NIST researchers have developed a new method to synchronize optical clocks separated by up to 4 km of open air to within a few millionths of a billionth of a second. This represents a thousand-fold improvement over conventional radio frequency synchronization methods.
The technique involves using two optical clocks, each emitting a train of sharp, coherent optical pulses. By comparing the arrival times of these pulses at both locations, the clocks can be synchronized to within femtosecond precision. The method relies on the reciprocity of the atmosphere, allowing the researchers to cancel out fluctuations caused by turbulence and building sway.
This breakthrough could enable dramatic advances in tests of general relativity, coherent sensing, and the future redefinition of the second. The researchers are now working on extending the technique to moving platforms to support a broader range of real-world applications.
Source: https://www.nist.gov/news-events/news/2016/04/optical-clocks-synched-femtoseconds-through-air
Keywords: Optical, Femtosecond, Time, Metrology
