Interference-Controlled Nonclassical Photon Emission via Cavity-Mediated Spin Exchange

The generation of nonclassical light with strong photon antibunching and appreciable brightness remains an important goal in quantum technologies. Here, we demonstrate that cavity-mediated spin-exchange interactions provide a route to overcome this constraint by amplifying spectral anharmonicity. In a two-emitter cavity-QED system with a controllable relative phase φ, the resulting interference-interaction mechanism reshapes the dressed-state manifold and enables switching between distinct quantum emission regimes. For φ = 0, constructive interference yields highquality single-photon emission with near-perfect antibunching, suppressing g₁(2) (0) by more than three orders of magnitude while maintaining a substantial intracavity photon population. Conversely, for φ = π, destructive interference suppresses direct single-photon excitation and selectively enhances two-photon excitation, producing signatures of correlated two-photon emission with appreciable intracavity photon populations and suppressed higher-order excitations. Our work establishes interference-engineered interactions as a mechanism for the controllable selection of single-photon and photon-pair emission, opening new opportunities for programmable nonclassical light sources and quantum photonic applications.