Improved frequency ratio measurement with 87Sr and 171Yb optical lattice clocks at NMIJ

Abstract

We report improved frequency ratio measurement with 87Sr and 171Yb optical lattice clocks at the National Metrology Institute of Japan. The 87Sr optical lattice clock is enhanced with several major modifications and is re-evaluated with a reduced uncertainty of 1.1 × 10−16. We employed a 171Yb optical lattice clock with an uncertainty of 4 × 10−16 that was developed for contributing to International Atomic Time. The measurement result is ν Yb/ν Sr = 1.207 507 039 343 338 58(49)sys(6)stat with a fractional uncertainty of 4.1 × 10−16, which is 3.4 times smaller than our previous measurement result.