Experimental EPR-Steering of Bell-local States. (arXiv:0909.0805v1 [quant-ph])

Entanglement is the defining feature of quantum mechanics, and understanding
the phenomenon is essential at the foundational level and for future progress
in quantum technology. The concept of steering was introduced in 1935 by
Schr"odinger as a generalization of the Einstein-Podolsky-Rosen (EPR) paradox.
Surprisingly, it has only recently been formalized as a quantum information
task with arbitrary bipartite states and measurements, for which the existence
of entanglement is necessary but not sufficient. Previous experiments in this
area have been restricted to the approach of Reid [PRA 40, 913], which followed
the original EPR argument in considering only two different measurement
settings per side. Here we implement more than two settings so as to be able to
demonstrate experimentally, for the first time, that EPR-steering occurs for
mixed entangled states that are Bell-local (that is, which cannot possibly
demonstrate Bell-nonlocality). Unlike the case of Bell inequalities, increasing
the number of measurement settings beyond two--we use up to six--dramatically
increases the robustness of the EPR-steering phenomenon to noise.

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Original source : http://arxiv.org/abs/0909.0805...