Intermittent optical frequency measurements to reduce the dead time uncertainty of frequency link

TL;DR

This paper demonstrates that intermittent optical frequency measurements can significantly reduce dead time uncertainty in frequency links, achieving high-precision absolute frequency evaluation of a strontium lattice clock.

Contribution

It introduces a method of using homogeneous intermittent measurements over multiple days to lower dead time uncertainty in frequency transfer to TAI.

Findings

Achieved an absolute frequency measurement of the $^{87}$Sr clock transition with $1.1 imes 10^{-15}$ uncertainty.

Reduced dead time uncertainty by applying homogeneous intermittent measurement over five-day grids.

Confirmed the systematic uncertainty of the clock at $8.6 imes 10^{-17}$.

Abstract

The absolute frequency of the $^{87}{\rm Sr}$ lattice clock transition was evaluated with an uncertainty of $1.1\times 10^{-15}$ using a frequency link to the international atomic time (TAI). The frequency uncertainty of a hydrogen maser used as a transfer oscillator was reduced by homogeneously distributed intermittent measurement over a five-day grid of TAI. Three sets of four or five days measurements as well as systematic uncertainty of the clock at $8.6\times 10^{-17}$ have resulted in an absolute frequency of $^{87}{\rm Sr}\ {}^1S_0 - {}^3P_0$ clock transition to be 429 228 004 229 872.85 (47) Hz.