Data from: Direct generation of spatially entangled qudits using quantum nonlinear holography - variances

Nonlinear holography shapes the amplitude and phase of generated new
harmonics using nonlinear processes. Classical nonlinear holography
influenced many fields in optics, from information storage,
de-multiplexing of spatial information and all-optical control of
accelerating beams. Here, we extend the concept of nonlinear holography to
the quantum regime. We directly shape the spatial quantum correlations of
entangled photon pairs in two-dimensional patterned nonlinear photonic
crystals using spontaneous parametric down conversion, without any pump
shaping. The generated signal-idler pair obeys a parity conservation law
that is governed by the nonlinear crystal. Furthermore, the quantum states
exhibit quantum correlations and violate the Clauser-Horne-Shimony-Holt
inequality, thus enabling entanglement-based quantum key distribution. Our
demonstration paves the way for controllable on-chip quantum optics
schemes utilizing the high-dimensional spatial degree of freedom.