Couplings between Photons and Ensemble of Emitters in a High-$Q$ Cavity at Mesoscopic Excitation Levels

TL;DR

This paper explores how increasing excitation levels in a high-Q cavity affect photon-emitter coupling, revealing a mesoscopic regime where coherent interactions enable quantum photonic device development.

Contribution

It introduces the concept of mesoscopic excitation levels in cavity QED systems, highlighting their role in enabling multi-emitter-photon couplings at high energies.

Findings

Coherent coupling persists at high excitation levels when emitter lifetime exceeds a threshold.

Pump-induced dephasing suppresses energy exchange at very high excitation levels.

Mesoscopic excitation facilitates multi-photon and multi-emitter interactions for quantum devices.

Abstract

We investigate the coupling between an ensemble of individual emitters and multiple photons in a high-$Q$ cavity at the mesoscopic excitation level. The master equation theory is used to calculate the emission spectrum of the cavity QED system. The increasing excitation level not only pumps the system to the high-energy multi-emitter-photon states, but also introduces the pump-induced dephasing that suppresses the coherent energy exchange (coupling) between photons and emitters. When the emitter lifetime exceeds a threshold, we observe the mesoscopic excitation level i.e., the system is pumped to high energy states whilst the coherent couplings between these states are not yet suppressed. The mesoscopic excitation enables the couplings between multi-emitter-photon states, and thereby, paves the way to building quantum photonic devices based on multiple photons and nonlinear effects.