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

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.