## Field trial of differential-phase-shift quantum key distribution using polarization independent frequency up-conversion detectors

Optics Express, Vol. 15, Issue 24, pp. 15920-15927 (2007)

http://dx.doi.org/10.1364/OE.15.015920

Acrobat PDF (117 KB)

### Abstract

We report a field trial of differential phase shift quantum key distribution (QKD) using polarization independent frequency up-conversion detectors. A frequency up-conversion detector is a promising device for achieving a high key generation rate when combined with a high clock rate QKD system. However, its polarization dependence prevents it from being applied to practical QKD systems. In this paper, we employ a modified polarization diversity configuration to eliminate the polarization dependence. Applying this method, we performed a long-term stability test using a 17.6-km installed fiber. We successfully demonstrated stable operation for 6 hours and achieved a sifted key generation rate of 120 kbps and an average quantum bit error rate of 3.14 %. The sifted key generation rate was not the estimated value but the effective value, which means that the sifted key was continuously generated at a rate of 120 kbps for 6 hours.

© 2007 Optical Society of America

## 1. Introduction

1. C. H. Bennett, F. Bessette, G. Brassard, L. Salvail, and J. Smolin, “Experimental quantum cryptography,” J. Cryptology **5**,3–28 (1992). [CrossRef]

2. N. Gisin, G. Ribordy, W. Tittel, and H. Zbinden, “Quantum cryptography,” Rev. Mod. Phys. **74**,145–195 (2002). [CrossRef]

3. D. Stucki, N. Gisin, O. Guinnard, G. Ribordy, and H. Zbinden, “Quantum key distribution over 67 km with a plug&play system,” New J. Phys. **4**, 41 (2002). [CrossRef]

6. X. -F. Mo, B. Zhu, Z. -F. Han, Y. -Z. Gui, and G. -C. Guo, “Faraday-Michelson system for quantum cryptography,” Opt. Lett. **30**, 2632–2634 (2005). [CrossRef] [PubMed]

*µ*m telecom band. These include frequency up-conversion detectors [8

8. M. A. Albota and F. N. C. Wong, “Efficient single-photon counting at 1.55 um by means of frequency upconversion,” Opt. Lett. **29**, 1449 (2004). [CrossRef] [PubMed]

10. C. Langrock, E. Diamanti, R. V. Roussev, Y. Yamamoto, M. M. Fejer, and H. Takesue, “Highly efficient single photon detection at communication wavelengths by use of upconversion in reverse-proton-exchanged periodically poled *LiNbO*_{3} waveguides,” Opt. Lett. **30**, 1725 (2005). [CrossRef] [PubMed]

11. N. Namekata, S. Sasamori, and S. Inoue, “800 MHz single-photon detection at 1550-nm using an InGaAs/InP avalanche photodiode operated with a sine wave gating,” Opt. Express **14**, 10043–10049 (2006). [CrossRef] [PubMed]

12. G. N. Gol’tsman, O. Okunev, G. Chulkova, A. Lipatov, A. Semenov, K. Smirnov, B. Voronov, A. Dzardanov, C. Williams, and Roman Sobolewski, ” Picosecond superconducting single-photon optical detector,” Appl. Phys. Lett. **79**, 705–707 (2001). [CrossRef]

13. A. Verevkin, J. Zhang, Roman Sobolewski, A. Lipatov, O. Okunev, G. Chulkova, A. Korneev, K. Smirnov, G. N. Gol’tsman, and A. Semenov, “Detection efficiency of large-active area NbN single-photon superconducting detectors in the ultraviolet to near-infrared range,” Appl. Phys. Lett. **80**, 4687–4689 (2002). [CrossRef]

14. E. Diamanti, H. Takesue, T. Honjo, K. Inoue, and Y. Yamamoto, “Performance of various quantum key distribution systems using 1.55 um up-conversion single-photon detectors,” Phys. Rev. A , **72**, 052311 (2005). [CrossRef]

15. H. Takesue, E. Diamanti, T. Honjo, C. Langrock, M. M. Fejer, K. Inoue, and Y. Yamamoto, “Differential phase shift quantum key distribution experiment over 105 km fibre,” New J. Phys. **7**,232 (2005). [CrossRef]

16. E. Diamanti, H. Takesue, C. Langrock, M. M. Fejer, and Y. Yamamoto, “100 km differential phase shift quantum key distribution experiment with low jitter up-conversion detectors,” Opt. Express **14**, 13073–13082 (2006). [CrossRef] [PubMed]

17. N. Namekata, G. Hujii, S. Inoue, T. Honjo, and H. Takesue, “Quantum key distribution using single-photon detectors based on a sinusoidally gated InGaAs/InP avalanche photodiode,” Appl. Phys. Lett. **91**, 011112 (2007). [CrossRef]

18. D. Rosenberg, J. W. Harrington, P. R. Rice, P. A. Hiskett, C. G. Peterson, R. J. Hughes, A. E. Lita, S. W. Nam, and J. E. Nordholt, “ Long-distance decoy-state quantum key distribution in optical fiber,” Phys. Rev. Lett. **98**, 010503 (2007). [CrossRef] [PubMed]

19. H. Takesue, S. W. Nam, Q. Zhang, R. H. Hadfield, T. Honjo, K. Tamaki, and Y. Yamamoto, “Quantum key distribution over 40 dB channel loss using superconducting single-photon detectors,” Nature Photonics **1**, 343 (2007). [CrossRef]

20. H. Takesue, E. Diamanti, C. Langrock, M. M. Fejer, and Y. Yamamoto, “1.5- *µ*m single photon counting using polarization-independent up-conversion detector,” Opt. Express **14**, 13067–13072 (2006) [CrossRef] [PubMed]

## 3. Polarization-independent frequency up-conversion detectors

*µ*msignal pulse (photon) was input into a fiber-coupled polarization beam splitter (PBS), which split the polarization of the incoming photon into horizontally and vertically polarized pulses. All the components after the PBS, described below, were connected with polarization maintaining fibers. The horizontally polarized pulse was directly input into a polarization maintaining 50:50 coupler. The vertically polarized pulse was input into a fiber delay line as a horizontally polarized pulse by twisting the axis at the connection between the PBS output fiber and the delay fiber. The pulse passed through the delay line, and was input into the polarization maintaining 50:50 coupler. The delay line was used to avoid interference at the 50:50 coupler. Since the pulse width in our experiment was 66 ps, we chose a delay time of 200 ps. One output of the 50:50 coupler was connected to a wavelength division multiplexer (WDM) coupler, which meant this setup had an intrinsic loss of 3 dB. The excess loss from the PBS to the 50:50 coupler was 2 dB. The 1.5-

*µ*msignal pulse output from the 50:50 coupler was combined with a strong pump light whose wavelength was 980 nm at a wavelength division multiplexer (WDM) coupler, and injected into a PPLN waveguide. In the PPLN waveguide, a 600 nm photon was generated via the sum frequency generation (SFG) process. The converted signal, pump, and spurious light after the PPLN waveguide were separated by using a combination consisting of a short-pass filter, prisms and a spatial filter. The SFG photon was detected with a single photon counting module (SPCM) based on a Si-APD (MPD). The jitter of this Si-APD was low enough to discriminate a 1-GHz signal [16

16. E. Diamanti, H. Takesue, C. Langrock, M. M. Fejer, and Y. Yamamoto, “100 km differential phase shift quantum key distribution experiment with low jitter up-conversion detectors,” Opt. Express **14**, 13073–13082 (2006). [CrossRef] [PubMed]

23. R. T. Thew, S. Tanzilli, L. Krainer, S. C. Zeller, A. Rochas, I. Rech, S. Cova, H. Zbinden, and N. Gisin, “Low jitter up-conversion detectors for telecom wavelength GHz QKD,” New J. Phys. **8**,32 (2006). [CrossRef]

## 4. Experimental setup

*LiNbO*

_{3}intensity modulator. The pulse width was 66 ps. Each pulse was randomly phase-modulated by 0,

*π*with a

*LiNbO*

_{3}phase modulator. We used a pseudo-random bit sequence with a length of 11 k bits as the phase modulation signal. The pulse was attenuated to 0.2 photons per pulse and then transmitted to Bob’s site over the installed fiber. The start pulse, which indicated the head of a pseudo-random bit sequence, was generated by a distributed feedback laser with an electro-absorption modulator (EA-DFB), and transmitted over the other installed fiber. The interval of the start pulse was 11

*µ*sec. The excess losses of these installed fibers were 7.0 and 7.2 dB, respectively. After the transmission, the 1-GHz pulse stream was input into a Mach-Zehnder interferometer based on planar lightwave circuit technology. The path length difference and the excess loss were 20 cm and 2.0 dB, respectively. The extinction ratio was greater than 20 dB and the polarization dependence was negligible [22

22. T. Honjo, K. Inoue, and H. Takahashi, “Differential-phase-shift quantum key distribution experiment with a planar light-wave circuit Mach-Zehnder interferometer,” Opt. Lett. **29**, 2797 (2004). [CrossRef] [PubMed]

## 5. Results

*µ*sec per start pulse. As a result of the effect of the time window and the dead time of the TIA, the sifted key generation rate was 30 % lower than the count rate.

24. E. Waks, H. Takesue, and Y. Yamamoto, “Security of differential-phase-shift quantum key distribution against individual attacks,” Phys. Rev. A **73**,012344 (2006). [CrossRef]

26. T. Tsurumaru, “Sequential attack with intensity modulation on the differential-phase-shift quantum-key-distribution protocol,” Phys. Rev. A **75**, 062319 (2007). [CrossRef]

## 6. Summary

## Acknowledgment

## References and links

1. | C. H. Bennett, F. Bessette, G. Brassard, L. Salvail, and J. Smolin, “Experimental quantum cryptography,” J. Cryptology |

2. | N. Gisin, G. Ribordy, W. Tittel, and H. Zbinden, “Quantum cryptography,” Rev. Mod. Phys. |

3. | D. Stucki, N. Gisin, O. Guinnard, G. Ribordy, and H. Zbinden, “Quantum key distribution over 67 km with a plug&play system,” New J. Phys. |

4. | C. Elliott, A. Colvin, D. Pearson, O. Pikalo, J. Schlafer, and H. Yeh, “Current status of the DARPA Quantum Network,”, quant-ph/0503058. |

5. | T. Hasegawa, T. Nishioka, H. Ishizuka, J. Abe, K. Shimizu, and M. Matsui, “Field experiments of quantum cryptosystem in 96km installed fibers,” CLEO/Europe-EQEC 2005, EG-10, Munich (2005). |

6. | X. -F. Mo, B. Zhu, Z. -F. Han, Y. -Z. Gui, and G. -C. Guo, “Faraday-Michelson system for quantum cryptography,” Opt. Lett. |

7. | A. Tanaka, W. Maedasn, A. Tajima, and S. Takahashi, “Fortnight quantum key generation field trial using QBER monitoring,” LEOS 2005 , 557–558 (2005). |

8. | M. A. Albota and F. N. C. Wong, “Efficient single-photon counting at 1.55 um by means of frequency upconversion,” Opt. Lett. |

9. | A. P. Vandevender and P. G. Kwiat, “High efficiency single photon detection via frequency up-conversion,” J. Mod. Opt. |

10. | C. Langrock, E. Diamanti, R. V. Roussev, Y. Yamamoto, M. M. Fejer, and H. Takesue, “Highly efficient single photon detection at communication wavelengths by use of upconversion in reverse-proton-exchanged periodically poled |

11. | N. Namekata, S. Sasamori, and S. Inoue, “800 MHz single-photon detection at 1550-nm using an InGaAs/InP avalanche photodiode operated with a sine wave gating,” Opt. Express |

12. | G. N. Gol’tsman, O. Okunev, G. Chulkova, A. Lipatov, A. Semenov, K. Smirnov, B. Voronov, A. Dzardanov, C. Williams, and Roman Sobolewski, ” Picosecond superconducting single-photon optical detector,” Appl. Phys. Lett. |

13. | A. Verevkin, J. Zhang, Roman Sobolewski, A. Lipatov, O. Okunev, G. Chulkova, A. Korneev, K. Smirnov, G. N. Gol’tsman, and A. Semenov, “Detection efficiency of large-active area NbN single-photon superconducting detectors in the ultraviolet to near-infrared range,” Appl. Phys. Lett. |

14. | E. Diamanti, H. Takesue, T. Honjo, K. Inoue, and Y. Yamamoto, “Performance of various quantum key distribution systems using 1.55 um up-conversion single-photon detectors,” Phys. Rev. A , |

15. | H. Takesue, E. Diamanti, T. Honjo, C. Langrock, M. M. Fejer, K. Inoue, and Y. Yamamoto, “Differential phase shift quantum key distribution experiment over 105 km fibre,” New J. Phys. |

16. | E. Diamanti, H. Takesue, C. Langrock, M. M. Fejer, and Y. Yamamoto, “100 km differential phase shift quantum key distribution experiment with low jitter up-conversion detectors,” Opt. Express |

17. | N. Namekata, G. Hujii, S. Inoue, T. Honjo, and H. Takesue, “Quantum key distribution using single-photon detectors based on a sinusoidally gated InGaAs/InP avalanche photodiode,” Appl. Phys. Lett. |

18. | D. Rosenberg, J. W. Harrington, P. R. Rice, P. A. Hiskett, C. G. Peterson, R. J. Hughes, A. E. Lita, S. W. Nam, and J. E. Nordholt, “ Long-distance decoy-state quantum key distribution in optical fiber,” Phys. Rev. Lett. |

19. | H. Takesue, S. W. Nam, Q. Zhang, R. H. Hadfield, T. Honjo, K. Tamaki, and Y. Yamamoto, “Quantum key distribution over 40 dB channel loss using superconducting single-photon detectors,” Nature Photonics |

20. | H. Takesue, E. Diamanti, C. Langrock, M. M. Fejer, and Y. Yamamoto, “1.5- |

21. | K. Inoue, E. Waks, and Y. Yamamoto, “Differential-phase-shift quantum key distribution using coherent light,” Phys. Rev. A |

22. | T. Honjo, K. Inoue, and H. Takahashi, “Differential-phase-shift quantum key distribution experiment with a planar light-wave circuit Mach-Zehnder interferometer,” Opt. Lett. |

23. | R. T. Thew, S. Tanzilli, L. Krainer, S. C. Zeller, A. Rochas, I. Rech, S. Cova, H. Zbinden, and N. Gisin, “Low jitter up-conversion detectors for telecom wavelength GHz QKD,” New J. Phys. |

24. | E. Waks, H. Takesue, and Y. Yamamoto, “Security of differential-phase-shift quantum key distribution against individual attacks,” Phys. Rev. A |

25. | M. Curty, L. L. X. Zhang, H. K. Lo, and N. Lutkenhaus, “Sequential attacks against differential-phase-shift quantum key distribution with weak coherent states,” Quantum Information & Computation , |

26. | T. Tsurumaru, “Sequential attack with intensity modulation on the differential-phase-shift quantum-key-distribution protocol,” Phys. Rev. A |

**OCIS Codes**

(190.4370) Nonlinear optics : Nonlinear optics, fibers

(270.0270) Quantum optics : Quantum optics

**ToC Category:**

Nonlinear Optics

**History**

Original Manuscript: September 10, 2007

Revised Manuscript: November 9, 2007

Manuscript Accepted: November 14, 2007

Published: November 16, 2007

**Citation**

T. Honjo, S. Yamamoto, T. Yamamoto, H. Kamada, Y. Nishida, O. Tadanaga, M. Asobe, and K. Inoue, "Field trial of differential-phase-shift quantum key distribution using polarization independent frequency up-conversion detectors," Opt. Express **15**, 15920-15927 (2007)

http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-15-24-15920

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### References

- C. H. Bennett, F. Bessette, G. Brassard, L. Salvail, and J. Smolin, "Experimental quantum cryptography," J. Cryptology 5, 3-28 (1992). [CrossRef]
- N. Gisin, G. Ribordy, W. Tittel, and H. Zbinden, "Quantum cryptography," Rev. Mod. Phys. 74, 145-195 (2002). [CrossRef]
- D. Stucki, N. Gisin, O. Guinnard, G. Ribordy, and H. Zbinden, "Quantum key distribution over 67 km with a plug&play system," New J. Phys. 4, 41 (2002). [CrossRef]
- C. Elliott, A. Colvin, D. Pearson, O. Pikalo, J. Schlafer, and H. Yeh, "Current status of the DARPA Quantum Network," quant-ph/0503058.
- T. Hasegawa, T. Nishioka, H. Ishizuka, J. Abe, K. Shimizu, and M. Matsui, "Field experiments of quantum cryptosystem in 96km installed fibers," CLEO/Europe-EQEC 2005, EG-10, Munich (2005).
- X. -F. Mo, B. Zhu, Z. -F. Han, Y. -Z. Gui, and G. -C. Guo, "Faraday-Michelson system for quantum cryptography," Opt. Lett. 30, 2632-2634 (2005). [CrossRef] [PubMed]
- A. Tanaka, W. Maeda, A. Tajima, and S. Takahashi, "Fortnight quantum key generation field trial using QBER monitoring," LEOS 2005, 557-558 (2005).
- M. A. Albota and F. N. C. Wong, "Efficient single-photon counting at 1.55 um by means of frequency upconversion," Opt. Lett. 29, 1449 (2004). [CrossRef] [PubMed]
- A. P. Vandevender and P. G. Kwiat, "High efficiency single photon detection via frequency up-conversion," J. Mod. Opt. 15, 1433-1445 (2004).
- C. Langrock, E. Diamanti, R. V. Roussev, Y. Yamamoto, M. M. Fejer, and H. Takesue, "Highly efficient single photon detection at communication wavelengths by use of upconversion in reverse-proton-exchanged periodically poled LiNbO3 waveguides," Opt. Lett. 30, 1725 (2005). [CrossRef] [PubMed]
- N. Namekata, S. Sasamori, and S. Inoue, "800 MHz single-photon detection at 1550-nm using an InGaAs/InP avalanche photodiode operated with a sine wave gating," Opt. Express 14, 10043-10049 (2006). [CrossRef] [PubMed]
- G. N. Gol’tsman, O. Okunev, G. Chulkova, A. Lipatov, A. Semenov, K. Smirnov, B. Voronov, A. Dzardanov, C. Williams, and Roman Sobolewski, " Picosecond superconducting single-photon optical detector," Appl. Phys. Lett. 79, 705-707 (2001). [CrossRef]
- A. Verevkin, J. Zhang, Roman Sobolewski, A. Lipatov, O. Okunev, G. Chulkova, A. Korneev, K. Smirnov, G. N. Gol’tsman, and A. Semenov, "Detection efficiency of large-active area NbN single-photon superconducting detectors in the ultraviolet to near-infrared range," Appl. Phys. Lett. 80, 4687-4689 (2002). [CrossRef]
- E. Diamanti, H. Takesue, T. Honjo, K. Inoue, and Y. Yamamoto, "Performance of various quantum key distribution systems using 1.55 um up-conversion single-photon detectors," Phys. Rev. A, 72, 052311 (2005). [CrossRef]
- H. Takesue, E. Diamanti, T. Honjo, C. Langrock, M. M. Fejer, K. Inoue, and Y. Yamamoto, "Differential phase shift quantum key distribution experiment over 105 km fibre," New J. Phys. 7, 232 (2005). [CrossRef]
- E. Diamanti, H. Takesue, C. Langrock, M. M. Fejer, and Y. Yamamoto, "100 km differential phase shift quantum key distribution experiment with low jitter up-conversion detectors," Opt. Express 14, 13073-13082 (2006). [CrossRef] [PubMed]
- N. Namekata, G. Hujii, S. Inoue, T. Honjo, and H. Takesue, "Quantum key distribution using single-photon detectors based on a sinusoidally gated InGaAs/InP avalanche photodiode," Appl. Phys. Lett. 91, 011112 (2007). [CrossRef]
- D. Rosenberg, J. W. Harrington, P. R. Rice, P. A. Hiskett, C. G. Peterson, R. J. Hughes, A. E. Lita, S. W. Nam, and J. E. Nordholt, " Long-distance decoy-state quantum key distribution in optical fiber," Phys. Rev. Lett. 98, 010503 (2007). [CrossRef] [PubMed]
- H. Takesue, S. W. Nam, Q. Zhang, R. H. Hadfield, T. Honjo, K. Tamaki, and Y. Yamamoto, "Quantum key distribution over 40 dB channel loss using superconducting single-photon detectors," Nature Photonics 1, 343 (2007). [CrossRef]
- H. Takesue, E. Diamanti, C. Langrock, M. M. Fejer, and Y. Yamamoto, "1.5- m single photon counting using polarization-independent up-conversion detector," Opt. Express 14, 13067-13072 (2006) [CrossRef] [PubMed]
- K. Inoue, E. Waks, and Y. Yamamoto, "Differential-phase-shift quantum key distribution using coherent light," Phys. Rev. A 68, 022317 (2003). [CrossRef]
- T. Honjo, K. Inoue, and H. Takahashi, "Differential-phase-shift quantum key distribution experiment with a planar light-wave circuit Mach-Zehnder interferometer," Opt. Lett. 29, 2797 (2004). [CrossRef] [PubMed]
- R. T. Thew, S. Tanzilli, L. Krainer, S. C. Zeller, A. Rochas, I. Rech, S. Cova, H. Zbinden, and N. Gisin, "Low jitter up-conversion detectors for telecom wavelength GHz QKD," New J. Phys. 8, 32 (2006). [CrossRef]
- E. Waks, H. Takesue, and Y. Yamamoto, "Security of differential-phase-shift quantum key distribution against individual attacks," Phys. Rev. A 73, 012344 (2006). [CrossRef]
- M. Curty, L. L. X. Zhang, H. K. Lo, and N. Lutkenhaus, "Sequential attacks against differential-phase-shift quantum key distribution with weak coherent states," Quantum Information & Computation, 7 (7), 665-688 (2007).
- T. Tsurumaru, "Sequential attack with intensity modulation on the differential-phase-shift quantum-keydistribution protocol," Phys. Rev. A 75, 062319 (2007). [CrossRef]

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