Measurement-device-independent quantum key distribution over 200 km
  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. 
Yan-Lin Tang, Hua-Lei Yin, Si-Jing Chen, Yang Liu, Wei-Jun Zhang, Xiao   Jiang, Lu Zhang, Jian Wang, Li-Xing You, Jian-Yu Gu...
quant-ph