Entanglement generation from parametric scattering of excitons in 2D semiconductor

Excitons in a semiconductor monolayer form a collective resonance that can reflect resonant light with extraordinarily high efficiency. This effect can be understood as a continuum analog of a similar phenomenon observed in atomic arrays with sub-wavelength spacing. Besides the optically active bright states, there is a sector of momentum-constrained dark exciton states, which are completely decoupled from the light field. In this work, we show how finite-range interactions between Rydberg-state excitons lead to significant scattering of excitons from the driven bright states toward the dark state manifold. We discuss and characterize the buildup of quantum entanglement between pairs of scattered excitons, and how these correlations map to the light field in emission.