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arXiv:2405.05869

Comment on: Testing the speed of the spooky action at a distance in a tabletop experiment. [Sci Rep 13, 8201 (2023)]

Bruno Cocciaro, S. Faetti, Leone Fronzoni

Published May 9, 2024• 0 citations
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Abstract

In 1989, Eberhard proposed a v-causal model where quantum correlations between entangled particles are established by communications moving at a superluminal speed v_t > c in a preferred frame. In successive years, several experiments established lower bounds for the possible tachyons velocities. In a recent paper, Luigi Santamaria Amato et al. performed an interesting east-west aligned tabletop experiment under the assumption that the preferred frame is the Cosmic Microwave Background (CMB). In that paper, they criticize long-distance experiments but here we show that most of their criticisms are not applicable to long-distance tunnel experiments where the highest lower bound was obtained.

DOI
10.48550/arxiv.2405.05869

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In 1989, Eberhard proposed a v-causal model where quantum correlations between entangled particles are established by communications moving at a superluminal speed v_t > c in a preferred frame. In successive years, several experiments established lower bounds for the possible tachyons velocities. In a recent paper, Luigi Santamaria Amato et al. performed an interesting east-west aligned tabletop experiment under the assumption that the preferred frame is the Cosmic Microwave Background (CMB). In that paper, they criticize long-distance experiments but here we show that most of their criticisms are not applicable to long-distance tunnel experiments where the highest lower bound was obtained.
As shown in the famous EPR paper (Einstein, Podolsky e Rosen, 1935), Quantum Mechanics is non-local. The Bell theorem and the experiments by Aspect and many others, ruled out the possibility of explaining quantum correlations between entangled particles using local hidden variables models (except for implausible combinations of loopholes). Some authors (Bell, Eberhard, Bohm and Hiley) suggested that quantum correlations could be due to superluminal communications (tachyons) that propagate isotropically with velocity v t > c in a preferred reference frame. For finite values of v t , Quantum Mechanics and superluminal models lead to different predictions. Some years ago a Geneva group and our group did experiments on entangled photons to evidence possible discrepancies between experimental results and quantum predictions. Since no discrepancy was found, these experiments established only lower bounds for the possible tachyon velocities v t . Here we propose an improved experiment that should lead us to explore a much larger range of possible tachyon velocities V t for any possible direction of velocity of the tachyons preferred frame.
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.
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.
Bell experiments constrain local/common-cause explanations of quantum correlations under the corresponding assumptions. A distinct experimental program tests a more specific class of models in which the observed nonlocal correlations are explained by a hidden causal influence propagating in a preferred frame between spatially separated events at a finite superluminal speed c<v<∞. Yin et al. obtained a lower bound of order 104c for the corresponding finite-speed preferred-frame model; Bancal et al. showed that, for the finite-speed causal-influence model class they studied, choosing an arbitrarily large but finite v does not remove the problem of operational superluminal signalling; Santamaria Amato et al. demonstrated a tabletop feasibility speed-bound scheme in the CMB frame; Li, Hu, Deng, and Scarani proposed cluster-state witnesses for a more direct test of finite-speed hidden-influence models. The present work examines how this experimentally tested model class relates to the current Bell/EPR interpretation of the Theory of Harmonic Field Resonance (THFR). The central structural comparison is that, in THFR, the Bell/EPR correlation is not modelled as a hidden influence propagating from one already realized detector event to another through effective spacetime. Therefore, experimental lower bounds on finite-speed hidden influence are not lower bounds on a fundamental “THFR Bell speed.” For the purposes of this work, a structural class of Bell/EPR models compatible with the current THFR causal architecture is defined. At the level of the Bell-binding mechanism, this class is disjoint by construction from the finite-speed hidden-influence class, because the latter requires a finite superluminal propagation parameter v and a corresponding influence-cone structure, whereas the THFR class does not employ such objects for Bell binding. The established correspondence has the epistemic status EXTERNAL STRUCTURAL CORRESPONDENCE. The work is a theoretical model-class comparison and does not present a quantitative derivation of Bell statistics from the mathematical apparatus of THFR.
Quantum mechanics is a non local theory. To recover the locality principle some physicists suggested that the correlations between entangled particles could be established by communications propagating with a velocity v t > c in a preferred frame. In the previous DICE conference we reported the preliminary results of a high sensitivity experiment to test the superluminal models. Here we report the final results. No breaking of the quantum predictions has been found. Then, we infer that the velocity of the quantum communications has to be higher than a lower bound of the order of some millions of times the light velocity.
As shown in the EPR paper (Einstein, Podolsky e Rosen, 1935), Quantum Mechanics is a non-local Theory. The Bell theorem and the successive experiments ruled out the possibility of explaining quantum correlations using only local hidden variables models. Some authors suggested that quantum correlations could be due to superluminal communications that propagate isotropically with velocity v t > c in a preferred reference frame. For finite values of v t and in some special cases, Quantum Mechanics and superluminal models lead to different predictions. So far, no deviations from the predictions of Quantum Mechanics have been detected and only lower bounds for the superluminal velocities v t have been established. Here we describe a new experiment that increases the maximum detectable superluminal velocities and we give some preliminary results.