Physical implementation for entanglement purification of Gaussian   continuous variable quantum states
  We give a detailed description of the entanglement purification protocol which generates maximally entangled states with high efficiencies from realistic Gaussian continuous variable entangled states. The physical implementation of this protocol is extensively analyzed using high finesse cavities and cavity enhanced cross Kerr nonlinearities. In particular, we take into account many imperfections in the experimental scheme and calculate their influences. Quantitative requirements are given for the relevant experimental parameters. 
Lu-Ming Duan, G. Giedke, J. I. Cirac, and P. Zoller