# [SPDC](@id spdc_ref)

The `spdc` module models a source composed of two Two-Mode Squeezed Vacuum (TMSV) states whose idler modes are swapped, realizing what is colloquially called an "SPDC" entanglement source. This is not to be confused with the fact that there are two Spontaneous Parametric Down-Conversion (SPDC) processes occuring. This is a standard unheralded source of dual-rail entangled photon pairs.

## Type

```@docs
Genqo.spdc.SPDC
```

## Source Metrics

```@docs
Genqo.spdc.fidelity
Genqo.spdc.spin_density_matrix
```

## Internal Matrices

```@docs
Genqo.spdc.covariance_matrix
Genqo.spdc.loss_bsm_matrix_fid
Genqo.spdc.dmijZ
```
