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Acta Physica Sinica

Stable differential-phase-shift quantum key distribution based on weak coherent pulses

Zhao Feng, Lu Yi-Qun, Wang Fa-Qiang, Chen Xia, Mingming Li, Banghong Guo, Liao Chang-Jun, Songhao Liu, (1)华南师范大学信息光电子科技学院，广州 510006; (2)华南师范大学信息光电子科技学院，广州 510006;陕西理工学院电信工程系，汉中 723003

Published Jan 1, 2007• 2 citations

Abstract

Differential phase shift quantum key distribution(DPSQKD) experiment based on weak coherent pulses have been performed in the laboratory. We encoded the bit information between the consecutive pulses. The bit information was decoded at Bob's side by Michelson-Faraday interferometer and single photon detector. This kind of quantum key distribution system can provide stable key distribution process, high efficiency of key creation, and high security key. So it is easily implemented in optical fibers using readily available optical telecommunication tools. We experimented DPSQKD over 76 km on fiber, the error rate of the sifted key is 5.3%. The quantum key distribution process is controlled by micro-computer based on ARM (advanced RISC(reduced instruction set computing) machines) processor.

DOI: 10.7498/aps.56.2175

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Quantum-key distribution has been studied as an ultimate method for secure communications, and now it is emerging as a technology that can be deployed in real fiber networks. Here, we present our QKD experiments based on the differential- phase-shift QKD protocol. A DPSQKD system has a simple configuration that is easy to implement with conventional optical communication components, and it is suitable for a high-clock rate system. Moreover, although the DPS-QKD system is implemented with an attenuated laser source, it is inherently secure against strong eavesdropping attacks called photon number-splitting attacks, which pose a serious threat to conventional QKD systems with attenuated laser sources. We also describe three types of single-photon detectors that are suitable for high-speed, long-distance QKD: an up-conversion detector, a superconducting single-photon detector, and a sinusoidally gated InGaAs avalanche photodiode. We present our recordsetting QKD experiments that employed those detectors.

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We propose an auto-compensating differential phase shift scheme for quantum key distribution with a high key-creation efficiency, which skillfully makes use of automatic alignment of the photon polarization states in optical fiber with modified Michelson interferometers composed of unequal arms with Faraday mirrors at the ends. The Faraday-mirrors-based Michelson interferometers not only function as pulse splitters, but also enable inherent compensation of polarization mode dispersion in the optic-fiber paths at both Alice's and Bob's sites. The sequential pulses encoded by differential phase shifts pass through the quantum channel with the same polarization states, resulting in a stable key distribution immune to the polarization mode dispersion in the quantum channel. Such a system features perfect stability and higher key creation efficiency over traditional schemes.