Electro-optically switchable spatial-mode entangled photon pairs using a modified Mach-Zehnder interferometer.

In this Letter, we propose and analyze a switchable integrated optical waveguide device employing a modified Mach-Zehnder interferometer, capable of generating nondegenerate, maximally spatial-mode entangled photon pairs. Using an integrated electro-optic phase modulator, we show the possibility of on-demand switching of spatial-mode entangled state from a Φ+ to a Ψ+ state and vice versa. Such a versatile device with the potential of easy manipulation of the "spatial-mode" degree of freedom, should be very interesting in realizing integrated optical chips for quantum information processing.