  Enhancement of entanglement enhancement is necessary for most quantum
communication protocols many of which are defined in Hilbert spaces larger than
two. In this work we present the experimental realization of entanglement
concentration of orbital angular momentum entangled photons produced in the
spontaneous parametric down-conversion process which have been shown to provide
a source for higher dimensional entanglement. We investigate the specific case
of three dimensions and the possibility of generating different entangled
states out of an initial state. The results presented here are of importance
for pure states as well as for mixed states.
