Ground-State Entanglement in a Coupled-Cavity Model

TL;DR

This paper investigates ground-state entanglement in a two-site coupled cavity model, revealing how different phases exhibit distinct entanglement properties and providing insights into entanglement's relation to phase transitions and experimental observables.

Contribution

It introduces a detailed analysis of bipartite entanglement across various phases in a coupled cavity system, highlighting multipartite entanglement in the polaritonic superfluid phase.

Findings

Unique entanglement signatures characterize each phase.

Multipartite entanglement is present in the polaritonic superfluid.

Entanglement relates to phase transitions and observable quantities.

Abstract

Bipartite entanglement entropies are calculated for the ground state of the two-excitation subspace in a two-site coupled cavity model. Each region in the phase diagram (atomic insulator, polaritonic insulator, photonic superfluid, and polaritonic superfluid) is found to be characterized by unique entanglement properties. In particular, the polaritonic superfluid region exhibits multipartite entanglement among the two atoms and two cavity fields. This system provides a toy model in which a number of intriguing aspects of entanglement can be studied, such as the relationship of entanglement to phase transitions, entanglement of particles with different dimensionality, and the connection between experimentally accessible local observables and entanglement entropies.