Tackling the blackbody shift in a strontium optical lattice clock

TL;DR

This paper presents methods to mitigate black body radiation shifts in a 87-Sr optical lattice clock, including dc Stark shift measurements and cryogenic operation, to significantly improve clock accuracy.

Contribution

It introduces a feasible technique for transporting ultracold atoms to enable precise blackbody shift measurements and proposes cryogenic conditions to further enhance clock precision.

Findings

Transport of atoms over 50 mm in 300 ms is feasible.

Blackbody radiation contribution can be reduced below 2×10^-17 at room temperature.

Cryogenic environment at 77 K can lower uncertainty to a few parts in 10^-18.

Abstract

A major obstacle for optical clocks is the frequency shift due to black body radiation. We discuss how one can tackle this problem in an optical lattice clock; in our case 87-Sr: firstly, by a measurement of the dc Stark shift of the clock transition and, secondly, by interrogating the atoms in a cryogenic environment. Both approaches rely on transporting ultracold atoms over several cm within a probe cycle. We evaluate this approach of mechanically moving the optical lattice and conclude that it is feasible to transport the atoms over 50 mm within 300 ms. With this transport a dc Stark shift measurement will allow to reduce the contribution of the blackbody radiation to the fractional uncertainty below 2 * 10^-17 at room temperature by improving the shift coefficient known only from atomic structure calculations up to now. We propose a cryogenic environment at 77 K that will reduce this contribution to few parts in 10^-18.