Nonclassical properties of Hermite polynomial's excitation on squeezed   vacuum and its decoherence in phase-sensitive reservoirs
  We introduce Hermite polynomial excitation squeezed vacuum (SV) H_{n}(O)S(r)|0> with O=u a+v a^{{+}}. We investigate analytically the nonclassical properties according to Mandel's Q parameter, second correlation function, squeezing effect and the negativity of Wigner function (WF). It is found that all these nonclassicalities can be enhanced by H_{n}(O)operation and adjustable parameters u and v. In particular, the optimal negative volume delta_{opt}of WF can be achieved by modulating u and v for n>=2,while delta is kept unchanged for n=1. Furthermore, the decoherence effect of phase-sensitive enviornment on this state is examined. It is shown that delta with bigger ndiminishes more quickly than that with lower n, which indicates that single-photon subtraction SV presents more roboustness. Parameter Mof reservoirs can be effectively used to improve the nonclassicality. 
Shi-You Liu, Ya-Zhou Li, Li-Yun Hu, Jie-Hui Huang, Xue-Xiang Xu, and   Xiang-Yang Tao
quant-ph