Absolute measurement of the ${}^{1}S_{0}$ - ${}^{3}P_{0}$ clock transition in neutral ${}^{88}$Sr over the 330 km-long stabilized fibre optic link

TL;DR

This paper reports ultra-stable optical lattice clocks using ${}^{88}$Sr with a frequency measurement over a 330 km fiber link, achieving unprecedented stability and confirming the transition frequency with high precision.

Contribution

First measurement of the ${}^{1}S_{0}$ - ${}^{3}P_{0}$ transition frequency in ${}^{88}$Sr with sub-10^{-17} stability over a long fiber link, validating previous standards.

Findings

Stability below 7×10^{-17} achieved

Absolute frequency measured as 429228066418008.3 Hz

Results agree with BIPM recommendations

Abstract

We report a stability below $7\times 10{}^{-17}$ of two independent optical lattice clocks operating with bosonic ${}^{88}$Sr isotope. The value (429228066418008.3(1.9)${}_{syst}$(0.9)${}_{stat}$~Hz) of the absolute frequency of the ${}^{1}S_{0}$ - ${}^{3}P_{0}$ transition was measured with an optical frequency comb referenced to the local representation of the UTC by the 330 km-long stabilized fibre optical link. The result was verified by series of measurements on two independent optical lattice clocks and agrees with recommendation of Bureau International des Poids et Mesures.