Witnessing Entanglement with Second-Order Interference
  Second-order interference and Hanbury-Brown and Twiss type experiments can provide an operational framework for the construction of witness operators that can test classical and nonclassical properties of a Gaussian squeezed state (GSS), and provide entanglement witness operators to study the separability properties of correlated Gaussian squeezed sates. 
Magdalena Stobi\'nska and Krzysztof W\'odkiewicz