Nonclassicality Quasiprobability of Single-Photon Added Thermal States
  We report the experimental reconstruction of a nonclassicality quasiprobability for a single-photon added thermal state. This quantity has significant negativities, which is necessary and sufficient for the nonclassicality of the quantum state. Our method presents several advantages compared to the reconstruction of the P function, since the nonclassicality filters used in this case can regularize the quasiprobabilities as well as their statistical uncertainties. A-priori assumptions about the quantum state are therefore not necessary. We also demonstrate that, in principle, our method is not limited by small quantum efficiencies. 
T. Kiesel, W. Vogel, M. Bellini and A. Zavatta
quant-ph