Security bound of continuous-variable measurement-device-independent quantum key distribution with imperfect phase reference calibration
Hongxin Ma, Peng Huang, Tao Wang, Dongyun Bai, Shiyu Wang, Wan‐Su Bao, Guihua Zeng · Physical Review A · 2019
Phase reference calibration is a necessary procedure in practical continuous-variable measurement-device-independent quantum key distribution (CV-MDI-QKD) for the need of Bell-state measurement. However, the phase reference calibration may become imperfect in practical applications. We explored the practical security of CV-MDI-QKD with imperfect phase reference calibration under realistic conditions of lossy and noisy quantum channels. Specifically, a comprehensive framework is developed to model and characterize the imperfection of the practical phase reference calibration operation, which is mainly caused by the nonsynchronization of two remote lasers in senders. Security analysis shows that the imperfect phase reference calibration has significant side effects on the performance and security of the CV-MDI-QKD protocol. A tight security bound to thermal excess noise introduced by imperfect phase reference calibration is derived for reverse reconciliation against one-mode collective Gaussian attack in the asymptotic limit, and the upper threshold of this imperfection tolerated by the system is obtained. This security analysis framework can eliminate the security hazards caused by imperfect phase reference calibration without changing the existing CV-MDI-QKD system structure. In addition, this work will improve the practical security framework of CV-MDI-QKD protocol and provide theoretic instruction for the experimental implementation of CV-MDI-QKD protocol.