The Quantum Origin of Diffraction from Bright and Dark States

Abstract: Diffraction, a cornerstone of wave optics, is reinterpreted through bright and dark collective states. In the continuous-mode framework, the diffraction pattern arises from projection onto a single bright mode, while dark-region photons populate orthogonal dark modes. Unlike the classical view of destructive interference as field cancellation, the quantum description shows photons persisting in detector-uncoupled states. Our approach thus resolves a key limitation of Glauber's theory by identifying the detectable and undetectable modes, offering a complete particle-based explanation for diffraction.