Purcell-enhanced two-photon emission from a quantum dot via dark-state biexciton loading.

Generating light in well-defined photon-number states is central to photonic quantum technologies. While deterministic single-photon sources are well established, producing efficient two-photon states from individual emitters remains challenging. Here we demonstrate a high-efficiency two-photon emitter using the degenerate biexciton-exciton cascade in a Purcell-enhanced quantum dot-micropillar system. Leveraging polarization-selective p-shell excitation, we achieve effective biexciton loading and identify stimulated emission as a key mechanism enhancing two-photon temporal correlation. The emitter exhibits a two-photon correlation of g(0) = 3,966(324), with a two-photon fraction of 0.983(1), and operates in a hybrid, predominantly cascade-dominated regime where cavity-stimulated two-photon emission coexists with the conventional biexciton-exciton cascade. These findings represent progress towards developing practical, on-demand, solid-state two-photon sources.