# [SIGSAG](@id sigsag_ref)

The `sigsag` module models a heralded dual-rail entanglement source architecture proposed by Yousef Chahine et al. as an alternative to the cascaded source architecture. The nomenclature of "SIGSAG" refers to the fact that this source could be implemented with a single Sagnac source.

## Type

```@docs
Genqo.sigsag.SIGSAG
```

## Source Metrics

```@docs
Genqo.sigsag.fidelity
Genqo.sigsag.probability_success
```

## Internal Matrices

```@docs
Genqo.sigsag.covariance_matrix
Genqo.sigsag.loss_bsm_matrix_fid
Genqo.sigsag.loss_bsm_matrix_pgen
```
