  We demonstrate the capability to discretize the frequency spectrum of
broadband energy-time entangled photons by means of a spatial light modulator
to encode qudits in various bases. Exemplarily, we implement three different
discretization schemes, namely frequency bins, time bins and Schmidt modes.
Entangled qudits up to dimension $d=4$ are then revealed by two-photon
interference experiments with visibilities violating a $d$-dimensional Bell
inequality.
