Multi-photon, multi-mode polarization entanglement in parametric down-conversion

The paper addresses the problem as to whether the microscopic photon polarization entanglement leaves any trace in the regime of high parametric down-conversion efficiency, where the number of down-converted photons can be rather large, and in which form. A local version of Stokes operators is defined and quantum correlation between operators measured from symmetric portions of the far field beam cross-section is studied.