Quan Runai, Zhai Yiwei, Wang Mengmeng, Hou Feiyan, Wang Shaofeng, Xiang Xiao, Liu Tao, Zhang Shougang, Dong Ruifang
Key Laboratory of Time and Frequency Primary Standards, National Time Service Center, Chinese Academy of Sciences, Xi'an, 710600, China.
University of Chinese Academy of Sciences, Beijing, 100049, China.
Sci Rep. 2016 Jul 25;6:30453. doi: 10.1038/srep30453.
Based on the second-order quantum interference between frequency entangled photons that are generated by parametric down conversion, a quantum strategic algorithm for synchronizing two spatially separated clocks has been recently presented. In the reference frame of a Hong-Ou-Mandel (HOM) interferometer, photon correlations are used to define simultaneous events. Once the HOM interferometer is balanced by use of an adjustable optical delay in one arm, arrival times of simulta- neously generated photons are recorded by each clock. The clock offset is determined by correlation measurement of the recorded arrival times. Utilizing this algorithm, we demonstrate a proof-of-principle experiment for synchronizing two clocks separated by 4 km fiber link. A minimum timing stability of 0.44 ps at averaging time of 16000 s is achieved with an absolute time accuracy of 73.2 ps. The timing stability is verified to be limited by the correlation measurement device and ideally can be better than 10 fs. Such results shine a light to the application of quantum clock synchronization in the real high-accuracy timing system.
基于参量下转换产生的频率纠缠光子之间的二阶量子干涉，最近提出了一种用于同步两个空间分离时钟的量子策略算法。在Hong-Ou-Mandel（HOM）干涉仪的参考系中，利用光子相关性来定义同时发生的事件。一旦通过在一个臂中使用可调光学延迟使HOM干涉仪达到平衡，每个时钟就会记录同时产生的光子的到达时间。时钟偏移量由记录的到达时间的相关性测量确定。利用该算法，我们展示了一个原理验证实验，用于同步由4公里光纤链路分隔的两个时钟。在平均时间为16000秒时实现了0.44皮秒的最小定时稳定性，绝对时间精度为73.2皮秒。经证实，定时稳定性受相关性测量装置的限制，理想情况下可优于10飞秒。这些结果为量子时钟同步在实际高精度定时系统中的应用带来了曙光。
