Generation of NPT Entanglement from Nonclassical Photon Statistics
  With a product state of the form $\rho_{in} = \rho_a\otimes|0>_b_b< 0|$ as input, the output two-mode state $\rho_{{\rm out}}$, of the beam splitter is shown to be NPT whenever the photon number distribution (PND) statistics $\{p(n_a) \}$ associated with the possibly mixed state $\rho_a$ of the a_mode is antibunched or otherwise nonclassical, i.e., if $\{p(n_a)\}$ fails to respect any one of an infinite of classicality conditions. 
J. Solomon Ivan, N. Mukunda, and R. Simon