The optical clock is the most accurate atomic clock at present. How to effectively improve its performance has always been the focus of the field.

Recently, researchers led by Prof. CHANG Hong and Dr. LU Xiaotong from the National Time Service Center (NTSC) of the Chinese Academy of Sciences developed a dual-excitation strontium atomic optical clock whose measurement accuracy exceeded the Dick limit.

Based on the strontium optical clock with frequency stability of 1E-18 in their previous study, the researchers solved the key problem 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 could reduce the clock feedback period by half, thus directly reducing the Dick effect by half, and finally increasing the frequency stability of the clock by 1.4 times.

Related research results were published in Applied Physics Letters on Dec. 7.

"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 which are now increasingly contributing to international timekeeping", one 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.