Triple photons: a challenge in nonlinear and quantum optics

This article is devoted to the generation and the quantum correlations of triple photons, which correspond to the creation of three highly correlated photons from the splitting of a single photon by a phase-matched third-order parametric nonlinear process. These triples constitute a Greenberger-Home-Zeilinger state of light and are interesting from a fundamental point of view but also for new schemes of quantum cryptography. We give here the classical and quantum descriptions of triple photon generation, we report on the first experimental demonstration of such a generation, and we calculate the Wigner function of three-photon quantum states of light.