7/27/2019 Metrology for QKD - a quantum optical communication technology

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Receiver characterisationDE, DCP, APP

A bre optic power meter is calibrated at the 100 pW level,traceable to the cryogenic radiometer (1). The calibrated power

meter measures the output of a pulsed laser, transmitted through

a calibrated variable attenuator, at a similar power level (2). The

attenuator reduces the pulse output to the single photon level,

which is used to calibrate the QKD receiver (3). The laser pulses aresynchronised to the QKD detector gates, which can be operating

at a 1 GHz gate frequency. Uncer tainty (k=2) ~ 1-2 %.

Objective To develop a pan-European measurement infrastructure to develop standards andcharacterisation facilities for commercial Quantum Key Distribution (QKD) devices.

• QKD is a physical (as opposed to algorithmic) process

• Security depends on physical performance of system at time of key creation (as well asalgorithmic post-processing)

• QKD devices therefore require independent physical characterisation in order toconvince end-users that the technology is working within specication

• Focus of project is on optical layer of faint-pulse (weak coherent pulse) QKD, using

phase encoding in bre, and operating in the 1550 nm spectral region

Transmitter

• Mean photon number(s) (µ)

• Probability distribution

• Temporal pulse jitter, duration

• Wavelength

• Spectral bandwidth

• Spectral indistinguishability(with respect to phase setting)

Tunable single-photon spectrometer

Operating range 1270→ 1630 nm

FSR = 119 GHz

Δνcavity

= 600 MHz

PNR detector tree structure

• Four click/no-click detectors (commercial SPADs)

• Three pigtailed commercial 50:50 beam splitters

• Smart gating to minimise detector dead-time eects

An open system QRNG

Heralded single photon sourceBrida et al., Appl. Phys. Lett. 101, 221112 (2012)

Scaleable source based onsynchrotron radiation forcalibrating single-photon receivers

ETSI QKD-ISG

• An Industry Specication Group (ISG) of the European Telecommunications Standards Institute (ETSI) brings togetheractors from all over the world from science, industry, and commenceto address standardisation issues in quantum cryptography, andquantum technology in general.

• INRIM, NPL, and PTB who are members of the ETSI QKD-ISG, facilitateinformation exchange between the ISG and MIQC

• These laboratories have contributed to the ISG Group Specication

document – ‘Quantum Key Distribution (QKD); Components andInternal Interfaces’

Transmitter characterisation

Applying current capability to QKD

Key parameters identied for characterisation

Advances beyond existing capability

Channel• Spectral attenuation

• Chromatic dispersion

• Optical length

• Backscatter

• Polarisation mode dispersion,dependent loss, decoherence

• Wavelength multiplexed brelink performance

Receiver

• De tection e ciency (DE)

• Detection linearity

• Dark count probability (DCP)

• After-pulse probability (APP)

• Deadtime and recovery time

• Temporal jitter

• Back-ash

• Detector indistinguishability(multi-detector receiver)

Mach-Zehnderinterferometer

Mach-ZehnderinterferometerPulsed laser

Random setting

Random setting

Detector 2

Detector 1

Intensitymodulator

Phasemodulator

Phasemodulator

Attenuator

Transmitter (Alice)

Receiver (Bob)

Rationale

Metrology for QKD –a quantum optical technology

C J Chunnilall, I P Degiovanni, S Peters, A G Sinclair

IND06: Metrology for Industrial Quantum Communications www.migc.org Sep 2011 – Aug 2014

System optimisation

Measured μ, Δμ

Expected QBER, ΔQBER

- Bit rate and distance

- Privacy amplication

System stability

‘Natural’ change;

Performance-changing attacks

Security from hacking

(Side-channels)

Basis and bit indistinguishability

(pulses, detectors)

QKD

European Association of National Metrology Institutes

Requires measurement of the physical parameters of the system

QKD transmitter (pulsedsource, various mu values)

Synchronisation

Strict proportionality of ring current and emitted radiation

Can vary spectral radiant power over 11 orders of magnitude without changing emitted spectrum

Calibrated, gated photoncounting detector

µ

A gated photon counting detector is calibrated in a similar fashion

to that shown on the left for a QKD receiver. This measures the mean

photon number, μ, of the pulses emitted by the QKD transmitter.

Systems utilizing a decoy state protocol will require various μ values to

be measured. The detector gates are synchronised to the transmitter

pulses, which may be operating at a 1 GHz gate frequency. Uncertainty(k=2) ~ 1-2 %.

See Friday 9.40 talk – S V Polyakov et al. See Thursday 10.50 talk – M Legré et al.See Friday 11.25 talk – C J Chunnilall et al.

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PTB CryogenicRadiometer

PTB referenceInGaAs detector

Metrology LightSource – dedicated

electron storageof PTB

SuperconductingSingle Photon

Detector

Is it performing as it should?

: –I

–

Low-jitter detectors and high-bandwidth switch controller made it possible toreduce Δt

switch, reaching much better discrimination and g(2)(0) values.

Spectral indistinguishability

Tool for single photon characterisation Improved accuracy Standards

Probability distribution Random settings

Primary standardCryogenic radiometer

Synchronisation

Calibrated bre opticpower meter

Pulsed laser Calibrated variable attenuator QKD receiver (gated photoncounting detector)

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2

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