development of new medical techniques such as thevisualization of physical states based on 3D body sounds.

M. Nakano, R. Shibue, K. Kashino, S. Tsukada, and H. Tomoike, EUSIPCO 2020, pp.1452-1456 (2020).

AND operation with different wavelengths
Optical input/output (a.u.)

A0

S. Kita, K. Nozaki, K. Takata, A. Shinya, and M. Notomi, Commun. Phys. 3, 33 (2020).

FabricatedΨ gateBias

Optical input/output (a.u.)

As a key device for ultralow-latency processing, we haved e m ons t r at ed t he hig h -p e rfo rma n c e o p e ra tio n o f a 3 μm -l o n g
photonic logic gate,“Ψ (psai) gate”, for the first time. The gate
delay is only ~30 fs, which is 300 times shorter than a conventionale l e c t r o n i c g a t e . B y i n t r o d u c i n g“b i a s l i g h t”, t h e f u n c t i o n o f
the logic operations can be switched between AND/XNOR/NOR etc. Plus, it is wavelength insensitive, which means it cansimultaneously perform different logic operations for different
wavelength channels in a single gate. We believe this concept ofΨ gates is indispensable for achieving low-latency and low-energy
consumption data processing based on photo-electronic converged
processors.

時間 (ナノ秒)

Schematic of a quantum internet.

1.5

A
B
AND
0

0.5
1.0
Time (ns)

1.5

13

NTT Fellow

Shingo Tsukada
Medicine, Physiology, Biomedical
interface & data analysis

The title of "NTT Fellow" is reserved for our most giftedscientist and engineers whose research and development
activities have brought them significant distinction
both within NTT and internationally. Our "Fellows" areextremely highly regarded. Next the title of "SeniorDistinguished Researcher" is given to outstanding
individuals who haveestablished themselves as global

intellectual leaders of their own research areas. The"Distinguished Researcher" title is given to innovative
researchers whose impressive achievement has beenrecognized both within and outside NTT.
They all are responsible for leading innovative researchand cutting-edge technical developments in research areas
Research Subject

Biological Information Elucidationconsidered important to NTT.
D e c e m b e r 31 , 2020

Using Advanced Medical Materials

Senior Distinguished Researcher

Hideki Yamamoto

Masaya Notomi

Hiroshi Yamaguchi

Koji Muraki

Nanophotonics Center ProjectManagerQuantum and Nano Device
Research

Quantum Solid State Physics
Research Group Leader

Research Subject

Research Subject

Research Subject

Photon Manipulation in Photonic
Nanostructures

Nano-mechanics in
Semiconductors

Electron Correlation in
Semiconductor Nanostructures

Akira Fujiwara

William John Munro

Hiroki Takesue

Research Center for Theoretical
Quantum Physics Project Manager

Quantum Science and Technology
Laboratory Executive Manager

Multidisciplinary Materials Design andScience Laboratory Executive Manager

Research Subject

Research Subject

Research Subject

Research Subject

Design and thin-film synthesis of novel
superconductors and magnetic materials withelucidation of the underlying physics

Ultimate Electronics Using
Semiconductor Nanostructures

The Design of Quantum Technologies

Quantum Communication
Experiments in
Telecommunication Band
Coherent Ising Machine

Distinguished Researcher

Norio Kumada
Katsuhiko Nishiguchi

Shiro Saito
Imran Mahboob

Haruki Sanada
Koji Azuma

Kengo Nozaki
Hiroki Mashiko

Takahiro Inagaki
Hajime Okamoto

Gento Yamahata

14

Publication List

The total number of NTT Basic Research Laboratories papers published ininternational journals in 2020 is 84 with an average impact factor of 4.923.
The 2019 impact factor of those individual journals are shown in ( ).

PHYSICAL REVIEW B (3.575)

9
8

PHYSICAL REVIEW A (2.777)
7

PHYSICAL REVIEW APPLIED (4.194)
6

PHYSICAL REVIEW LETTERS (8.385)

6

OPTICS EXPRESS (3.669)
5

COMMUNICATIONS PHYSICS (4.684)

5

JAPANESE JOURNAL OF APPLIED PHYSICS (1.376)
4

APPLIED PHYSICS LETTERS (3.597)

4

PHYSICAL REVIEW RESEARCH (N/A)
3

ACS PHOTONICS (6.864)
NATURE PHOTONICS (31.241)

2

SCIENCE ADVANCES (13.117)

1

PHYSICAL REVIEW X (12.577)

1

NATURE COMMUNICATIONS (12.121)

1

CARBON (8.821)

1

NANOPHOTONICS (7.491)

1

SCIENTIFIC REPORTS (3.998)

1

APL MATERIALS (3.819)

1

OPTICS LETTERS (3.714)

1

NEW JOURNAL OF PHYSICS (3.539)

1

APPLIED PHYSICS EXPRESS (3.086)

1

1

2

3

4

5

6

7

8

9

Number of Presentations

Number of Patents

88

79（33 Invited talks）

List of Award Winners
JSAP fellow

Study of Ultimate Control of Electrons Using Silicon Nanodevices

Akira Fujiwara

The Young Scientists' Prize, the Commendation for Science and Technology by the Minister of Education, Culture, Sports,
Science and Technology
Research on control of spin states and quantum transport in semicondtor quantum nanostructures

2020 PROSE AWARDS in the subject of Chemistry and Physics

Chemical, Gas, and Biosensors for Internet of Things and Related Applications (Elsevier)

CHEMINAS Young Excellence Award

Development of mobile plate for cell manipulation using microfabrication technology

Keiko Takase

Kohji Mitsubayashi, Osamu Niwa, Yuko Ueno

Tetsuhiko Teshima

42th CHEMINAS Poster Award

Three-dimensional extracellular recording by self-folding graphene electrode array
Koji Sakai, Tetsuhiko Teshima, Yuko Ueno, Hiroshi Nakashima, Masumi Yamaguchi

The 2nd Hyogo-Kansai Caterpillar STEM Award, Outstanding Achievement Award
Electrical control of spin-orbit interaction using semiconductor nanowire

Keiko Takase

JSAP Paper Award

Electron aspirator using electron–electron scattering in nanoscale silicon
Himma Firdaus, Tokinobu Watanabe, Masahiro Hori, Daniel Moraru, Yasuo Takahashi, Akira Fujiwara, Yukinori Ono10