Rotating wave approximation and entropy

TL;DR

This paper explores how going beyond the rotating wave approximation in composite quantum systems reveals that counter-rotating terms relate to entropy and induce irreversible evolution, leading to entangled generalized coherent states.

Contribution

It demonstrates that counter-rotating terms are connected to the entropy operator and cause irreversible dynamics, extending the understanding of quantum system evolution beyond standard approximations.

Findings

Counter-rotating terms relate to the entropy operator.

Vacuum state evolves into a generalized entangled coherent state.

Irreversible time evolution arises from neglected Hamiltonian components.

Abstract

This paper studies composite quantum systems, like atom-cavity systems and coupled optical resonators, in the absence of external driving by resorting to methods from quantum field theory. Going beyond the rotating wave approximation, it is shown that the usually neglected counter-rotating part of the Hamiltonian relates to the entropy operator and generates an irreversible time evolution. The vacuum state of the system is shown to evolve into a generalized coherent state exhibiting entanglement of the modes in which the counter-rotating terms are expressed. Possible consequences at observational level in quantum optics experiments are currently under study.