Integrated source of path-entangled photon pairs with efficient pump self-rejection

We present a scheme for an integrated four-wave mixing source of narrow-band path-entangled photon pairs with efficient spatial pump self-rejection. The scheme is based on correlated loss in a system of waveguides in Kerr nonlinear media. We demonstrate that this setup allows for upwards of 100dB pump rejection, without additional filtering. The effect is reached by driving the symmetric collective mode that is strongly attenuated by an engineered dissipation, while photon pairs are born in the antisymmetric mode. A similar set-up can additionally be realized for generation of two-photon NOON states, also with pump self-rejection. We discuss implementation of the scheme by means of the coherent diffusive photonics, and demostrate its feasibility both in glass (such as fused silica-glass and IG2), and planar semiconductor waveguide structures in indium phosphide (InP) and in silicon.