Quantum teleportation criteria for continuous variables
  We discuss the criteria presently used for evaluating the efficiency of quantum teleportation schemes for continuous variables. It is argued that the fidelity criterion used so far has some severe drawbacks, and that a fidelity value larger than 2/3 is actually required for successful quantum teleportation. This value has never been reached experimentally so far. 
Philippe Grangier and Frederic Grosshans