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BEIJING, Oct. 7 (Xinhua) -- A Chinese team has realized, for the first time in the world, the ultra-high-precision time-frequency dissemination, a technique to monitor and synchronize clocks, over a long distance, more than 100 kilometers. The scientific achievement could help set higher standards for the global timing, navigation and positioning, the wide-area quantum communication and the testing of physics basic principles. The research group led by Pan Jianwei from University of Science and Technology of China described in a study published in the Nature this week the time-frequency dissemination with an instability of less than 4E-19 at 10,000 seconds through a free-space link of 113 kilometers in Urumqi, capital of northwest China's Xinjiang Uygur Autonomous Region. It means that the clock's error would be kept within one second in 100 billion years, surpassing the benchmark of redefining the fundamental unit of the "second," which is set to be discussed in the General Conference on Weights and Measures in 2026. Previous attempts at free-space dissemination of time and frequency at such high precision did not extend beyond dozens of kilometers, which are inadequate for high-precision transmission in satellite-to-ground links, according to the study. This is "a major breakthrough" that may have impacts on "fundamental physics" like "search for dark matter, test of fundamental constant, test of relativity," said Nature's peer-reviewers of this paper.
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