Gravitational wave-induced photon superradiance in atoms

The effects of spacetime curvature on atoms are typically very small. However, we argue that spontaneous buildup of quantum coherence enables atoms in an array to cooperate and amplify their response to gravitational waves. This cooperation manifests as gravitational wave-induced photon superradiance --- delayed, intense, and directional emission of photons at frequencies shifted by the gravitational wave frequency. This effect arises in a regime distinct from flat-spacetime superradiance, which allows gravitational effects to dominate the collective atomic response. The effect persists despite common experimental challenges like position disorder and partial filling, motivating an assessment of coherent atom arrays as a platform for broadband gravitational wave sensing. Our findings demonstrate a coupling interface between general relativistic gravity and quantum matter under laboratory settings in a many-body system, with implications for both fundamental science and practical applications.