Angular Schmidt spectrum of entangled photons: derivation of an exact formula and experimental characterization for non-collinear phase matching


Abstract: We derive an exact computationally-efficient formula for the angular Schmidt spectrum of orbital angular momentum (OAM)-entangled states produced by parametric down-conversion (PDC). Our formula yields the true spectrum and does not suffer from convergence issues arising due to infinite summations, as has been the case with previously derived formulas. We use this formula to experimentally characterize the angular Schmidt spectrum of entangled photons produced by PDC with non-collinear phase matching. We report measurements of very broad angular Schmidt spectra, corresponding to the angular Schmidt numbers up to 229. Our studies can have important implications for OAM-based quantum information applications.

Phys. Rev. A 97, 063846 (2018)

Girish Kulkarni