Cavity Quantum Electrodynamics with Atom Arrays in Free Space

TL;DR

This paper proposes a novel cavity QED platform using ordered atom arrays in free space, enabling strong light-matter interactions without traditional cavities, with potential for high cooperativity and dynamic control.

Contribution

It introduces a cavity QED architecture based on atom arrays in free space, matching conventional cavity parameters and simplifying experimental implementation.

Findings

Array cavity can achieve cooperativity of about 10 with $^{87}$Rb atoms.

Cooperativity can exceed $10^4$ with optimal atom placement.

Proposes a spatially dependent AC Stark shift to replace cavity curvature.

Abstract

Cavity quantum electrodynamics (cavity QED) enables the control of light-matter interactions at the single-photon level, rendering it a key component of many quantum technologies. Its practical realization, however, is complex since it involves placing individual quantum emitters close to mirror surfaces within a high-finesse cavity. In this work, we propose a cavity QED architecture fully based on atoms trapped in free space. In particular, we show that a pair of two-dimensional, ordered arrays of atoms can be described by conventional cavity QED parameters. Such an atom-array cavity exhibits the same cooperativity as a conventional counterpart with matching mirror specifications even though the cavity coupling strength and decay rate are modified by the narrow bandwidth of the atoms. We estimate that an array cavity composed of $^{87}\mathrm{Rb}$ atoms in an optical lattice can reach a cooperativity of about $10$. This value can be increased suppressing atomic motion with larger trap depths and may exceed $10^4$ with an ideal placement of the atoms. To reduce the experimental complexity of our scheme, we propose a spatially dependent AC Stark shift as an alternative to curving the arrays, which may be of independent interest. In addition to presenting a promising platform for cavity QED, our work creates opportunities for exploring novel phenomena based on the intrinsic nonlinearity of atom arrays and the possibility to dynamically control them.