Experimental realization of hyper-entangled two-photon states
  We report on the the experimental realization of hyper-entangled two photon states, entangled in polarization and momentum. These states are produced by a high brilliance parametric source of entangled photon pairs with peculiar characteristics of flexibility in terms of state generation. The quality of the entanglement in the two degrees of freedom has been tested by multimode Hong-Ou-Mandel interferometry. 
C. Cinelli, M. Barbieri, F. De Martini and P. Mataloni