Faraday-Michelson system for quantum cryptography.
Quantum key distribution provides unconditional security for communication. Unfortunately, current experimental schemes are not suitable for long-distance fiber transmission because of phase drift or Rayleigh backscattering. In this Letter we present a unidirectional intrinsically stable scheme that is based on Michelson-Faraday interferometers, in which ordinary mirrors are replaced with 90 degree Faraday mirrors. With the scheme, a demonstration setup was built and excellent stability of interference fringe visibility was achieved over a fiber length of 175 km. Through a 125 km long commercial communication fiber cable between Beijing and Tianjin, the key exchange was performed with a quantum bit-error rate of less than 6%, which is to our knowledge the longest reported quantum key distribution experiment under field conditions.
Mo
Xiao-Fan
XF
Key Lab of Quantum Information, University of Science and Technology of China, Hefei Anhui 230026, China.
Zhu
Bing
B
Han
Zheng-Fu
ZF
Gui
You-Zhen
YZ
Guo
Guang-Can
GC