Bell states generation with spatial pump filtering in nonlinear adiabatic waveguiding structures

We propose a novel integrated scheme for the generation of Bell states, which allows simultaneous spatial filtering of pump photons. It is achieved through spontaneous parametric down-conversion in the system of nonlinear adiabatically coupled waveguides. We also demonstrate that the adiabatic couplers open the possibility to maintain the purity of generated Bell states in a relatively fabrication-fault-tolerant way.