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arXiv:0810.4452

Comment on: Testing the speed of 'spooky action at a distance'

Johannes Kofler, Rupert Ursin, Brukner, Caslav, Anton Zeilinger

Published Oct 24, 2008• 0 citations
arXivHTMLPDF

Abstract

In a recent experiment, Salart et al. addressed the important issues of the speed of hypothetical communication and of reference frames in Bell-type experiments. The authors report that they "performed a Bell experiment using entangled photons" and conclude from their experimental results that "to maintain an explanation based on spooky action at a distance we would have to assume that the spooky action propagates at speeds even greater than the bounds obtained in our experiment", exceeding the speed of light by orders of magnitude. Here we show that, analyzing the experimental procedure, explanations with subluminal or even no communication at all exist for the experiment.

DOI
10.48550/arxiv.0810.4452

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In a recent experiment, Salart et al. addressed the important issues of the speed of hypothetical communication and of reference frames in Bell-type experiments. The authors report that they "performed a Bell experiment using entangled photons" and conclude from their experimental results that "to maintain an explanation based on spooky action at a distance we would have to assume that the spooky action propagates at speeds even greater than the bounds obtained in our experiment", exceeding the speed of light by orders of magnitude. Here we show that, analyzing the experimental procedure, explanations with subluminal or even no communication at all exist for the experiment.
In their well-known paper, Einstein, Podolsky, and Rosen called the nonlocal correlation in quantum entanglement a "spooky action at a distance." If the spooky action does exist, what is its speed? All previous experiments along this direction have locality and freedom-of-choice loopholes. Here, we strictly closed the loopholes by observing a 12 h continuous violation of the Bell inequality and concluded that the lower bound speed of spooky action was 4 orders of magnitude of the speed of light if Earth's speed in any inertial reference frame was less than 10(-3) time the speed of light.
Nonlocality, probably the principal friction between Quantum Physics and Relativity, disturbed the physicists even more than realism since it looks to originate superluminal signalling, the Einsteinian "Spooky action at a distance". From 2000 on, several tests to set lower bounds of the Spooky action at a distance velocity ([Formula: see text]) have been performed. They are usually based on a Bell Test performed in km long and carefully balanced experimental setups to fix a more and more improved bound making some assumptions dictated by the experimental conditions. By exploiting advances in quantum technologies, we performed a Bell's test with an improved bound in a tabletop experiment of the order of few minutes, thus being able to control parameters otherwise uncontrollable in an extended setup or in long lasting experiments.
Abstract Claims that entanglement, or non-local interaction ("spooky action-at-a-distance), has been experimentally proven are false. The claims are based entirely on the fact that the results of experiments performed to test that issue (EPR-Bohm experiments) violate various theoretical inequalities (Bell Inequalities).The various Bell Inequalities used to interpret the results of EPR-Bohm experiments are shown to be inappropriate for such experiments. The inequalities do not correctly provide for the correlation between the particles in each pair, which is the essence of such experiments; and therefore the inequalities are irrelevant. Claims that the results of such experiments, because they violate the inequalities, require the conclusion that the measurement of one particle in an "entangled" pair can instantly affect the state of its partner, even at great distances, are untrue and need to be modified.
In 1964 John Bell proved a theorem2 allowing the experimental test of whether what Einstein derided as “spooky actions at a distance” actually exist. We will see that they do. Bell's theorem can be displayed with a simple, nonmathematical thought experiment suitable for a physics course at any level. And a simple, semi-classical derivation of the quantum theory result can be given for physics students. These entanglement phenomena are today applied in industrial laboratories and are increasingly discussed in the popular literature. Unfortunately, they are also misappropriated by the purveyors of pseudoscience, something physicists have a responsibility to address.3 Students can be intrigued by the quantum strangeness physics has encountered at a boundary of our discipline.