Experimental realization of associative memory in a quantum-optical spin glass*

Associative memory refers to a content addressable memory that dynamically pattern-corrects erroneous input states. We demonstrate an associative memory in a quantum-optical setting by employing ultracold clouds of atoms coupled via photonic interactions in a mode-degenerate optical cavity. Holographic imaging of input and output cavity light provides microscopic access to the spin glass states. We show that operation of this device in a spin glass regime outperforms the memory capacity of the seminal Hopfield model. We demonstrate memories in 20-site networks and show that we can store and pattern-recall up to 18 memories in an N = 16 spin network. The operation in the spin glass regime challenges the notion that associative memory breaks down in a glass. We describe why this occurs and propose future explorations of quantum-optical spin glasses and neural networks.