Why is QKD not used?             Towards high-performance CVQKD               Practical security considerations           ...
Why is QKD not used?                  Towards high-performance CVQKD                    Practical security considerationsQ...
Why is QKD not used?                  Towards high-performance CVQKD                    Practical security considerationsQ...
Why is QKD not used?             Towards high-performance CVQKD               Practical security considerationsTwo technol...
Why is QKD not used?                 Towards high-performance CVQKD                   Practical security considerationsGau...
Why is QKD not used?           Towards high-performance CVQKD             Practical security considerationsOptical setup6/20
Why is QKD not used?             Towards high-performance CVQKD               Practical security considerationsSpeed limit...
Why is QKD not used?                 Towards high-performance CVQKD                   Practical security considerationsRan...
Why is QKD not used?             Towards high-performance CVQKD               Practical security considerationsChannel vir...
Why is QKD not used?              Towards high-performance CVQKD                Practical security considerations How to i...
Why is QKD not used?              Towards high-performance CVQKD                Practical security considerations What is ...
Why is QKD not used?            Towards high-performance CVQKD              Practical security considerations Set of avail...
Why is QKD not used?              Towards high-performance CVQKD                Practical security considerations How to g...
Why is QKD not used?                                              Towards high-performance CVQKD                          ...
Why is QKD not used?              Towards high-performance CVQKD                Practical security considerations Finite s...
Why is QKD not used?                  Towards high-performance CVQKD                    Practical security considerations ...
Why is QKD not used?                  Towards high-performance CVQKD                    Practical security considerations ...
Why is QKD not used?              Towards high-performance CVQKD                Practical security considerations Imperfec...
Why is QKD not used?              Towards high-performance CVQKD                Practical security considerations Summary ...
Why is QKD not used?              Towards high-performance CVQKD                Practical security considerations Enquire ...
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Experimental demonstration of continuous variable quantum key distribution over 80 km of standard telecom fiber

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Experimental demonstration of continuous variable quantum key distribution over 80 km of standard telecom fiber

  1. 1. Why is QKD not used? Towards high-performance CVQKD Practical security considerations Experimental Demonstration of Continuous-Variable Quantum Key Distribution over 80 km of Standard Telecom Fiber Paul Jouguet, S´bastien Kunz-Jacques, Anthony e Leverrier, Philippe Grangier, Eleni Diamanti SeQureNet, T´l´com ParisTech ee 2012-09-141/20
  2. 2. Why is QKD not used? Towards high-performance CVQKD Practical security considerationsQKD: four main limitations (1/2) Speed Not enough for OTP: not a serious issue Physical parameters estimation over large blocks: hardware drifts, latency Distance Asymmetric crypto is not limited Trusted nodes are not a good solution: quantum repeaters are required2/20
  3. 3. Why is QKD not used? Towards high-performance CVQKD Practical security considerationsQKD: four main limitations (2/2) Security Incomplete security proofs Distance between proofs and practical implementations Deployment QKD requires a dark fiber: $$$ WDM compatibility: lowers QKD extra premium3/20
  4. 4. Why is QKD not used? Towards high-performance CVQKD Practical security considerationsTwo technologies Discrete variables Continuous variables medium photon phase/polar. field amplitude-phase detection photon counters coherent detection range 100 km 25km rate 1Mb/s 10kb/s components active cooling standard integration WDM WDM security yes yes4/20
  5. 5. Why is QKD not used? Towards high-performance CVQKD Practical security considerationsGaussian protocol Losses and excess noise lower the SNR.5/20
  6. 6. Why is QKD not used? Towards high-performance CVQKD Practical security considerationsOptical setup6/20
  7. 7. Why is QKD not used? Towards high-performance CVQKD Practical security considerationsSpeed limitations Delay between classical and quantum signals (200ns) Laser pulsed with a tunable frequency (1MHz) Data acquisition speed (up to 5MHz) Filtering: tradeoff between speed and electronic noise (current cutoff at 10MHz, 100MHz feasible arxiv:1006.1257 Yue-Meng Chi et al.) High-speed error correction: LDPC codes (GPU) or polar codes (CPU) (up to 10Mbit/s) (arxiv:1204.5882, P. Jouguet and S. Kunz-Jacques)7/20
  8. 8. Why is QKD not used? Towards high-performance CVQKD Practical security considerationsRange limitations High error-correction efficiency, even at low SNRs Finite-size effects Low SNR Alice/Bob synchronization mechanism Low-loss LO path Excess noise (imperfect relative phase estimation) New SNR regions allowed by error-correction techniques.8/20
  9. 9. Why is QKD not used? Towards high-performance CVQKD Practical security considerationsChannel virtualization Idea introduced by Leverrier (Phys. Rev. A 77, 042325 (2008)) Translates the initial problem into a channel coding problem on a good channel Good means very efficient error-correcting codes available Usual suspect: BIAWGNC9/20
  10. 10. Why is QKD not used? Towards high-performance CVQKD Practical security considerations How to improve the efficiency of the multidimensional scheme? Improve the approximation between the virtual channel and the target channel Improve the efficiency of the codes on the target channel (Phys. Rev. A 84, 062317 (2011), P. Jouguet, S. Kunz-Jacques and A. Leverrier)10/20
  11. 11. Why is QKD not used? Towards high-performance CVQKD Practical security considerations What is a good code for the BIAWGNC? A code is designed for a channel and a SNR Free parameter: the code rate R = n−m , m the number of n parity-check equations, n the length Low SNR / Lot of redundancy / Low rate R Efficiency β (SNR) = C (SNR) Typical values: Slice reconciliation: β = 90%, SNR= 3, @30km Multidimensional reconciliation: β = 89%, SNR= 0.5, @50km11/20
  12. 12. Why is QKD not used? Towards high-performance CVQKD Practical security considerations Set of available codes β SNR 93.6% 1.097 93.1% 0.161 95.8% 0.075 96.9% 0.029 96.6% 0.0145 95.9% 0.0072512/20
  13. 13. Why is QKD not used? Towards high-performance CVQKD Practical security considerations How to get more flexibility on the SNR? Possible to design codes with lower rates Not necessary: repetition codes Shortening, puncturing Optimization on the modulation variance13/20
  14. 14. Why is QKD not used? Towards high-performance CVQKD Practical security considerations Theoretical secret key rate Parameters: VA ∈ {1, 100}, T = 10−0.2d/10 , ξ = 0.01, η = 0.6, Velec = 0.01 1 SNR=1.097 (1) 1 SNR=0.161 (2) 0.1 SNR=0.075 (3) 2 SNR=0.029 (4) Key rate (secret bits/pulse) 3 SNR=0.0145 (5) 0.01 SNR=0.00725 (6) 4 5 0.001 6 0.0001 10−5 10−6 0 20 40 60 80 100 120 140 160 180 Distance (km)14/20
  15. 15. Why is QKD not used? Towards high-performance CVQKD Practical security considerations Finite size effects First analysis for discrete modulation protocols in Phys. Rev. A 81, 062343 (2010), Leverrier et al. Statistical uncertainty over estimated parameters (T , ξ) n K= N (βI (x; y ) −S PE (y ; E ) − ∆(n)) Extended analysis for Gaussian modulation, including imperfect homodyne detection (efficiency, electronic noise) and shot noise estimation (Phys. Rev. A 86, 032309 (2012), poster 33) Main effect: uncertainty on the excess noise ξ15/20
  16. 16. Why is QKD not used? Towards high-performance CVQKD Practical security considerations Experimental results Parameters: d = 53km, η = 0.552, Velec = 0.015, SNR= 0.17, β = 94%, = 10−10 0.002 excess noise std dev of the experimental excess noise std dev of the theoretical estimator (108 samples) std dev of the theoretical estimator (106 samples) 0.0015 Excess noise (shot noise units) 0.001 0.0005 0 -0.0005 0 5 10 15 20 Time (hours)16/20
  17. 17. Why is QKD not used? Towards high-performance CVQKD Practical security considerations Experimental results Parameters: d = 53km,80km, η = 0.552, Velec = 0.015, SNR=0.17,0.08, β = 94%, = 10−10 100000 asymptotic theoretical key rate nite-size theoretical key rate (108 samples) asymptotic experimental point nite-size experimental point (108 samples) 10000 Key rate (bit/s) 1000 100 0 20 40 60 80 100 Distance (km)17/20
  18. 18. Why is QKD not used? Towards high-performance CVQKD Practical security considerations Imperfect preparation Thermal noise (Phys. Rev. A 81, 022318 (2010), Usenko and Filip) Gaussian modulation: truncated and discretized (finite amount of randomness) Can be taken into account into the security proof (Phys. Rev. A 86, 032309 (2012), poster 33) But a lot of random numbers are required (+ sifting and multidimensional protocol) Calibration procedures Calibration of the homodyne detection Calibration of the phase noise18/20
  19. 19. Why is QKD not used? Towards high-performance CVQKD Practical security considerations Summary Long distance CVQKD with Gaussian modulation is possible thanks to low SNR error-correction capability Computing-power consuming because of decoding close to the threshold We use GPU (30× faster than CPU plus friendly Moore’s law) Higher secure distance with virtual Gaussian post-selection? (arxiv:1205.6933, J. Fiurasek, N. J. Cerf, arxiv:1206.0936, N. Walk et al.) Work on WDM coming19/20
  20. 20. Why is QKD not used? Towards high-performance CVQKD Practical security considerations Enquire about Cygnus An open and customizable CVQKD research platform Tests/demonstrations of integration in optical networks20/20

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