A strontium lattice clock with inaccuracy and its frequency

Abstract

We have measured the absolute frequency of the optical lattice clock based on ^87 Sr at PTB with an uncertainty of $3.9\times {{10}^{-16}}$ using two caesium fountain clocks. This is close to the accuracy of todayʼs best realizations of the SI second. The absolute frequency of the 5 s ^2 1 S _0 – 5s5p ^3 P _0 transition in ^87 Sr is $429\;228\;004\;229\;873$ .13(17) Hz. Our result is in excellent agreement with recent measurements performed in different laboratories worldwide. We improved the total systematic uncertainty of our Sr frequency standard by a factor of five and reach $3\times {{10}^{-17}}$ , opening new prospects for frequency ratio measurements between optical clocks for fundamental research, geodesy or optical clock evaluation.

Keywords

• optical lattice clock
• SI second
• relativistic geodesy