We describe an optical atomic clock based on quantum-logic spectroscopy of the 1 S0 ↔ 3 P0 transition in 27 Al + with a systematic uncertainty of 9.4 × 10 −19 and a frequency stability of 1.2 × 10 −15 / √ τ. 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.
We have measured the quadratic Zeeman coefficient for the 1 S0 ↔ 3 P0 optical clock transition in 27 Al + , C2 = −71.944(24) MHz/T 2 , and the unperturbed hyperfine splitting of the 25 Mg + 2 S 1/2 ground electronic state, ∆W/h = 1 788 762 752.85(13) Hz, with improved uncertainties. Both constants are relevant to the evaluation of the 27 Al + quantum-logic clock systematic uncertainty. The measurement of C2 is in agreement with a previous measurement and a new calculation at the 1 σ level. The measurement of ∆W is in good agreement with a recent measurement and differs from a previously published result by approximately 2σ. With the improved value for ∆W , we deduce an improved value for the nuclear-to-electronic g-factor ratio gI /gJ = 9.299 308 313(60) × 10 −5 and the nuclear g-factor for the 25 Mg nucleus gI = 1.861 957 82(28) × 10 −4 . Using the values of C2 and ∆W presented here, we derive a quadratic Zeeman shift of the 27 Al + quantum-logic clock of ∆ν/ν = −(9241.8 ± 3.7) × 10 −19 , for a bias magnetic field of B ≈ 0.12 mT.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.