We demonstrate a nonlinear AlGaAs photonic chip generating biphotons with nonclassical spatial correlations. Photon pairs are generated by parametric down conversion in a waveguide array and simultaneously spread through quantum walks along the various waveguides. This concept implements a compact and versatile source of spatially entangled states, operating at room temperature and telecom wavelength, that could serve as a workbench for simulating condensed matter problems on-chip.

Integrated quantum photonics is a key tool towards large scale quantum technologies. In this work we present an AlGaAs-based photonic circuit for the on-chip generation of broadband orthogonally polarized photons and the deterministic separation of the photons into separate spatial modes, facilitating their further use in protocols. We demonstrate that 85% of the pairs are deterministically separated by the chip over a full 60 nm bandwidth and we assess the chip operation in the quantum regime via a Hong-Ou-Mandel experiment displaying a raw visibility of 75.5% over the same full bandwidth.

The Wigner phase-space formulation for systems possessing SU(1,1) symmetry has been defined by Seyfarth et al. [Quantum 4, 317 (2020)] tackling the difficulty in defining a suitable operational definition of the Wigner function. To further investigate this formulation, we propose a non-linear optical setup that incorporates photon-number-resolving detectors, which would enable a direct and comprehensive point-by-point sampling of the SU(1,1) Wigner function. We discuss the visualization of various two-mode quantum states and the effect of the losses in such a detection scheme.

Spontaneous Four Wave Mixing (SFWM) which generates photonic pairs is studied if it is addressed by optical vortices carrying an orbital angular momentum (OAM). We show that the output beams are OAM-correlated and that the entanglement depends on the 4-level scheme used to realize SFWM.