Spontaneous Parametric Down Conversion (SPDC) is a nonlinear process of light, meaning it is a process that doesn't preserve the frequency of a light signal, and cannot be described by regular transmission functions.

In our case, we shoot a blue laser beam into a BBO crystal, which mediates the splitting of blue photons to pairs of photons with lower energy as a means of creating single photons. In standard setups, the pairs of low energy photons  are entangled in frequency (in accordance with conservation of energy). The goal of this research is to find a way to minimize this entanglement in frequency, for experiments in other degrees of freedom of the photons not to be affected by this entanglement in spectrum.

The first step of the research, which is presented here, is a simulation of the joint two-photon spectrum of the emitted photons in an SPDC process in a BBO crystal.