A posteriori teleportation

Abstract

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 Bellstate 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 effects the efficiency of the experiment. This suggests that the measure of fidelity used by Braunstein and Kimble is unsuitable for our experiment During the detection of the teleported photons, no selection was performed based on the properties of these photons. Therefore, no a posteriori 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 state...". Braunstein and Kimble do not, therefore, reveal a principle flaw in our teleportation procedure, but merely address a non-trivial practical question.

Quantum Feedback for Protection of Schrödinger Cat States

“…In this case, one is able to monitor the progressive emergence of classical properties from the quantum ones. In this context, an important achievement has been obtained by Monroe et al 5 , who have prepared a trapped 9 Be + ion in a superposition of spatially separated coherent states and detected the quantum coherence between the two localized states. However, the decoherence of the superposition state has not been observed in this experiment.…”

“…These codes always require the entanglement of a large number of qubits, and will become practical only if quantum networks of tens of qubits become available. Up to now, the polarization states of three photons have been entangled at most 9 . Entangled states of two Rydberg atoms 10 or of two trapped ions 11 at most can be generated.…”

Concentration and purification scheme for two partially entangled photon pairs

“…In a teleportation experiment [2,19], where a nonlinear crystal is pumped twice by a short pulse, γ 2 is of order ∼10 −4 . The conventional photon detectors (e. g., EG&G SPCM) typically have the dark count rates of order 100 s −1 , which gives the value of ν ∼10 −6 for the coincidence time ∼10 ns.…”

Teleportation scheme ofS-level quantum pure states by two-level Einstein-Podolsky-Rosen states

“…Sixia Yu et.al., investigated canonical quantum teleportation of finite-level unknown states by introducing a canonically conjugated pair of quantum phase and number [8]. The successful experimental realization of quantum telepartation of unknown polarization states carried on a photon [9] and the succedent experiments about finite-level quantum system teleportation [10,11] have aroused a series of discussions [12,13,14] and further research of this topic from various aspects [15,16,17]. Possible applications have been considered in Ref.…”