  A significant hurdle for quantum information and processing using bosonic
systems is stochastic phase errors which occur as the photons propagate through
a channel. These errors will reduce the purity of states passing through the
channel and so reducing the channels capacity. We present a scheme of passive
linear optical unitary averaging for protecting unknown Gaussian states
transmitted through an optical channel. The scheme reduces the effect of phase
noise on purity, squeezing and entanglement, thereby enhancing the channel via
probabilistic error correcting protocol. The scheme is robust to loss and
typically succeeds with high probability. We provide both numerical simulations
and analytical approximations tailored for relevant parameters with the
improvement of practical and current technology. We also show the asymptotic
nature of the protocol, highlighting both current and future relevance.
