Cryogenic Optical Lattice Clock with Low 10-20 Blackbody Radiation Stark Uncertainty

Hassan, Youssef Salahuddin Sayed

Published Apr 14, 2025• 0 citations

Abstract

Controlling the Stark perturbation from ambient thermal radiation is key to advancing the performance of many atomic frequency standards. This thermal radiation perturbs the atomic energy levels, inducing a Stark shift to the clock frequency conventionally known as the BBR shift. For over four decades, the BBR shift has been a persistent challenge in the pursuit of better atomic clock performance. For room-temperature optical lattice clocks (OLCs) based on Yb and Sr, the BBR shift represents the largest uncanceled systematic frequency shift while typically also constituting the largest source of uncertainty in these state-of-the-art clocks at the ≈ 1 × 10−18 level. In this thesis, I report on the design, assembly and integration of a BBR enclosure, or “shield,” that achieves an unprecedented BBR shift uncertainty of 1.7 × 10−20 by furnishing the interrogated atoms with a near-ideal BBR environment at a cryogenic temperature, while still allowing all the critical quantum control functions required for clock operation. Also, I present a novel lattice loading technique, known as ratchet loading, which enables programmable control over the spatial distribution of ultra-cold atoms confined in an optical lattice. This method allows for the loading of a large number of atoms, effectively reducing quantum projection noise (QPN) while also mitigating frequency shifts caused by atomic interactions. Additionally, ratchet loading facilitates the creation of spatially resolved atomic ensembles along the lattice, making it particularly useful for lattice light shift measurements and potentially advantageous for emerging techniques that probe atomic coherence beyond the local oscillator (LO) coherence time. With the near-elimination of blackbody radiation (BBR) uncertainty and improved clock stability for systematic evaluations, the realization of a mid- to low-10−19 uncertainty Yb optical lattice clock is now more attainable than ever.

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