Abstract
We report on an evaluation of an optical clock that uses the transition of a single ion as the reference. In contrast to previous work, we estimate the effective temperature of the blackbody radiation that shifts the reference transition directly during operation from the corresponding frequency shift and the well-characterized sensitivity to thermal radiation. We measure the clock output frequency against an independent ion clock, based on the electric octupole (E3) transition, and determine the frequency ratio with a total fractional uncertainty of . Relying on a previous measurement of the (E3) clock frequency, we find the absolute frequency of the clock transition to be 444 779 044 095 485.277(59) Hz. Our result reduces the uncertainty by a factor of 3 compared with the previously most accurate measurement and may help to resolve so far inconsistent determinations of this value. We also show that for three simultaneously interrogated ions, the increased number causes the expected improvement of the short-term frequency instability of the optical clock without degrading its systematic uncertainty.
- Received 15 December 2022
- Revised 17 April 2023
- Accepted 18 July 2023
DOI:https://doi.org/10.1103/PhysRevLett.131.083002
Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.
Published by the American Physical Society