Photon production from the vacuum close to the super-radiant transition: When Casimir meets Kibble-Zurek

TL;DR

This paper proposes a method to generate photons from vacuum near a super-radiant transition by using a driven ensemble of atoms in a cavity, linking the dynamical Casimir effect to the Kibble-Zurek mechanism, and suggesting feasible experiments.

Contribution

It introduces a novel approach to simulate the dynamical Casimir effect via a low-frequency driven quantum phase transition in the Dicke model, connecting it to defect formation mechanisms.

Findings

Photon production is stimulated near the super-radiant transition.

Spectral properties reveal the critical nature of the system.

The approach is feasible with current cavity QED setups.

Abstract

The dynamical Casimir effect (DCE) predicts the generation of photons from the vacuum due to the parametric amplification of the quantum fluctuation of an electromagnetic field\cite{casimir1,casimir2}. The verification of such effect is still elusive in optical systems due to the very demanding requirements of its experimental implementation. This typically requires very fast changes of the boundary conditions of the problem, such as the high-frequency driving of the positions of the mirrors of a cavity accommodating the field. Here, we show that an ensemble of two-level atoms collectively coupled to the electromagnetic field of a cavity (thus embodying the quantum Dicke model\cite{dicke}), driven at low frequencies and close to a quantum phase transition, stimulates the production of photons from the vacuum. This paves the way to an effective simulation of the DCE through a mechanism that has recently found an outstanding experimental demonstration\cite{esslinger}. The spectral properties of the emitted radiation reflect the critical nature of the system and allow us to link the detection of DCE to the Kibble-Zurek mechanism for the production of defects when crossing a continuous phase transition\cite{KZ1,KZ2}. We illustrate the features of our proposal by addressing a simple cavity quantum-electrodynamics (cQED) setting of immediate experimental realisation.