arXiv subjects

Marian Kupczynski

Publications and source records attributed to Marian Kupczynski.

At least 19 recordsLinked to original sources

arXiv2026

Comment on Consequences of the single-pair measurement of the Bell parameter

Genovese and Piacentini [Phys.Rev.A 111, 022204 (2025)] claim that in a recent experiment[S.Virzì et al., Quantum Sci. Technol. 9, 045027 (2024)] the Bell parameter was measured on a single pair of photons thus it challenges several conclusions and discussions on the meaning of Bell inequalities as well as certain QM interpretations. We explain that the parameter measured in Virzi et al. experiment it is not the Bell parameter S which was discussed and estimated in many loophole free tests. Therefore, this experiment neither challenges our understanding of Bell Tests nor allows having doubts about Bohr complementarity and contextuality.

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arXiv2025

Statistical Contextual Explanation of Quantum Paradoxes

We celebrate this year hundred years of quantum mechanics but there is still no consensus regarding its interpretation and limitations. In this article we advocate the statistical contextual interpretation which is free of paradoxes. State vectors and various operators are purely mathematical entities allowing making quantitative probabilistic predictions. State vector describes an ensemble of identically prepared physical systems and a specific operator represents a class of equivalent measurements of a physical observable. A collapse of wave function is not a mysterious and instantaneous physical process. A collapsed quantum state describes a new ensemble of physical systems prepared in a particular way. Probabilities are objective properties of random experiments in which empirical frequencies stabilize. Therefore, quantum probabilities do not provide a complete description of individual physical systems and their interactions. Whether these probabilities can be explained as emergent is an open question which cannot be settled by philosophical discussions and no-go theorems. It can be only answered by more detailed study of experimental data then it is usually done. Bell Tests allowed rejecting Bell local and Bell causal hidden variable models but we even don't know whether quantum probabilities provide a complete description of existing experimental data. Time series of experimental data may contain much more information than it is obtained using empirical frequencies and histograms. Therefore, predictable completeness of quantum mechanics has be tested and not taken for granted.

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arXiv2024

Quantum Nonlocality: how does Nature do it?

In his article in Science, Nicolas Gisin claimed that quantum correlations emerge from outside space time. We explain that they are due to space time symmetries. This paper is a critical review of metaphysical conclusions found in many recent articles. It advocates the importance of contextuality, Einstein causality and global symmetries. Bell tests allow only rejecting probabilistic coupling provided by a local hidden variable model, but they do not justify metaphysical speculations about quantum nonlocality and objects which know about each other state, even when separated by large distances. The violation of Bell inequalities in physics and in cognitive science can be explained using the notion of Bohr contextuality. If contextual variables, describing varying experimental contexts, are correctly incorporated into a probabilistic model, then the Bell and CHSH inequalities cannot be proven and nonlocal correlations may be explained in an intuitive way. We also elucidate the meaning of statistical independence assumption incorrectly called free choice, measurement independence or no conspiracy. Since correlation does not imply causation, the violation of statistical independence should be called contextuality and it does not restrict the experimenter freedom of choice. Therefore, contrary to what is believed, closing the freedom of choice loophole does not close the contextuality loophole.

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arXiv2023

My discussions of quantum foundations with John Stewart Bell

In 1976, I met John Bell several times in CERN and we talked about a possible violation of optical theorem, purity tests, EPR paradox, Bell inequalities and their violation. I review our discussions, and explain how they were related to my earlier research. I also reproduce handwritten notes, which I gave to Bell during our first meeting and a handwritten letter he sent to me in 1982. We have never met again, but I have continued to discuss BI-CHSH inequalities and their violation in several papers. The research stimulated by Bell papers and experiments performed to check his inequalities led to several important applications of quantum entanglement in quantum information and quantum technologies. Unfortunately, it led also to extraordinary metaphysical claims and speculations about quantum nonlocality and retro-causality, which in our opinion John Bell would not endorse today. BI-CHSH inequalities are violated in physics and in cognitive science, but it neither proved the completeness of quantum mechanics nor its nonlocality. Quantum computing advantage is not due to some magical instantaneous influences between distant physical systems. Therefore one has to be cautious in drawing far-reaching philosophical conclusions from Bell inequalities.

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arXiv2023

Response: Kupczynski Contextual Locally Causal Probabilistic Models are constrained by Bell theorem

In our contextual model, statistical independence is violated, thus it is not constrained by Bell Theorem. Individual outcomes are created locally in a deterministic way in a function of setting dependent variables describing measuring instruments and variables describing physical systems, at the moment of their interactions. These setting dependent variables may be correlated, but not necessarily due to spooky influences or superdeterminism. In several Bell Tests, two time series of distant clicks are converted into finite samples containing pairs of non zero outcomes. This data not only violates CHSH inequalities but also nonsignalling. Our model allows explaining both the raw and the final data in these experiments. Moreover, our model, does not compromise experimenters freedom of choice. The violation of nonsignaling is neither consistent with quantum description of an ideal EPRB experiment nor with standard local realistic and stochastic hidden variable models, thus the title of this article and its conclusion: Kupczynski escape route for local realism is not available are misleading.

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arXiv2023

Contextuality or nonlocality; what would John Bell choose today?

A violation of Bell-CHSH inequalities does not justify speculations about quantum non-locality, conspiracy and retro-causation. Such speculations are rooted in a belief that setting dependence of hidden variables in a probabilistic model, called a violation of measurement independence, would mean a violation of experimenters freedom of choice. This belief is unfounded because it is based on a questionable use of Bayes Theorem and on incorrect causal interpretation of conditional probabilities. In Bell-local realistic model, hidden variables describe only photonic beams created by a source, thus they cannot depend on randomly chosen experimental settings. However, if hidden variables describing measuring instruments are correctly incorporated into a contextual probabilistic model a violation of inequalities and an apparent violation of no-signaling reported in Bell tests can be explained without evoking quantum nonlocality. Therefore, for us, a violation of Bell-CHSH inequalities proves only that hidden variables have to depend on settings confirming contextual character of quantum observables and an active role played by measuring instruments. Bell thought that he had to choose between nonlocality and the violation of experimenters freedom of choice. From two bad choices he chose nonlocality. Today he would probably choose the violation of statistical independence understood as contextuality.

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arXiv2023

Commentary: Is the moon there if nobody looks -- Bell inequalities and physical reality

Marian Kupczynski(MK)is the author of a controversial paper published (2020) in the journal Frontiers in Physics. The work is built around a mathematical claim by MK which is actually false, and MK's logical reasoning around his claim is also incorrect. The same claim was made by him in several other recent papers published in other journals. A proof that the claimed result is false is the main content of our present "Comment". It is purely a mathematical counter-example to a mathematical claim in a number of MK's papers.

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arXiv2022

Is the Moon there if nobody looks: A reply to Gill and Lambare

In a recent preprint Gill and Lambare, criticize our paper published in Frontiers in Physics. Their criticism is unfounded and misleading. They define a probabilistic coupling, in which BI-CHSH hold for all finite samples. It does not mean, that BI-CHSH hold in our model, in which four incompatible experiments are described by setting dependent random variables implemented on 4 disjoint dedicated probability spaces. A joint probability distribution of these random variables does not exist and may not be used to derive inequalities. Moreover, their probabilistic coupling is useless, for a subsequent contextual model, which we construct to describe final data from Bell tests and to explain, in a locally causal way, the reported violations of inequalities and apparent violations of no-signaling. Neither quantum probabilistic model of an ideal EPRB experiment nor local realistic and stochastic hidden variable models may explain reported non-signaling Therefore; it is obvious that our model extends the set of probability distributions of possible measurements allowed in the standard hidden variable models. Gill and Lambare seem not understand , the main message of our paper, that the violation of BI-CHSH and Eberhard inequalities by finite samples in Bell Tests, no matter how well these tests are designed and performed, does not allow for doubt regarding the existence of objective external physical reality and causal locality in Nature. Our contextual model does not want to circumvent Bell Theorem. Therefore the title of Gill and Lambare paper and the conclusion: Kupczynski's escape route for local realism is not available are misleading and have nothing to do with the content and conclusions of our paper.

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arXiv2022

Comment on Causal Networks and Freedom of Choice in Bell's Theorem

Bell inequalities may only be derived, if hidden variables do not depend on the experimental settings. The stochastic independence of hidden and setting variables is called: freedom of choice, free will, measurement independence or no conspiracy. By imbedding the Bell causal structure in a larger causal network the authors correctly prove, that one can explain and quantify possible violation of measurement independence without evoking the super-determinism. They assume the independence of the variables that causally determine the settings and investigate how they might become correlated with hidden variables. Using their extended causal networks they derive a contextual probabilistic model on which their further correct results are based. The authors seem to ignore that contextual probabilistic model may be derived directly using only probabilistic concepts and incorporating correctly setting dependent variables describing measuring instruments. In these contextual probabilistic models experimenters freedom of choice is not compromised and the results of Bell Tests including an apparent violation of Einsteinian nonsignaling may be explained in a locally causal way. Talking about freedom of choice is misleading and is rooted in incorrect understanding of Bayes Theorem. We explain why freedom of choice should be called noncontextuality and why its violation in Bell Tests confirms only the contextual character of quantum observables. Therefore, contextuality and not experimenters freedom of choice are important resources in quantum information.

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arXiv2021

Contextuality-by-Default description of Bell tests: Contextuality as the rule not as an exception

Contextuality and entanglement are valuable resources for quantum computing and quantum information. Bell inequalities are used to certify entanglement; thus, it is important to understand why and how they are violated. Quantum mechanics and behavioral sciences teach us that random variables measuring the same content (the answer to the same Yes or No question) may vary, if measured jointly with other random variables. Alice and Bob raw data confirm Einsteinian non-signaling, but setting dependent experimental protocols are used to create samples of coupled pairs of distant outcomes and to estimate correlations. Marginal expectations, estimated using these final samples, depend on distant settings. Therefore, a system of random variables measured in Bell tests is inconsistently connected and it should be analyzed using a Contextuality-by-Default approach, what is done for the first time in this paper. The violation of Bell inequalities and inconsistent connectedness may be explained using a contextual locally causal probabilistic model in which setting dependent variables describing measuring instruments are correctly incorporated. We prove that this model does not restrict experimenters freedom of choice which is a prerequisite of science. Contextuality seems to be the rule and not an exception; thus, it should be carefully tested.

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arXiv2021

Entanglement and Quantum Nonlocality Demystified

Quantum nonlocality is presented often as the most remarkable and inexplicable phenomenon known to modern science which was confirmed in the experiments proving the violation of Bell Inequalities (BI). It has been known already for a long time that the probabilistic models used to prove BI for spin polarization correlation experiments (SPCE) are incompatible with the experimental protocols of SPCE. In particular these models use a common probability space together with joint probability distributions for various incompatible coincidence experiments and/or conditional independence (Bell's locality). Strangely enough these results are not known or simply neglected. Therefore so called Bell's or quantum nonlocality has nothing to do with the common notion of the non-locality and it should be rather called quantum non-Kolmogorovness or quantum contextuality. We quickly explain the true meaning of various Bell's locality assumptions and show that if local variables describing the measuring instruments are correctly taken into consideration then BI can no longer be proven. Of course we do not question the usefulness of the long range correlations characterizing the entangled physical systems in the domain of Quantum Information. However one should not forget that the anti-correlations cannot be perfect, that the wave function should not be treated as an attribute of the individual quantum system which can be change instantaneously and that the unperformed experiments have no results.

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arXiv2021

A comment on: the violations of locality and free choice are equivalent resources in Bell experiments

In a recent paper published in PNAS authors prove that locality and free choice are equivalent resources which need to be relaxed in order to fully reproduce some statistics in Bell experiments (while always maintaining realism). We explain that their assumption of free choice is simply counterfactual definiteness or noncontextuality. Therefore the resource in Bell experiments is contextuality and not the violations of locality and/or of free choice. It is definitely less mind boggling conclusion because experimenters` freedom of choice is a prerequisite of science,

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arXiv2020

Is the Moon there if nobody looks: Bell Inequalities and Physical Reality

Various Bell inequalities are trivial algebraic properties satisfied by each line of particular data spreadsheets.It is surprising that their violation in some experiments, allows to speculate about the existence of nonlocal influences in Nature and to doubt the existence of the objective external physical reality. Such speculations are rooted in incorrect interpretations of quantum mechanics and in a failure of local realistic hidden variable models to reproduce quantum predictions for spin polarisation correlation experiments. These hidden variable models use counterfactual joint probability distributions of only pairwise measurable random variables to prove the inequalities. In real experiments Alice and Bob, using 4 incompatible pairs of experimental settings, estimate imperfect correlations between clicks, registered by their detectors. Clicks announce detection of photons and are coded by 1 or -1. Expectations of corresponding ,only pairwise measurable, random variables are estimated and compared with quantum predictions. These estimates violate significantly the inequalities. Since all these random variables cannot be jointly measured , a joint probability distribution of them does not exist and various Bell inequalities may not be derived. Thus it is not surprising that they are violated. Moreover,if contextual setting dependent parameters describing measuring instruments are correctly included in the description, then imperfect correlations between the clicks may be explained in a locally causal way. In this paper we review and rephrase several arguments proving that the violation of various Bell inequalities may neither justify the quantum nonlocality nor allow for doubt regarding the existence of atoms, electrons and other invisible elementary particles which are building blocks of the visible world around us including ourselves.

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arXiv2020

Contextuality as the Key to understand Quantum Paradoxes

This short note is an introduction to the slides from our talks given in 2018 during the Advanced School of Quantum Foundations and Quantum Computation in Joao Pessoa , Brazil. In these talks, addressed to participants with a limited knowledge of quantum foundations, we defined locality, causality, randomness, counterfactual definiteness and we explained EPR-Bohm paradoxes. In particular we discussed in great detail various Bell-type inequalities and the implications of their violation in spin polarisation correlation experiments. Finally we explained why and how the predictive completeness of quantum mechanics may be tested by more careful examination of the time-series of experimental data

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arXiv2018

Quantum Mechanics and modelling of physical reality

Quantum mechanics led to spectacular technological developments, discovery of new constituents of matter and new materials. However there is still no consensus on its interpretation and limitations. Some scientists and scientific writers promote some exotic interpretations and evoke quantum magic. In this paper we point out that magical explanations mean the end of the science. Magical explanations are misleading and counterproductive. We explain how a simple probabilistic locally causal model is able to reproduce quantum correlations in Bell tests. We also discuss difficulties of mathematical modelling of the physical reality and dangers of incorrect mental images. We examine in detail when and how a probabilistic model may describe completely a random experiment. We give some arguments in favor of contextual statistical interpretation of quantum mechanics. We conclude that we still do not know whether the quantum theory provides a complete description of physical phenomena and we explain how it may be tested. We also point out that there remain several open questions and challenges which we discuss in some detail. In particular there is still no consensus about how to reconcile quantum theory with general relativity and cosmology.

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arXiv2017

Is Einsteinian no-signalling violated in Bell Tests?

Relativistic invariance is a physical law verified in several domains of physics. The impossibility of faster than light influences is not questioned by quantum theory. In quantum electrodynamics, in quantum field theory and in the standard model relativistic invariance is incorporated by construction. Quantum mechanics predicts strong long range correlations between outcomes of spin projection measurements performed in distant laboratories. In spite of these strong correlations marginal probability distributions should not depend on what was measured in the other laboratory what is called shortly: non-signalling. In several experiments, performed to test various Bell-type inequalities, some unexplained dependence of empirical marginal probability distributions on distant settings was observed . In this paper we demonstrate how a particular identification and selection procedure of paired distant outcomes is the most probable cause for this apparent violation of no-signalling principle. Thus this unexpected setting dependence does not prove the existence of superluminal influences and Einsteinian no-signalling principle has to be tested differently in dedicated experiments. We propose a detailed protocol telling how such experiments should be designed in order to be conclusive. We also explain how magical quantum correlations may be explained in a locally causal way.

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arXiv2017

Can we close the Bohr-Einstein quantum debate?

Recent experiments allowed concluding that Bell-type inequalities are indeed violated thus it is important to understand what it means and how can we explain the existence of strong correlations between outcomes of distant measurements. Do we have to announce that: Einstein was wrong, Nature is nonlocal and nonlocal correlations are produced due to the quantum magic and emerge, somehow, from outside space time? Fortunately such conclusions are unfounded because if supplementary parameters describing measuring instruments are correctly incorporated in a theoretical model then Bell-type inequalities may not be proven .We construct a simple probabilistic model explaining these correlations in a locally causal way. In our model measurement outcomes are neither predetermined nor produced in irreducibly random way. We explain in detail why, contrary to the general belief; an introduction of setting dependent parameters does not restrict experimenters' freedom of choice. Since the violation of Bell-type inequalities does not allow concluding that Nature is nonlocal and that quantum theory is complete thus the Bohr-Einstein quantum debate may not be closed. The continuation of this debate is not only important for a better understanding of Nature but also for various practical applications of quantum phenomena.

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arXiv2016

What do we learn from computer simulations of Bell experiments?

Contrary to counterfactual definiteness quantum theory teaches us that measuring instruments are not passively reading predetermined values of physical observables. Counterfactual definiteness allows proving Bell inequalities. If the contextual character of quantum measurements is correctly taken into account the proofs of these inequalities may not be done. In recent computer simulations of idealized Bell experiment predetermined successive outcomes of measurements for each setting and predetermined time delays of their registrations are calculated. Time windows and time delays are used to select various samples. Correlations, estimated using these selected samples are consistent with the predictions of quantum theory and the time window dependence is similar to the dependence observed in some real experiments. It is an important example how correlations can be explained without evoking quantum non-locality. However by using a suitable post-selection one may prove anything. Since before the post-selection generated samples may not violate Bell inequalities as significantly as finite samples generated using quantum predictions thus one may not conclude that counterfactual definiteness is not able to distinguish classical from quantum physics. Moreover we show that for each choice of a time window there exists a contextual hidden variable probabilistic model consistent with the post-selection procedure used by the authors what explains why they are able to reproduce quantum predictions.

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