$^{174}\mathrm{Yb}^+$-$^{113}\mathrm{Cd}^+$ sympathetic-cooling bi-species Coulomb crystal applied to microwave frequency standard

TL;DR

This paper demonstrates a bi-species Coulomb crystal of Yb+ and Cd+ ions for microwave frequency standards, achieving significant reductions in key uncertainties and confirming the feasibility of a sympathetic-cooled cadmium-ion clock system.

Contribution

It introduces a Yb+-Cd+ bi-species Coulomb crystal for microwave standards, improving uncertainty levels and validating its potential for high-precision ion clocks.

Findings

Uncertainty due to second-order Doppler effect reduced to 5×10^{-16}

Uncertainty from second-order Zeeman effect reduced to 4×10^{-16}

Feasibility of Yb+-Cd+ sympathetic cooling for microwave clocks confirmed

Abstract

We reported the realization of a $^{174}\mathrm{Yb}^+$-$^{113}\mathrm{Cd}^+$ bi-species Coulomb crystal comprising $^{174}\mathrm{Yb}^+$ ions as coolant and verified its potential for application as a $^{113}\mathrm{Cd}^+$ microwave frequency standard employing sympathetic cooling.The two species of massive ions stably trapped in a Paul trap make up this large two-component crystal. The $^{113}\mathrm{Cd}^+$ ions are trapped in the center, which reduces considerably RF heating and excess micromotion to which the $^{113}\mathrm{Cd}^+$ ions are subjected. Under this scheme, the uncertainty due to the second-order Doppler effect is reduced to $5\times10^{-16}$, which represents an order of magnitude improvement over sympathetic cooled $^{40}\mathrm{Ca}^+$-$^{113}\mathrm{Cd}^+$ crystal. The uncertainty from the second-order Zeeman effect, which contributes the largest uncertainty to the microwave-ion frequency standard, is reduced to $4\times10^{-16}$. The relevant AC Stark shift uncertainty is estimated to be $4\times10^{-19}$. These results indicate using $^{174}\mathrm{Yb}^+$ as coolant ions for $^{113}\mathrm{Cd}^+$ is far superior and confirm the feasibility of a sympathetic-cooled cadmium-ion microwave clock system employing a $^{174}\mathrm{Yb}^+$-$^{113}\mathrm{Cd}^+$ two-component crystal.