Generation of a precise time scale assisted by NTSC-SrⅡ optical lattice clock

Abstract Owing to their exceptional performance characteristics, optical atomic clocks enable the generation of time scales that demonstrate superior accuracy and stability compared to conventional microwave clocks. This paper presents an experimental optical time scale based on the NTSC-SrⅡ optical lattice clock as the reference and a hydrogen maser as the flywheel oscillator. The time scale TS (SrⅡ), generated through post-processing analysis over a two-month period, achieves a peak-to-peak time variation of 0.39 ns relative to Coordinated Universal Time (UTC) and reaches a frequency stability of 1.94 × 10 −16 at 5 d. In addition, a physical optical time scale TS*(SrⅡ) was realized for approximately one month, and the peak-to-peak time difference is 0.3 ns compared to UTC. These results demonstrate that optical time scales maintain competitive performance even when the optical clock operates with limited and non-uniformly distributed uptime. This work constitutes an essential step toward a redefinition of the second of the International System of Units based on an optical transition.