Dissipation-induced bistability in the two-photon Dicke model.

The Dicke model is a paradigmatic quantum-optical model describing the interaction of a collection of two-level systems with a single bosonic mode. Effective implementations of this model made it possible to observe the emergence of superradiance, i.e.

Multielectron Ground State Electroluminescence.

The ground state of a cavity-electron system in the ultrastrong coupling regime is characterized by the presence of virtual photons. If an electric current flows through this system, the modulation of the light-matter coupling induced by this nonequilibrium effect can induce an extracavity photon emission signal, even when electrons entering the cavity do not have enough energy to populate the excited states. We show that this ground state electroluminescence, previously identified in a single-qubit system [Phys.