# Comparison of semiclassical and quantum models of a two-level atom-cavity QED system in the strong coupling regime

## TL;DR

This paper compares semiclassical and quantum models of a two-level atom-cavity system in the strong coupling regime, revealing significant differences in their predictions of transmission spectra, with quantum models accurately capturing multiphoton effects.

## Contribution

The study provides a detailed numerical comparison showing that quantum models accurately predict multiphoton spectra, unlike semiclassical models which predict bistability.

## Key findings

- Quantum model captures multiphoton transmission spectra.
- Semiclassical model predicts bistability instead of multiphoton effects.
- Strong coupling regime causes divergence between models.

## Abstract

We present a numerical study comparing semiclassical and quantum models of a damped, strongly interacting cavity QED system composed of a single two-level atom interacting with a single quantized cavity mode driven externally by a tunable monochromatic field. We compute the steady state transmission spectrum of the coupled system under each model and show that in the strong coupling regime, the two models yield starkly different results. The fully quantum mechanical model of the system correctly yields the expected multiphoton transmission spectra while the semiclassical approach results in a bistable spectrum.