Interspecies clock comparison below 5 × 10^-18 uncertainty with a transportable clock

2026/08/03 by Chetan Vishwakarma, Ingo Nosske, Tim Lücke +6
Physics and Astronomy · #physics.atom-ph #quant-ph

paper · pdf

8 pages, 3 figures

arxiv created 2026/08/03 · arxiv updated 2026/08/04

Abstract

We report a measurement of the optical frequency ratio between the ²S_1/2(F=0)--²F_7/2(F=3) electric-octupole (E3) transition of ¹⁷¹Yb⁺ and the ¹S₀--³P₀ transition of ⁸⁷Sr, ν_Yb⁺/ν_Sr = 1.495 991 618 544 900 588 1(65). Reaching a fractional uncertainty of 4.3 × 10^-18, this result improves upon the previous best by more than a factor of three and is among the few that meet the requirements for interspecies clock comparisons specified by the roadmap towards the redefinition of the SI second. The comparison is between a transportable optical lattice clock and a stationary single-ion clock. It spans a period of nearly two years, during which the transportable clock was intermittently operated off-campus. The ratio was reproducibly measured during four separate campaigns, which are consistent within their statistical uncertainties. The results demonstrate reproducible 10^-18 level operation of the transportable clock and thus validate its application for chronometric geodesy and as a transfer standard for inter-institute clock comparisons, e.g., in the absence of optical fiber links.

Citations

• Improved systematic evaluation of a strontium optical clock with uncertainty below 1 × 10 − 18
• Atomic thermometry in optical lattice clocks
• Transportable strontium lattice clock with 4 × 10^-19 blackbody radiation shift uncertainty
• Coordinated international comparisons between optical clocks connected via fiber and satellite links
• High-Stability Single-Ion Clock with 5.5×10^-19 Systematic Uncertainty
• Validating a lutetium frequency reference
• The CIPM list "Recommended values of standard frequencies": 2021 update