Measurement-device-independent quantum key distribution (MDIQKD) protocol is immune to all attacks on detection and guarantees the information-theoretical security even with imperfect single photon detectors. Recently, several proof-of-principle demonstrations of MDIQKD have been achieved. Those experiments, although novel, are implemented through limited distance with a key rate less than 0.1 bps. Here, by developing a 75 MHz clock rate fully-automatic and highly-stable system, and superconducting nanowire single photon detectors with detection efficiencies more than 40%, we extend the secure transmission distance of MDIQKD to 200 km and achieve a secure key rate of three orders of magnitude higher. These results pave the way towards a quantum network with measurement-device-independent security.
@article{arxiv.1407.8012,
title = {Measurement-device-independent quantum key distribution over 200 km},
author = {Yan-Lin Tang and Hua-Lei Yin and Si-Jing Chen and Yang Liu and Wei-Jun Zhang and Xiao Jiang and Lu Zhang and Jian Wang and Li-Xing You and Jian-Yu Guan and Dong-Xu Yang and Zhen Wang and Hao Liang and Zhen Zhang and Nan Zhou and Xiongfeng Ma and Teng-Yun Chen and Qiang Zhang and Jian-Wei Pan},
journal= {arXiv preprint arXiv:1407.8012},
year = {2015}
}