Radium Ion Optical Clock

Abstract

We report the first operation of a Ra${}^{+}$ optical clock, a promising high-performance clock candidate. The clock uses a single trapped ${}^{226}$Ra${}^{+}$ ion and operates on the $7s{}^2{S}_{1/2}\to$ $6d{}^2{D}_{5/2}$ electric quadrupole transition. By self-referencing three pairs of symmetric Zeeman transitions, we demonstrate a frequency instability of 1.1$\times 10^{-13}$/$\sqrt{\tau }$, where $\tau$ is the averaging time in seconds. The total systematic uncertainty is evaluated to be $\Delta \nu /\nu =9\times 10^{-16}$. Using the clock, we realize the first measurement of the ratio of the $D_{5/2}$ state to the $S_{1/2}$ state Landé $g$-factors: $g_D/g_S$ = 0.5988053(11). A Ra${}^{+}$ optical clock could improve limits on the time variation of the fine structure constant, $\dot{\alpha }/\alpha$, in an optical frequency comparison. The ion also has several features that make it a suitable system for a transportable optical clock.

Main text 5 pages, 3 figures. Supplemental material 5 pages, 1 figure

References in corpus (8)

• Systematic evaluation of an atomic clock at 2e-18 total uncertainty
• An ${}^{27}$Al${}^{+}$ quantum-logic clock with systematic uncertainty below $10^{-18}$
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• Laser Cooling of Radium Ions
• Measurements of electric quadrupole transition frequencies in ${}^{226}$Ra${}^{+}$
• Absolute frequency measurement of the 7s${}^2$ ${}^1$S${}_0$ $-$ 7s7p ${}^1$P${}_1$ transition in ${}^{225}$Ra

Cited by in corpus (1)

• Measuring the stability of fundamental constants with a network of clocks