Route from spontaneous decay to complex multimode dynamics in cavity QED

TL;DR

This paper investigates the transition from simple decay to complex multimode dynamics in cavity QED systems, revealing how coupling strength influences different dynamical regimes and emphasizing the role of the nonlinear Lamb shift.

Contribution

It introduces a Green's function approach to accurately analyze non-Markovian dynamics and the crossovers between decay, oscillations, and revivals in multimode cavity QED.

Findings

Identification of three dynamical regimes as coupling increases

Quantitative description of quantum revivals related to cavity round-trip time

Highlighting the importance of the nonlinear Lamb shift in regime transitions

Abstract

We study the non-Markovian quantum dynamics of an emitter inside an open multimode cavity, focusing on the case where the emitter is resonant with high-frequency cavity modes. Based on a Green's function technique suited for open photonic structures, we study the crossovers between three distinct regimes as the coupling strength is gradually increased: (i) overdamped decay with a time scale given by the Purcell modified decay rate, (ii) underdamped oscillations with a time scale given by the effective vacuum Rabi frequency, and (iii) pulsed revivals. The final multimode strong coupling regime (iii) gives rise to quantum revivals of the atomic inversion on a time scale associated with the cavity round-trip time. We show that the crucial parameter to capture the crossovers between these regimes is the nonlinear Lamb shift, accounted for exactly in our formalism.