General simulation method for spontaneous parametric down- and parametric up-conversion experiments

Spontaneous parametric down-conversion (SPDC) sources are an important technology for quantum sensing and imaging. We demonstrate a general simulation method, based on modeling from first principles, reproducing the spectrally and spatially resolved abso-lute counts of a SPDC experiment. By additionally simulating parametric up-and down-conversion processes with thermal photons as well as effects of the optical system we accomplish good agreement with the experimental results. This method is broadly ap-plicable and allows for the separation of contributing processes, virtual characterization of SPDC sources, and enables the simulation of many quantum based applications.