# Epidemic dynamics in open quantum spin systems

## TL;DR

This paper investigates how epidemic-like spreading dynamics manifest in open quantum spin systems, revealing different phase transitions depending on classical or quantum effects, with implications for Rydberg atom experiments.

## Contribution

It introduces a quantum model for epidemic dynamics in open many-body systems and analyzes phase transitions influenced by classical and quantum effects.

## Key findings

- Different non-equilibrium phase transitions depending on classical or quantum dominance
- Potential observability of phenomena in Rydberg gases with long-range interactions
- Identification of conditions for epidemic spreading in quantum regimes

## Abstract

We explore the non-equilibrium evolution and stationary states of an open many-body system which displays epidemic spreading dynamics in a classical and a quantum regime. Our study is motivated by recent experiments conducted in strongly interacting gases of highly excited Rydberg atoms where the facilitated excitation of Rydberg states competes with radiative decay. These systems approximately implement open quantum versions of models for population dynamics or disease spreading where species can be in a healthy, infected or immune state. We show that in a two-dimensional lattice, depending on the dominance of either classical or quantum effects, the system may display a different kind of non-equilibrium phase transition. We moreover discuss the observability of our findings in laser driven Rydberg gases with particular focus on the role of long-range interactions.