Two-photon-interaction effects in the bad-cavity limit

TL;DR

This paper investigates two-photon interactions in a bad-cavity quantum system, revealing enhanced emission rates and temperature-dependent effects that influence the dynamics and coherence of two-level systems.

Contribution

It introduces a novel effective master equation for two-photon coupled systems, highlighting fundamental differences from dipolar interactions and their impact on system behavior.

Findings

Enhanced spontaneous-like emission rate including thermal effects

Faster generation of steady-state coherence

Temperature-dependent collective effects

Abstract

Various experimental platforms have proven to be valid testbeds for the implementation of nondipolar light-matter interactions, where atomic systems and confined modes interact via two-photon couplings. Here, we study a damped quantum harmonic oscillator interacting with $N$ two-level systems via a two-photon coupling in the so-called bad-cavity limit, in the presence of finite-temperature baths and coherent and incoherent drivings. We have succeeded in applying a recently developed adiabatic elimination technique to derive an effective master equation for the two-level systems, presenting two fundamental differences compared to the case of a dipolar interaction: an enhancement of the two-level systems spontaneous-like emission rate, including a thermal contribution and a quadratic term in the coherent driving, and an increment of the effective temperature perceived by the two-level systems. These differences give rise to striking effects in the two-level systems dynamics, including a faster generation of steady-state coherence and a richer dependence on temperature of the collective effects, which can be made stronger at higher temperature.