High-dimensional mode analyzers for spatial quantum entanglement

By analyzing entangled photon states in terms of high-dimensional spatial mode superpositions, it becomes feasible to expose high-dimensional entanglement, and even the nonlocality of twin photons. To this end, a proper analyzer should be designed that is capable of handling a large number of spatial modes, while still being convenient to use in an experiment. We compare two variants of a high-dimensional spatial mode analyzer on the basis of classical and quantum considerations. These analyzers have been tested in classical optical experiments.