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This Defense Intelligence Reference Document (DIA-08-1003-016), dated 30 March 2010 and produced by the Defense Intelligence Agency under its Advanced Aerospace Weapon System Applications (AAWSA) Program, reviews quantum entanglement and nonlocality. It asks whether they could carry observer-to-observer signals faster than light or backward in time, with real-time control of a Mars rover as an example. It finds no compelling answer yet and says the question must be settled by experiment.
UNCLASSIFIED//FOR QFFICI0k Yli'F ~Ulk¥ Do these EPR experiments constitute a demonstration of the existence of quantum non locality? There is more than one way of interpreting the implications of the experimental results (Reference 1, 2), and one can find much discussion in the literature as to whether it is locality or "realism" (the objective observer-independent reality of external events) that has been refuted by these EPR measurements. Noble Laureate Anthony Leggett of the University of Illinois recently pushed this issue somewhat further (Reference 10). He demonstrated that by focusing on the falloff of correlations with elliptical polarization rather than the linear polarization used in the Bell Inequality EPR experiments, one can compare the predictions of quantum mechanics with a class of nonlocal realistic theories that he constructed. The resulting Leggett Inequalities can be used in the same way as the Bell Inequalities, but to test theories incorporating nonlocal realism instead of local realism. Anton Zeilinger's group at the Institute for Quantum Optics and Quantum Information (IQOQI) in Vienna performed a definitive test of the Leggett Inequalities (Reference 11). The results show that using elliptically polarized entangled photons, the Leggett Inequalities in two observables are violated by 3.6 and by 9 standard deviations. This is interpreted as a statistically significant falsification of the whole class of nonlocal realistic theories constructed by Leggett. The IQOQI group summarizes its results with the statement "We believe that our results lend strong support to the view that any future extension of quantum theory that is in agreement with experiments must abandon certain features of realistic descriptions." It is our view, however, that this is mainly an exercise in demolishing a "strawman." Leggett's nonlocal realistic theories assume that when entangled photons emerge from their emission source, they are in a definite state of polarization. It is well known that when that assumption (and no others) is made, one does not observe the quantum mechanical prediction of Malus's Law for the correlations of the photon pair. However, Leggett solves that problem by assuming an unspecified nonlocal connection mechanism between the detection systems that fixes the discrepancy. In effect, the two measurements talk to each other nonlocally in such a way that the detected linearly polarized photons obey Malus's Law and produce the same linear polarization correlations predicted by quantum mechanics calculations. Leggett then shows that this nonlocal "fix" cannot be extended into the realm of elliptical polarization, and that quantum mechanics and this type of nonlocal realistic theories give differing predictions for the elliptic polarization correlations. In other words, the "reality" that is being tested is whether the photon source is initially emitting the entangled photons in a definite state of polarization. It is this version of "reality" that has been falsified by the IQOQI measurements. It is our view that this assumption, clearly inconsistent with the formalism of quantum mechanics, is invalid, and that nature is both nonlocal and unrealistic, if by realism one means that when entangled photons emerge from their emission source, they are in a definite state of polarization. This very restricted definition of realism is not required, and it is assumed that the intrinsic non locality of standard quantum mechanics is a physical fact. It is noted that the several polarization bases used in these kinds of polarization EPR experiments make demonstrating the quantum nonlocal connections straightforward but also make it effectively impossible to use those connections for observer-to- 3 UNCLASSIFIED//f811. 8FFUiii,r.k I.Iii O•lk¥
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Report, from the dia collection. The PDF is mirrored here; the original link is above. 32 pages are in the text index: search them above, or from the library's search.