The concept of realism in quantum mechanics means that results of measurement are caused by physical variables, hidden or observable. Local hidden variables were proved unable to explain results of measurements on entangled particles tested far away from one another. Then, some physicists embraced the idea of nonlocal hidden variables. The present article proves that this idea is problematic, that it runs into an impasse vis-à-vis the special relativity.
The concept of realism in quantum mechanics means that results of measurement are caused by physical variables, hidden or observable. Local hidden variables were proved unable to explain results of measurements on entangled particles tested far away from one another. Then, some physicists embraced the idea of nonlocal hidden variables. The present article proves that this idea is problematic, that it runs into an impasse vis-à-vis the special relativity.
Quantum mechanics is widely believed to be inconsistent with local realism because J.S. Bell proved the contradiction between quantum mechanics and the hidden variable theories based on reality and locality of matter. As described herein, the relation between quantum mechanics and local realism is discussed. This paper presents the question of whether any version of local realism is contradicted by quantum mechanics. The answer is negative. An interpretation is proposed by which the contradiction is explained using physical variables of two types: (1) physical variables of the first type, such as positions and angles (i.e. coordinates), are realistic variables and always possess definite values independently of measurements; (2) those of the second type, such as momenta, angular momenta, and spins (i.e., conserved quantities), are non-realistic variables, which possess no value before measurement. Value definiteness of the first type provides a reliable basis to physical reality of matter, and non-reality of the second type might solve the problem of inconsistency between quantum mechanics and local realism.
Accepting nonlocal quantum correlations requires us to reject special relativity and/or probability theory. We can retain both by revising our interpretation of quantum mechanics regarding the handling of separated systems, as quantum mechanics conflicts with local realism only in its treatment of separated systems. We cannot use the joint probability formula for cases of separated measurements. We use the marginals (partial traces) together with whatever priors we have from an understanding of the system. This program can reconcile quantum mechanics with local realism. An apparent obstacle to this program is the experimental evidence, but we argue that the experiments have been misinterpreted, and that when correctly interpreted they confirm local realism. We describe a local realistic account of one important Einstein-Poldosky-Rosen-Bohm (EPRB) experiment (Weihs et al6) that claims to demonstrate nonlocal entanglement. We present a local realistic system (experiment) that can be calibrated into both quantum and classical correlation domains via adjustment of parameters (‘hidden variables’) of the apparatus. Weihs incorrectly dismisses these parameters as uncritical. Nonlocal entanglement is seen to be an error. The rest of quantum mechanics remains intact, and remains highly valued as a powerful probability calculus for observables. Freed from the incoherent idea of nonlocal entanglement, we can leverage powerful classical ideas, such as semiclassical radiation theory, stochastic dynamics, classical noncommutativity/contextuality, measurement effects on state, etc., to augment or complement quantum mechanics. When properly interpreted and applied, quantum mechanics lives in peaceful harmony with the local realist conception, and both perspectives offer useful paradigms for describing systems.
Explaining observations in terms of cause-and-effect (causal) relations is central to empirical science. However, in his seminal 1964 work [1], John Bell showed that the correlations between entangled quantum systems cannot be explained in terms of, possibly hidden, cause and effect relations. After four decades of experimental effort, Bell's prediction has recently been confirmed in an unambiguous way by a series of loophole-free Bell-test experiments [2-4]. These experiments, however, cannot reveal where exactly quantum mechanics breaks with our classical notion of cause and effect. Specifically, Bell's theorem is based on the central assumptions of realism and local causality. Realism posits that physical systems have real, objective properties, independent of whether we observe them or not, and local causality assumes that causal influences cannot propagate faster than the speed of light.
Local realism reduces to the proposition that local determinate reality is the necessary and sufficient cause of every physical effect. By any standard account, quantum theory requires that local realism is false, because it embeds the famously spooky premise that some physical effects require causes that are instantly effective from arbitrarily far away. Nonetheless, quantum theory has replaced local realism as the foundation of science because, whereas local realism allegedly cannot violate the Bell inequality, quantum theory is taken to do so in accord with experiments. Here we prove, however, that an epistemic contextual model of local realism solves a puzzle about independent random measurements of local hidden variables in a way that causally explains observed Bell violations. We also reveal exactly how the Bell inequality fails to represent the local realistic prediction. Finally, we show that any theory that denies local realism comprises an unfalsifiable causal claim that is freely adjustable to make arbitrary predictions, which thus provide no validation of its causal claim. Results revitalize the hypothesis that local realism prevails. Keywords: Local Realism. Bell Violations. Photons. Entanglement. Quantum Physics.
A new interpretation of quantum mechanics is presented in which there is one hidden variable. This could be described as “partial realism” where sometimes quantum variables have real values before we measure and sometimes they don’t. While one hidden variable is insufficient to explain Bell nonlocality, it is allowed by Bell’s inequality. This can help solve the measurement problem and is in principle testable. In addition, a theory of nonlocality emerges directly from this assumption. From the perspective of an outside observer, not correlated with an observed system, we treat all interactions within the system as unitary. However, from the perspective of an “observer” inside the system, we treat all new entanglements as “micromeasurements”, as a projection onto some basis of measurement. One particle can act as a measurement device on another and give the other particle a defined value on one possible measurement axis from an inside perspective. This means that the wave function, from the outside view, will at times describe an objective, fundamentally stochastic uncertainty, at other times a subjective uncertainty that reflects only our lack of knowledge, and at yet other times a combination of both. The standard wave function describes the total uncertainty, the minimal uncertainty that is present for any observer outside of the system, whereas for an “observer” inside the system, only the objective, fundamentally stochastic part of the uncertainty remains, and this can be described by an inner wave function. The hidden variable is invisible to the outside observer.
Local realism is causation by ordinary causal signals. What we mean by ordinary is this. First, these signals have fully determinate properties, whether measured or not. Second, they can only cause effects precisely at the spacetime locality of their physical existence. By contrast, as Einstein famously observed, quantum causal signals are spooky because they can cause effects where they do not in fact exist. Indeed, the only evidence that quantum causal signals possess any physical existence at all is that they seem to explain every effect you could ever measure. Unless you think about it. Take the simplest case: One photon, one spin measurement, up or down. The quantum explanation is essentially that we draw the answer from a bag that contains no answers such that physical reality obtains precisely from its own absence. This is known as the problem. But the problem is obviously not measurement. The problem is that quantum theory has literally no explanation for any specific measurement result. On the other hand, local realism does. Spin Up and Spin Down for photons must, at the end of the day, be analogous to Heads Up and Heads Down for ordinary fair coins. The quantum counterclaim, here, is that there is no compelling solution set of local hidden variables that makes this analogy work for an EPR experiment. Furthermore, many claim that the Bell inequality rules out any such solution set. On the other hand, anyone who thinks that the Bell inequality has some single uncontested meaning has not been reading the literature. The paper noted below claims both to provide local hidden variables that constitute a compelling local realistic solution for an EPR experiment and to explain how such solutions have been falsely denied. See viXra:1704.0078 - Local Realism Explains Bell Violations - for a demonstration that all empirical evidence taken to support quantum theory over local realism plausibly does the reverse. The article comprises 8 pages, 4 figures, 6 equations, 32 references, a graph of testable predictions, and two paragraphs that purport to expose how the Bell inequality misrepresents the local realistic predictions for the EPR experiment. Thoughtful feedback appreciated (apyake@gmail.com).