Pure Dephasing of Light-Matter Systems in the Ultrastrong and Deep-Strong Coupling Regimes

TL;DR

This paper explores how pure dephasing impacts light-matter systems in ultrastrong and deep-strong coupling regimes, revealing gauge-dependent effects that are crucial for accurate modeling in quantum technologies.

Contribution

It demonstrates the gauge dependence of dephasing effects in ultrastrong coupling regimes and highlights potential inaccuracies when neglecting this in quantum system modeling.

Findings

Dephasing effects are gauge-dependent in ultrastrong coupling.

Neglecting gauge effects can lead to unphysical results.

Results are demonstrated on quantum Rabi and Hopfield models.

Abstract

Pure dephasing originates from the non-dissipative information exchange between quantum systems and environments, and plays a key-role in both spectroscopy and quantum information technology. Often pure dephasing constitutes the main mechanism of decay of quantum correlations. Here we investigate how pure dephasing of one of the components of a hybrid quantum system affects the dephasing rate of the system transitions. We find that, in turn, the interaction, in the case of a light-matter system, can significantly affect the form of the stochastic perturbation describing the dephasing of a subsystem, depending on the adopted gauge. Neglecting this issue can lead to wrong and unphysical results when the interaction becomes comparable to the bare resonance frequencies of subsystems, which correspond to the ultrastrong and deep-strong coupling regimes. We present results for two prototypical models of cavity quantun electrodynamics: the quantum Rabi and the Hopfield model.