  The experimental realization of multidimensional quantum states may lead to
unexplored and interesting physics, as well as advanced quantum communication
protocols. The orbital angular momentum of photons is a well suitable discrete
degree of freedom for implementing high-dimensional quantum systems. The
standard method to generate and manipulate such photon modes is to use bulk and
fixed optics. Here the authors demonstrate the utilization of a spatial light
modulator to manipulate the orbital angular momentum of entangled photons
generated in spontaneous parametric downconversion. They show that their setup
allows them to realize photonic entanglement of up to 21 dimensions, which in
principle can be extended to even larger dimensions.
