A high-cooperativity confocal cavity QED microscope

TL;DR

This paper demonstrates a confocal cavity QED microscope achieving exceptionally high cooperativity over 110, enabling advanced quantum sensing and imaging with a resolution matching photon-mediated interaction ranges.

Contribution

It introduces a confocal cavity design that surpasses previous cooperativity limits, combining high cooperativity with imaging capabilities in a multimode resonator.

Findings

Achieved cooperativity >110 in a confocal cavity

Demonstrated 1.7-μm imaging resolution matching interaction range

Validated results through superradiance threshold and transmission measurements

Abstract

Cavity QED with cooperativity far greater than unity enables high-fidelity quantum sensing and information processing. The high-cooperativity regime is often reached through the use of short, single-mode resonators. More complicated multimode resonators, such as the near-confocal optical Fabry-P\'{e}rot cavity, can provide intracavity atomic imaging in addition to high cooperativity. This capability has recently proved important for exploring quantum many-body physics in the driven-dissipative setting. In this work, we show that a confocal cavity QED microscope can realize cooperativity in excess of 110. This cooperativity is on par with the very best single-mode cavities (which are far shorter) and 21$\times$ greater than single-mode resonators of similar length and mirror radii. The 1.7-$\mu$m imaging resolution is naturally identical to the photon-mediated interaction range. We measure these quantities by determining the threshold of cavity superradiance when small, optically tweezed Bose-Einstein condensates are pumped at various intracavity locations. Transmission measurements of an ex situ cavity corroborate these results. We provide a theoretical description that shows how cooperativity enhancement arises from the dispersive coupling to the atoms of many near-degenerate modes.