Experimentally realizable characterizations of continuous variable   Gaussian states
  Measures of entanglement, fidelity and purity are basic yardsticks in quantum information processing. We propose how to implement these measures using linear devices and homodyne detectors for continuous variable Gaussian states. In particular, the test of entanglement becomes simple with some prior knowledge which is relevant to current experiments. 
M. S. Kim, Jinhyoung Lee, and W. J. Munro