Vacuum Rabi oscillation induced by virtual photons in the ultrastrong coupling regime

TL;DR

This paper demonstrates how virtual photons in the ground state of an ultrastrongly coupled atom-field system can induce observable vacuum Rabi oscillations, enabling probing of ground state structures.

Contribution

It introduces an interaction scheme where virtual photons enable coherent atomic transitions, revealing a new way to explore ground state properties in the ultrastrong coupling regime.

Findings

Virtual photons enable vacuum Rabi oscillations.

Effective vacuum Rabi frequency is proportional to virtual photon amplitude.

The scheme can probe ground state structures in ultrastrong coupling.

Abstract

We present an interaction scheme that exhibits a dynamical consequence of virtual photons carried by a vacuum-field dressed two-level atom in the ultrastrong coupling regime. We show that, with the aid of an external driving field, virtual photons provide a transition matrix element that enables the atom to evolve coherently and reversibly to an auxiliary level accompanied by the emission of a real photon. The process corresponds to a type of vacuum Rabi oscillation, and we show that the effective vacuum Rabi frequency is proportional to the amplitude of a single virtual photon in the ground state. Therefore the interaction scheme could serve as a probe of ground state structures in the ultrastrong coupling regime.