The optical lattice clock based on strontium atoms, NIM-Sr1, developed by the National Institute of Metrology, China (NIM), has been approved to calibrate the International Atomic Time (TAI), which marks a milestone in China’s research process of optical clocks.China will further participate in the calibration of TAI, and make more efforts in the research on time and frequency.

To achieve the highest accuracy, the International Bureau of Weights and Measures (BIPM) combines the output of some 450 atomic clocks in about 70 national laboratories and timekeeping institutions worldwide to determine TAI, which is the basis for Coordinated Universal Time (UTC), the world’s civil time standard.

Atomic clocks deviate 1 second in millions of years, while the latest developed optical clocks deviate 1 second in billions to hundreds of billions of years, which can be used to further improve the accuracy of TAI.

Following NIM5, a strontium atom fountain clock developed by NIM, the data of NIM-Sr1 and NIM6, another new atomic fountain clock developed by NIM, is released in the BIPM Circular T No. 454, which is a monthly publication of the BIPM Time Department, source of traceability to Coordinated Universal Time (UTC) for the local realizations UTC(k) maintained by national institutes.

Currently, three Chinese timekeepers contribute to TAI and highlight China’s advance in the field of time and frequency. They ensure the security and controllability of China’s time and frequency system, and support the stable development of quantum technology and the quantum industry.