Simultaneous two initial clock states preparation for thulium optical clock

TL;DR

This paper demonstrates a method for preparing two initial clock states in thulium atoms to improve the accuracy of optical clocks by canceling the second-order Zeeman effect, using efficient optical pumping and numerical simulations.

Contribution

It introduces a novel approach to prepare two hyperfine states simultaneously in thulium atoms for optical clock operation, enhancing systematic effect cancellation.

Findings

Successful optical pumping into both target states with high efficiency.

Population of 36% and 3.8% in the desired states achieved.

Numerical simulations align well with experimental results.

Abstract

Due to the low sensitivity of the thulium optical clock to black-body radiation and good accuracy and stability estimations, it appears to be one of the most promising transportable optical clocks. One of the leading systematic effects for Tm clock transition, namely the second-order Zeeman effect, can be canceled by probing two clock transitions between different hyperfine levels of ground and metastable states during the clock operation. We prepare the atoms in $m_F=0$ state of both ground hyperfine levels simultaneously and excite alternately two clock transitions. Here we demonstrate efficient optical pumping into both target states via single-frequency radiation at 418.8 nm. The resulting population of $m_F=0$ states of ground hyperfine levels is 36% and 3.8% of the initial number of atoms with less than 4% and 0.4% on non-zero magnetic sublevels, correspondingly. We performed numerical simulations of the optical pumping process which is able to explain experimental results reasonably well.