Quantum information transfer from spin to orbital angular momentum of   photons
  The optical "spin-orbit" coupling occurring in a suitably patterned nonuniform birefringent plate known as `q-plate' allows entangling the polarization of a single photon with its orbital angular momentum (OAM). This process, in turn, can be exploited for building a bidirectional "spin-OAM interface", capable of transposing the quantum information from the spin to the OAM degree of freedom of photons and \textit{vice versa}. Here, we experimentally demonstrate this process by single-photon quantum tomographic analysis. Moreover, we show that two-photon quantum correlations such as those resulting from coalescence interference can be successfully transferred into the OAM degree of freedom. 
Eleonora Nagali, Fabio Sciarrino, Francesco De Martini, Lorenzo   Marrucci, Bruno Piccirillo, Ebrahim Karimi, and Enrico San...