Entanglement generation from degeneracy breaking of superradiant Liouvillian steady states by local operations

Abstract

Superradiance is a collective optical effect where emitters cooperatively radiate with a maximal intensity scaling proportional to the square of the number of emitters. Despite the superradiant cascade transitioning through highly entangled states, it has been shown that, for dynamics along the Dicke ladder, superradiance need not generate entanglement between the emitters. By contrast, we show how introducing incoherent local processes -- normally considered detrimental to both entanglement and superradiance -- can generate high levels of inter-emitter entanglement. We develop a general framework, using degenerate non-Hermitian perturbation theory, for the study of superradiant Liouvillian steady-state degeneracy breaking by these local operations from a few emitters up into the thermodynamic limit. From this, we are able to show that entanglement becomes ubiquitous in this regime and demonstrate its robustness against other forms of symmetric environmental noise. In the regime where pumping dominates, we find that population accumulates towards the maximally entangled minimal pseudo-spin states, corresponding to multi-emitter singlet states. This provides a deeper insight into many-body entanglement and the curious connection between local operations and entanglement generation.