  We examine one asymmetric adnd two fully symmetric Gaussian
continuous-variable systems in terms of their tripartite and bipartite
entanglement properties. We treat pure states and are able to find analytic
solutions using the undepleted pump approximation for the Hamiltonian models,
and standard beamsplitter relations for a model that mixes the outputs of
optical parametric oscillators. Our two symmetric systems exhibit perfect
tripartite correlations, but only in the unphysical limit of infinite
squeezing. For more realistic squeezing parameters, all three systems exhibit
both tripartite and bipartite entanglement. We conclude that none of the
outputs are completely analogous to either GHZ or W states, but there are
parameter regions where they produce T states introduced by Adesso \etal The
qualitative differences in the output states for different interaction
parameters indicate that continuous-variable tripartite quantum information
systems offer a versatility not found in bipartite systems.
