Observation and cancellation of the dc Stark shift in strontium optical lattice clocks

TL;DR

This paper investigates the dc Stark shift in strontium optical lattice clocks caused by trapped charges on nearby dielectric surfaces, demonstrating methods to eliminate and accurately measure this shift to improve clock precision.

Contribution

It provides the first detailed observation and cancellation method for the dc Stark shift in strontium lattice clocks, enhancing their accuracy.

Findings

Trapped charges cause a measurable dc Stark shift.

UV light can eliminate surface charges.

Residual shifts can be characterized at the 10^{-18} level.

Abstract

We report on the observation of a dc Stark frequency shift at the $10^{-13}$ level by comparing two strontium optical lattice clocks. This frequency shift arises from the presence of electric charges trapped on dielectric surfaces placed under vacuum close to the atomic sample. We show that these charges can be eliminated by shining UV light on the dielectric surfaces, and characterize the residual dc Stark frequency shift on the clock transition at the $10^{-18}$ level by applying an external electric field. This study shows that the dc Stark shift can play an important role in the accuracy budget of lattice clocks, and should be duly taken into account.