  Entanglement and quantum interference are key ingredients in a variety of
quantum information processing tasks. Harnessing the generation and
characterization of entanglement in high-dimensional state spaces is a
necessary prerequisite towards practical quantum protocols. Here, we use
quantum interference on a beam splitter to engineer hyperentanglement in
polarization and discrete frequency degrees of freedom (DOF). We show how
independent measurements of polarization and frequency DOF allow for the
verification of high-dimensional entanglement in the combined state space.
These results may indicate new paths towards practical exploitation of
entanglement stored in multiple degrees of freedom, in particular in the
context of high-dimensional quantum information processing protocols.
