Quantum Innovation 2022
Nov. 29, 2022 Online

From Quantum Repeater Networks
to the Quantum Internet
Hideo Kosaka https://kosaka-lab.ynu.ac.jp

Professor, Yokohama National University
Director, Quantum Information Research Center
Research fellow, The University of TokyoJapan1

Q. Information Research Center
https://moonshot.ynu.ac.jp

https://qic.ynu.ac.jp/

Assistant
Professor

CenterDirector

Professor

Assistant
Professor

Associate
Professor

Hideo Kosaka

Toshihiko Baba Nobuyuki YoshikawaYuki Yamanashi Christopher Ayala Fumihiro Inoue Yoshihiro Shimazu Yuhei Sekiguchi Hodaka Kurokawa Akira Kamimaki

Shinichiro Fujii

Visiting
Professor

VisitingProfessor

Adjunct
Teaching
Staff

Professor

Associate
Professor

Associate
Professor～50 members

Associate
Professor

Associate
Professor

Assistant
Professor

Visiting
Professor

Visiting
Associate
Professor

Visiting
Associate
Professor

Visiting
Professor

Visiting
Associate
Professor

Visiting
Researcher

Satoshi Iwamoto Masahiro Nomura Toshiharu Makino Tokuyuki Teraji

Shinobu Onoda

Kazuki Koshino

Hirotaka Terai

Katsuaki Tanabe

Ryo Sasaki

Visiting
Professor

Intellectual
Property
Producerhttps://qurep.ynu.ac.jp

Kinya Kumazawa Annelies Volders

2

CONTENTS
1. Quantum Internet
2. Quantum Computer Networks
3. Quantum Repeater Networks

3

Development steps toward Quantum Internet1. Trusted node QKD system➢ Quantum enhanced security but not absolutely secure< 100km< 100kmClassical

2. Quantum repeater–based QKD system➢ Absolutely secure quantum network➢ Long-distance & multiparty connections

Classical
data

Quantum

3. Quantum computer network➢ Require quantum interface at end nodes
Quantum
Quantum
Quantum Interface

Quantum
dataQuantum
4Quantum Internet
Quantum
Computer
Networks

Project

Quantum
Repeater
Networks+

Q. computeruser

https://moonshot.ynu.ac.jp

https://qurep.ynu.ac.jp

Program

Program

QR
Q. repeater

AgencyphotonQ. sensor
AgencyQR

QR
QR

Shortdistance
Nanotechphase

ProjectLong
distance

Q. storage

Devicephase

Basic research

Systemphase
10～30 year

Protocolphase

Servicephase

Applied research
5Quantum Computer
NetworksProject

https://moonshot.ynu.ac.jp
Program

Agency6

Development Roadmap for
Superconductor Quantum Computer
NISQ

FTQC

KawasakiInter module connection
beyond 1K qubits

QuantumCommunication
beyond 10K qubits
7

Moonshot Quantum Computer Program
FTQC

Net QC(short distance)

Superconducting
qubit

8

Quantum Interface Project
https://moonshot.ynu.ac.jp

PM Hideo Kosaka(Director of Quantum Information Research Center)

World-wide Nanotechnology Researchersin 8 universities and 5 national institutes
Diamond Q. Memory Opto-Mech. Resonator Piezo-MW Resonator➢ Hideo Kosaka➢ Satoshi Iwamoto➢ Hideo Kosaka➢ Nobuyuki Yoshikawa➢ Hiromitsu KatoToshiharu Makino➢ Toshihiko Baba

➢ Tokuyuki Teraji➢ Masahiro Nomura➢ Shinobu Onoda➢ Satoshi Fujii➢ Kazuki Koshino➢ Fumihiro Inoue➢ Yoshihiro Shimazu➢ Hirotaka Terai➢ Kunihiro Inomata➢ Ryo Sasaki➢ Katsuaki Tanabe

9Quantum Interface Project
Quantum interface

Blind Q. computing
Q. computer

User

QKD network

QRQ. media conv.

IFQ. repeater

QRQROptical photon

Q. sensor
IFQR

Q. memory

IF

Distributed
Q. computing

Q. media conv.

Microwave photon

Q. storage

Opto-Mechanical Crystal

Supercon.
qubit

Phononic
crystal

Piezo
Microwavephoton

Acoustic
phononQuantum
Memory Photonic
crystal

Opticalfiber
Opticalphoton

10Optically connected QCs
Quantum Computer

Microwave line (10mK)

Optical fiber (RT)

Logical qubit
integrated circuit
1K～10K qubits

Scalable!

Q. memory
control circuit

Quantuminterface

Optical fiber

Bias circuit
forfreq. tuning
Dilution refrigerator（10mK）One link from one logical qubit could be enough

11Opto-Mechanical Crystal QI
Conversion between EM field (mwave) - EM field (Optical)~5 GHz~500 THz

with 5-orders different Frequency & Spatial-mode

EO modulator

AO modulator

Electro-Optic modulator
Fast but low extinction ratio

Acousto-Optic modulator
High extinction ratio but slow

High power optical pumps are needed
Heterodyne
detection(Yale)

6mm
LN bulk

EO or AO resonator

Carrier frequency

0.5mm
SiN membrane

w0~1MHz(JILA)

Opto-Mechanical Crystal (OMC) + Color Center (CC)High-efficiency, High-bandwidth, High-repetition, High-fidelity & On-demand

12Principle = Quantum Media Conversion
OpticalPhoton
Ion

AtomMagnon

Exciton(Color center)

ElectronSpin

PhononSuperconducting
qubit(Mechanical wave)

13Mechanism of OMC-QI with CC
Macroscopic quantum
Spatial mode
matching

Microwave
photonE

Superconducting Microwave resonator
Qubit
E

Vibration
bridgesmacro & micro
Spatial mode
conversion
Lattice

Microscopic quantum

Frequency mode
conversion

Molecule

Piezo

M+Q

Mechanical resonator

O+q

Optical resonator

Eeq

Electro-Mechanical coupling

OpticalphotonCC

Opto-Mechanical coupling

TransducerwOwMg

Microwave Mechanicalresonator
resonator

Microwave photon

Piezo

Opticalresonator

wO~500 THz

wM~5 GHz

Dipoles with
5-orders different
frequency+CC -Optical photon

H. Kurokawa, M. Yamamoto, Y. Sekiguchi & H. Kosaka, arXiv:2202.07888, Phys. Rev. Appl. in press (2022).

14

Conventional OMC-QI
Homogeneous structure ⇒ Heterogeneous structure
Chicago(Cleland)

AlN

Stanford(Naeini)

LiNbO3A. N. Cleland 2016

EPFL & IBM(Kippenberg & P. Seidler) GaP

T. J. Kippenberg & P. Seidler 2022

A. Naeini 2020

Delft(Groblacher)

GaAs

S. Groblacher 2020

Caltech

LN/Si(Painter)

2022

AlN/SiO. Painter 2020

DelftGaP

QphoX LN/Si

S. Groblacher 2021

S. Groblacher 2022

(Groblacher)15

Diamond Opto-Mechanical Crystal
Heterogeneous structure with Piezo is required for QI
Harvard, Caltech(Loncar, Painter, Lukin)

M. J. Burek et al.,
Optica 3, 1404 (2016).

Harvard(Loncar)

SiV

Optical mode
Optical Q = 176,000 @ 1,529 nm
Mechanical Q = 4,100 @ 5.5 GHz @RT

Stanford(Naeini)

NVJ. Cady et al., Quantum
Science and Technology
4, 024009 (2019).

G. Joe et al., CLEO (2021)

Mechanical mode

Optical Q ~ 10,000 @ 1,544 nm
Mechanical Q = 22,000 @ 9.2 GHz @4K

MIT(Englund)
SiliconPhotonic
IntegratedCircuit

SiV, GeV

Wan et.al., Nature(2020)

Diamond
Mouradian et.at.,APL(2017)

Raniwala et.at., Arxiv(2022)

Optical Q = 42,000 @ 1,542 nm
Mechanical Q = 118 @ 5.9 GHz @RT

Optical Q = 14,000 @ 637 nm

16Advantage of diamond OMC-QI
Conversion efficiency - Carrier frequency

High frequency >5GHz is needed
for low thermal noise

Diamond-based OMC

Thermal noise - Carrier frequency

0.01
QphoX(Groblacher)

1E-6

LN/Si
AlN/SiCaltechStanford(Naeini)(Painter)

Delft

Heterostructure

1E-8 (Groblacher)Chicago

AlN
LN
Si+AlN
GaAs
GaP(Cleland)

1E-10(Groblacher)

Delft

1E-12

2

Homostructure
EPFL(Kippenberg)

468Frequency (GHz)

Error>0.4%/hm

30mK

Error
>0.01%/hm

10mK> 8 GHz

Carrier frequency w0 （GHz）

Diamond hetero structure
204

Piezo-electric e
3.7

LN

321

1.6

AlN
00.1

0.15

GaP

GaAs

AlN

LN

Sound Velocity (km/s)

Piezoelectric Coefficient (C/m2)

50mK> 5 GHz

10Carrier frequency w0 (GHz)

100mK

Low temperature

1E-4

ノイズ光子数noiseThermal

MOC Efficiency
efficiency hConversion

115

Sound velocity∝ rigidity c

18 km/sHigh modulus

Low dissipation
at high frequency

9.6
Si

Fast velocity

Wavelength match
photon - phonon

Electromechanical Diamondcoupling
10e2/c50

GaP GaAs

AlN

LN

Si Diamond

17Advantage of memory-based QIConversion efficiency – Band widthAO

1(membrane)

EO

EO

Conv. efficiency h3mm

Atomicensemble

B=24MHzLow bitrate
Rareearth

10-5

Memory base

EO
OMC

EOMagnon

10-10100kHz

10MHz

1MHz

Memory-based QI No photon noise
Photon scattering No thermal noiseHigh fidelity + High rep. rate
= High bitrate

Conventional

Si+LN
B=15MHz

Conventional QI High photon noiseHigh optical pump High thermal noise

Direct conversion ~ 0.5MHz

Bandwidth B (bitrate R)
500kHzEntanglement
generation rate
betweenSC qubits

Direct conversion
100kHzMemory-based conv. ~ 20kHz

10kHz

Conversion
20%

MemoryMemory1kHz

Conversion Efficiency hH. Kurokawa, M. Yamamoto, Y. Sekiguchi & H. Kosaka, arXiv:2202.07888, Phys. Rev. Appl. in press (2022).

18

Fabrication challenge for Diamond OMC
Microwave Mechanicalresonator
resonator

Opticalresonator

Piezo material

Microwave photon

CC

Microwave res.

Microwavephoton+

Optical photon-Piezo&CC
OpticalphotonOptical res.

Mechanical res.

Superconducting
microwave resonator
NbTiN/Si
Q = 8,000@ 5GHz,15 mK

Diamond piezo-electricmechanical resonator
AlN/Diamond
Q = 10,000@ 5GHz,5 K

Diamond photonic crystal
optical resonator
Diamond nanobeam

00500mm
100nm line width

H. Terai

S11 (dB)

S21 (dB)-10-20-30
15 mK
100 mK
300 mK
700 mK-40-50
4.80

4.82

4.84

4.86

4.88

Frequency (GHz)T. Makino, H. Kato

4.901mm-2-4300 K
5K-6
5.21mm pitch

S. Fujii

5.3

Frequency (GHz)T. Makino, H. Kato

5.4

250nm pitch, 260nm width, 500nm high

S. Iwamoto

T. Makino, H. Kato

19

Quantum Repeater
Networks
Project

https://qurep.ynu.ac.jp/
Program

Program

AgencyAgency20

QuTech / TU Delft

2021

Multiparty Quantum Repeater Network

First demonstrationof diamond-based
Quantum Internet?
M. Pompili et.al. , Science 372, 259–264 (2021)

2015

1.3km Quantum Repeater
電子BS電子Diamonds
B.Hensen et.al., Nature 526, 682 (2015)21

Global Quantum Network Program
1. Quantum crypto linkA) High-performance quantum cryptographyB) Photon detection

2. Trusted nodes

A) Highly reliable key management server technologiesB) Highly distributed technologies

1.A
Environmental resistance BB84

1.A
High-speed BB84

1.A
CVQKD

1.A
Twin-Field QKD

3. Quantum repeaterA) Quantum memory optical linkB) Quantum repeater elementarytechnologies
4. Network operationA) Network control and management

22Quantum Repeater Project
https://qurep.ynu.ac.jp/23

LocalRemoteent measurement ent generation

Memory-based Quantum Repeater
DLCZ

YNU

Emission-emission

Emission-absorption
emission

photonabsorption

beam splitter

Need of interferometer No need of interferometerbeam splitter

Quantum memories(enable Complete BSM)

Probabilistic
× No scalability

Deterministic〇

ScalableOn-demand24

Comparison of diamond QR schemes
QuTechHigh B-field

Spin 1/2
PseudoTLS

Single-photon interference
emissionemission

ee

13C

13C

13C

subjects to photon lossof only a half pathe13C

13C

13CHigh bitrate with extreme loss

YNU
B=0Single-photon absorption
Integration
with SC qubit

does not rely on
extreme lossemission absorptionee13C

13C

13C

e13C

13C

13C

3-level system

High fidelity without loss limit

25Required functions for YNU QR scheme
Manipulate degenerate qubitwith holonomic quantum gate

B=0
1. Universal quantum gates
2. Entangled emission

3. Quantum teleportation trasfer
eee

①
13C

13C

13C

13C

13C

13C

4. Complete Bell measurement + 5. Quantum error correction★ Nature Photonics, 10,507-511(2016)★Communications Physics, 2, 74 (2019)★ Nature Photonics, 11, 309-314 (2017)★Communications Physics, 4, 264 (2021)★ Nature Photonics, 16, 662-666 (2022)★Communications Physics, 5, 102 (2022)
Physical Review Letters, 114, 053603 (2015)★ Nature Communications, 7, 11668 (2016)
Physical Review Applied, 12, 051001 (2019)★ Nature Communications, 9, 3227 (2018)26

Entangled emission & absorption
1. Entanglement generation
3. Bell state measurement

2. Entangled emission
pe2

3e1
13C

13C

Entangled emission

spin-orbit coupled state

Entangled absorption
|A2

|A2

|s + photon|+1

electronQuantum
teleportation
into carbon|s -

|s + photon

|+1

|-1

Communications Physics, 4, 264 (2021)

electron|s -|-1

Physical Review Letters, 114, 053603 (2015)

Fidelity ~ 100%27

Quantum Teleportation into a Memory
We have succeeded to exclusive transfer and store a quantum statefrom an optical photon to a selected carbon quantum memory

Collaboration

B=0
Joerg Wrachtrup(U. Stuttgart)

Nature Photonics, 10, 507(2016)

Communications Physics 2, 74 (2019)28

Performances of YNU QR device(Single NV- @ 5K, B=0)①②③e13C④13C⑤Functions

Status

Universal quantum gate fidelity (e)99.97%

Gate speed (e)180 MHz

Entangled emission fidelity (e & p)

98%

Photon generation rate (ZPL)

10 Kcps

Quantum teleportation fidelity (p→C)

94%

Memory time (e / C)

0.1s / 1s

Complete Bell measurement fidelity (2C) 90%
Single-shot readout fidelity (C)99.7%

Quantum error correction fidelity(N+2C)

83%

Controllable memory number(e+N+8C)

10We succeeded to achieve all the functions required for on-demand QR

29

Challenge for higher efficiency & multimode0G (1mm)
High-purity
diamondAntenna

1G (100mm)

2G (10mm)

Cross-bar MW antenna

Diamond

Diamond

Diamond100mm

1mm

5G (10nm)

4G (100nm)

3G (1mm)Ring MW antenna
10mm

1mm

SIL
10nm
f100nmNV1Å

Nanobeam single ion
implantation
Multimode~1Kbits
Optical QRAM

Nature Photonics, 16, 662-666 (2022)

Diamondphotonic crystal

Diamondmicro lens (SIL)

Emit/abs enhance

Emit/abs increasex 1000x 50

30

Development Roadmap of YNU QR
Node B

Node A

Optical fiber 10 m
2 μm

Entanglement Generation rate（b/s）

NV2 μmEmission

Absorption

Heralded by
low-noise SNSPD

NVphoton

1kb/s

QuTech scheme

103(Single-photon interference)

40 b/s101

Current

10-1

10-310b/s
0.1b/s0.001b/s

High fidelity without limit
x 100

10-5x 10002

x 1000SpaceTime
Frequency

10-7 10-7b/s

Bulk

Shigehito
Miki

1Mb/s

Microlens

SSPD

Photonic crystal Multimode31

Publications on YNU QR scheme ★: Nature Journals①★ Nature Communication 2016

Universal quantum gate

Nature Communications, 7, 11668 (2016)★ Nature Photonics 2017
Nature Photonics, 11, 309-314 (2017)★ Nature Communications 2018
②Entangled emission

Nature Communications, 9, 3227 (2018)

Optics Letters 2018
Optics Letters, 43, 2380-2383 (2018)

Physical Review Applied 2019
③Quantum teleportation transfer

Physical Review Applied, 12, 051001 (2019)★ Nature Photonics 2022
Nature Photonics, 16, 662-666 (2022)★ Communications Physics 2021
Communications Physics, 4, 264 (2021)④

Phys. Rev. Lett. 2015

Complete Bell measurement

Physical Review Letters, 114, 053603 (2015)

e13C

⑤

Quantum error correction★ Nature Photonics 2016
Nature Photonics, 10, 507-511 (2016)
13C★ Communications Physics 2019
Communictions Physics, 2, 74 (2019)

Applied Physics Letters 2022
Appl. Phys. Lett. 120, 194002 (2022)

All under B=0★ Communications Physics 2022
Communications Physics 5, 102 (2022)

32

Summary
We are developing diamond-based
Quantum Interface device for Quantum Computer Networks
andQuantum Repeater device for Quantum Repeater Networks
toward Quantum Internet.

Project

Quantum
Computer
Networks+Quantum
Repeater
Networks

Q. computeruser

https://moonshot.ynu.ac.jp

https://qurep.ynu.ac.jp

Program

Program

QR
Q. repeater

AgencyShortdistance

Projectphoton

Q. sensor

QR

QR
QR

Q. storage

AgencyLong
distance

33