Realistic teleportation with linear optical elements

We calculate the highest possible information gain in a measurement of enta ngled states when employing a beamsplitter. The result is used to evaluate the fidelity, averaged over all unknown inputs, in a realistic teleportatio n protocol that takes account of the imperfect detection of Bell states. Fi nally, we introduce a probabilistic teleportation scheme, where measurement s are made in a partially entangled basis. (C) 2001 Elsevier Science B.V. A ll rights reserved.