Kavli Affiliate: Xiang Zhang
| First 5 Authors: Xiao-Yong Liu, Xiao-Yong Liu, , ,
| Summary:
Optical atomic clocks play a crucial role in fundamental physics,
relativistic geodesy, and the future redefinition of the SI second. Standard
operation relies on cyclic interrogation sequences, which alternate between
atomic interrogation and dead time used for state preparation and readout. This
approach introduces the Dick effect, where laser frequency noise aliases onto
the atomic transition frequency. Although reducing laser noise improves clock
stability, the Dick effect remains a key limitation. In this work, we
demonstrate a zero-dead-time optical clock based on two interleaved ensembles
of cold $^87textSr$ atoms. Our system significantly suppresses this noise
and achieves a fractional frequency instability at the $10^-19$ level between
10,000 and 20,000 seconds over repeated measurements, with a best value of $2.9
times 10^-19$ at $tau = 20,000$ seconds. The estimated long-term stability
based on the combined data of these measurements reaches $2.5 times 10^-19$
at one day. These results represent a more than ninefold improvement over a
conventional single-ensemble clock, highlighting its potential for
next-generation timekeeping applications.
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