Enhancing optical lattice clock coherence times with erasure conversion

TL;DR

This paper demonstrates a hyperfine-resolved readout method for ${}^{87}$Sr optical lattice clocks that significantly extends atomic coherence times beyond 100 seconds by converting certain errors into erasures, improving clock precision.

Contribution

The authors introduce a hyperfine-resolved readout technique that mitigates decoherence from Raman scattering and radiative decay, enabling longer coherence times in optical lattice clocks.

Findings

Achieved atomic coherence times exceeding 100 s and 150 s with Ramsey and spin echo sequences.

Demonstrated mitigation of decoherence from lattice Raman scattering and radiative decay.

Enhanced measurement stability without performance loss.

Abstract

Increasing coherent interrogation times is central to advancing the precision of optical clocks. Synchronous differential optical clock comparisons have now demonstrated atomic coherence times that far exceed the coherence time of the clock laser. While atom coherence times are then primarily limited by errors induced by lattice Raman scattering, excited clock state radiative decay, and broadening from two-body collisions, many of these errors take the atoms out of the clock transition subspace, and can therefore be converted into "erasure" errors if the appropriate readout scheme is employed. Here we experimentally demonstrate a hyperfine-resolved readout technique for ${}^{87}$Sr optical lattice clocks that mitigates decoherence from Raman scattering induced by the lattice as well as radiative decay. By employing hyperfine-resolved readout in synchronous differential comparisons between ${}^{87}$Sr ensembles with both Ramsey and spin echo spectroscopy sequences, we achieve enhanced atomic coherence times exceeding 100 s and 150 s, respectively, enabling longer coherent measurements without a reduction in performance. We anticipate that this hyperfine-resolved readout technique will benefit applications of state-of-the-art optical lattice clock comparisons in which the coherence times are constrained by Raman scattering or radiative decay.