Does Bell's theorem imply nonlocality using a false assumption

In summary, the author of the papers mentioned argues that Bell tests cannot refute local realism because they employ a wrong analysis. He claims that the quantum joint prediction cannot be recovered in an experiment with separated measurements, and that the correct quantum mechanics prediction for an EPRB experiment must use the marginals (via reduced density matrices) and not the joint distribution. He also criticizes the application of Lüders’ rule to the EPR problem, stating that it is not validly applicable and leads to the postulation of nonlocality. However, his arguments and claims are highly skeptical and may not be valid as they contradict the standard predictions of quantum mechanics and do not follow the established methods of comparison with experimental data.
  • #1
Ali Lavasani
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In https://arxiv.org/ftp/arxiv/papers/1409/1409.5158.pdf, the author (Donald A. Graft) concludes that Bell tests cannot refute local realism, because they employ a wrong analysis. He says:

"The quantum joint prediction cannot be recovered in an experiment with separated (marginal) measurements, just as for classical probability. Quantum mechanics correctly applied does not predict a violation of the CH inequality. The correct quantum mechanics prediction for an EPRB experiment must use the marginals (via reduced density matrices) and not the joint distribution. The source distribution in an EPRB experiment may be a joint one, but joint statistics cannot be recovered because the experiment yields only separated (marginal) measurements. A well-developed statistical field of study decomposes correlated joint distributions into the marginals plus an additional function called a copula. There would be no need for this field if any arbitrary joint distribution could be recovered through its marginals. Therefore, we cannot and do not apply the quantum joint prediction to EPRB experiments."

Also in https://arxiv.org/ftp/arxiv/papers/1309/1309.1153.pdf he mentions:

"Most importantly, quantum mechanics is shown to be compatible with local realism, by means of correct handling of separated systems. We cannot use the joint probability formula for cases of separated measurements; instead we use the marginals (partial traces or reduced density matrices) together with whatever priors we have from an understanding of the system. Specification of what are separated measurements is delicate but has been adequately addressed here. If we accept this small reinterpretation of quantum mechanics, nonlocality is eliminated. The experiments when correctly interpreted confirm the local realist position. Nonlocal entanglement is seen to be an error."

Another error he claims to have found is the application of Luder's rule to the EPR problem in https://arxiv.org/pdf/1607.01808.pdf. Here he says:

Lüders’ rule was developed for the treatment of ensembles [6], so its application to individual projection events is already problematic. Furthermore, by blindly applying Lüders’ rule to physical scenarios for which it is not validly applicable, such as EPR, nonlocality is in effect simply postulated by fiat, whereas Lüders’ rule is in reality not only incorrect for EPR, but is not needed to account for experiments correctly designed and analyzed. Prediction using Lüders’ rule is not a unique necessary quantum mechanical calculation for EPR. Alternative quantum mechanical calculations giving different results are available and required.

I don't completely understand this author's arguments, but I can't be convinced that all physicists have been making such basic mistakes for decades. Can anyone illuminate this case in a clear and rigorous way?
 
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  • #2
Ali Lavasani said:
Quantum mechanics correctly applied does not predict a violation of the CH inequality.

If this were true, then since the CH inequality is in fact violated in experiments, QM "correctly applied" would be falsified by experiment.

I haven't had time to read any of these papers in detail, but just from the above, I am highly skeptical that this person has actually produced a valid refutation of the standard arguments regarding the Bell Inequalities and EPR.
 
  • #3
PeterDonis said:
If this were true, then since the CH inequality is in fact violated in experiments, QM "correctly applied" would be falsified by experiment.

I haven't had time to read any of these papers in detail, but just from the above, I am highly skeptical that this person has actually produced a valid refutation of the standard arguments regarding the Bell Inequalities and EPR.
He is actually claiming that the data obtained in experiments doesn't show a violation, and I have quoted his reasons in the body of my question. I'd like to know whether he is right about the math stuff like "joint" and "marginal" probability and "use of Luder's law" used in the analysis of the data. These don't seem complex concepts to me, so I'm wondering how Bell and others haven't noticed it (if true).
 
  • #4
Ali Lavasani said:
He is actually claiming that the data obtained in experiments doesn't show a violation

The quotes you give don't give enough information to know what he's basing such a claim on. But I don't think it matters, because he doesn't get to make up his own way of comparing the standard QM predictions with experiments. The standard QM predictions already tell you how to compare them with experiments. If he has some different way of doing it, then he's not talking about standard QM, he's talking about some personal theory of his that he chooses to call "quantum mechanics".
 
  • #5
Ali Lavasani said:
I'd like to know whether he is right about the math stuff like "joint" and "marginal" probability and "use of Luder's law" used in the analysis of the data.

I couldn't say without reading the papers, and I don't know when I'll have time to do that. But my Bayesian prior is extremely high that he's making a mistake somewhere.
 
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  • #7
Thread will remain closed. Great responses by PeterDonis. :smile:
 

Related to Does Bell's theorem imply nonlocality using a false assumption

1. What is Bell's theorem and how does it relate to nonlocality?

Bell's theorem is a mathematical proof that demonstrates the existence of nonlocality in quantum mechanics. It shows that the predictions of quantum mechanics cannot be explained by any local hidden variable theory, meaning that particles can have instantaneous correlations with each other regardless of distance.

2. What is the false assumption in Bell's theorem that leads to nonlocality?

The false assumption in Bell's theorem is that local hidden variables exist, meaning that the properties of particles are predetermined and do not change based on measurements or interactions. This assumption is not supported by experimental evidence in quantum mechanics.

3. Can Bell's theorem be used to prove the existence of nonlocality?

No, Bell's theorem does not prove the existence of nonlocality. It simply demonstrates that local hidden variable theories cannot explain the behavior of particles in quantum mechanics. Nonlocality is still a topic of debate and has not been definitively proven.

4. Are there any alternative explanations for the results of Bell's theorem?

Yes, there are alternative explanations for the results of Bell's theorem. Some scientists argue that the observed correlations in quantum mechanics can be explained by a nonlocal hidden variable theory, while others propose that the results are due to the limitations of our current understanding of quantum mechanics.

5. How does the concept of nonlocality impact our understanding of the universe?

The concept of nonlocality challenges our traditional understanding of cause and effect, as it suggests that particles can have instantaneous correlations with each other regardless of distance. This has implications for our understanding of space, time, and the fundamental laws of nature. It also has potential applications in fields such as quantum computing and communication.

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