Effect of the Atomic Dipole-Dipole Interaction on the Phase Diagrams of Field-Matter Interactions

TL;DR

This paper investigates how atomic dipole-dipole interactions influence quantum phase diagrams in the two-level Dicke model, revealing observable quantum phase transitions through fluctuations in atomic populations and photon numbers.

Contribution

It introduces a quantum information approach to analyze the effects of atomic dipole-dipole interactions on phase transitions in the Dicke model, considering finite particle numbers and different approximations.

Findings

Quantum phase transitions are detectable via atomic population fluctuations.

Photon number fluctuations also indicate phase transitions.

Conditional probability distributions reveal phase transition information in weak matter-field interactions.

Abstract

Quantum information measures are used to study the quantum phase diagrams of the two-level Dicke model including the atomic dipole-dipole interaction, for a finite number of particles, with and without the rotating-wave approximation, which yields the conservation of the total number of excitations in the first case and its parity in the general case. We show that the quantum phase transitions can be observed in the fluctuation of the atomic populations and that of the number of photons, and also that the conditional probability distribution of the population of the excited state with zero photons carries the information of the quantum phase transitions when the matter-field interaction is weak.