Determining the dimensionality of bipartite orbital-angular-momentum   entanglement using multi-sector phase masks
  The Shannon dimensionality of orbital angular momentum (OAM) entanglement produced in spontaneous parametric down-conversion can be probed by using multi-sector phase analysers. We demonstrate a spatial light modulator-based implementation of these analysers, and use it to measure a Schmidt number of about 50. 
D. Giovannini, F. M. Miatto, J. Romero, S. M. Barnett, J. P. Woerdman,   M. J. Padgett
quant-ph