Measurement-device-independent quantum key distribution over 200 km

TL;DR

This paper demonstrates a significant advancement in measurement-device-independent quantum key distribution by extending the secure transmission distance to 200 km and greatly increasing the key rate using advanced detectors and system stability.

Contribution

Developed a high-speed, fully-automatic MDIQKD system with superconducting detectors, enabling secure communication over 200 km, surpassing previous distance and rate limitations.

Findings

Extended secure transmission distance to 200 km

Achieved a key rate three orders of magnitude higher than previous work

Demonstrated system stability and high detection efficiency

Abstract

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.