Quantum entanglement maintained by virtual excitations in an ultrastrongly-coupled-oscillator system

TL;DR

This paper investigates how virtual excitations in an ultrastrongly-coupled harmonic oscillator system can sustain quantum entanglement, providing analytical insights and exploring entanglement dynamics in different system conditions.

Contribution

It offers an analytical expression for the ground state and analyzes entanglement related to virtual excitations in ultrastrong coupling, including dynamics in open and closed systems.

Findings

Ground state entanglement is maintained by virtual excitations.

Analytical expression for the ground state derived.

Entanglement dynamics studied in open and closed systems.

Abstract

We study the effect of quantum entanglement maintained by virtual excitations in an ultrastrongly-coupled harmonic-oscillator system. Here, the quantum entanglement is caused by the counterrotating interaction terms and hence it is maintained by the virtual excitations. We obtain the analytical expression for the ground state of the system and analyze the relationship between the average excitation numbers and the ground-state entanglement. We also study the entanglement dynamics between the two oscillators in both the closed- and open-system cases. In the latter case, the quantum master equation is microscopically derived in the normal-mode representation of the coupled-oscillator system. This work will open a route to the study of quantum information processing and quantum physics based on virtual excitations.