The spatial shape of entangled photon states generated in non-collinear, walking parametric downconversion

We address the spatial shape of entangled photon states generated in spontaneous parametric downconversion in non-collinear geometries, when the interacting waves exhibit Poynting vector walk-off. We discuss how such shape depends on the interplay between the state ellipticity caused by the non-collinear geometry, and the Poynting vector walk-off. In particular, we study the impact of the new features exhibited by walking entangled photons on the implementation of quantum protocols based on the spiral spectra of the entangled photons.