${}^{171}$Yb${}^{+}$ optical clock with $2.2\times 10^{-18}$ systematic uncertainty and absolute frequency measurements

Abstract

A full evaluation of the uncertainty budget for the ytterbium ion optical clock at the National Physical Laboratory (NPL) was performed on the electric octupole (E3) ${}^2{\mathrm{S}}_{1/2}\to {}^2{\mathrm{F}}_{7/2}$ transition. The total systematic frequency shift was measured with a fractional standard systematic uncertainty of $2.2\times 10^{-18}$. Furthermore, the absolute frequency of the E3 transition of the ${}^{171}$Yb${}^{+}$ ion was measured between 2019 and 2023 via a link to International Atomic Time (TAI) and against the local caesium fountain NPL-CsF2. The absolute frequencies were measured with fractional standard uncertainties between $3.7\times 10^{-16}$ and $1.1\times 10^{-15}$, and all were in agreement with the 2021 BIPM recommended frequency.

16 pages, 8 figures, submitted to Metrologia