Stabilizing Arrays of Photonic Cat States via Spontaneous Symmetry Breaking.

The controlled generation and the protection of entanglement is key to quantum simulation and quantum computation. At the single-mode level, protocols based on photonic cat states hold strong promise as they present unprecedentedly long-lived coherence and may be combined with powerful error correction schemes. Here, we demonstrate that robust ensembles of "many-body photonic cat states" can be generated in a Bose-Hubbard model with pair hopping via a spontaneous U(1) symmetry-breaking mechanism.