Cryogenic Optical Lattice Clock with $1.7\times 10^{-20}$ Blackbody Radiation Stark Uncertainty

TL;DR

This paper presents a cryogenic optical lattice clock with unprecedented control over blackbody radiation Stark shifts, achieving a fractional frequency uncertainty of 1.7×10⁻²⁰, and provides new measurements of BBR Stark coefficients for ytterbium.

Contribution

The work introduces a dynamically actuated radiation shield for cryogenic OLCs, significantly reducing BBR perturbations and enabling precise measurement of BBR Stark coefficients.

Findings

Achieved a fractional frequency uncertainty of 1.7×10⁻²⁰.

Reduced the uncertainty of the BBR Stark coefficient by 30%.

Verified the static BBR coefficient for Yb at the 10⁻¹⁸ level.

Abstract

Controlling the Stark perturbation from ambient thermal radiation is key to advancing the performance of many atomic frequency standards, including state-of-the-art optical lattice clocks (OLCs). We demonstrate a cryogenic OLC that utilizes a dynamically actuated radiation shield to control the perturbation at $1.7\times10^{-20}$ fractional frequency, a factor of $\sim$40 beyond the best OLC to date. Our shield furnishes the atoms with a near-ideal cryogenic blackbody radiation (BBR) environment by rejecting external thermal radiation at the part-per-million level during clock spectroscopy, overcoming a key limitation with previous cryogenic BBR control solutions in OLCs. While the lowest BBR shift uncertainty is realized with cryogenic operation, we further exploit the radiation control that the shield offers over a wide range of temperatures to directly measure and verify the leading BBR Stark dynamic correction coefficient for ytterbium. This independent measurement reduces the literature-combined uncertainty of this coefficient by 30%, thus benefiting state-of-the-art Yb OLCs operated at room temperature. We verify the static BBR coefficient for Yb at the low $10^{-18}$ level.