We report improved frequency ratio measurement with $^{87}$Sr and $^{171}$Yb optical lattice clocks at the National Metrology Institute of Japan (NMIJ). The $^{87}$Sr optical lattice clock is enhanced with several major modifications and is re-evaluated with a reduced uncertainty of $1.1\times10^{-16}$. We employed a $^{171}$Yb optical lattice clock with an uncertainty of $4\times10^{-16}$ that was developed for contributing to International Atomic Time (TAI). The measurement result is $\nu_{\mathrm{Yb}}/\nu_{\mathrm{Sr}}$ = 1.207 507 039 343 338 58(49)$_{\mathrm{sys}}$(6)$_{\mathrm{stat}}$ with a fractional uncertainty of $4.1\times10^{-16}$, which is 3.4 times smaller than our previous measurement result.

中文翻译：

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在 NMIJ 使用 87Sr 和 171Yb 光学晶格时钟改进频率比测量

我们报告了日本国家计量院 (NMIJ) 使用 $^{87}$Sr 和 $^{171}$Yb 光学晶格时钟改进的频率比测量。$^{87}$Sr 光学晶格钟经过几项重大修改后得到增强，并通过降低 $1.1\times10^{-16}$ 的不确定性重新评估。我们采用了 $^{171}$Yb 光学晶格时钟，其不确定性为 $4\times10^{-16}$，该时钟是为国际原子时 (TAI) 做出贡献而开发的。测量结果为 $\nu_{\mathrm{Yb}}/\nu_{\mathrm{Sr}}$ = 1.207 507 039 343 338 58(49)$_{\mathrm{sys}}$(6)$_ {\mathrm{stat}}$ 的分数不确定性为 $4.1\times10^{-16}$，比我们之前的测量结果小 3.4 倍。