Epidemic growth and Griffiths effects on an emergent network of excited atoms

TL;DR

This paper demonstrates how the excitation dynamics in a driven ultracold Rydberg atom gas mimic epidemic spreading on complex networks, revealing insights into non-equilibrium criticality and Griffiths effects.

Contribution

It introduces a microscopic SIS model linking excitation growth to emergent network dynamics and Griffiths phases in a controllable quantum system.

Findings

Growth of excitations follows sub-exponential dynamics similar to epidemics

Identification of Griffiths phase effects in the excitation dynamics

Development of a quantitative model connecting microscopic processes to network behavior

Abstract

Whether it be physical, biological or social processes, complex systems exhibit dynamics that are exceedingly difficult to understand or predict from underlying principles. Here we report a striking correspondence between the collective excitation dynamics of a laser driven ultracold gas of Rydberg atoms and the spreading of diseases, which in turn opens up a highly controllable experimental platform for studying non-equilibrium dynamics on complex networks. We find that the competition between facilitated excitation and spontaneous decay results in a fast growth of the number of excitations that follows a characteristic sub-exponential time dependence which is empirically observed as a key feature of real epidemics. Based on this we develop a quantitative microscopic susceptible-infected-susceptible (SIS) model which links the growth and final excitation density to the dynamics of an emergent heterogeneous network and rare active region effects associated to an extended Griffiths phase. This provides physical insights into the nature of non-equilibrium criticality in driven many-body systems and the mechanisms leading to non-universal power-laws in the dynamics of complex systems.