Partially coherent spontaneous parametric downconversion: Twisted Gaussian biphotons

Partially coherent optical beams present phenomena that may not appear in perfectly beams. In this regard, spontaneous parametric downconversion is an intriguing physical process, since the properties of pump laser beam are transferred to quantum down-converted photon pairs. Here, authors study transfer twist phase, a novel property so-called twisted Gaussian Schell model beams, from photons. The show non-zero phase can lead highly entangled yet mixed states. correlations near/far-field intensity measurements, two-photon covariance matrix as well orbital angular momentum modes, explored. derive expressions for purity state and relate it transverse spatial coherence beam. Their main results utilize Wigner function formalism be applied number scenarios involving partially sources contribute recent interest spatially correlated pairs produced states, with possible applications communication imaging.