Print Recently, the Strontium optical lattice clock research team led by Prof. CHANG Hong from the National Time Service Center (NTSC) of the Chinese Academy of Sciences (CAS) successfully developed a strontium optical lattice clock with both frequency stability and systematic uncertainty better than 2×10⁻¹⁸. This achievement marks China's research and development in the field of optical lattice clocks has entered world’s leading ranks.
The 27th General Conference on Weights and Measures (CGPM) in 2022 passed a resolution to redefine the time unit "second" by 2030, and put forward specific requirements for optical clock performance. The Strontium optical lattice clock is currently one of the most precise atomic clocks in the world, with its systematic uncertainty already two orders of magnitude lower than that of the cesium fountain clock used in the current definition of the second. It is considered one of the most promising candidates for the future redefinition of the second.
This research was published online on June 2 in a leading international academic journal in metrology, Metrologia, titled "NTSC SrII Optical Lattice Clock with Uncertainty of 2×10⁻¹⁸".
The reviewers noted: "The newly developed Strontium optical clock at the National Time Service Center(NTSC) has achieved the world's second-smallest uncertainty among optical clocks."
"The Strontium optical lattice clock we developed fully meets the performance requirements for the redefinition of the 'second', making China the second country after the United States to achieve optical lattice clock performance (frequency stability and uncertainty) better than 2×10⁻¹⁸," said Prof. CHANG Hong, leader of this research team.
"To achieve this ultra-high precision and stability, we deeply integrated several cutting-edge technologies—innovatively combining moving optical lattice technology, Faraday cage technology, active temperature-controlled thermal shield technology, and shallow optical lattice technology based on the inclined lattice. These advancements successfully resolved persistent measurement challenges for critical frequency shifts—including blackbody radiation and density shifts—in conventional strontium optical lattice clocks, suppressing them to the 10-19 level while consistently maintaining DC Stark shifts at 10-20. Combined with an efficient cold-atom quantum reference preparation process and narrow-linewidth laser technology, the system achieved a frequency stability of 3.6×10-16 (τ/s)-0.5 and 1.2×10-18 (57,000 s), with a total systematic uncertainty of 1.96×10-18," said Associate Prof. LU Xiaotong, the first author this paper.
The newly developed Strontium optical lattice clock by NTSC advance efforts toward redefining the second and strengthen foundational physics research capabilities.
The setup of the NTSC SrII optical lattice clock(Imaged by NTSC)