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We present an improved differential phase shift quantum key distribution schemewhich features auto-compensation,high efficiency,and excellent practicality. Alice modulates continuous laser using an intensity modulator based on polarization to generate coherent pulse train. Bob employs a Fraday-Michelson interferometer instead of a traditional M-Z interferometer,which automatically compensates for the polarization mode dispersion caused by the changes of environment and improves the stability of the interference visibility. The present scheme not only has a simpler configuration,but also offers a higher key creation efficiency than traditional schemes. Furthermore,it enhances the security of the system. With the proposed experimental setup,a stable quantum key distribution was performed over 80km fiber with a quantum bit-error rate of less than 4%.
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Keywords:
- quantum cryptography /
- quantum key distribution /
- differential phase shift /
- intensity modulator based on polarization
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