Suppression of collisional shifts in a strongly interacting lattice clock

TL;DR

This paper demonstrates that increasing atomic interactions in a lattice clock suppresses collisional frequency shifts, significantly improving accuracy without sacrificing precision, as shown with the JILA Sr lattice clock.

Contribution

The study introduces a novel approach where strong atomic interactions inhibit collisional shifts, enhancing lattice clock accuracy at high atom densities.

Findings

Reduced collisional frequency shift by over tenfold

Lowered uncertainty to the $10^{-17}$ level

Maintained precision while improving accuracy

Abstract

Optical lattice clocks have the potential for extremely high frequency stability owing to the simultaneous interrogation of many atoms, but this precision may come at the cost of systematic inaccuracy due to atomic interactions. Density-dependent frequency shifts can occur even in a clock that uses fermionic atoms if they are subject to inhomogeneous optical excitation [1, 2]. Here we present a seemingly paradoxical solution to this problem. By dramatically increasing the strength of atomic interactions, we suppress collisional shifts in lattice sites containing $N$ > 1 atoms; strong interactions introduce an energy splitting into the system, and evolution into a many-particle state in which collisions occur is inhibited. We demonstrate the effectiveness of this approach with the JILA Sr lattice clock by reducing both the collisional frequency shift and its uncertainty by more than a factor of ten [3], to the level of $10^{-17}$. This result eliminates the compromise between precision and accuracy in a many-particle system, since both will continue to improve as the particle number increases.