Abstract

A Hg-based optical lattice clock has a potential to realize 10⁻¹⁸ -level uncertainty because of its low susceptibility to the blackbody radiation [1]. Moreover, a relatively large nuclear charge 𝑍 of Hg allows exploring the variation of the fine-structure constant [2] by referencing, e.g., Sr clocks with smaller 𝑍. After the first demonstration of laser cooling of neutral Hg [1], the determination of the magic wavelength [3] and an absolute frequency measurement of the clock transition [4] have been reported.

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