Quantum correlated steady states under competing collective and individual decay

TL;DR

This paper investigates how collective and individual decay processes compete in a driven spin system, revealing a phase transition, quantum bistability, and dynamical switching between correlated states, with implications for quantum technologies.

Contribution

It demonstrates the emergence of quantum bistability and phase transition due to competing dissipation processes in many-body spin systems, highlighting the formation of correlated steady states under realistic conditions.

Findings

First-order phase transition observed in steady states.

Existence of quantum bistability with two stable states.

Dynamical switching and quantum jumps between states.

Abstract

Collective dissipation can generate useful quantum correlations, while ubiquitous individual decay destroys them. We study the interplay between these two competing processes considering a driven system of many spins (``atoms") undergoing both collective and individual dissipation (``radiation"). In steady state and depending on drive, we find that the system exhibits a first-order phase transition and quantum bistability: its quantum state is a mixture of two many-body states associated with the two competing decay processes. Accordingly, one of these states closely resembles a correlated ``coherently radiating spin state" (CRSS) -- the solution of purely collective dissipation -- exhibiting spin-squeezing entanglement. We predict dynamical switching between the two stable states, manifest as many-body quantum jumps in the various observables of spin and radiation. Macroscopically, the switching rate tends to vanish and the system can reside in a correlated CRSS for long times. This reveals how correlated dissipative physics emerges at the presence of decorrelating individual decay, opening a path for unlocking collective dissipation phenomena in realistic quantum platforms and applications. We discuss consequences for experiments in collective radiation.