Measurement-device-independent quantum key distribution over untrustful metropolitan network

TL;DR

This paper demonstrates a measurement-device-independent quantum key distribution network over a 200 km metropolitan area, achieving high secure key rates and enhanced security against untrustful relays and detection attacks, advancing practical secure quantum communications.

Contribution

The authors constructed and field-tested a star-topology MDIQKD network over a large metropolitan area, demonstrating its practicality and security advantages over trusted relay systems.

Findings

Continuous operation for one week with stable secure key generation

Secure key rate ten times higher than previous field tests

Security against untrustful relays and detection attacks

Abstract

Quantum cryptography holds the promise to establish an information-theoretically secure global network. All field tests of metropolitan-scale quantum networks to date are based on trusted relays. The security critically relies on the accountability of the trusted relays, which will break down if the relay is dishonest or compromised. Here, we construct a measurement-device-independent quantum key distribution (MDIQKD) network in a star topology over a 200 square kilometers metropolitan area, which is secure against untrustful relays and against all detection attacks. In the field test, our system continuously runs through one week with a secure key rate ten times larger than previous result. Our results demonstrate that the MDIQKD network, combining the best of both worlds --- security and practicality, constitutes an appealing solution to secure metropolitan communications.