  We consider the problem of evaluating the entanglement of non-Gaussian mixed
states generated by photon subtraction from entangled squeezed states. The
entanglement measures we use are the negativity and the logarithmic negativity.
These measures possess the unusual property of being computable with linear
algebra packages even for high-dimensional quantum systems. We numerically
evaluate these measures for the non-Gaussian mixed states which are generated
by photon subtraction with on/off photon detectors. The results are compared
with the behavior of certain operational measures, namely the teleportation
fidelity and the mutual information in the dense coding scheme. It is found
that all of these results are mutually consistent, in the sense that whenever
the enhancement is seen in terms of the operational measures, the negativity
and the logarithmic negativity are also enhanced.
