  We study the measurement-induced non-Gaussian operation on the single- and
two-mode \textit{Gaussian} squeezed vacuum states with beam splitters and
on-off type photon detectors, with which \textit{mixed non-Gaussian} states are
generally obtained in the conditional process. It is known that the
entanglement can be enhanced via this non-Gaussian operation on the two-mode
squeezed vacuum state. We show that, in the range of practical squeezing
parameters, the conditional outputs are still close to Gaussian states, but
their second order variances of quantum fluctuations and correlations are
effectively suppressed and enhanced, respectively. To investigate an
operational meaning of these states, especially entangled states, we also
evaluate the quantum dense coding scheme from the viewpoint of the mutual
information, and we show that non-Gaussian entangled state can be advantageous
compared with the original two-mode squeezed state.
