Two-photon emission from uniform acceleration: Unruh excitation, radiative decay, and field entanglement

Abstract: We analyze the two-photon emission process of a uniformly accelerated Unruh-DeWitt detector interacting with a massless scalar field in Minkowski spacetime. Using second-order perturbation theory, we derive the exact final quantum state of the field and classify the emitted photon pairs according to their directional decomposition into Unruh modes: right-right (RR), left-left (LL), and mixed (RL/LR) channels. The RR and LL contributions produce photon pairs within a single Rindler wedge, while RL and LR emissions generate entanglement across wedges. The first emission arises from a counter-rotating (Unruh) excitation, followed by a rotating Wigner-Weisskopf-like decay. Our results reveal how acceleration imprints entanglement and thermal structure on the radiation, offering new insight into quantum field theory in non-inertial frames and potential applications in relativistic quantum information.