Quantum image control through polarization entanglement in parametric down-conversion

We demonstrate both theoretically and experimentally the manipulation of quantum entangled images, using the coupling between polarization entanglement and the entanglement for the transverse degrees of freedom. Starting from a two-crystal bright source of polarization-entangled photons, we arrive at a configuration in which we are able to prepare superposition states for the down-converted angular spectrum while the polarization superposition state is preserved. This scheme allows us to select the detected quantum image by performing projections onto polarization subspaces. We also demonstrate the potential of the system for applications to quantum cryptography of images.