Comblike entangled spectrum for composite spin-orbit modes from hyperconcentration

I propose a practical scheme of hyperconcentration, by which two-qubit photon spin and two-qudit orbital angular momentum (OAM) maximally entangled states can be distilled simultaneously. The original nonmaximally hyperentangled photon pairs are generated by parametric down conversion and the symmetrical procrustean concentration is then performed using pairs of spatial light modulators (operating on OAM) and partial polarizing interferometers (operating on spin). Furthermore, I show that a generalized Shannon dimensionality can be introduced to evaluate the performance, which is maximized with the formation of a comblike entangled spectrum for composite spin-orbit modes. The results hold promise for ultrahigh-dimensional quantum-information processing.