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.

中文翻译：

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演示171Yb光学点阵时钟近乎连续运行半年

光学晶格时钟在频率稳定性和精度方面超过了初级 Cs 微波时钟，并且是重新定义国际单位制 (SI) 中秒的有希望的候选者。然而，光学晶格钟的鲁棒性还没有达到可与 Cs 喷泉钟相比的水平，Cs 喷泉钟通过近乎连续的运行对国际原子时 (TAI) 做出贡献。在本文中，我们报告了 $^{171}$Yb 光学晶格时钟的长期运行情况，半年的覆盖率为 80.3%，其中前 24 天的正常运行时间为 93.9%，最后 35 天的正常运行时间为 92.6%。天。这使得光学晶格时钟与 TAI 在数月内几乎无死区时间的频率比较成为可能，这提供了到 SI 秒的链接，不确定性低 $10^{-16}$。通过使用此链接，$^{1}$S$_{0}-^{3}$P$_{0}$$^{171}$Yb 的时钟转换的绝对频率测量为 518 295 836 590 863.54(26 ) Hz 的不确定性为 $5.0\times10^{-16}$。该值与建议的频率 $^{171}$Yb 一致，作为秒的次要表示。