Single-Ion Atomic Clock with $3\times 10^{-18}$ Systematic Uncertainty

Abstract

We experimentally investigate an optical frequency standard based on the ${}^2{S}_{1/2}(F=0)\to {}^2{F}_{7/2}(F=3)$ electric octupole (\textit{E}3) transition of a single trapped ${}^{171}$Yb${}^{+}$ ion. For the spectroscopy of this strongly forbidden transition, we utilize a Ramsey-type excitation scheme that provides immunity to probe-induced frequency shifts. The cancellation of these shifts is controlled by interleaved single-pulse Rabi spectroscopy which reduces the related relative frequency uncertainty to $1.1\times 10^{-18}$. To determine the frequency shift due to thermal radiation emitted by the ion's environment, we measure the static scalar differential polarizability of the \textit{E}3 transition as $0.888(16)\times 10^{-40}$ J m${}^2$/V${}^2$ and a dynamic correction $\eta (300\text{K})=-0.0015(7)$. This reduces the uncertainty due to thermal radiation to $1.8\times 10^{-18}$. The residual motion of the ion yields the largest contribution $(2.1\times 10^{-18})$ to the total systematic relative uncertainty of the clock of $3.2\times 10^{-18}$.

5 pages, 4 figures