On the critical exponent of a quantum noise driven phase transition: the open system Dicke-model

TL;DR

This paper investigates the quantum phase transition in an open-system Dicke-model realized with a Bose-Einstein condensate in an optical cavity, focusing on how openness affects critical exponents and quantum correlations.

Contribution

It provides new insights into the critical behavior and quantum correlations of the open-system Dicke-model, highlighting differences from the ground state phase transition.

Findings

Critical exponents differ significantly from the ground state case.

Entanglement properties are markedly altered by the open-system dynamics.

Steady-state quantum correlations exhibit unique critical behavior.

Abstract

The quantum phase transition of the Dicke-model has been observed recently in a system formed by motional excitations of a laser-driven Bose--Einstein condensate coupled to an optical cavity [1]. The cavity-based system is intrinsically open: photons can leak out of the cavity where they are detected. Even at zero temperature, the continuous weak measurement of the photon number leads to an irreversible dynamics towards a steady-state which exhibits a dynamical quantum phase transition. However, whereas the critical point and the mean field is only slightly modified with respect to the phase transition in the ground state, the entanglement and the critical exponents of the singular quantum correlations are significantly different in the two cases.