Signatures of Dissipation Driven Quantum Phase Transition in Rabi Model

TL;DR

This paper investigates a dissipative quantum Rabi model, revealing a non-perturbative Beretzinski-Kosterlitz-Thouless quantum phase transition driven by coupling strength, with implications for quantum systems in viscous environments.

Contribution

It demonstrates a non-perturbative quantum phase transition in the dissipative Rabi model using advanced computational methods, even at low dissipation levels.

Findings

Quantum phase transition occurs in the Ohmic regime with varying coupling.

Signatures of the transition are observable in time and frequency domains.

Transition occurs in the deep strong coupling regime for low to moderate dissipation.

Abstract

By using worldline Monte Carlo technique, matrix product state and a variational approach \`a la Feynman, we investigate the equilibrium properties and relaxation features of the dissipative quantum Rabi model, where a two level system is coupled to a linear harmonic oscillator embedded in a viscous fluid. We show that, in the Ohmic regime, a Beretzinski-Kosterlitz-Thouless quantum phase transition occurs by varying the coupling strength between the two level system and the oscillator. This is a non perturbative result, occurring even for extremely low dissipation magnitude. By using state-of-the-art theoretical methods, we unveil the features of the relaxation towards the thermodynamic equilibrium, pointing out the signatures of quantum phase transition both in the time and frequency domains. We prove that, for low and moderate values of the dissipation, the quantum phase transition occurs in the deep strong coupling regime. We propose to realize this model by coupling a flux qubit and a damped LC oscillator.