Time synchronization is one of the most crucial issues that must be addressed in developing quantum key distribution (QKD) systems. It not only lets the transmitter and the receiver to assign a sequence number to each event and then do correct basis reconciliation, but also allows to increase signal-to-noise ratio. Time synchronization in satellite communications is especially complicated due to such factors as high loss, signal fading, and Doppler effect. In this work, a simple, efficient, and robust algorithm for time synchronization is proposed. It was tested during experiments on QKD between Micius, the world’s first quantum communications satellite, and an optical ground station located in Russia. The obtained synchronization precision lies in the range from 467 to 497 ps. The authors compare their algorithm for time synchronization with the previously used methods. The proposed approach can also be applied to terrestrial QKD systems.

时间同步是开发量子密钥分发（QKD）系统时必须解决的最关键问题之一。它不仅允许发送器和接收器为每个事件分配序列号，然后进行正确的基础协调，而且还允许提高信噪比。卫星通信中的时间同步由于高损耗、信号衰落、多普勒效应等因素而变得尤为复杂。在这项工作中，提出了一种简单、高效、鲁棒的时间同步算法。它在世界上第一颗量子通信卫星墨子号和位于俄罗斯的光学地面站之间的 QKD 实验中进行了测试。获得的同步精度在467 至497 ps 范围内。作者将他们的时间同步算法与以前使用的方法进行了比较。所提出的方法也可以应用于地面 QKD 系统。