Cavity QED with an ultracold ensemble on a chip: prospects for strong magnetic coupling at finite temperatures

TL;DR

This paper explores the potential for strong magnetic coupling between an ultracold atomic ensemble and a microwave cavity on a chip, enabling coherent quantum state transfer and collective phenomena at finite temperatures.

Contribution

It demonstrates the feasibility of achieving strong collective coupling in a cavity QED system with ultracold atoms, even with minimal single atom coupling, at finite thermal photon numbers.

Findings

Strong collective coupling observed via cavity transmission spectrum

Coherent transfer of excitation between atomic qubits and microwave photons

Potential to study superradiant decay and micromaser building

Abstract

We study the nonlinear dynamics of an ensemble of cold trapped atoms with a hyperfine transition magnetically coupled to a resonant microwave cavity mode. Despite the minute single atom coupling one obtains strong coupling between collective hyperfine qubits and microwave photons enabling coherent transfer of an excitation between the long lived atomic qubit state and the mode. Evidence of strong coupling can be obtained from the cavity transmission spectrum even at finite thermal photon number. The system makes it possible to study further prominent collective phenomena such as superradiant decay of an inverted ensemble or the building of a narrowband stripline micromaser locked to an atomic hyperfine transition.