Quantum clock synchronization schemes utilizing frequency-entangled pulses have flourished for their potentially superior precision to the classical protocols. In this Letter, a new experimental record based on the second-order quantum interference algorithm is reported, to the best of our knowledge. The synchronization accuracy between two parties separated by a 6 km fiber coiling link, which is evaluated by the time offset shift relative to that with the fibers removed, has been measured to be $13\pm 1\mathrm{ps}$. The stability in terms of time deviation (TDEV) of 0.81 ps at an averaging time of 100 s has been achieved. The long-term synchronization stability is seen determined by the measurement device, and a minimum stability of 60 fs has been reached at 25,600 s. Furthermore, for the first time to the best of our knowledge, we quantify the performance of this quantum synchronization scheme, and very good agreements with the experimental results have been achieved. According to the quantum simulation, further improvements for both the synchronizing stability and accuracy can be expected.

中文翻译：

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飞秒级基于二阶量子干扰的量子时钟同步的仿真与实现

利用频率纠缠脉冲的量子时钟同步方案因其潜在的优于传统协议的精度而蓬勃发展。在本信中，据我们所知，报告了基于二阶量子干扰算法的新实验记录。已测量了由6 km的光纤盘绕链路分隔的两方之间的同步精度，该精度通过相对于移除光纤的时间偏移来评估。$13\pm \mathrm{1个}\mathrm{ps}$。在平均时间为100 s的时间偏差（TDEV）方面达到了0.81 ps的稳定性。通过测量设备可以确定长期的同步稳定性，并且在25,600 s时已达到60 fs的最小稳定性。此外，据我们所知，这是我们第一次对这种量子同步方案的性能进行量化，并且与实验结果取得了很好的一致性。根据量子模拟，可以期待同步稳定性和准确性的进一步提高。