Unconditional Quantum Teleportation

Abstract

Quantum teleportation of optical coherent states was demonstrated experimentally using squeezed-state entanglement. The quantum nature of the achieved teleportation was verified by the experimentally determined fidelity Fexp = 0.58 +/- 0.02, which describes the match between input and output states. A fidelity greater than 0.5 is not possible for coherent states without the use of entanglement. This is the first realization of unconditional quantum teleportation where every state entering the device is actually teleported.

Entanglement purification for quantum communication

“…In the past years, entangled states have been used to experimentally demonstrate both dense coding 11 10− and teleportation 15 12− . Very recently, entanglement-assisted quantum cryptography has also been implemented using entangled photons 18 16− .…”

Quantum channel of continuous variable teleportation and nonclassicality of quantum states

“…More practical scheme of the continuous variable teleportation has been proposed [3,4,5] in which a two-mode squeezed-vacuum state is employed as an entangled state. The first experiment was performed by using quantum optical fields [6]. A two-mode squeezed-vacuum was generated from a sub-threshold optical parametric § E-mail:psasaki@crl.go.jp oscillator (OPO) and the teleportation of a coherent state was demonstrated with the fidelity of 0.58 ± 0.02 which was higher than the predicted classical limit of 1/2.…”

Teleportation and measurement

“…The first experimental implementations of this idea were reported by Boschi et al [2], Bouwmeester et al [3], and Furusawa et al [4]. In all of these papers the justification of teleportation is based on three very different assumptions: the existence of EPR states, the collapse of the wave function after the measurement and the exchange of classical information from Alice to Bob.…”

“…The second operation, W , represents a measurement that allows Bob to change the state of his particle 3 into an identical copy of the (unknown) input state of particle 1. In the experiment of Furusawa et al [4], the system is a single mode of an electromagnetic field, U is realized by a measurement of the quadratures performed by Alice and W by a linear displacement of the quadratures performed by Bob according to the result of the Alice measurement. Our analysis proves that this experiment constitutes evidence of teleportation without the need of any extra assumption.…”