Synchronization system for quantum key distribution

In commercial quantum key distribution (QKD) systems, precise synchronization between the reference frequency generators of the transmitter and receiver is critical for ensuring stable operation. This paper presents an implementation of a frequency offset correction system for a QKD device. It provides a detailed description of the optical synchronization scheme, a two-stage frequency correction algorithm, and a noise-robust method for the automatic detection of quantum state transmission and reception start times. The proposed solutions were validated through a series of experiments using a real QKD device based on the BB84 protocol. The results confirm the stable performance of all system components, with the achieved synchronization accuracy ensuring reliable secret key distribution between remote nodes.