A posteriori teleportation

Abstract

Bouwmeester et al. reply — Braunstein and Kimble observe correctly that, in the Innsbruck experiment, one does not always observe a teleported photon conditioned on a coincidence recording at the Bell-state analyser. In their opinion, this affects the fidelity of the experiment, but we believe, in contrast, that it has no significance, and that when a teleported photon appears, it has all the properties required by the teleportation protocol. These properties can never be achieved by “abandoning teleportation altogether and transmitting randomly selected polarization states” as Braunstein and Kimble suggest. The fact that there will be events where no teleported photons are created merely affects the efficiency of the experiment. This suggests that the measure of fidelity used by Braunstein and Kimble is unsuitable for our experiment.

Main

During the detection of the teleported photons, no selection was performed based on the properties of these photons. Therefore, no aposteriori measurement in the usual sense as a selective measurement was performed. The detection of the teleported photon could have been avoided altogether if we had used a more expensive detector, p, that could distinguish between one- and two-photon absorption. The inability of our teleportation experiment to perform such refined detections does not, however, imply that “a teleported state can never emerge as a freely propagating state⃛”. Braunstein and Kimble do not, therefore, reveal a principal flaw in our teleportation procedure, but merely address a non-trivial practical question.