I A new realistic stochastic interpretation of Quantum Mechanics

[PAllen]

TL;DR

I attended a lecture that discussed the approach in the 3 papers listed below. It seems to be a genuinely new interpretation with some interesting features and claims.

These papers claim to present a realistic stochastic interpretation of quantum mechanics that obeys a stochastic form of local causality. (A lecture I recently attended mentioned these papers). It also claims the Born rule as a natural consequence rather than an assumption. This appears to me to be a genuinely new interpretation. I have not delved into the papers in detail, but figured some people here may be interested.

https://arxiv.org/abs/2302.10778
https://arxiv.org/abs/2309.03085
https://arxiv.org/abs/2402.16935

 

[DrChinese]

I saw the last of these papers when it was dropped into Arxiv a few days ago. The first thing I look for is their treatment of remote Entanglement Swapping* and GHZ**. These are some of the strongest experiments against all forms of local realism. If you aren't addressing these, then you really can't make any useful/serious claims in today's environment.

Of course, those seminal works aren't mentioned at all. (There is a passing GHZ reference, but it is not discussed at all.) The main idea of the paper seems to be to define local causality in a very specific manner, then deny that. Well, experiment reigns supreme. I will give this a better look once modern (last 30 years) experiments are explained in terms of the new interpretation. This paper is closer to 1980's era ideas. ***


*In these experiments, distant photons are entangled (and violate a Bell inequality) that have never existed in a common backward light cone. Pretty hard to get locality with that.

**In these experiments, each and every individual run violates realism (since he assumes locality). The quantum prediction is exactly opposite the realistic prediction, and experiment matches QM.

***Note that everyone already agrees that there is signal locality; and that the many demonstrations of quantum nonlocality are probabilistic, and therefore do not constitute evidence of what might be labeled as "causal" anyway.

 

[pines-demon]

I saw the last of these papers when it was dropped into Arxiv a few days ago. The first thing I look for is their treatment of remote Entanglement Swapping* and GHZ**. These are some of the strongest experiments against all forms of local realism. If you aren't addressing these, then you really can't make any useful/serious claims in today's environment.

Why do you have so high regard of entanglement swapping?

 

[gentzen]

Of course, those seminal works aren't mentioned at all. (There is a passing GHZ reference, but it is not discussed at all.) The main idea of the paper seems to be to define local causality in a very specific manner, then deny that. Well, experiment reigns supreme. I will give this a better look once modern (last 30 years) experiments are explained in terms of the new interpretation. This paper is closer to 1980's era ideas.

Given that those paper talk about "a new formulation of quantum theory, alongside the Hilbert-space, path-integral, and quasiprobability formulations", my guess is that this is not the most suitable metric for evaluating the usefulness of this new formulation.
The pure formalism presented in the two older papers suffered from an unclear status of causal locality. I have not studied the newest paper in any detail yet, but if it manages to overcome this problem, then it constitutes nice incremental progress for this new formulation.

 

[PeroK]

Don't we have enough interpretations already? Unless something is making testable predictions then what is the point? Mathematically I'm sure you can cook things an infinite number of ways.

 

[gentzen]

Don't we have enough interpretations already? Unless something is making testable predictions then what is the point? Mathematically I'm sure you can cook things an infinite number of ways.

Indeed, this is the point that Barandes will have to address. (Edit: Well, actually not new predictions, just new applications.) And certainly he tries, but I have no idea yet whether he came closer to an answer. Note however that most interpretations are based on the Hilbert-space formulation, so a new formulation based on a different foundation is not necessarily bad. But also the path-integral formulation had to justify itself by applications which it handles better than the simpler Hilbert-space formulation. This will be the relevant metric in the end for Barandes' new formulation.

 

[A. Neumaier]

Unless something is making testable predictions then what is the point?

How can an interpretation of an existing theory make testable predictions different from that theory?

 

[A. Neumaier]

GHZ**.
[...]
**In these experiments, each and every individual run violates realism (since he assumes locality). The quantum prediction is exactly opposite the realistic prediction, and experiment matches QM.

What do you say to the following statement, which seems contrary to your claims? (taken from p.6-7 of M. Kupczynski, Quantum Nonlocality: how does Nature do it? Entropy 26 (2024), 191.)

“Local realism, i.e., realism plus relativistic limits on causation, was debated by Einstein and Bohr using metaphysical arguments, and recently has been rejected by Bell tests” [14]. Such a conclusion is imprecise, misleading and has been a source of unfounded speculations about quantum magic.

As Wiseman correctly pointed out in [46]: “the usual philosophical meaning of “realism” is the belief that entities exist independent of the mind, a worldview one might expect to be foundational for scientists.” This point of view was also shared by Bell, who was in fact a realist [38,55,56]. The local realism should be rather called local determinism (LD) or counterfactual definiteness (CFD) [38,46] and defined as follows: results of any measurement on an individual system are predetermined by some ontic properties, which have definite values, whether they are measured or not.

 

[lodbrok]

Don't we have enough interpretations already? Unless something is making testable predictions then what is the point? Mathematically I'm sure you can cook things an infinite number of ways.

The point is Conceptual clarity. Besides, it hints at opportunities for testable predictions and new applications. I've only read the first paper, but it's solid work—a highly recommended read, in my opinion.

 

[DrChinese]

Why do you have so high regard of entanglement swapping?

Because these can be configured to demonstrate a lot of no-go's and/or correlations that defy the usual spacetime and ordering conventions while violating a Bell inequality (such as CHSH).

Here is one in which "...the resulting correlations between particles that do not share any common past are
strong enough to violate a Clauser-Horne-Shimony-Holt (CHSH) inequality". In other words, the final entangled pairs (photons 1 & 4) have never been close enough to each other for a hidden signal or other mutual rapport to be established between them at light speed or less. So this is a very unambiguous demonstration of quantum nonlocality.

High-fidelity entanglement swapping with fully independent sources
"Entanglement swapping allows to establish entanglement between independent particles that never
interacted nor share any common past."

Field test of entanglement swapping over 100-km optical fiber with independent 1-GHz-clock sequential time-bin entangled photon-pair sources
"Entanglement swapping is a unique feature of quantum physics. By entangling two independent parties that have never interacted before, entanglement swapping has been used in the study of physics foundations such as nonlocality and wave-particle duality. ... The integrity of an experimental realization of entanglement swapping is ensured only by satisfying these criteria: proper causal disconnection between relevant events, and independent quantum sources without common past."

You can even choose to entangle the target photons after the fact with these experiments. In all cases, the order of the observations and the swap make no difference to the statistical outcome.

So yes, I like these experiments a lot. I go straight to the references to check. When they are omitted from consideration, it is a sure sign - after discussing traditional (i.e. older) Bell tests - that this is where they stumble. So not much point in reading their "hand-waving". The OP references are a good example.

 

[pines-demon]

Because these can be configured to demonstrate a lot of no-go's and/or correlations that defy the usual spacetime and ordering conventions while violating a Bell inequality (such as CHSH).

Here is one in which "...the resulting correlations between particles that do not share any common past are
strong enough to violate a Clauser-Horne-Shimony-Holt (CHSH) inequality". In other words, the final entangled pairs (photons 1 & 4) have never been close enough to each other for a hidden signal or other mutual rapport to be established between them at light speed or less. So this is a very unambiguous demonstration of quantum nonlocality.

High-fidelity entanglement swapping with fully independent sources
"Entanglement swapping allows to establish entanglement between independent particles that never
interacted nor share any common past."

Field test of entanglement swapping over 100-km optical fiber with independent 1-GHz-clock sequential time-bin entangled photon-pair sources
"Entanglement swapping is a unique feature of quantum physics. By entangling two independent parties that have never interacted before, entanglement swapping has been used in the study of physics foundations such as nonlocality and wave-particle duality. ... The integrity of an experimental realization of entanglement swapping is ensured only by satisfying these criteria: proper causal disconnection between relevant events, and independent quantum sources without common past."

You can even choose to entangle the target photons after the fact with these experiments. In all cases, the order of the observations and the swap make no difference to the statistical outcome.

So yes, I like these experiments a lot. I go straight to the references to check. When they are omitted from consideration, it is a sure sign - after discussing traditional (i.e. older) Bell tests - that this is where they stumble. So not much point in reading their "hand-waving". The OP references are a good example.

I agree, It is just that I have never seen a entanglement swapping mention in an interpretation discussion. Is there any interpretation that convince you more with regard to entanglement swapping ?

 

[DrChinese]

DrChinese said:
GHZ**.
[...]
**In these experiments, each and every individual run violates realism (since he assumes locality). The quantum prediction is exactly opposite the realistic prediction, and experiment matches QM.

Neumaier asks:
What do you say to the following statement, which seems contrary to your claims? (taken from p.6-7 of M. Kupczynski, Quantum Nonlocality: how does Nature do it? Entropy 26 (2024), 191.) ...

You have actually made my point nicely.

I had read several of Kupczynski's other papers, including "Entanglement and Quantum Nonlocality Demystified" (originally 2012). This and the one you cite (cleverly and intentionally titled the same as a Gisin paper with an opposing viewpoint) also fail to mention GHZ at all*. Which was the basis for the claim we are discussing. So the rest of Kupczynski's points really don't matter to me if they can't deal with GHZ or other modern no-go's that go farther than Bell (1964).

My** claim: In GHZ, local realism predicts completely different results than quantum mechanics in each and every trial (as I'm sure you know). From "Multi-Photon Entanglement and Quantum Non-Locality":

"We conclude that the local realistic model predicts none of the terms occurring in the quantum prediction and vice versa. This implies that, whenever local realism predicts a specific result definitely to occur for a measurement on one of the photons based on the results for the other two, quantum physics definitely predicts the opposite result. For example, if two photons are both found to be H' polarized, local realism predicts the third photon to carry V' polarization while the quantum state predicts H' polarization. This is the GHZ contradiction between local realism and quantum physics."***

Once you combine the results of Entanglement Swapping (ES) experiments with GHZ experiments, many proposed "local realistic" explanations immediately fall by the wayside, including many that are simply "local". So the "preliminaries" of such explanations won't really matter; I skip to the sections on ES and GHZ. If there are any. If they aren't present, the bookmark goes into the "denier" bin.

*And skip over Entanglement Swapping with a brief mention.

**You keep referring to what I say as "my" claims. I am quoting claims verbatim from generally accepted sources and authors. I am simply repeating claims I agree with, but are basically textbook level as of 2024.

***If you have a single generally accepted reference that says the GHZ theorem is false, I'd love to see it. Note that I already have plenty of links to GHZ deniers - none of whom are generally accepted in the realm of quantum physics. So no need to present any of those.

 

[DrChinese]

I agree, It is just that I have never seen a entanglement swapping mention in an interpretation discussion. Is there any interpretation that convince you more with regard to entanglement swapping ?

Yes and no. And a fair question, by the way.

I am certainly disappointed that many "valid" interpretations claim to solve the issues present with Entanglement Swapping (and GHZ) without providing a clear picture of how that is accomplished. For example, many MWI advocates claim it is local*, but can't draw me a picture of that locality might work. Bell rules out local realism of course.

It's when a new interpretation claims to solve the outstanding quantum riddles by simply redefining the terms until their conclusion is "proven" - that's when I pull out ES. There are a surprising number of papers (and authors) I encounter each year that claim to demonstrate QM is actually local realistic. I look for novel angles, but generally the arguments tend to be similar.


*There are others here (such as myself) that believe that for MWI to make any sense, there must be a nonlocal or even a global component. It would look a lot better to me if that were explicitly factored in to match experiment.

 

[DrChinese]

These papers claim to present a realistic stochastic interpretation of quantum mechanics that obeys a stochastic form of local causality. (A lecture I recently attended mentioned these papers). It also claims the Born rule as a natural consequence rather than an assumption. This appears to me to be a genuinely new interpretation. I have not delved into the papers in detail, but figured some people here may be interested.

https://arxiv.org/abs/2302.10778
https://arxiv.org/abs/2309.03085
https://arxiv.org/abs/2402.16935

These are all by Jacob Barandes. Here is an interpretation from 2014 called the Minimal Modal Interpretation of Quantum Theory: "We introduce a realist, unextravagant interpretation of quantum theory that builds on the existing physical structure of the theory and allows experiments to have definite outcomes*..."

Of course, definite (noncontextual) outcomes are directly contradicted by GHZ - assuming locality, which they apparently do: "At the same time, we will argue that our interpretation is ultimately compatible with Lorentz invariance and is nonlocal only in the mild sense familiar from the framework of classical gauge theories."

The punchline: One of the two authors/creators of this interpretation is Barandes. (I did not search for this, I found it in my existing bookmarks of local realists.)


*Presumably independent of context.

 

[PeterDonis]

Here is an interpretation from 2014

It doesn't look to me like the actual interpretation presented in that paper fits the description in the quotes you give (which are, of course, from the paper, so the paper itself looks inconsistent to me). The actual interpretation includes entangled wave functions as "ontic states". This could be called "realist", but it is not "noncontextual", and to call it "nonlocal only in the mild sense familiar from the framework of classical gauge theories" does not strike me as a very good description.

 

[PeterDonis]

The first thing I look for is their treatment of remote Entanglement Swapping* and GHZ**...

Of course, those seminal works aren't mentioned at all.

I had a similar reaction on reading the papers linked to in the OP: I thought, ok, interesting, but when are you going to account for Bell inequality violations? I never saw that done (let alone accounting for the even more counterintuitive phenomena you describe).

 

[Vanadium 50]

How can an interpretation of an existing theory make testable predictions different from that theory?

Obviously it can't. However, it can make otherwise difficult calculations tractable.

Consider "method of images" - much like an interpretation. Some problems become very easy. If you want an actual QM examples, consider B-Bbar mixing at the B-factories. Copemhagen makes it quickly clear why you need time dependence and some of the odder features, like tagging the flavor of one B by the flavor of the 2nd one, even if it decays later. You can of course show this any way you like, but this way is intuitive and quick.

 

[PAllen]

These are all by Jacob Barandes. Here is an interpretation from 2014 called the Minimal Modal Interpretation of Quantum Theory: "We introduce a realist, unextravagant interpretation of quantum theory that builds on the existing physical structure of the theory and allows experiments to have definite outcomes*..."

Of course, definite (noncontextual) outcomes are directly contradicted by GHZ - assuming locality, which they apparently do: "At the same time, we will argue that our interpretation is ultimately compatible with Lorentz invariance and is nonlocal only in the mild sense familiar from the framework of classical gauge theories."

The punchline: One of the two authors/creators of this interpretation is Barandes. (I did not search for this, I found it in my existing bookmarks of local realists.)


*Presumably independent of context.

That appears to be a different interpretation. That paper is referenced in the first of the new ones as having developed one very specific technique which is also used in the new interpretation.

 

[bob012345]

Are all experiments that suggest non-locality theory or interpretation independent?

 

[lodbrok]

I had a similar reaction on reading the papers linked to in the OP: I thought, ok, interesting, but when are you going to account for Bell inequality violations? I never saw that done (let alone accounting for the even more counterintuitive phenomena you describe).

The third paper mentioned above specifically went into a lot of detail about EPR and Bell's theorem, concluding:

By invoking this microphysical notion of causation, one can formulate a more straightforward criterion (55) for causal locality than Bell’s principle of local causality—in either of its equivalent forms (10) or (11). As this paper has shown, quantum theory, regarded as a theory of unistochastic processes, satisfies this improved criterion, and is therefore arguably a causally local theory. Remarkably, one therefore arrives at what appears to be acausally local hidden-variables formulation of quantumtheory, despite many decades of skepticism that such atheory could exist.

 

[PeterDonis]

Are all experiments that suggest non-locality theory or interpretation independent?

It depends on what you mean by "nonlocality".

"Nonlocality" defined as "violations of the Bell inequalities and related conditions" is an experimental fact, and so is independent of any interpretation.

Other definitions of "nonlocality" might not be.

 

[PeterDonis]

The third paper mentioned above specifically went into a lot of detail about EPR and Bell's theorem

Yes, but it never explains how the claimed interpretation in the paper actually accounts for violations of the Bell inequalities. It just defines a different notion of "causal locality" and shows that QM, at least in the formulation given in the paper, satisfies it. But this notion is not at all new: it's just defining "causal locality" as "the local statistics of Bob's measurement don't depend on what Alice chooses to measure", which has been known for decades and doesn't give any help at all in understanding what does produce Bell inequality violations.

In other words, all this supposedly different notion amounts to is saying that whatever it is that produces Bell inequality violations, it's not a local property of either of the two entangled systems in isolation; it's a property of the overall system. Well, gee, thanks for pointing out the obvious.

 

[bob012345]

It depends on what you mean by "nonlocality".

"Nonlocality" defined as "violations of the Bell inequalities and related conditions" is an experimental fact, and so is independent of any interpretation.

Other definitions of "nonlocality" might not be.

Do you mean the Aspect experiment? If so, doesn't that require some framework to interpret what the data means?

 

[PeterDonis]

Do you mean the Aspect experiment?

That was one experiment that showed Bell inequality violations, yes.

If so, doesn't that require some framework to interpret what the data means?

It requires analysis of the data to take into account the fact that the photon detectors used are not perfect; they will miss some fraction of photons. But such techniques are well developed and don't depend on any particular interpretation of QM. They also have less and less impact on the results as detectors get more and more efficient.

Given the above data analysis, it requires no "framework" at all to test whether the Bell inequalities are violated. That's just straightforward math.

 

[bob012345]

That was one experiment that showed Bell inequality violations, yes.


It requires analysis of the data to take into account the fact that the photon detectors used are not perfect; they will miss some fraction of photons. But such techniques are well developed and don't depend on any particular interpretation of QM. They also have less and less impact on the results as detectors get more and more efficient.

Given the above data analysis, it requires no "framework" at all to test whether the Bell inequalities are violated. That's just straightforward math.

Ok, thanks. Just one more question. You said it doesn't depend on any particular interpretation of QM. But you have to assume QM itself right?

 

[pines-demon]

If so, doesn't that require some framework to interpret what the data means?

You can interpret it using purely classical arguments and see what happens. All the results so far on Bell tests show that Bell inequalities are violated and thus we cannot reproduce them using a purely classical theory.

 

[PeterDonis]

You said it doesn't depend on any particular interpretation of QM. But you have to assume QM itself right?

You don't have to assume any theory to look at the results of an experiment. You only have to assume a theory if you want to compare its predictions with the results of an experiment.

So you don't have to assume QM to look at the results of experiments like the Aspect experiment and see that they violate the Bell inequalities. As I've said, that's just straightforward math. (Note that the Bell inequalities themselves have nothing to do with QM. They are just inequalities that would be satisfied if the world worked a certain way. The fact that they are violated in actual experiments shows that the world doesn't work that way, but in itself it doesn't tell you how to construct a better model.) You only have to assume QM if you want to compare QM's predictions with the experimental results. (Doing that shows that the results match QM's predictions.)

 

[DrChinese]

Are all experiments that suggest non-locality theory or interpretation independent?

No, but they should be.

The theory of ordinary quantum mechanics - which predicts the experiments that suggest non-locality - has advanced over time as entanglement theory exploded. So no one really knew that Remote Entanglement Swapping was a real thing 35 years ago. Ditto with the GHZ Theorem, which was discovered about 35 years ago as well. But they knew about Bell after Aspect and other important variations. Even today, many who are familiar with the basics of Bell and entanglement are not equally familiar with recent (10-20 years) advances in experiment. So when I say there is some theory dependence, I really mean according to how up to date one is. Entanglement theory is moving very fast, as theory goes, so I would not expect everyone to be able to keep up unless this is all they do.

With interpretations, it's the wild west. Papers denying any form of nonlocality are common. Papers denying any form of contextuality (i.e. they are pushing realistic concepts) are common. And it is surprising how many papers still push local realism of a form ruled out by Bell's Theorem. Of course, you can't much publish in a peer-reviewed journal going against Bell. But in the Arxiv, they come regularly.

Of course, I would not really call a paper or two denying the existence of nonlocality a true interpretation in the first place. Most interpretations are more of a seed of an idea, rather than a full fledged interpretation featuring an interesting or useful viewpoint, basic idea, or hypothetical mechanism.

---

Are Barandes' latest works a new interpretation? He claims it "plausibly resolves the measurement problem, and deflates various exotic claims about superposition, interference, and entanglement." Big talk! The word "entanglement" appears a grand total of once in the 3rd one ("New Prospects for a Causally Local Formulation of Quantum Theory" which he names the "Unistochastic" interpretation). He says too: "...the unistochastic formulation of quantum theory reviewed in this paper lies outside the wave-function paradigm...". Maybe it's a whole new theory?

The last statement before his conclusion, which is referring to a traditional Alice/Bob Bell test is: "The only causal influences on the observer-subsystem A [source of entangled pairs] are from the two subsystems Q [Alice] and R [Bob], which both intersect the past light cone of A [the source]." This statement might* work for such a simple example; but it obviously won't apply in a Remote Entanglement Swapping example in which there is no such intersect in the past light cone. That's a huge flop.

DrChinese grade: F. Don't waste our time in 2024 giving examples from 1981. I won't be waiting for his next paper.


*I would deny it.

 

[PeterDonis]

Maybe it's a whole new theory?

As far as I can tell, it's mathematically equivalent to standard QM. I might describe it as a sort of weird variant of the Bohmian interpretation, where there are unobservable particle positions as underlying hidden variables, but stochastic dynamics for these particles, set up in just the right way to match the predictions of standard QM, takes the place of the initial distribution of particle positions in the Bohmian interpretation, which is likewise set up in just the right way to match the predictions of standard QM.

 

[A. Neumaier]

You keep referring to what I say as "my" claims. I am quoting claims verbatim from generally accepted sources and authors. I am simply repeating claims I agree with

This makes them your claims, too.

Note that by making a very selective choice, you heavily bias the quite controversial collection of claims in the literature towards your own preference. That's why I refer to your claims.