metrology for quantum cryptography: the european effort

Metrology for quantum cryptography: the European effort (and beyond)

m.genovese@inrim.it

M.Genovese

http://www.etsi.org/technologies-clusters/technologies/quantum-key-distribution

The Industry Specification Group (ISG) on Quantum Key Distribution (QKD) of the European Telecommunications Standards Institute (ETSI ISG-QKD) is addressing standardisation issues in quantum cryptography, and quantum technology in general

QUANTUM PHOTONIC TECHNOLOGIES

Started from the outcome of the EC FP6-project SECOQC (Secure Communication based on Quantum Cryptography), an Industry Specification Group (ISG) of the European Telecommunications Standards Institute (ETSI).

Applied Communication SciencesAustrian Institute of Technology (AIT)BMWi - Federal Ministry of Economics and TechnologyCadzow Communications Consulting Ltd (UK)DCMS Department for culture, Media and Sport Organization ( former BIS)Facultad de Informatica, Universidad Politecnica de MadridHewlett-Packard, Centre de Compétences FranceInstitut Mines TelecomIstituto Nazionale di Ricerca Metrologica (INRIM)Mitsubishi Electric RCENational Institute of Information and Communications Technology (NICT)NTT CorporationSWISSCOM SATELEFONICA S.A.THALESTOSHIBA RESEARCH EUROPE LTDTubitak UekaeUniversida Politecnica de MadridUniversity of Waterloo

Arche Finanz GmbHID Quantique SASK Telecom

JRP EXL02 - SIQUTE

Squqis

…….

IND06: Metrology for Industrial Quantum Communicationshttp://www.miqc.org/

Objective: development of a pan-European measurement infrastructure (standards,measurement facilities, …) for practical QKD system

• QKD components require independent characterisation in order to convince end-users that the technology is working within specification

• 3 year project (ended Aug 2014)

Towards Radiometric Quantum Standards

Photon emitters Traceable characterisation of commercial QKD sources:• Attenuated laser pulses

Photon receiversTraceable calibration of commercial QKD receivers:• Gated photon counting detectors

Key Measurement Outputs of MIQC

Quantum channel (optical fibre) and RNG • Traceable characterisation of single mode optical fibre• Characterisation of propagation of photon state in single mode fibre• Open system true physical quantum random number generator (QRNG)• QRNG physically characterised and tested under different operating

conditions

Phase encoded, attenuated laser pulse QKD over fibre at 1550 nm

Detectors’ parameters considered [1/2]Parameter Symbol Units Definition Measurement approach

Photon detectionprobability

h probability/gate

The probability that a photon incident at the optical input will be detected within a detection gate.

Via a calibrated laser light source and a calibrated filter

Dark countprobability

Pdark (probability/gate)

The probability that a detector registers a detection event per gate, despite the absence of optical illumination.

As above (1)

Afterpulse probability Pafterpulse (probability/gate)

The probability that a detector registers a false detection event in the absence of illumination, conditional on a true photon detection event in the preceding detection gate.

As above (1)

Dead time Tdead ns/µs The smallest time duration after which the detection efficiency is independent of previous photon detection history.

Via a train of two optical pulses with tuneable temporal separation

Recovery Time Trec ns/µs The time duration after a photon detection event for the detection efficiency to return to 99% of its steady-state value. This is only important if the detector is passively quenched

As above (4)

Receiver’s Detectors

Detectors’ parameters considered [2/2]Parameter Symbol Units Definition Measurement approach

Maximum count rate Cmax MHz/GHz The maximum rate of photon detection events under strong illumination condition in the single/few photon/gate regime.

This will be determined by the photon detection efficiency, the dead time, and dark counts

Timing jitter Tjitter ps/ns The uncertainty in determining the arrival time of a photon at the optical input.

Measure the FWHM in the distribution of detection times

Maximum clock frequency

Fmax MHz/GHz The maximum clock frequency at or below which a detector can be operated in a QKD system without giving rise to an intolerable bit error rate.

Spectral Responsivity Rs unitless The photon detection efficiency as a function of wavelength of the incident photons.

Via a calibrated laser light source with known wavelength (wavemeter) and a calibrated filter

Receiver’s Detectors

Detection probability

Photon Detection Probability

Detection efficiency of the InGaAs-SPAD

pulsed@1,55 µm

Laserattenuators-30dB …-60 dB

counter

pulse/delaygenerator

amplifier + VoltmeterCalibrated InGaAs-DiodeIssues

- Attenuators Calibration From CW to pulsed source - Nonlinearity & Deadtimes- From CW to pulsed source- …

Optical power traceability chain (SI)

0.005 % uncertainty

visible wavelengths,0.5 mW,collimated, free-space laser radiation

1 % uncertainty (k = 2)

1550 nm,100 pW,output from optical fibre

Primary standardCryogenic radiometry

NMI reference detectors

Low power reference detector

Photon emitters Traceable characterisation of commercial QKD sources:• Attenuated laser pulses

Photon receiversTraceable calibration of commercial QKD receivers:• Gated photon counting detectors

Key Measurement Outputs of MIQC

Quantum channel (optical fibre) and RNG • Traceable characterisation of single mode optical fibre• Characterisation of propagation of photon state in single mode fibre• Open system true physical quantum random number generator (QRNG)• QRNG physically characterised and tested under different operating

conditions

Phase encoded, attenuated laser pulse QKD over fibre at 1550 nm

Source parameters considered [1/2]Parameter Symbol Units Definition Measurement approachFrequency (Rep.Rate)

F Hz The frequency set by the pulse generator

Measure via standard traceable frequency calibration techniques

Mean photon number

µ Photons/pulse

Average number of photons per pulse emitted by Alice

a) calibrated detector and commercial attenuator

b) calibrated detector and traceable attenuator based on InGaAs photodiodes

c) reconstruction of probability distribution

d) Photon number resolving detector based on commercial single photon detector in tree configuration

Mean photon number variation

σµ As above

Source timing jitter JS ps or ns The uncertainty in the emission time of a photon at the optical output.

Measure FWHM of distribution of photon emission times with respect to pulse generator signal

Emitter’s Sources

Source parameters considered [2/2]Parameter Symbol Units Definition Measurement approachSource wavelength λ nm Wavelength of photons

that are emitted.Wavemeter

Spectral line width δ GHz Bandwidth of the emitted photons.

Beat note measurement or Fabry-Perot interferometer.

Spectral indistinguishability

sind Unitless The extent to which the encoded states can be distinguished through spectral measurement.

Fabry-Perot interferometer: compare spectra of differentencoding states

Temporal indistinguishability

tind Unitless The extent to which theencoded states can bedistinguished throughtemporal measurement.

The probability distribution with respect to time for laser output pulses is measured. tind is calculated according to reference [12].

Polarisation state Polarisation reconstruction

Emitter’s Sources

Source photon number statistics

i) Calibrated detector and commercial attenuator

Setup• Calibrated power meter can be used to measure flux (approaches detection limit of

power meter)• Mean photon number measured using calibrated photon-counting detector

(correcting for the non-linear behavior)

( )10 AP

f hc−µ =

λMean photon number:

Source photon number statistics

ii) Reconstruction of probability distribution

Photon number distribution

For on/off detectors like SPAD with quantum efficiency 𝜼𝜼, the probability of no-clicks is:

“ON/OFF” Tomography

-Truncating the p.d. to a certain 𝑁𝑁-Changing the value of the quantum efficiency 𝜂𝜂𝜇𝜇

Poissonian

ReconstructedG. Zambra, M. Bondani, A. Andreoni, G. Brida, M. Gramegna, M.G., A. Rossi, M.G.A. Paris , PRL 95, 063602 (2005)

Source photon number statistics

iii) PNR detector based on tree configuration

Detector Tree:4 click/no-click detectors

BS

BS

BS

( )( )

(2) (3) (4) ( ), , 1

nn

P ng g g g

P=

• By measuring higher-order g(n), it is possible to deconvolvethe underlying number and kind (poissonian, pseudo-termal or single-photon) of occupied modes of a light field.

Deconvolving the p.d. of incoming photons

Goldschmidt et al., PRA 88, 013822 (2013)

• POVM reconstruction F. Piacentini et al.; Opt. Lett. 40(2015) 1549.

• Novel (entanglemet-assisted) quantumcharacterisation technique for PNRdetector Brida et al., PRL 108, 253601 (2012)

Noiseless Heralded SPS

HBT

∆tswitchg(2) =

∆tswitch = 2nsBrida et al., APL 101, 221112 (2012)

Photon emitters Traceable characterisation of commercial QKD sources:• Attenuated laser pulses

Photon receiversTraceable calibration of commercial QKD receivers:• Gated photon counting detectors

Key Measurement Outputs of MIQC

Quantum channel (optical fibre) and RNG • Traceable characterisation of single mode optical fibre• Characterisation of propagation of photon state in single mode fibre• Open system true physical quantum random number generator (QRNG)• QRNG physically characterised and tested under different operating

conditions

Phase encoded, attenuated laser pulse QKD over fibre at 1550 nm

Optical time-domain reflectometeroperating at single-photon level

PULSE GENERATOR

LASER

ATT 1:99

DUT

OTDR operating at single-photon level

PULSE GENERATOR

LASER

ATT 1:99

DUT

0 50 100 150 2001

10

100

1000

Coun

ts

t/ns

Backscattered Signal

FUTURE PERSPECTIVES

• MIQC was just the beginning …– Relevant parameters non-considered (e.g. parameters related

to side-channel attacks, or other QKD hacking technique) – Open-Air QKD Visible– Other QKD protocols to be considered (e.g. entanglement

based)– Producers more involved– …

MIQC2

i.degiovanni@inrim.it

MIQC2

i.degiovanni@inrim.it

QKD with orthogonal states

• Controfactual Noh QKD protocol

Quantum Bit Error Rate (QBER)QBERS1 = 0,071 ± 0,014

QBERS0 = 0,070 ± 0,016

PRA 82 (062309 (2010) Las. Phys. Lett. 9 247 (2012)

SPS with colour centres in diamond• "Electroluminescence from a diamond device with

ion-beam-micromachined buried graphitic electrodes", J. Forneris et al.Nuclear Instruments and Methods in Physics Research B 348 (2015) 187.

• "Single-photon emitters based on NIR color centers in diamond coupled with solidimmersion lenses", D. Gatto Monticone et al. IJQI 12 (2014) 1560011.

• "Beating the Abbe Diffraction Limit in Confocal Microscopy via Nonclassical PhotonStatistics» D. Gatto Monticone et al. Phys. Rev. Lett. 113, 143602 (2014)

• ……..

Goldenberg & Vaidman protocol

INRIM QUANTUM TECH GROUP

8 quantum optics labspermanent staff: M.G., G. Brida, I. Degiovanni, M.Gramegna, I.Ruo Bercheranon permanent staff: G.Adenier,A.Avella, A. Meda, G.Giorgi*, E.Moreva, F. Piacentini, M.Roncaglia*,P.Traina; PhD students: M.Levi,N.Samantaray, S.Pradyumna