Key distillation from Gaussian states by Gaussian operations
  We study the secrecy properties of Gaussian states under Gaussian operations. Although such operations are useless for quantum distillation, we prove that it is possible to distill a secret key secure against any attack from sufficiently entangled Gaussian states with non-positive partial transposition. Moreover, all such states allow for key distillation, when Eve is assumed to perform finite-size coherent attacks before the reconciliation process. 
M. Navascues, J. Bae, J. I. Cirac, M. Lewenstein, A. Sanpera and A.   Acin