As the most accurate atomic clock at present, how to effectively improve the performance of optical clock has always been the focus of attention. Recently, the National Time Service Center has made innovative progress in this field.

Prof. CHANG Hong and Dr. LU Xiaotong from National Time Service Center proposed and realized the dual-excitation strontium atomic optical clock, which realized the measurement accuracy beyond the Dick limit, thus effectively improving the measurement accuracy of the optical lattice clock.

On the basis of the strontium optical clock with frequency stability of 1E-18 which has been realized at the beginning of this year (Jpn. J. Appl. Phys. 59, 070903 (2020)), they have solved the key technique of simultaneously and independently detecting multiple independent clock transitions, and realized the closed-loop operation of dual-excitation strontium atomic optical clock. Compared with the traditional optical lattice clock, the dual-excited strontium atomic optical clock can reduce the clock feedback period by half, thus directly reducing the Dick effect by a half, and finally increasing the frequency stability of the clock by 1.4 times.

Related research results were published, titled “Synchronous Frequency Comparison Beyond the Dick Limit Based on Dual-Mathematical Spectrum in an Optical Lattice Clock”, in Applied Physics Letters (Appl. Phys. Lett. 117, 231101 (2020)).

"The authors present a creative, novel method to simultaneously probe multiple components of an optical lattice clock transition …. This scheme would result in a dramatic reduction in required operating time across essentially all experiments …. This innovative technology might find real world application in the optical clocks now increasingly contributing to international timekeeping", the referee noted in his/her review comments.

This research was supported by the National Natural Science Foundation of China, the Key Research Project of Frontier Science of the Chinese Academy of Sciences, and the Strategic Priority Research Program of the Chinese Academy of Sciences.

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