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

Baolin Zhang; Zixiao Ma; Yao Huang; Huili Han; Ruming Hu; Yuzhuo Wang; Huaqing Zhang; Liyan Tang; Tingyun Shi; Hua Guan; Kelin Gao

arXiv · 2506.17423

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

Baolin Zhang·Zixiao Ma·Yao Huang·Huili Han·Ruming Hu·Yuzhuo Wang·Huaqing Zhang·Liyan Tang·Tingyun Shi·Hua Guan·Kelin Gao

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Abstract

We report a single-ion optical clock based on the 4S_1/2-3D_5/2 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/mT^2, 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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Baolin Zhang, Zixiao Ma, Yao Huang, Huili Han, Ruming Hu, Yuzhuo Wang, Huaqing Zhang, Liyan Tang, Tingyun Shi, Hua Guan, Kelin Gao. 2025-06-20. A Liquid-Nitrogen-Cooled Ca+ Ion Optical Clock with a Systematic Uncertainty of 4.4E-19. https://arxiv.org/abs/2506.17423

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