## Continuous operation of a one-way quantum key distribution system over installed telecom fibre

Optics Express, Vol. 13, Issue 2, pp. 660-665 (2005)

http://dx.doi.org/10.1364/OPEX.13.000660

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### Abstract

We demonstrate a robust, compact and automated quantum key distribution system, based upon a one-way Mach-Zender interferometer, which is actively compensated for temporal drifts in the photon phase and polarization. The system gives a superior performance to passive compensation schemes with an average quantum bit error rate of 0.87% and a duty cycle of 99.6% for a continuous quantum key distribution session of 19 hours over a 20.3km installed telecom fibre. The results suggest that actively compensated QKD systems are suitable for practical applications.

© 2005 Optical Society of America

## 1. Introduction

2. P. D. Townsend, J. G. Rarity, and P. R. Tapster, “Single photon interference in 10km long fibre optical fibre interferometer,” Electron. Lett. **29**, 634–635(1993). [CrossRef]

9. D. S. Bethune and W. P. Risk, “Autocompensating quantum cryptography,” New J. Phys. **4**, 42.1–42.15(2002). [CrossRef]

10. C. H. Bennett, “Quantum cryptography using any two nonorthogonal states,” Phys. Rev. Lett. **68**, 3121–3124(1992). [CrossRef] [PubMed]

2. P. D. Townsend, J. G. Rarity, and P. R. Tapster, “Single photon interference in 10km long fibre optical fibre interferometer,” Electron. Lett. **29**, 634–635(1993). [CrossRef]

3. P. D. Townsend, “Secure key distribution system based on quantum cryptography,” Electron. Lett. **30**, 809–811(1994). [CrossRef]

5. C. Gobby, Z. L. Yuan, and A. J. Shields, “Quantum key distribution over 122km standard telecom fiber,” Appl. Phys. Lett. **84**, 3762–3764(2004). [CrossRef]

6. A. Muller, T. Herzog, B. Huttner, W. Tittel, H. Zbinden, and N. Gisin, “Plug & play systems for quantum cryptography,” Appl. Phys. Lett. **70**, 793–795(1997). [CrossRef]

9. D. S. Bethune and W. P. Risk, “Autocompensating quantum cryptography,” New J. Phys. **4**, 42.1–42.15(2002). [CrossRef]

6. A. Muller, T. Herzog, B. Huttner, W. Tittel, H. Zbinden, and N. Gisin, “Plug & play systems for quantum cryptography,” Appl. Phys. Lett. **70**, 793–795(1997). [CrossRef]

7. D. Stucki, N. Gisin, O. Guinnard, R. Ribordy, and H. Zbinden, “Quantum key distribution over 67 km with a plug&play system,” New J. Phys. **4**, 41.1–41.8(2002). [CrossRef]

7. D. Stucki, N. Gisin, O. Guinnard, R. Ribordy, and H. Zbinden, “Quantum key distribution over 67 km with a plug&play system,” New J. Phys. **4**, 41.1–41.8(2002). [CrossRef]

7. D. Stucki, N. Gisin, O. Guinnard, R. Ribordy, and H. Zbinden, “Quantum key distribution over 67 km with a plug&play system,” New J. Phys. **4**, 41.1–41.8(2002). [CrossRef]

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

## 2. Experimental setup

5. C. Gobby, Z. L. Yuan, and A. J. Shields, “Quantum key distribution over 122km standard telecom fiber,” Appl. Phys. Lett. **84**, 3762–3764(2004). [CrossRef]

^{-6}, while APD2 for the strong reference pulse, cooled by a thermal-electric cooler to -40°C, has a dark count probability of 2×10

^{-5}. The overall detection efficiency of APD0 and APD1 is around 11%. Their detection rate is balanced because of the higher intrinsic efficiency of APD1, despite of the 18% splitting loss to APD2. Active stabilization of the phase drift is achieved by using the count rate in the reference detector APD2 to control the bias applied to the fibre stretcher in Bob’s AMZI.

## 3. Results and discussion

*ie*., the fraction of the time is it actually distributing key material, is an important parameter for assessing the performance of different QKD schemes. The system may sometimes encounter a short period of sharp phase drift it fails to compensate, for example, during reset of the fibre stretcher voltage or a sudden shock. As a result, it stops key sifting, and all photons received during this period are wasted. The duty cycle η is defined here as

5. C. Gobby, Z. L. Yuan, and A. J. Shields, “Quantum key distribution over 122km standard telecom fiber,” Appl. Phys. Lett. **84**, 3762–3764(2004). [CrossRef]

13. A. Yoshizawa, R. Kaji, and H. Tsuchida, “10.5 km fiber-optic quantum key distribution at 1550 nm with a key rate of 45 kHz,” Japanese J. Appl. Phys. **43**, L735–L737(2004). [CrossRef]

## 4. Summary

## References and links

1. | C. H. Bennett and G. Brassard, “Quantum Cryptography: Public key distribution and coin tossing,” in |

2. | P. D. Townsend, J. G. Rarity, and P. R. Tapster, “Single photon interference in 10km long fibre optical fibre interferometer,” Electron. Lett. |

3. | P. D. Townsend, “Secure key distribution system based on quantum cryptography,” Electron. Lett. |

4. | R. J. Hughes, G. L. Morgan, and C. G. Peterson, “Quantum key distribution over a 48 km optical fibre network,” J. Mod. Phys. |

5. | C. Gobby, Z. L. Yuan, and A. J. Shields, “Quantum key distribution over 122km standard telecom fiber,” Appl. Phys. Lett. |

6. | A. Muller, T. Herzog, B. Huttner, W. Tittel, H. Zbinden, and N. Gisin, “Plug & play systems for quantum cryptography,” Appl. Phys. Lett. |

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

8. | M. Bourennane, F. Gibson, A. Karlsson, A. Hening, P. Jonsson, T. Tsegaye, D. Ljunggren, and E. Sundberg, “Experiments on long wavelength (1550nm) ‘plug and play’ quantum cryptography systems,” Opt. Express |

9. | D. S. Bethune and W. P. Risk, “Autocompensating quantum cryptography,” New J. Phys. |

10. | C. H. Bennett, “Quantum cryptography using any two nonorthogonal states,” Phys. Rev. Lett. |

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

12. | G. Ribordy, J. D. Gautier, H. Zbinden, and N. Gisin, “Performance of InGaAs/InP avalanche photodiodes as gated-mode photon counters,” Appl. Opt. |

13. | A. Yoshizawa, R. Kaji, and H. Tsuchida, “10.5 km fiber-optic quantum key distribution at 1550 nm with a key rate of 45 kHz,” Japanese J. Appl. Phys. |

**OCIS Codes**

(060.4510) Fiber optics and optical communications : Optical communications

(270.0270) Quantum optics : Quantum optics

**ToC Category:**

Research Papers

**History**

Original Manuscript: November 3, 2004

Revised Manuscript: January 19, 2005

Published: January 24, 2005

**Citation**

Zhiliang Yuan and A. Shields, "Continuous operation of a one-way quantum key distribution system over installed telecom fibre," Opt. Express **13**, 660-665 (2005)

http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-13-2-660

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### References

- C. H. Bennett and G. Brassard, �??Quantum Cryptography: Public key distribution and coin tossing,�?? in Proc. of the IEEE Int. Conf. on Computers, Systems and Signal Processing, Bangalore, India (Institute of Electrical and Electronics Engineers, New York, 1984), pp. 175-179.
- P. D. Townsend, J. G. Rarity, and P. R. Tapster, �??Single photon interference in 10km long fibre optical fibre interferometer,�?? Electron. Lett. 29, 634-635(1993). [CrossRef]
- P. D. Townsend, �??Secure key distribution system based on quantum cryptography,�?? Electron. Lett. 30, 809-811(1994). [CrossRef]
- R. J. Hughes, G. L. Morgan, and C. G. Peterson, �??Quantum key distribution over a 48 km optical fibre network,�?? J. Mod. Phys. 47, 533-547(2000).
- C. Gobby, Z. L. Yuan, and A. J. Shields, �??Quantum key distribution over 122km standard telecom fiber,�?? Appl. Phys. Lett. 84, 3762-3764(2004). [CrossRef]
- A. Muller, T. Herzog, B. Huttner, W. Tittel, H. Zbinden, and N. Gisin, �??Plug & play systems for quantum cryptography,�?? Appl. Phys. Lett. 70, 793-795(1997). [CrossRef]
- D. Stucki, N. Gisin, O. Guinnard, R. Ribordy, and H. Zbinden, �??Quantum key distribution over 67 km with a plug&play system,�?? New J. Phys. 4, 41.1-41.8(2002). [CrossRef]
- M. Bourennane, F. Gibson, A. Karlsson, A. Hening, P. Jonsson, T. Tsegaye, D. Ljunggren, and E. Sundberg, �??Experiments on long wavelength (1550nm) �??plug and play�?? quantum cryptography systems,�?? Opt. Express 4, 383-387(1999). [CrossRef] [PubMed]
- D. S. Bethune and W. P. Risk, �??Autocompensating quantum cryptography,�?? New J. Phys. 4, 42.1-42.15(2002). [CrossRef]
- C. H. Bennett, �??Quantum cryptography using any two nonorthogonal states,�?? Phys. Rev. Lett. 68, 3121-3124(1992). [CrossRef] [PubMed]
- N. Gisin, G. Ribordy, W. Tittel, and H. Zbinden, �??Quantum cryptography,�?? Rev. Mod. Phys. 74, 145-195(2002). [CrossRef]
- G. Ribordy, J. D. Gautier, H. Zbinden, and N. Gisin, �??Performance of InGaAs/InP avalanche photodiodes as gated-mode photon counters,�?? Appl. Opt. 37, 2272-2277(1998). [CrossRef]
- A. Yoshizawa, R. Kaji, and H. Tsuchida, �??10.5 km fiber-optic quantum key distribution at 1550 nm with a key rate of 45 kHz,�?? Japanese J. Appl. Phys. 43, L735-L737(2004). [CrossRef]

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