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

Understand

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.