Study of optical clocks based on ultracold 171Yb atoms**Project supported by the National Key Basic Research and Development Program of China (Grant Nos. 2016YFA0302103, 2017YFF0212003, and 2016YFB0501601), the Municipal Science and Technology Major Project of Shanghai, China (Grant No. 2019SHDZX01), the National Natural Science Foundation of China (Grant No. 11134003), and the Excellent Academic Leaders Program of Shanghai, China (Grant

Abstract

The optical atomic clocks have the potential to transform global timekeeping, relying on the state-of-the-art accuracy and stability, and greatly improve the measurement precision for a wide range of scientific and technological applications. Herein we report on the development of the optical clock based on 171Yb atoms confined in an optical lattice. A minimum width of 1.92-Hz Rabi spectra has been obtained with a new 578-nm clock interrogation laser. The in-loop fractional instability of the 171Yb clock reaches 9.1 × 10−18 after an averaging over a time of 2.0 × 104 s. By synchronous comparison between two clocks, we demonstrate that our 171Yb optical lattice clock achieves a fractional instability of .