Extraordinary low systematic frequency shifts in bi-colour thulium optical clock

TL;DR

This paper demonstrates a bi-colour thulium optical clock with remarkably low systematic frequency shifts, achieved through simultaneous interrogation of two transitions, making it highly suitable for transportable and space-based applications.

Contribution

The study introduces a bi-colour thulium optical clock that significantly reduces sensitivity to Zeeman and Stark shifts, enhancing stability and robustness for practical use.

Findings

Quadratic Zeeman shift suppressed by at least three orders of magnitude

Tensor lattice Stark shift reduced below 10^-18 fractional frequency

Suitable for transportable and space-based optical clock applications

Abstract

Optical atomic clocks have already overcome the eighteenth decimal digit of instability and uncertainty demonstrating incredible control over external perturbations of the clock transition frequency. At the same time there is an increasing demand for atomic and ionic transitions with minimal sensitivity to external fields, with practical operational wavelengths and robust readout protocols. One of the goals is to simplify clock's operation maintaining its relative uncertainty at low 10-18 level. It is especially important for transportable and envisioned space-based optical clocks. We proved earlier that the 1.14um inner-shell magnetic dipole transition in neutral thulium possesses very low blackbody radiation shift compared to other neutrals. Here we demonstrate operation of a bi-colour thulium optical clock with extraordinary low sensitivity to the Zeeman shift due to a simultaneous interrogation of two clock transitions and data processing. Our experiment shows suppression of the quadratic Zeeman shift by at least three orders of magnitude. The effect of tensor lattice Stark shift can be also reduced to below 10-18 in fractional frequency units. All these features make thulium optical clock almost free from hard-to-control systematic shifts. Together with convenient cooling and trapping laser wavelengths, it provides great perspectives for thulium lattice clock as a high-performance transportable system.