Demonstration of the nearly continuous operation of an $^{171}$Yb optical lattice clock for half a year

TL;DR

This paper demonstrates nearly continuous half-year operation of an $^{171}$Yb optical lattice clock with high uptime, enabling precise frequency measurement and comparison with TAI, advancing the robustness of optical clocks for redefining the second.

Contribution

The study achieves long-term, high-uptime operation of an $^{171}$Yb optical lattice clock, enabling nearly dead-time-free frequency comparison with TAI over months.

Findings

Achieved 80.3% coverage over half a year.

Measured the $^{171}$Yb clock transition frequency with fractional uncertainty of 5.0×10⁻¹⁶.

Confirmed the $^{171}$Yb frequency aligns with the recommended secondary standard.

Abstract

Optical lattice clocks surpass primary Cs microwave clocks in frequency stability and accuracy, and are promising candidates for a redefinition of the second in the International System of Units (SI). However, the robustness of optical lattice clocks has not yet reached a level comparable to that of Cs fountain clocks which contribute to International Atomic Time (TAI) by the nearly continuous operation. In this paper, we report the long-term operation of an $^{171}$Yb optical lattice clock with a coverage of 80.3% for half a year including uptimes of 93.9% for the first 24 days and 92.6% for the last 35 days. This enables a nearly dead-time-free frequency comparison of the optical lattice clock with TAI over months, which provides a link to the SI second with an uncertainty of low $10^{-16}$. By using this link, the absolute frequency of the $^{1}$S$_{0}-^{3}$P$_{0}$ clock transition of $^{171}$Yb is measured as 518 295 836 590 863.54(26) Hz with a fractional uncertainty of $5.0\times10^{-16}$. This value is in agreement with the recommended frequency of $^{171}$Yb as a secondary representation of the second.