A multimode cavity QED Ising spin glass

TL;DR

This paper demonstrates a driven-dissipative cavity QED system realizing a spin glass with ultracold atoms, exhibiting equilibrium-like spin glass phenomena such as replica symmetry breaking despite being inherently nonequilibrium.

Contribution

It introduces a novel multimode cavity QED setup to simulate a spin glass with ultracold atoms, revealing equilibrium spin glass features in a driven-dissipative system.

Findings

Observation of replica symmetry breaking (RSB) in a nonequilibrium system

Measurement of the Parisi function q(x) and Edwards-Anderson overlap q_EA

Evidence of ultrametric structure in the spin glass states

Abstract

We realize a driven-dissipative Ising spin glass using cavity QED in a novel ``4/7" multimode geometry. Gases of ultracold atoms trapped within the cavity by optical tweezers serve as effective spins. They are coupled via randomly signed, all-to-all Ising cavity-mediated interactions. Networks of up to n = 25 spins are holographically imaged via cavity emission. The system is driven through a frustrated transverse-field Ising transition, and we show that the entropy of the spin glass states depends on the rate at which the transition is crossed. Despite being intrinsically nonequilibrium, the system exhibits phenomena associated with Parisi's theory of equilibrium spin glasses, namely replica symmetry breaking (RSB) and ultrametric structure. For system sizes up to n = 16, we measure the Parisi function q(x), Edwards-Anderson overlap q_EA, and ultrametricity K-correlator; all indicate a deeply ordered spin glass under RSB. The system can serve as an associative memory and enable aging and rejuvenation studies in driven-dissipative spin glasses at the microscopic level.