performance limits for quantum key distribution networks · 2019-06-11 · 100g quantum encryption...

© 2019 Toshiba Research Europe Ltd

Andrew Shields

Toshiba Research Europe Ltd

Cambridge Research Laboratory, UK

ITU-T Workshop, Shanghai, 5-7 June 2019

Performance Limits for Quantum

Key Distribution Networks

1© 2019 Toshiba Research Europe Ltd

Detect unauthorised eavesdropping on fibre

Distribute secret digital keys that are secure from future advances in cryptanalysis and computing

(even advances in quantum computing)

Secrecy can be tested directly!!-quantum theory dictates that

eavesdropping unavoidably alters

encoding of single photons

Quantum Communications-each bit encoded on a single photon

Quantum Key Distribution


Photon source: intensity-modulated weak laser pulses from telecom laser diode

by using three intensities effect of multi-photon pulses can be mitigated (‘decoy pulse method’)

QKD System Design

QKD: Quantum Key Distribution

Qubit encoding: phase difference (f) between two pulses after interferometer

active feedback used to compensate phase and polarization drifts

Photon detectors: room temperature Geiger mode avalanche photo-diodes

‘self-differencing’ technique allows photon detection at GHz rates

clock

encoding interferometerphoton source

control electronics

decoding interferometer detectors

control electronics

quantum channel

clock channel

backward reconciliation

forward reconciliation

f

All channels can be combined onto same fibre using wavelength divisional multiplexing


NPL

Cambridge

Bristol

London

Reading

Adastral Park

(BT)

TREL

Long distance links from Cambridge – London - Bristol

Integration of QKD and 100G encrypted data transport

QKD technology supplied by Toshiba and IdQuantique

Metro QKD Networks in Cambridge and Bristol

Image©2017 Data SIO, NOAA, US Navy, GEBCO, Landsat/Copernicus, Map data ©2017 Geobasis-DE/BKG(©2009), Google.

UK Quantum Network


CAPE

TREL

NewM

A

B

C

ENG

QKD

sys.

Distance

(km)

Secure Key

Rate (Mb/s)

Quantum Bit

Error Rate (%)

A 5.0 3.26±0.11 2.26±0.13

B 10.6 2.63±0.29 2.88±0.20

C 9.8 3.20±0.23 2.17±0.28

QKD Performance

SKR and QBER averaged over 1 month

Image©2017 Google, Infoterra Ltd + Bluesky, Getmapping plc, The GeoInformation Group. Mapdata©2017 Google.

Cambridge Quantum Network

QKD Performance

Highest key rates recorded in field trial

Stable operation over 18 months

http://www.google.co.uk/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=0ahUKEwjk4obflcvNAhWpB8AKHS_fBNwQjRwIBw&url=http://www.las-hq.com/case-study-university-of-cambridge&psig=AFQjCNHQC48tPXez14KTt-p5B8KZ7ammlA&ust=1467218680565312


CAPE

TREL

NewM

A

B

C

ENG

Image©2017 Google, Infoterra Ltd + Bluesky, Getmapping plc, The GeoInformation Group. Mapdata©2017 Google.

100G Quantum Encryption Field Trial

Combine QKD & encrypted data on each fibre

100Gb/s encrypted data (~1530nm)

Quantum channel (~1550nm)

Refresh AES encryption key with QKD keys

Results

Low QBER = 2.8% (increase due to Raman

noise caused by data lasers is negligible)

High average secure key rate (= 3.1 Mb/s)

Error-free data transport (after forward error

correction)

http://www.google.co.uk/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=0ahUKEwjk4obflcvNAhWpB8AKHS_fBNwQjRwIBw&url=http://www.las-hq.com/case-study-university-of-cambridge&psig=AFQjCNHQC48tPXez14KTt-p5B8KZ7ammlA&ust=1467218680565312


Simple REST-based interface for applications

to request key from QKD network

Encryptor requests AES key every ~1.4s

Extensive testing in Cambridge Network

QKD System

RE

ST

QKD System

RE

ST

Standardised Interface for Key Delivery

QKD network

REST-based interface standardised

by ETSI Industry Specification

Group in QKD

Implemented by QKD vendors

(Toshiba, IdQuantique) and

encryptor vendors (ADVA, Senetas)

A simple route to develop ‘quantum-

ready’ products

ETSI Industry Specification Group in QKD

Current Interests: Network interfaces for interoperability

QKD network architecture and security

Security evaluation and Common Criteria certification

Membership (40 members/participants)

QKD vendors, network equipment vendors, network

operators, system integrators, NMIs and government labs,

academia.


Secure key rate vs fibre length (channel loss)

is main performance measure of QKD

1. ‘Normal’: determined by loss budget

3. High Loss: limited by detector noise

detector dark counts

Raman noise from data lasers

loss budget

dominated

detector noise

dominated

loss of standard optical

fibre = 0.2 dB/km

detector and Raman noise

comparable to signal

modulation error and

detector afterpulse noise

processing

bottleneck

105 km (RT)

17 Mb/s

Fibre length (km)

QB

ER

(%

)S

ecu

re B

it R

ate

(b

/s)

2. Low Loss: limited by processing bottleneck

sifting, error correction and privacy

amplification can limit at high rate

Measuring the Performance of QKD Systems

Three regimes of performance…

key rate = 17 Mb/s at 0dB channel loss

EC: Error Correction; PA: Privacy Amplification

Alice

1GHz x 0.42

channel

x h

Bob

x0.5

detector

x0.25

sifting EC/PA

x0.88 x0.37


overcome processing bottleneck with fast, real-time post-processing hardware

Increasing the Secure Key Rate

high-speed photon detection (>100 MCounts/s) with self-differencing

APD detectors (room temperature)

high-speed sifting (>60 Mb/s) through 10G communication interface

privacy amplification hardware > 108 Mb/s

error correction hardware > 55 Mb/s

Yuan et al. J Lightwave Technology 36, 3427 (2018)

first demonstration with secure key rate > 10 Mb/s

compact prototype (3U)

real-time key generation

continuous operation > 1 month

secure key rate = 13.7 Mb/s


Extend range of QKD system by reducing detector dark count noise

2.2%

242

3.2%

105

reduced dark count noise

extend with low

noise APD detectors

Fibre length (km)

QB

ER

(%

)S

ecure

Bit R

ate

(b/s

) RT detector

TE-cooled (-60oC)

detector

Frohlich et al, Optica 4, 163 (2017) using BB84 protocol

Reduced dark count noise extends range of

practical QKD to 242 km

Expt. points ( ) use detector temperature optimised

for each distance

See also Korzh et al, Nat. Phot. 9, 163 (2015) using Stirling

cooler and COW protocol

Increasing the Range of QKD Links

On chip thermo-electric

cooling of detector

Detector dark count rate

reduced to ~ 10c/s (-60oC)

TE: Thermo Electric; RT: Room Temperature


Twin Field QKD

‘normal’ QKD

TF-QKD

(untrusted

mid-station)

A new protocol to extend the range of QKD (and increase key rate at long distances)

Lucamarini et al. Nature 557, 400 (2018)

TF-QKD could allow Secret Key Capacity to be overcome

Key rate scales as transmission h0.5 (rather than h1.0 )

much higher key rate at long distance

Secret Key Capacity ∝ 𝜂

∝ 𝜂0.5

which is equivalent to…


TF-QKD has stimulated interest…

1. X. Ma, P. Zeng & H. Zhou, “Phase-matching QKD”, arXiv:1805.05538 (15 May 2018). Also @ Phys. Rev. X 8, 031043

(2018).

2. K. Tamaki, H.-K. Lo, W. Wang & M. Lucamarini, “IT security of QKD overcoming the repeaterless secret key capacity

bound”, arXiv:1805.05511 (15 May 2018).

3. X.-B. Wang, Z.-W. Yu & X.-L. Hu, “Sending or not sending: Twin-Field QKD with large misalignment error”,

arXiv:1805.09222 (28 May 2018).

4. C. Cui, Z.-Q. Yin, R. Wang, W. Chen, S. Wang, G.-C. Guo & Z.-F. Han, “Phase-matching QKD without phase post-

selection”, arXiv:1807.02334 (6 Jul 2018).

5. M. Curty, K. Azuma & H.-K. Lo, “Simple security proof of Twin-Field type QKD protocol”, 1807.07667 (19 Jul 2018).

6. Z.-W. Yu, X.-L. Hu, C. Jiang, H. Xu & X.-B. Wang, “Sending-or-not Twin-Field QKD in practice”, 1807.09891 (25 Jul 2018).

7. J. Lin & N. Lütkenhaus, “A simple security analysis of phase-matching MDI-QKD”, 1807.10202 (26 Jul 2018). Also @

Phys. Rev. A 98, 042332 (2018).

M. Lucamarini, Z.L. Yuan, J.F. Dynes & A.J. Shields, “Overcoming the rate-distance limit of quantum key distribution

without quantum repeaters”, Nature 557, 400 (2 May 2018)


Secure Key Rates of TF-QKD

Nature Photonics, advanced online

http://dx.doi.org/10.1038/s41566-019-0377-7

QKD with channel loss of 90.8 dB

(~100x best fibre demo to date)

Secret key rate using TF-QKD

protocol in Nature 557, 400 (2018)

Secret key rate using TF-QKD

protocol in Wang et al, PRA 98,

062323 (2018)

Experimental TF-QKD exceeds

both ideal (dashed) and realistic

(dotted) secret key capacity (SKC)

Secure key rate is >103 value

reported for max loss of conv. QKD (Boaron et al; 71.9 dB; 0.25 b/s)

Secure key rate is > 106 value

reported for max loss of MDI-QKD (Yin et al; 64.6 dB; 0.0003 b/s)

Equivalent to 567km of ultra-low

loss fibre (0.16 dB/km) or 454km of

standard fibre (0.2 dB/km)

Other expts: Liu et al, arXiv:1902.06268; Zhong et al, arXiv:1902.10209; Wang et al, arXiv:1902.06884 (2019)


Improving reliability (continuous operation on installed fibre over years)

and ability to integrate in network (co-existence with multiple data channels)

Secure key rates > 10 Mb/s (>30,000 256-AES keys/sec) achieved in continuous, real-time operation

Outlook: standards for interoperability, security certification

consensus on standards important for development of market

Quantum Cryptography offers Information Theoretic Security – not vulnerable to future advances in

cryptanalysis or computing (including quantum computing)

Summary

Twin Field QKD demonstrated with loss exceeding 80 dB (>500 km of ULL fibre)


Further info: www.quantum.toshiba.co.uk

Acknowledgements

James Dynes, Zhiliang Yuan, Winci Tam, Andrew Sharpe,

Marco Lucamarini, Mirko Pittaluga, Mariella Minder, George Roberts,

Tom Roger, Tao Paraiso, Mirko Sanzaro, Innocenzo de Marco,

Davide Marangon

Toshiba Research Europe Ltd., Cambridge, UK

A Dixon, Y Tanizawa, A Murakami, R Takahashi

R&D Centre, Toshiba Corporation, Japan

Cathy White, Andrew Lord

BT, Martlesham Heath, Ipswich, Suffolk, UK

Adrian Wonfor, Richard Penty, Ian White

University of Cambridge

Joo Cho, A Klar, H Griesser, M Eiselt, A Straw, T Edwards

ADVA Optical Networking

Funding

EQUIP

FQNET

QCALL

Collaborators


Thank you

performance limits for quantum key distribution networks · 2019-06-11 · 100g quantum encryption...

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