An $^{27}$Al$^{+}$ quantum-logic clock with systematic uncertainty below $10^{-18}$

TL;DR

This paper reports a $^{27}$Al$^{+}$ quantum-logic optical clock achieving a systematic uncertainty below 10^{-18}, with enhanced stability and reduced systematic effects through improved trapping and control techniques.

Contribution

The paper introduces a highly precise $^{27}$Al$^{+}$ optical clock with systematic uncertainty under 10^{-18}, demonstrating advancements in trap design and systematic error reduction.

Findings

Systematic uncertainty below 10^{-18} achieved.

Enhanced clock stability with 1.2×10^{-15}/√τ.

Reduced systematic errors from trap improvements.

Abstract

We describe an optical atomic clock based on quantum-logic spectroscopy of the $^1$S$_0$ $\leftrightarrow$ $^3$P$_0$ transition in $^{27}$Al$^{+}$ with a systematic uncertainty of ${9.4 \times 10^{-19}}$ and a frequency stability of ${1.2\times10^{-15}/\sqrt{\tau}}$. A $^{25}$Mg$^{+}$ ion is simultaneously trapped with the $^{27}$Al$^{+}$ ion and used for sympathetic cooling and state readout. Improvements in a new trap have led to reduced secular motion heating, compared to previous $^{27}$Al$^{+}$ clocks, enabling clock operation with ion secular motion near the three-dimensional ground state. Operating the clock with a lower trap drive frequency has reduced excess micromotion compared to previous $^{27}$Al$^{+}$ clocks. Both of these improvements have led to a reduced time-dilation shift uncertainty. Other systematic uncertainties including those due to blackbody radiation and the second-order Zeeman effect have also been reduced.