Optical to microwave clock frequency ratios with a nearly continuous strontium optical lattice clock

TL;DR

This paper demonstrates a nearly continuous operation of a strontium optical lattice clock over several weeks, enabling precise measurement of frequency ratios with microwave standards, advancing optical clock reliability.

Contribution

It reports the first long-term stable operation of a strontium optical lattice clock and its use in reproducibly measuring optical to microwave frequency ratios.

Findings

Over 80% uptime in several weeks of operation

Reproducible measurement of frequency ratios

Potential for redefining the SI second

Abstract

Optical lattice clocks are at the forefront of frequency metrology. Both the instability and systematic uncertainty of these clocks have been reported to be two orders of magnitude smaller than the best microwave clocks. For this reason, a redefinition of the SI second based on optical clocks seems possible in the near future. However, the operation of optical lattice clocks has not yet reached the reliability that microwave clocks have achieved so far. In this paper, we report on the operation of a strontium optical lattice clock that spans several weeks, with more than 80% uptime. We make use of this long integration time to demonstrate a reproducible measurement of frequency ratios between the strontium clock transition and microwave Cs primary and Rb secondary frequency standards.