Replica symmetry breaking in a quantum-optical vector spin glass

We report the observation of replica symmetry breaking and a spin glass

(SG) phase in a quantum optical system. Spin glasses underpin a wide array of

complex topics, including neural networks and combinatorial optimization. A

network of N=8 ultracold gases with pseudospin degrees of freedom are placed

inside a confocal cavity, which mediates controllable sign-changing interactions

between the 8 network nodes. The network evolves into an ordered phase as the

atoms are pumped through a super-radiant phase transition. We holographically

reconstruct the cavity emission to measure the spin states. Repeated measure-

ments of the spin states produce a Parisi-like distribution, indicating that the

system is in an SG phase. This experimental platform opens new avenues for

the study of driven-dissipative quantum systems, the emergence of glassy states

of matter, and physical optimization approaches.