01

Message from the Director

We at NTT Basic Research Laboratories (BRL) are extremely
grateful for your interest and support in our research activities.
Our laboratories’ central mission is to promote progress inscience and innovations in leading-edge technology that canadvance NTT's long-term business, overcoming current limitationsin speed, size, and of course energy consumption.
To achieve this, scientists & engineers in the fields of physics,
chemistry, biology, mathematics, electronics, informatics, andmedicine, conduct fundamental research in material, physical, andquantum science.
An "open door" management policy allows us to collaborate
with many universities and research institutes from all over
the world, as well as other laboratories within NTT, further
enhancing our ability to achieve our missions. We have regularlyorganized international symposiums and workshops at our Atsugi
R&D center to disseminate our research achievements andcommunicate with fellow scientists, engineers and the public.
Unfortunately, in 2021, we had to postpone the "NTT-BRL
School" for young researchers due to the COVID-19 pandemic,
but remotely held "ISNTT", an international symposium focusedon the latest developments in materials, physical, and quantum
sciences for future technologies. We also remotely held ourAdvisory Board meeting showcasing our latest achievements andreceiving their advice & recommendations for the future.
All of these activities enable us to realize our "open door" policy
and mission.
Your continued support would be highly appreciated.

Director of NTT Basic Research Laboratories

02

Activity Report

Advisory Board
The aim of the Advisory Board isto provide a critical and objective
evaluation of our research plans andactivities. This enables us to employ
strategic management in a timely
manner. Proposals and advice received
at this biennial board meeting are

Advanced Applied Physical Science Laboratory

Photonic Nano-structure Research GroupWe are aiming to establish ultimate large-scale photonic integration technology for massively and ultimately
integrating ultra-small optical devices with various functions by using nanophotonics such as photonic crystal,silicon photonics, plasmonics technologies. We also conduct research aiming at the ultimate reduction of energy
consumption of optical information processing. In future we will introduce sophisticated optical network in theprocessor chip and aim to realize ultra high speed ultra low energy consumption processor.

Ultra-compact and ultra-low power Integrated nano-photonics and circuits
NanophotodetectornShrink of opticalcommunication distance

Bias
p

Au

outputSignal B

Optical transistor

Optical data-com(1m–100m)

Optical logic gate

Signal A

NanomodulatorpnOptical fiber tele-com(> 1 km)Hybrid system with nano-material and nano-photonics
MIM WG+
Converter

Optical layerθ

Optical switch

Inter-chip-com(1mm–1cm)

Graphene
2 µm

Si WG

SiN PhC+
ZnO NW

Nano Laserθ≧60°

Topological
Photonics

Novel photonic phenomena in nanostructures

Many-core CMOS layer
Intra-chip nanophotonic
computing ( < mm)Students

Dr. M. Notomi(Project Manager)

Dr. A. Shinya(Group Leader)

Dr. E. Kuramochi

Dr. H. Taniyama

Dr. H. Sumikura

Dr. K. Nozaki

Dr. M. Takiguchi

Dr. M. Ono

Dr. S. Kita

Dr. K. Takata

Dr. N. Takemura
Dr. T. Yoda
(Research Associate) (Research Associate)

T. Uemura ( Tokyo Tech )W. Dai( Tokyo Tech )K. Kawasaki ( Tokyo Tech )T. Honda( Tokyo Tech )T. Kurihara ( Tokyo Tech )S. Otuka( Tokyo Tech )H. Yamada ( NAIST )NTT Basic Research Laboratories Advisory Board Meeting 2021

reflected in our actual ongoing researchand its management. The 11th meeting
was held online in February, 2021 dueto the global spread of the coronavirus.
At the meeting, we reported our latest
research results and received valuable
feedback.

ISNTTInternational Symposium on Novel maTerials andquantum Technologies

The International Symposium on NovelmaTerials and quantum Technologies (ISNTT)
focuses on the latest developments inmaterials, physical, and quantum sciences
for future technologies. This biennial
symposium brings together world leading
academics, scientists, and students with our
NTT BRL researchers to foster interactions,discussions, and collaborations. At ISNTT
2021 , k e y n o t e t a l k s w e r e g i v e n b y P r o f .
Pablo Jarillo-Herrero (MIT), Prof. Yoshiro
Hirayama (Tohoku University), Prof. Hidetoshi
Katori (University of Tokyo, RIKEN), and Prof.
Laurens W. Molenkamp (Würzburg University)
alongside 17 invited talks. In addition, 32
contributed presentations were given and 84
posters were presented. In its virtual format,
we had 346 participants from 20 countries
compared toabout 200 participants in theprevious symposium.

N T T- B R L S c h o o lFront image:

Nanophotonics

The NTT-BRL School’s mission is to foster the development ofyoung researchers and promote the international visibility of NTT.
Since 2017, the school has been held alongside ISNTT, enabling

By using photonic crystals and plasmons, we cancontrol light in structures that are as large as the
wavelength of light or deep-subwavelength. We

those young researchers to directly interact with world leading

have developed optical transistors and opticalexperts in the field. However, the ISNTT 2021 virtual format

resonators that operate at high speed and ultra-low

made this extremely difficult to achieve and so the school was
postponed until 2023 when the next symposium will take place.

energy by utilizing the nanophotonics technology,
and are aiming to realize highly integrated opticalinformation processing chips in the future.

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)…９5（１2）●Research Associate/Specialist…9●International Interns…1＊●Domestic Interns…15＊●Guest Researchers…1＊

P7●Thin-Film Materials

The population data of NTT-BRL members●Joint Researcher…8

Katsuya Oguri＊…Jan. to Dec. 2021 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, 2021

Advisor y Board

Chalmers University of Technology, Sweden

Prof. Per Delsing

Max-Planck-Institut für Festkörperforschung,Germany

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

Laboratoire Kastler Brossel,
Sorbone Universite, Ecole Normale
Superieure, CNRS, France

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

CEA Saclay, France

University of Twente, The Netherlands

Prof. Klaus von Klitzing

Imperial College London, U.K.

Prof. Sir Peter Knight

Prof. Sir Anthony J. Leggett

Prof. Allan H. MacDonald

Prof. Elisabeth Giacobino
Forschungszentrum Jülich, Germany

Prof. Andreas Offenhäusser

Prof. Christian GlattliProf. Dave H.A. Blank

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

Tohoku University

Prof. Hitonobu Tomoike

Prof. Masao Morita

Director, Physics & Informatics
Laboratories (PHI Lab), NTT Research, Inc.

University of Toyama

Prof. Yoshihisa Yamamoto

Prof. Kiyoshi Tamaki

05Multidisciplinar y Materials Design and Science Laborator yGroups and Research Themes

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

Achievements in 2021

600

200 nm[111][11-2][-110]

3
2

200

1
0

250 500 750 1000

0Temperature (K)Ferromagnetic

Superparamagnetic

High energy barrier
to suppress magnetization rotation

Magnetization rotationby thermal fluctuation

EnergyDiamond thin film

4

400

0

Fe nanoparticles

Ferro Superpara
magnetic magnetic

800

Epitaxial Intercalation Growth

Cu

hBN

N

B

N

Cu

hBN templating

B N B N H
HH

Cu

H-terminationhBNG

B N B N H
C C C
Cugraphene growth

Direction of magnetization（L） Diamond thin films embedded with Fe nanoparticles grown by our plasma CVD techniques（R） Unique magnetic properties due to the ferromagnetic and superparamagnetic state of Fe nanoparticles
and the schematic of the origin of their magnetic properties

Schematic of one-pot growth of hexagonal boron nitride/graphene heterostructure
via epitaxial intercalation. The scale bar is 2 μm.

Magnetic Properties of Fe Nanoparticles
Embedded in Diamond Thin Films

Epitaxial Intercalation Growth of Hexagonal Boron
Nitride/Graphene Vertical Heterostructure

A spin transistor, a device that utilizes spins as a new
information carrier, is expected to achieve ultralow-power
consumption due to its non-volatile functionality. Diamond isa promising material as a semiconductor but also expected
to show excellent spin transport properties even above room
temperature. Therefore, we are exploring the applicationof diamond to spintronics. In this study, we succeeded in
growing diamond thin films embedded with Fe nanoparticles
and observing the unique magnetic properties of the Fe
nanoparticles. Moreover, our analysis revealed the originof those properties. This result is a major step toward therealization of practical spin devices.

High-throughput synthesis of vertically stacked twodimensional materials with desired interlayer angles is essential
to investigate their novel physical properties and consequently
explore their potential practical applications. We havedemonstrated a novel method named“epitaxial intercalation”
for one-pot chemical vapor deposition growth of a hexagonalboron nitride (hBN)/graphene vertical heterostructure. In thismethod, graphene growth occurs at the interface between
hBN and a catalyst, leading to good and uniform interlayeralignment. The hBN/graphene heterostructure prepared thus
exhibits superior electronic properties such as high carrier
mobility.

M. Kawano, K. Hirama, and K. Kumakura, International Conference on New Diamond and Nano Carbons
2020/2021.

S. Wang, J. Crowther, H. Kageshima, H. Hibino, and Y. Taniyasu, ACS Nano 15, 14384 (2021).

Creation of On-chip Hydrogel Channels for
Reproducing In-vivo Environments

Heart Abnormality Detection Technology
for ECG Transmitters

To express and evaluate advanced mature cellular functions,
it is important to develop technologies to reproduce scaffolds
with structures and properties similar to those of biological tissues
in vitro. We have devised an on-chip method to fabricate a flow
channel that mimics blood vessels using a hydrogel with highbiocompatibility and permeability. In addition, by culturing cellson the layer-stacked gel and injecting drugs into the channels,
we succeeded in local chemical stimulation of cells throughmolecular diffusion. This result is expected to be developed
as a fundamental technology for reproducing the in-vivo
environment to analyze the detailed functions and kinetics ofcells.

To detect serious cardiac abnormalities early by utilizing thefunctional material hitoeTM, we have developed an algorithm
for detecting heart abnormalities that operates inside a
wearable device. The algorithm also suppresses false detectionof cardiac abnormalities caused by floating bioelectrodes
and body motion noise. We provided this technology to groupcompanies as a technology to detect heart abnormalities inusers of rehabilitation-support robots.
In the future, we will proceed with research and development
toward the realization of new services that support us in ourdaily lives, such as detection of the various types of heartdisease and visualization of potential heart disease risk factors.

R. Takahashi, H. Miyazako, A. Tanaka, and M. Yamaguchi, Lab Chip 21, 1307-1317 (2021).

Multidisciplinary Materials Design and Science Laboratory

Coercivity (Oe)Fe rod5Magnetization (µemu)

1000

Plasma07

Advanced Applied Physical Science Laborator yGroups and Research Themes

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.

08

Achievements in 2021

(b)

(a)

f

SingleelectroneQuantum dot

Optimalaccuracy

StrongWeak

Insulating layer
SiliconCapacitive coupling strength between
the gate electrode and quantum dot(a) Schematic of a silicon single-electron transfer device.
Electrons are transferred one by one by applying a highfrequency signal (frequency f) to the gate. (b) Capacitive couplingstrength dependence of the transfer error rate.

Discovering a Guideline for Minimizing
Single-electron Transfer Error Rate

Realization of an Optomechanical Device with
Extremely Low Optical Energy Loss

Single-electron transfer through a quantum dot can generate an
accurate current, and is expected to be applied to a quantum
current standard, which corresponds to a ruler with which
to measure electric current. For this application, the error
rate of the single-electron transfer must be sufficiently low.
In this study, we investigated the transfer mechanism in asilicon single-electron transfer device (Fig. a) in detail using
theoretical calculations, and found that there is an optimalaccuracy (i.e., the transfer error rate is minimized) in theintermediate regime of capacitive coupling between the gateelectrode and quantum dot (Fig. b). By fabricating a device witha structure in the intermediate regime, we can expect to realize
ultrahigh-precision single-electron transfer.

Optomechanical devices are attracting attention as functional
devices that add mechanical degrees of freedom to optical devices
such as light-emitting diodes. They have so far been built by usingeasy-to-process semiconductor materials. In contrast, we havesucceeded in creating a novel optomechanical device with ordersof magnitude smaller optical energy loss than conventional onesby using rare-earth-doped crystals, whose optical properties aresuperior to those of semiconductors. This achievement will lead tothe creation of ultrasmall, low-loss optical devices such as opticalamplifiers utilizing minute vibrations.

G. Yamahata, N. Johnson, and A. Fujiwara, Phys. Rev. B 103, 245306 (2021).

-20
-30

-18

Insertion Loss (dB)

Propagation Loss (dB/cm)

-10

-20

-22

0

0.06

0.12

0.18

Waveguide Length (cm)

0.24

-40
-50

Si

SiN
REO
200 nm

SiO2

-60
1400

1430

1460

1490

1520

Wavelength (nm)(a)

Er3+ ions absorp�on

1550

1580

20

SE = Pout(Ppump = 230 mW)/Pout(Ppump = 0)

Peak: ~16 dB/cm

15

2.4

1.8

Probe

1.2

Pump

10

0.6
5
0

Signal Enhancement (dB)α = 4.70±2.05 dB/cm (@ 1445.8 nm)

Signal Enhancement per Unit Length (dB/cm)

0

R. Ohta, L. Herpin, V. M. Bastidas, T. Tawara, H. Yamaguchi, and H. Okamoto, Phys. Rev. Lett. 126,047404 (2021).

0
1510

1520

1530

1540

Wavelength (nm)

1550

-0.6
1560

(b)

(a) Propagation loss spectrum of rare-earth oxide thin film waveguide.
(b) Signal enhancement spectrum of rare-earth oxide thin film waveguide.

Low-loss Rare-earth Oxide Thin
Film Waveguides and Optical Signal
Enhancement in Them

Excitonic Nonlinear Shifts in Photonic
Crystal Nanocavities with Buried Multiple
Quantum Wells

Expitaxial single-crystal rare-earth oxide thin films are oneof the most promising candidate materials for silicon-based
active photonic and quantum optical devices. We haveproposed and demonstrated low-loss waveguides based on themechanism of bound states in the continuum. We have also
successfully observed large optical signal enhancement in thetelecommunications band in these waveguides upon opticalpumping. Our results represent an important step towards
the realization of high-performance monolithically integrated
optical amplifiers and lasers on silicon, as well as provide us apromising platform for on-chip quantum memories.

A buried multiple-quantum-well well confines excitons,
so-called quasiparticles, in a nano-region. We demonstrated
large nonlinear refractive index changes in a photonic crystal
nanocavity with buried multiple-quantum-wells, which induce
large light-matter interactions. These structures can realize
attojoule-level all-optical photonic crystal switches and willcontribute to the future realization of high-performance opticalprocessors.

X. Xu, T. Inaba, T. Tsuchizawa, A. Ishizawa, H. Sanada, T. Tawara, H. Omi, K. Oguri, and H. Gotoh, Opt.
Express 29, 41132 (2021).

M. Takiguchi, K. Nozaki, H. Sumikura, N. Takemura, T. Fujii, E. Kuramochi, A. Shinya, S. Matsuo, and
M. Notomi, Appl. Phys. Lett., 118, 111101 (2021), Editors' Pick

Advanced Applied Physical Science Laboratory

Current:ef

Log(Error rate)Gateelectrode09

Quantum Science and Technology Laborator yGroups and Research Themes

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 2021(b)(a)
Phase sensitive amplifier (PSA)

Cut

DOPO pulses

Fast matrix
Multiplier
circuit

Optical modulator(c)Computation time [s]Frequency

Optical fiber(5 km)?
Cut(a)Schematic diagram of the CIM concept.
(b)Evaluation of computation time.
(c)Evaluation of solution accuracy.

100,000-spin Coherent Ising Machine
Coherent Ising machines (CIMs) are drawing attention as a
new type of computer that can solve combinatorial optimization
problems using a network of degenerate optical parametricoscillators (DOPOs). We have constructed a CIM based ona network of 100,000 DOPOs-the world's largest CIM. We
solved a maximum cut problem of a fully connected 100,000node graph, and found that the CIM could find approximate
solutions with a particular solution accuracy 1,000 times fasterthan simulated annealing (SA) implemented on a CPU. We
also found that the CIM operated at near the DOPO threshold
could deliver a broad solution distribution with some very goodsolutions compared with the distribution obtained by SA.

T. Honjo, T. Sonobe, K. Inaba, T. Inagaki, T. Ikuta, Y. Yamada, T. Kazama, K. Enbutsu, T. Umeki, R. Kasahara,
K. Kawarabayashi, and H. Takesue, Sci. Adv. 7, abh0952 (2021).

Interference pattern of two quantum walkers in the Mach-Zender interferometer.

Quantum Walks on a Two-dimensional Programmable62-qubit Superconducting Processor
Quantum walks have attracted considerable world-wide attention and havebeen experimentally realized in various platforms ranging from photonics
to trapped ions. However, the implementation of multi-particle quantum
walks in programmable devices has remained a technological challenge. In
our work, we have designed and fabricated an 8-by-8 square programablesuperconducting array with 62 functional superconducting qubits. The
design allows the creation of multiple excitations that play the role ofquantum walkers. We experimentally demonstrated high-fidelity singleparticle and two-particle quantum walks, which allows us to measure thepropagation velocity of information and to realize a two-particle MachZehnder interferometer. Our demonstration of 2D quantum walks shows thepotential of superconducting devices to exploit quantum advantages for
future applications in quantum search and universal quantum computation.

M. Gong, et al ., Science 372, 948 (2021).

(a) False-color electron micrograph of the sample.
(b) Magnified view of the quantum Hall junction. (c) Schematic of the measurement setup.
(d) Conductance I/V in measured as a function of V S . Conductance exceeding e²/3h
indicates the current enhancement due to the Andreev process.
(Inset) Schematic Andreev reflection of fractional quasiparticles.

Detection of High-frequency Defects inSuperconducting Qubits

Andreev Reflection of Fractional Quantum
Hall Quasiparticles

Parasitic two-level-system (TLS) defects are among thedominant sources of decoherence in superconducting qubits.
We realized a novel method of high-frequency TLS defectspectroscopy using a strong qubit drive. By irradiating a qubitwith a strong microwave pulse at the qubit transition frequency,
the qubit is dynamically coupled to an initially off-resonance
TLS defect, and defect characteristics are determined byprobing the qubit state relaxation. This method of TLS defectspectroscopy can be used for quality control in the fabricationof both flux-tunable and fixed-frequency qubits, enabling further
improvement of the coherence times of superconducting qubits.

We observed an Andreev-type reflection of a fractionallycharged quasiparticle in a semiconductor. In this phenomenon,
the incidence of fractionally charged quasiparticles at aninterface between fractional and integer quantum Hall statesof a two-dimensional electron system causes transmission ofan electron and reflection of a hole having a fractional charge.
This is an analogous process of Andreev reflection at a normal
metal-superconductor junction. Our observation will accelerate
the development of topological quantum information technology
based on exotic quantum Hall quasiparticles.

L. V. Abdurakhimov, I. Mahboob, H. Toida, K. Kakuyanagi, Y. Matsuzaki, and S. Saito, APS March Meeting
2021, abstract J28.00002 (2021).

M. Hashisaka, T. Jonckheere, T. Akiho, S. Sasaki, J. Rech, T. Martin, and K. Muraki, Nat. Commun. 12,2794 (2021).

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 yPhase/amplitude
measurement

Beamsplitter

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.
Research Themes
Extreme enhancement of light-matter interactions by using photonic
crystals and plasmonics● Integrable nanophotonic devices with extremely small energy
consumption● Novel optical platforms using nanomaterials and nanophotonics● Nanophotonic computations with photonics-electronics convergence●

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 Center for Theoretical Quantum
Physics established in July 2017 brings together diverse researchers(physicists, computer scientists, mathematicians and even chemists)
fro m a cross N T T to p u rsu e cut ting e dge resea rch in a hig hly
collaborative environment.
Research Themes
The foundation of quantum mechanics
Quantum matter
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
related N T T laboratories collaborate with the goal of creating
data - driven medicine using I CT and A I . T he B M C engages inbasic and applied research on AI analysis of medical and healthdata , genome informatio n a nd behavior informatio n , real-time
bio m o nito ring in d aily life , bio mim etic n a n o d evic es , a n d n ew
biocompatible materials. In addition, it promotes innovations inmedical and health fields in cooperation with partners at medical
institutes and Medical & Health Informatics Laboratories (M EILab), NTT Research Inc.
Research Themes
Personalized medicine by AI analysis of personal medical data (precision
medicine)●Cardiac modeling and rehabilitation activities supported by AI-telestethoscope and hitoe® ECG measurement●Lifestyle-related disease management based on noninvasive blood glucose
sensor and core body temperature sensor●Fabrication of implant materials and artificial neural networks thatcomplement biological functions●

12

Achievements in 2021

An exceptional point (EP) is a peculiar degeneracy of eigenstates,
which can be induced by processes where energy is not conserved,
such as gain and loss. In this work, we fabricated a system of two
coupled photonic crystal lasers that can be controlled independently
by current injection. By introducing the contrast of their absorption
loss, we observed the first spontaneous emission of lasers operated
at an EP. As a result, we successfully demonstrated the spectral
narrowing and enhanced radiation that are particular to the EP. Our
work will open up a new frontier of optical signal control by gain
and loss in nanophotonics.

(b)

(a)

p-InP

n-InP

Ch2

Embedded
InGaAlAs

Photon Count

1531.0

2 μm

Ch1

50000

1530.6
Wavelength (nm)Spontaneous Emission of Coupled Photonic
Crystal Lasers Operated under Exceptional
Point Degeneracy

40000

1530.230000

1529.820000

1529.4

Exceptional point(peak coalescence)1529.01528.68

64
20Channel 1, Current (μA)

10000
0

(a) Two coupled photonic crystal lasers based on current-injected buried heterostructure nanocavities.

K. Takata, K. Nozaki, E. Kuramochi, S. Matsuo, K. Takeda, T. Fujii, S. Kita, A. Shinya, and M. Notomi,
Optica 8, 184-192 (2021).

(b) Color plot of the spontaneous emission spectra of the device for constant current to channel 2 of(a)Twocoupledphotonic
crystallasersbased
on current-injectedburiedheterostructure
800 μAand different
current
to channel
1. Black
points:eigen-wavelengthsof theoreticalanalysis.
nano cavities.
(b)Color plot of the spontaneous emission spectra of the device for constant current tochannel 2 of 100 μA and different current to channel 1.Black points: eigen-wavelengthsof theoretical analysis.
Adapted with permission from ⓒ The Optical Society.

A Simple Low-latency Real-time Certifiable
Quantum Random Number Generator
Random numbers are important resources consumed withinmany applications used in our everyday lives. Generating truly
random numbers is a challenge; however, they can be generated
by measuring quantum mechanical systems. Previous quantum
random number generators (QRNGs) unfortunately suffer from highlatency between the initial request and the delivery of the random
bits. We have realized a low-latency real-time certifiable QRNG bymeasuring photonic time-bin states, where every 0.12 seconds wegenerate 8,192 random bits which are secure against all quantum
adversaries. Our semi-device-independent QRNG is ideal forthe realization of a high-speed continuously operating quantum
randomness beacon with high security.

Y. Zhang, H.-P. Lo, A. Mink, T. Ikuta, T. Honjo, H. Takesue, and W. J. Munro, Nat. Commun. 12, 1056 (2021).

Exercise Intensity Monitoring of Stroke
Rehabilitation Inpatients
Increasing the amount of daily activity through self-training has
been shown to improve physical strength as well as to facilitate
learning of motion skills for achieving independence in activities
performed in daily life To increase the amount of activity safely
and effectively, we have been facilitating a clinical study witha wearable monitoring system using functional textile‘hitoe’tomonitor the activity of stroke inpatients in a rehabilitation ward. In
this study, we developed a novel data imputation method by using
ensemble averaging. This method reduces day-to-day variationsof measured data and imputes data loss more effectively withsignificance compared with a conventional method. The method
enabled the visualization of the exercise intensity of 63 stroke
rehabilitation inpatients over a period of 24 hours.

T. Ogasawara, M. Mukaino, Y. Otaka, H. Matsuura, Y. Aoshima, T. Suzuki, H. Togo, H. Nakashima,
M. Yamaguchi, S. Tsukada, and E. Saitoh, J. Med. Biol. Eng. 41, 322–330 (2021).

Schematic diagram of the time-bin-based quantum random number generator.

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 research

Research Subject

Biological Information Elucidation
Using Advanced Medical Materials

and cutting-edge technical developments in research areas
considered important to NTT.
D e c e m b e r 31 , 2021

Senior Distinguished Researcher

Masaya Notomi

Hiroshi Yamaguchi

Nanophotonics Center ProjectManagerQuantum and Nano Device
Research

Koji Muraki

Hideki Yamamoto

Research Subject

Research Subject

Research Subject

Research Subject

Photon Manipulation in Photonic
Nanostructures

Nano-mechanics in
Semiconductors

Electron Correlation in
Semiconductor Nanostructures

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

Akira Fujiwara

William John Munro

Hiroki Takesue

Shiro Saito

Research Center for Theoretical
Quantum Physics Project Manager

Quantum Science and Technology
Laboratory Executive Manager

Quantum Optical Physics ResearchGroup Leader

Research Subject

Research Subject

Research Subject

Research Subject

Ultimate Electronics Using
Semiconductor Nanostructures

The Design of Quantum Technologies

Quantum Communication
Experiments in
Telecommunication Band
Coherent Ising Machine

Quantum information technologies
based on superconducting
quantum circuits

Multidisciplinary Materials Design andScience Laboratory Executive Manager

Distinguished Researcher

Norio Kumada
Katsuhiko Nishiguchi

Haruki Sanada
Imran Mahboob

Kengo Nozaki
Koji Azuma

Takahiro Inagaki
Hajime Okamoto

Gento Yamahata

14

Publication List

The total number of NTT Basic Research Laboratories papers published ininternational journals in 2021 is 67 with an average impact factor of 7.122.
The 2020 impact factor of those individual journals are shown in ( ).

NATURE COMMUNICATIONS (14.919)

4

PHYSICAL REVIEW LETTERS (9.161)

4

PHYSICAL REVIEW B (4.036)

4
4

APPLIED PHYSICS LETTERS (3.791)
PHYSICAL REVIEW APPLIED (4.985)

3

OPTICS EXPRESS (3.894)

3

PHYSICAL REVIEW A (3.14)

3
3

APPLIED PHYSICS EXPRESS (2.895)
SCIENCE (47.728)

2

NATURE PHYSICS (20.034)

2

OPTICA (11.104)

2

SCIENTIFIC REPORTS (4.38)

2

REVIEW OF SCIENTIFIC INSTRUMENTS (1.523)

2

JAPANESE JOURNAL OF APPLIED PHYSICS (1.48)

2
2

PHYSICAL REVIEW RESEARCH (N/A)
ACS NANO (15.881)

1

SCIENCE ADVANCES (14.143)

1

PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA (11.205)

1

NANOPHOTONICS (8.449)

1

NPJ QUANTUM INFORMATION (7.385)

1

1

2

Number of Presentations

Number of Patents

156

55

（33 Invited talks）

List of Award Winners

3

The Young Scientists' Award, the Commendation for Science and Technology by the Minister of Education, Culture, Sports,
Science and Technology
High-accuracy Single-electron Control Using Silicon Quantum Dots

Gento Yamahata

APSIPA Industrial Distinguished Leader

Nanofiber-Electroconductive Textile“hitoe”for ECG Monitoring and Cardiac Pacemaker Electrodes

Shingo Tsukada

IEICE Distinguished Achievement and Contributions Award
Masaya Notomi

JSAP Promotion and Nurturing of Female Researchers Contribution Award
Research on Functional Devices Based on Large-scale Graphene

American Physical Society
William John Munro

Makoto Takamura

Outstanding Referee

Kenta Takata

IEICE Best Paper Award

Methods for Reducing Power and Area and BDD-based Optical Light Circuits
Ryosuke Matsuo, Jun Shiomi, Tohru Ishihara, Hidetoshi Onodera, Akihiko Shinya, Masaya Notomi

JSAP Research Encouragement Award

Electron Paramagnetic Resonance Spectroscopy Using a Single Artificial Atom Communications Physics 2, March 2019, 33

JSAP Young Scientist Presentation Award

Novel Superconducting (CaCuO2 ) n /(Ca2 Fe2 O5 ) m Superlattices Prepared by MBE

Ai Ikeda

JSAP Young Researcher Best Presentation Award

Development of 3D-cultured Neuronal Network in Graphene-based Self-folding Electrode Array

JSAP Young Researcher Best Presentation Award

Quantum Transport Evidence of Weyl Fermions in an Epitaxial Ferromagnetic Oxide

Society for Chemistry and Micro-Nano Sytems Visual Movie Awards

Construction of Vessel-Like Tissue Using Fluidic Device Based on Hydrogel Film

Koji Sakai

Kosuke Takiguchi

Riku Takahashi

Hiraku Toida4