<sup>176</sup>Lu<sup>+</sup> clock comparison at the 10<sup>-18</sup> level via correlation spectroscopy.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 37134164.
- Also identified by DOI 10.1126/sciadv.adg1971 and PMC identifier 10156108.
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Abstract
The extreme precision of optical atomic clocks has led to an anticipated redefinition of the second by the International System of Units. Furthermore, accuracies pushing the boundary of 1 part in 10<sup>18</sup> and beyond will enable new applications, such as in geodesy and tests of fundamental physics. The <sup>1</sup><i>S</i><sub>0</sub> to <sup>3</sup><i>D</i><sub>1</sub> optical transition in <sup>176</sup>Lu<sup>+</sup> has exceptionally low sensitivity to external perturbations, making it suitable for practical clock implementations with inaccuracy at or below 10<sup>-18</sup>. Here, we perform high-accuracy comparisons between two <sup>176</sup>Lu<sup>+</sup> references using correlation spectroscopy. A comparison at different magnetic fields is used to obtain a quadratic Zeeman coefficient of -4.89264(88) Hz/mT for the reference frequency. With a subsequent comparison at low field, we demonstrate agreement at the low 10<sup>-18</sup> level, statistically limited by the averaging time of 42 hours. The evaluated uncertainty in the frequency difference is 9 × 10<sup>-19</sup> and the lowest reported in comparing independent optical references.