Experimental coherent one-way quantum key distribution with simplicity and practical security.

Abstract

Coherent one-way quantum key distribution (COW-QKD) has been widely investigated and even been deployed in real-world quantum network. However, the proposal of the zero-error attack has critically undermined its security guarantees, and existing experimental implementations have not yet established security against coherent attacks. In this work, we propose and experimentally demonstrate an information-theoretically secure COW-QKD protocol that can resist source side-channel attacks, with secure transmission distances up to 100 kilometers. Our system achieves a secure key rate on the order of kilobits per second over 50 kilometers in the finite-size regime, sufficient for real-time secure voice communication across metropolitan networks. Furthermore, we demonstrate the encrypted transmission of a logo with information-theoretic security over 100 kilometers of optical fiber. These results confirm that COW-QKD can simultaneously provide simplicity and security, establishing it as a strong candidate for deployment in small-scale quantum networks.