Tunable-range, photon-mediated atomic interactions in multimode cavity QED

TL;DR

This paper demonstrates that multimode cavity QED can create tunable, local photon-mediated interactions between atoms, enabling exploration of complex quantum many-body phenomena beyond mean-field models.

Contribution

The work experimentally shows how multimode cavity QED allows for tunable-range, local interactions between Bose-Einstein condensates, surpassing the limitations of single-mode cavities.

Findings

Interference of cavity modes enables tunable interaction range.

Symmetry of confocal cavity allows measurement of atom-atom interactions.

Atom coupling can be adjusted from short to long range.

Abstract

Optical cavity QED provides a platform with which to explore quantum many-body physics in driven-dissipative systems. Single-mode cavities provide strong, infinite-range photon-mediated interactions among intracavity atoms. However, these global all-to-all couplings are limiting from the perspective of exploring quantum many-body physics beyond the mean-field approximation. The present work demonstrates that local couplings can be created using multimode cavity QED. This is established through measurements of the threshold of a superradiant, self-organization phase transition versus atomic position. Specifically, we experimentally show that the interference of near-degenerate cavity modes leads to both a strong and tunable-range interaction between Bose-Einstein condensates (BECs) trapped within the cavity. We exploit the symmetry of a confocal cavity to measure the interaction between real BECs and their virtual images without unwanted contributions arising from the merger of real BECs. Atom-atom coupling may be tuned from short range to long range. This capability paves the way toward future explorations of exotic, strongly correlated systems such as quantum liquid crystals and driven-dissipative spin glasses.