Accurate time transfer has become a crucial issue for future space experiments which require increasing resolution over large distances. In 2008, a scheme combining homodyne detection and mode-locked femtosecond lasers was proposed that leads to a potential timing precision reaching the yoctosecond range; with a multimode quantum frequency comb as the input field, the sub-shot noise measurement for the time transfer can further improve the timing precision. Based on this scheme and applying the multimode squeezing frequency comb that was measured to have a phase quadrature quantum noise reduction of 1.5 dB at the analyzing frequency 2MHz, the measurable timing fluctuation was reduced from a shot-noise limited value of 8.9E-23s to 7.5E-23s. To our knowledge, this is the first experimental demonstration of the time transfer measurement that achieves a precision beyond the standard quantum limit (SQL).
@article{arxiv.1802.08384,
title = {Quantum improved measurement of time transfer},
author = {Shaofeng Wang and Xiao Xiang and Nicolas Treps and Claude Fabre and Ruifang Dong and Tao Liu and Shougang Zhang},
journal= {arXiv preprint arXiv:1802.08384},
year = {2018}
}