Quantum versus classical domains for teleportation with continuous variables

Quantum versus classical domains for teleportation with continuous variables

Braunstein, S.L., Fuchs, C.A., Kimble, H.J. and van Loock, P.
(2001): Physical Review A 64, 022321/1-16. (PDF)

ABSTRACT: By considering the utilization of a classical channel without quantum entanglement, fidelity F_classical = 1/2 has been established as setting the boundary between classical and quantum domains in the teleportation of coherent states of the electromagnetic field [S. L. Braunstein, C. A. Fuchs, and H. J. Kimble, J. Mod. Opt. 47, 267 (2000)]. We further examine the quantum-classical boundary by investigating questions of entanglement and Bell-inequality violations for the Einstein-Podolsky-Rosen states relevant to continuous variable teleportation. The threshold fidelity for employing entanglement as a quantum resource in teleportation of coherent states is again found to be F_classical = 1/2. Likewise, violations of local realism onset at this same threshold, with the added requirement of overall efficiency \eta > 2/3 in the unconditional case. By contrast, recently proposed criteria adapted from the literature on quantum-nondemolition detection are shown to be largely unrelated to the questions of entanglement and Bell-inequality violations.