A Liquid-Nitrogen-Cooled Ca+ Ion Optical Clock with a Systematic Uncertainty of 4.4E-19

2025/06/20 by Zhang, Baolin, Ma, Zixiao, Huang, Yao +8 · 2 citations
#Atomic Physics (physics.atom-ph) #FOS: Physical sciences #Optics (physics.optics)

paper · doi:10.48550/arxiv.2506.17423

Abstract

We report a single-ion optical clock based on the 4S₁/2-3D₅/2 transition of the 40Ca+ ion, operated in a liquid nitrogen cryogenic environment,achieving a total systematic uncertainty of 4.4E-19. We employ a refined temperature evaluation scheme to reduce the frequency uncertainty due to blackbody radiation (BBR), and the 3D sideband cooling has been implemented to minimize the second-order Doppler shift. We have precisely determined the average Zeeman coefficient of the 40Ca+ clock transition to be 14.345(40) Hz/mT², thereby significantly reducing the quadratic Zeeman shift uncertainty. Moreover, the cryogenic environment enables the lowest reported heating rate due to ambient electric field noise in trapped-ion optical clocks.

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• Coulomb crystallization of xenon highly charged ions in a laser-cooled Ca+ matrix
• Optical clocks with accuracy validated at the 19th digit

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