Perfect Intrinsic Squeezing at the Superradiant Phase Transition Critical Point

TL;DR

This paper demonstrates that the ground state of a photon-matter system at the superradiant phase transition point exhibits perfect squeezing, with quantum fluctuations minimized in one variable and diverging in its conjugate, revealing critical quantum behavior.

Contribution

It analytically shows perfect squeezing occurs at the critical point of the superradiant phase transition in the Dicke model, including effects of counter-rotating couplings.

Findings

Ground state is a two-mode squeezed vacuum at the critical point.

Quantum fluctuation variance vanishes at the transition, satisfying the Heisenberg principle.

Perfect squeezing is achieved precisely at the superradiant phase transition.

Abstract

The ground state of the photon-matter coupled system described by the Dicke model is found to be perfectly squeezed at the quantum critical point of the superradiant phase transition (SRPT). In the presence of the counter-rotating photon-atom coupling, the ground state is analytically expressed as a two-mode squeezed vacuum in the basis of photons and atomic collective excitations. The variance of a quantum fluctuation in the two-mode basis vanishes at the SRPT critical point, with its conjugate fluctuation diverging, ideally satisfying the Heisenberg uncertainty principle.