Non-classical states of light are required for many applications in quantum information, including secure quantum key distribution, quantum sensing and quantum computation. One of the main methods for generating non-classical light is spontaneous parametric down conversion (SPDC). The generated photons c an be entangled in many degrees of freedom. The properties of the generated quantum light depend on the parameters of the pump beam and the nonlinear crystal, but it is not a trivial task to predict the outcome of the SPDC process or to tailor it in order to obtain a desired state. This talk presents a systematic method to design and control SPDC processes. It is based on a classical simulator that we developed which enables us to precisely predict the first order and second order correlations between the generated single photons, and to reconstruct the density matrix of the quantum state. This enables to generate maximally entangled bi-photon states, bi-photon spatial qubits, qutrits and quqarts. I will also present some recent experimental results on the generation of spatial qudits in the Hermite-Gauss basis, as well as on the generation of N00N states and their applications for super-resolution.