# Strong-coupling limit of the driven dissipative light-matter interaction

## TL;DR

This paper investigates the strong-coupling thermodynamic limit of the driven dissipative Jaynes-Cummings oscillator, highlighting quantum fluctuations, photon blockade, bistability, and a quantum phase transition.

## Contribution

It provides a detailed analysis of quantum versus semiclassical responses in different regimes of the driven JC model, emphasizing the role of quantum fluctuations and phase transitions.

## Key findings

- Photon blockade persists at low dissipation.
- Bistability aligns semiclassical and quantum dynamics at certain driving amplitudes.
- Identification of a second-order quantum phase transition on resonance.

## Abstract

We approach the strong-coupling thermodynamic limit in the response of the open driven Jaynes-Cummings (JC) oscillator. We do so by highlighting the role of quantum fluctuations against the semiclassical response in three distinct regimes of operation. We begin by demonstrating the persistence of photon blockade, predicted in [H. J. Carmichael, Phys. Rev. X 5, 031028 (2015)], as a manifestation of the inherently-quantum and nonlinear JC spectrum revealed for vanishing dissipation. We then proceed to discuss the importance of bistability, which, despite being present in photon blockade, is able to provide an alignment between the semiclassical nonlinearity and quantum dynamics only for a driving amplitude having the same order of magnitude as the light-matter coupling strength. This resolution brings us to the critical point of the well-known quantum phase transition of second order on resonance, where the quantum and semiclassical pictures are once more contrasted for a varying participation of the two coherent interactions when going through the collapse of the quasi-energy spectrum.