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Photon wave function description of space-time entanglement in quantum imaging

Few photon systems are best described by their wave function rather than by the usual quantum field formalism. Until recently, the existence of a wave function for photons has been an object of controversy. Important breakthrough happened during the last ten years, sharpening the wave function concept and giving it a precise definition. We show how the photon wave function proposed by Bialynicki-Birula and Sipe connects to experimentally measurable quantities such as multi-photon quantum correlation functions and use it to investigate space-time entanglement of photon pairs produced in parametric down-conversion.