Nonequilibrium dark space phase transition

TL;DR

This paper introduces the concept of dark space phase transition in open quantum systems, revealing a nonequilibrium transition between classical and quantum coherent dark states with potential quantum information applications.

Contribution

It presents the first theoretical framework for dark space phase transitions, highlighting quantum interference effects leading to novel collective dynamical behavior.

Findings

Identification of two competing dark states: classical and quantum coherent

Discovery of a nonequilibrium phase transition in dark space

Potential applications in quantum information encoding

Abstract

We introduce the concept of dark space phase transition, which may occur in open many-body quantum systems where irreversible decay, interactions and quantum interference compete. Our study is based on a quantum many-body model, that is inspired by classical nonequilibrium processes which feature phase transitions into an absorbing state, such as epidemic spreading. The possibility for different dynamical paths to interfere quantum mechanically results in collective dynamical behavior without classical counterpart. We identify two competing dark states, a trivial one corresponding to a classical absorbing state and an emergent one which is quantum coherent. We establish a nonequilibrium phase transition within this dark space that features a phenomenology which cannot be encountered in classical systems. Such emergent two-dimensional dark space may find technological applications, e.g. for the collective encoding of a quantum information.