Entanglement and nonclassicality of photon-added two-mode squeezed   thermal state
  We introduce a kind of entangled state---photon-addition two-mode squeezed thermal state (TMSTS) by adding photons to each mode of the TMSTS. Using the P-representation of thermal state, the compact expression of the normalization factor is derived, a Jacobi polynomial. The nonclassicality is investigated by exploring especially the negativity of Wigner function. The entanglement is discussed by using Shchukin-Vogel criteria. It is shown that the photon-addtion to the TMSTS may be more effective for the entanglement enhancement than the photon-subtraction from the TMSTS. In addition, the quantum teleportation is also examined, which shows that symmetrical photon-added TMSTS may be more useful for quantum teleportation than the non-symmetric case. 
Li-Yun Hu, Fang Jia, and Zhi-Ming Zhang
quant-ph