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Joint Conference of the European Frequency and Time Forum and IEEE International Frequency Control Symposium (EFTF/IFCS)

Real-Time Synchronization of Clocks at Femtosecond Level Through a 113 km-Free-Space Link

Min Li, Qi Shen, Jian-Yu Guan, Ji-Gang Ren, Ting Zeng, Lei Hou, Yuan Wen Cao, Jin-Jian Han, Meng-Zhe Lian, Yanwei Chen, Meng Yang, Xinxin Peng, Shao-Mao Wang, Danyang Zhu, Yu-Xiang Cheng, Sheng‐Kai Liao, Juan Yin, Cheng-Zhi Peng, Haifeng Jiang, Qiang Zhang, Jian-Wei Pan

Published May 15, 2023• 0 citations

Abstract

SummaryHigh-precision time comparison and synchronization is required with the increasing application of the optical clocks in precise navigation, gravitational sensing, and relativity experiments. However, previous works at femtosecond-level time synchronization did not extend beyond dozens of kilometers. Here we demonstrate real-time synchronization of two optical clocks over a turbulent 113-km free space link via optical two-way time and frequency transfer. Despite optical power attenuation of 80dB due to atmospheric turbulence, the time deviation between two synchronized time scales is below 50 fs over a 15-hour measurement period, and a stability of less than 1.6 × 10−19at 10,000 s is achieved through an out-of-loop time-frequency transfer link. The ability to synchronize two distant optical clocks can support future precision navigation, and it also provides technical foundation for the future femtosecond clock synchronization over ground-to-satellite free-space paths.

DOI: 10.1109/eftf/ifcs57587.2023.10272080

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