Witnessing Entanglement with Second-Order Interference and Stokes   Parameters
  We propose to use Stokes parameter as an entanglement witness for correlated EPR mixed states of light. Such states can be generated with a beam splitter acting on two mixed squeezed states of light. Stokes witness operators are closely related to the Hanbury-Brown and Twiss interference and can be used to test entanglement in balanced homodyne experiments involving fluctuations of quantum quadratures of the electric field. 
Magdalena Stobi\'nska and Krzysztof W\'odkiewicz