Superdeterminism and the Mermin Device

[RUTA]

Superdeterminism as a way to resolve the mystery of quantum entanglement is generally not taken seriously in the foundations community, as explained in this video by Sabine Hossenfelder (posted in Dec 2021). In her video, she argues that superdeterminism should be taken seriously, indeed it is what quantum mechanics (QM) is screaming for us to understand about Nature. According to her video per the twin-slit experiment, superdeterminism simply means the particles must have known at the outset of their trip whether to go through the right slit, the left slit, or both slits, based on what measurement was going to be done on them. Thus, she defines superdeterminism this way:
Superdeterminism: What a quantum particle does depends on what measurement will take place.
In Superdeterminism: A Guide for the Perplexed she gives a bit more technical definition:





Theories that do not...

Continue reading...

 

[Lord Jestocost]

In
Superdeterminism: A Guide for the Perplexed
one reads:

"The two biggest problem with superdeterminism at the moment are (a) the lack of a generally applicable fundamental theory and (b) the lack of experiment."

 

[DrChinese]

Nice article. Obviously, one of the problems when discussing Superdeterminsm in a serious manner is that there really aren't any true candidates to knock down by way of experiment. I appreciate that Hossenfelder is trying to present something that could be knocked down, but in all honesty that won't reduce the seemingly infinite supply of alternate candidates.

So yes, you could simply say there are violations of Statistical Independence (SI). In your example, the 32/23 combinations produce a different outcome sets for certain hidden variable combinations. In an actual experiment with the 32 or 23 settings as static, you'd notice that immediately (since the results must still match prediction) - so there must be more to the SI violation so that this result does not occur. And just like that, the Superdeterminism candidate must morph yet again.

But one thing has mystified me in these discussions. Always, the superdeterminism candidate is presented as local (since the ultimate purpose of the candidate is to restore determinism and locality). In your reference to the Chen article, there is reference to the idea that "one can always conjecture that some factor in the overlap of the backwards light cones has controlled the presumably random choices".

There are at least 2 problems with this. First problem, that there needs to be *random choices* for the experiment to show SI. Unless the superdeterministic candidate has a mechanism to discern whether the measurement choice is being varied or not, it need not be random or subject to free will at all - it could be static (and therefore not demonstrate any deviation from the quantum mechanical expectation value - which is what we needed to demonstrate as a viable possibility). Second, and most importantly, the entangled particles subject to the Bell test need not have ever existed in a common light cone. And in fact, they need not have ever co-existed to be entangled. Or come from a common source at all. I'll supply more references as needed.

https://arxiv.org/abs/1209.4191
Entanglement Between Photons that have Never Coexisted

Yes, there seems to be a violation of SI. But that must simply be a result of quantum contextuality itself. And such contextuality must have a nonlocal element. But it is a special kind of nonlocal, not the kind that appears in Bohmian Mechanics (for example) where there are instantaneous effects regardless of distance. The overall context is traced out by components that are individually limited to c.

 

[Nullstein]

Nice article. Obviously, one of the problems when discussing Superdeterminsm in a serious manner is that there really aren't any true candidates to knock down by way of experiment. I appreciate that Hossenfelder is trying to present something that could be knocked down, but in all honesty that won't reduce the seemingly infinite supply of alternate candidates.

There is also an infinite supply of non-local candidate theories. In fact, there is an infinite supply of theories in most paradigms, so this isn't a proper argument against superdeterminism. And superdeterministic theories are actually much harder to construct than non-local ones, so the supply of superdeterministic theories is in some sense even smaller than the supply of non-local ones.

 

[PeroK]

When I click on the link to "Mermin's Challenge", it says I'm not allowed to edit that item.

 

[RUTA]

When I click on the link to "Mermin's Challenge", it says I'm not allowed to edit that item.

Sorry, I accidentally inserted my link as an author to that Insight. Hopefully, it's fixed now :-)

 

[RUTA]

In
Superdeterminism: A Guide for the Perplexed
one reads:

"The two biggest problem with superdeterminism at the moment are (a) the lack of a generally applicable fundamental theory and (b) the lack of experiment."

In the New Scientist article, it did say Ghosh was planning an experiment proposed by Sabine.

 

[RUTA]

In your example, the 32/23 combinations produce a different outcome sets for certain hidden variable combinations. In an actual experiment with the 32 or 23 settings as static, you'd notice that immediately (since the results must still match prediction) - so there must be more to the SI violation so that this result does not occur. And just like that, the Superdeterminism candidate must morph yet again.

If the instruction sets are produced in concert with the settings as shown in the Table, the 23/32 setting would produce agreement in 1/4 of the trials, which matches QM.

 

[Nullstein]

Second, and most importantly, the entangled particles subject to the Bell test need not have ever existed in a common light cone. And in fact, they need not have ever co-existed to be entangled. Or come from a common source at all. I'll supply more references as needed.

https://arxiv.org/abs/1209.4191
Entanglement Between Photons that have Never Coexisted

I don't see the relevance of this article. If you can locally explain the correlations of an ordinary Bell pair, you can also locally explain the results of this paper. This is just entanglement swapping, which can be explained locally (https://arxiv.org/abs/quant-ph/9906007).

 

[DrChinese]

If the instruction sets are produced in concert with the settings as shown in the Table, the 23/32 setting would produce agreement in 1/4 of the trials, which matches QM.

[And of course I know you are not arguing in favor of superdeterminism in your Insight.]

My mistake, yes, I see now that is a feature of the table. So basically, that would equivalent to saying that for the 23 case (to be specific) - which in the table is marked as follows (where rows 2/3/4, the 23 cases will add to 100% as follows:

-Row 2 occurs 50% of the time when 23 measurement occurs. Because this is doubled by design/assumption.
-Row 3 occurs 25% of the time when 23 measurement occurs.
-Row 4 occurs 25% of the time when 23 measurement occurs.
Total=100%

Could just as rationally be:

-Row 2 occurs 75% of the time when 23 measurement occurs.
-Row 3 occurs 0% of the time when 23 measurement occurs. This is so rows 2 and 3 add to 75%.
-Row 4 occurs 25% of the time when 23 measurement occurs.
Total=100%...Since the stats add up the same. After all, that would cause the RRG & GGR cases to be wildly overrepresented, but since we are only observing the 23 measurements, we don't see that the other (unmeasured) hidden variable (1) occurrence rate is dependent on the choice of the 23 basis. Since we are supposed to believe that it exists (that is the purpose of a hidden variable model) but has a value that makes it inconsistent with the 23 pairing (of course this inconsistency is hidden too).

Obviously, in this table, we have statistical independence as essentially being the same thing as contextuality. Which more or less orthodox QM is anyway. Further, it has a quantum nonlocal element, as the Bell tests with entanglement swapping indicate*. That is because the "23" choice was signaled to the entangled source so that the Row 2 case can be properly overrepresented. But in an entanglement swapping setup, there are 2 sources! So now we need to modify our superdeterministic candidate to account for a mechanism whereby the sources know to synchronize in such a way as to yield the expected results. Which is more or less orthodox QM anyway.

My point is that the explicit purpose of a Superdeterministic candidate is to counter the usual Bell conclusion, that being: a local realistic theory (read: noncontextual causal theory) is not viable. Yet we now are stuck with a superdeterministic theory which features local hidden variables, except they are also contextual and quantum nonlocal. I just don't see the attraction.

*Note that RBW does not have any issue with this type of quantum nonlocal element. The RBW diagrams can be modified to account for entanglement swapping, as I see it (at least I think so). RBW being explicitly contextual, as I understand it: "...spatiotemporal relations provide the ontological basis for our geometric interpretation of quantum theory..." And on locality: "While non-separable, RBW upholds locality in the sense that there is no action at a distance, no instantaneous dynamical or causal connection between space-like separated events [and there are no space-like worldlines.]" [From one of your papers (2008).]

 

[DrChinese]

I don't see the relevance of this article. If you can locally explain the correlations of an ordinary Bell pair, you can also locally explain the results of this paper. This is just entanglement swapping, which can be explained locally (https://arxiv.org/abs/quant-ph/9906007).

In your reference (1999), its Figure 3 is not a fair representation of the experiment I presented (2012). Deutsch is not what I would call a universally accepted writer on the subject, and "is a legendary advocate for the MWI". "Quantum nonlocality" is generally accepted in current science. And we've had this discussion here many a time. The nature of that quantum nonlocality has no generally accepted mechanism, however. That varies by interpretation.

The modern entanglement swapping examples have entangled particles which never exist in a common backward light cone - so they cannot have had an opportunity for a local interaction or synchronization. The A and B particles are fully correlated like any EPR pair, even though far apart and having never interacted*. That is quantum nonlocality, plain and simple. There are no "local" explanations for entanglement swapping of this type (that I have seen), of course excepting interpretations that claim to be fully local and forward in time causal (which I would probably dispute). Some MWI proponents makes this claim, although not all.*Being from independent photon sources, and suitably distant to each other.

 

[StevieTNZ]

Interesting to read there are some experiments planned to give evidence for (or against) superdeterminism.

 

[Demystifier]

Super-determinism is super-nonlocal

In her "Guide for the Perplexed", Sabine Hossenfelder writes:
"What does it mean to violate Statistical Independence? It means that fundamentally everything in the universe is connected with everything else, if subtly so. You may be tempted to ask where these connections come from, but the whole point of superdeterminism is that this is just how nature is. It’s one of the fundamental assumptions of the theory, or rather, you could say one drops the usual assumption that such connections are absent. The question for scientists to address is not why nature might choose to violate Statistical Independence, but merely whether the hypothesis that it is violated helps us to better describe observations."

I think this quote perfectly explains how super-determinism avoids quantum nonlocality. Not by replacing it with locality, but by replacing it with super-nonlocality!

In ordinary nonlocality, things get correlated over distance due to nonlocal forces. In super-nonlocality one does not need forces for that. They are correlated just because the fundamental laws of Nature (or God if you will) say so. You don't need to fine tune the initial conditions to achieve such correlations, it's a general law that does not depend on initial conditions. You don't need any complicated conspiracy for that, in principle it can be a very simple general law.

 

[martinbn]

Super-determinism is super-nonlocal

In her "Guide for the Perplexed", Sabine Hossenfelder writes:
"What does it mean to violate Statistical Independence? It means that fundamentally everything in the universe is connected with everything else, if subtly so. You may be tempted to ask where these connections come from, but the whole point of superdeterminism is that this is just how nature is. It’s one of the fundamental assumptions of the theory, or rather, you could say one drops the usual assumption that such connections are absent. The question for scientists to address is not why nature might choose to violate Statistical Independence, but merely whether the hypothesis that it is violated helps us to better describe observations."

I think this quote perfectly explains how super-determinism avoids quantum nonlocality. Not by replacing it with locality, but by replacing it with super-nonlocality!

In ordinary nonlocality, things get correlated over distance due to nonlocal forces. In super-nonlocality one does not need forces for that. They are correlated just because the fundamental laws of Nature (or God if you will) say so. You don't need to fine tune the initial conditions to achieve such correlations, it's a general law that does not depend on initial conditions. You don't need any complicated conspiracy for that, in principle it can be a very simple general law.

I thought that the motivation for superdeterminism wasn't to avoid nonlicality but nonclassicality. The claim being that the world is really classical, but somehow (through the special initial conditions and evolution laws) it only seems like quantum theory is a correct description.

 

[Demystifier]

I thought that the motivation for superdeterminism wasn't to avoid nonlicality but nonclassicality. The claim being that the world is really classical, but somehow (through the special initial conditions and evolution laws) it only seems like quantum theory is a correct description.

What exactly do you mean by non-classicality?

 

[Nullstein]

In your reference (1999), its Figure 3 is not a fair representation of the experiment I presented (2012).

Why do you think so?

Deutsch is not what I would call a universally accepted writer on the subject, and "is a legendary advocate for the MWI".

That's an ad hominem argument and also a personal opinion. Deutsch is a well respected physicist working in quantum foundations and quantum computing at Oxford university who has received plenty of awards.

"Quantum nonlocality" is generally accepted in current science. And we've had this discussion here many a time. The nature of that quantum nonlocality has no generally accepted mechanism, however. That varies by interpretation.

"Quantum nonlocality" is just another word for Bell-violating, which is of course accepted, because it has been demonstrated experimentally and nobody has denied that. The open question is the mechanism and superdeterminism is one way to address it.

The modern entanglement swapping examples have entangled particles which never exist in a common backward light cone - so they cannot have had an opportunity for a local interaction or synchronization.

That is not necessary, because entanglement swapping isn't really a physical process. It's essentially just an agreement between two distant parties, which photons to use for subsequent experiments. These two parties need information from a third party who has access to particles from both Bell pairs and who communicates with them over a classical channel at sub light speed.

The A and B particles are fully correlated like any EPR pair, even though far apart and having never interacted*. That is quantum nonlocality, plain and simple.

Again, nobody denied this. The statement is that entanglement produced by entanglement swapping can be explained if the correlations in the original Bell pairs can be explained. Entanglement swapping doesn't add to the mystery.

 

[RUTA]

[And of course I know you are not arguing in favor of superdeterminism in your Insight.]

Correct, I'm definitely not arguing for SD. If Statistical Independence is violated and QM needs to be underwritten as Sabine suggests, physics is not going to be fun for me anymore

Could just as rationally be:

-Row 2 occurs 75% of the time when 23 measurement occurs.
-Row 3 occurs 0% of the time when 23 measurement occurs. This is so rows 2 and 3 add to 75%.
-Row 4 occurs 25% of the time when 23 measurement occurs.
Total=100%...Since the stats add up the same. After all, that would cause the RRG & GGR cases to be wildly overrepresented, but since we are only observing the 23 measurements, we don't see that the other (unmeasured) hidden variable (1) occurrence rate is dependent on the choice of the 23 basis. Since we are supposed to believe that it exists (that is the purpose of a hidden variable model) but has a value that makes it inconsistent with the 23 pairing (of course this inconsistency is hidden too).

Right, we have no idea exactly how Statistical Independence is violated because it's all "hidden." My Table 1 is just an example to show what people refer to as the "conspiratorial nature" of SD. Sabine addresses that charge in her papers, too.

Obviously, in this table, we have statistical independence as essentially being the same thing as contextuality. Which more or less orthodox QM is anyway. Further, it has a quantum nonlocal element, as the Bell tests with entanglement swapping indicate*. That is because the "23" choice was signaled to the entangled source so that the Row 2 case can be properly overrepresented. But in an entanglement swapping setup, there are 2 sources! So now we need to modify our superdeterministic candidate to account for a mechanism whereby the sources know to synchronize in such a way as to yield the expected results. Which is more or less orthodox QM anyway.

My point is that the explicit purpose of a Superdeterministic candidate is to counter the usual Bell conclusion, that being: a local realistic theory (read: noncontextual causal theory) is not viable. Yet we now are stuck with a superdeterministic theory which features local hidden variables, except they are also contextual and quantum nonlocal. I just don't see the attraction.

Sabine points out that to evade the conclusion of Bell, you need to violate either or both of Statistical Independence or/and locality. She also points out that SD could violate both, giving you the worst of both worlds. I'll let the experimental evidence decide, but I'm definitely hoping for no SD

*Note that RBW does not have any issue with this type of quantum nonlocal element. The RBW diagrams can be modified to account for entanglement swapping, as I see it (at least I think so). RBW being explicitly contextual, as I understand it: "...spatiotemporal relations provide the ontological basis for our geometric interpretation of quantum theory..." And on locality: "While non-separable, RBW upholds locality in the sense that there is no action at a distance, no instantaneous dynamical or causal connection between space-like separated events [and there are no space-like worldlines.]" [From one of your papers (2008).]

We uphold locality and Statistical Independence in our principle account of QM as follows. Locality is not violated because there is no superluminal signaling. Statistical Independence is not violated because Alice and Bob faithfully reproduce the most accurate possible QM state and make their measurements in accord with fair sampling (independently and randomly). In this principle account of QM (ultimately based on quantum information theorists' principle of Information Invariance & Continuity, see the linked paper immediately preceding), the state being created in every trial of the experiment is the best one can do, given that everyone must measure the same value for Planck's constant regardless of the orientation of their measurement device. RBW is nonetheless contextual in the 4D sense, see here and here for our most recent explanations of that.

 

[DrChinese]

1. Locality is not violated because there is no superluminal signaling.

2. RBW is nonetheless contextual in the 4D sense, see here and here for our most recent explanations of that.

1. Certainly, RBW is local in the sense that Bohmian Mechanics is not. Bohmian Mechanics does not feature superluminal signaling either, and we know we don't want to label BM as "local".

So I personally wouldn't label RBW as you do ("local"); as I label it "quantum nonlocal" when a quantum system (your block) has spatiotemporal extent (your 4D contextuality) - as in the Bell scenario. But I see why you describe it as you do: it's because c is respected when you draw context vertices on a block (not sure that is the correct language to describe that). 2. Thanks for the references.

 

[PeterDonis]

That's an ad hominem argument

So is your response (although since your statements about Deutsch are positive, it might be better termed a "pro homine" argument):

Deutsch is a well respected physicist working in quantum foundations and quantum computing at Oxford university who has received plenty of awards.

None of these are any more relevant to whether Deutsch's arguments are valid than the things you quoted from @DrChinese. What is relevant is what Deutsch actually says on the topic and whether it is logically coherent and consistent with what we know from experiments.

 

[Nullstein]

So is your response (although since your statements about Deutsch are positive, it might be better termed a "pro homine" argument):None of these are any more relevant to whether Deutsch's arguments are valid than the things you quoted from @DrChinese. What is relevant is what Deutsch actually says on the topic and whether it is logically coherent and consistent with what we know from experiments.

I agree, I just wanted to defend Deutsch's reputation and point out that DrChinese did not address the argument in the article. I considered his response quite rude, given that I just argued based on a legit article by a legit researcher. The article contains detailed calculations, so one could just point to a mistake if there was one.

 

[RUTA]

1. Certainly, RBW is local in the sense that Bohmian Mechanics is not. Bohmian Mechanics does not feature superluminal signaling either, and we know we don't want to label BM as "local".

So I personally wouldn't label RBW as you do ("local"); as I label it "quantum nonlocal" when a quantum system (your block) has spatiotemporal extent (your 4D contextuality) - as in the Bell scenario. But I see why you describe it as you do: it's because c is respected when you draw context vertices on a block (not sure that is the correct language to describe that). 2. Thanks for the references.

I should be more precise, sorry. In the quantum-classical contextuality of RBW, "local" means "nothing moving superluminally" and that includes "no superluminal information exchange." That's because in our ontology, quanta of momentum exchanged between classical objects don't have worldlines.

Notice also that when I said RBW does not entail violations of Statistical Independence because the same state is always faithfully produced and measured using fair sampling, I could have said that about QM in general. Again, what I said follows from the fact that there are no "quantum entities" moving through space, there is just the spatiotemporal (4D) distribution of discrete momentum exchanges between classical objects. And that quantum-classical contextuality conforms to the boundary of a boundary principle and the relativity principle.

So, how do we explain violations of Bell's inequality without nonlocal interactions, violations of Statistical Indendence, or "shut up and calculate" (meaning "the formalism of QM works, so it's already 'explained'")? Our principle explanation of Bell state entanglement doesn't entail an ontology at all, so there is no basis for nonlocality or violations of Statistical Independence. And, it is the same (relativity) principle that explains time dilation and length contraction without an ontological counterpart and without saying, "the Lorentz transformations work, so it's already 'explained'". So, we do have an explanation of Bell state entanglement (and therefore of the Tsirelson bound).

 

[jbergman]

Continue reading...

From the experiment that they are trying to perform, the hope seems to be that if the detectors are prepared similar enough then statistical independence will be violated. In other words, that what we've seen as the statistical independence of measurements is an artifact of detectors in different states. Is that a correct reading here?

 

[RUTA]

From the experiment that they are trying to perform, the hope seems to be that if the detectors are prepared similar enough then statistical independence will be violated. In other words, that what we've seen as the statistical independence of measurements is an artifact of detectors in different states. Is that a correct reading here?

Well, my understanding is that the experiments will check for violations of randomness where QM predicts randomness. That means we should look for a theory X underwriting QM so that QM is just a statistical approximation to theory X. Then you can infer the existence of hidden variables (hidden in QM, but would be needed in theory X) whence either or both of nonlocality or/and the violation of Statistical Independence. Just my guess, I don't study SD.

 

[DrChinese]

1. That's an ad hominem argument and also a personal opinion. Deutsch is a well respected physicist working in quantum foundations and quantum computing at Oxford university who has received plenty of awards.

2. That is not necessary, because entanglement swapping isn't really a physical process. It's essentially just an agreement between two distant parties, which photons to use for subsequent experiments. These two parties need information from a third party who has access to particles from both Bell pairs and who communicates with them over a classical channel at sub light speed.

3. Again, nobody denied this. The statement is that entanglement produced by entanglement swapping can be explained if the correlations in the original Bell pairs can be explained. Entanglement swapping doesn't add to the mystery.

1. Relevant here if he is stating something that is not generally accepted (and the part in quotes was actually from another physicist). Local explanations of swapping are not, and clearly that is the tenor of the paper. Deutsch is of course a respected physicist (and respected by me), that's not the issue.

2. I specifically indicated how your citation differed from swapping using independent sources outside of a common light cone (which does not occur in Deutsch's earlier paper). There are no "local" explanations for how 2 photons that have never existed within a common light cone manage to be perfectly correlated (entangled) a la Bell. That you might need information from a classical channel to postselect pairs is irrelevant. No one is saying there is FTL signaling or the like.

3. Of course swapping adds to the mystery. And it certainly rules out some types of candidate theories. How can there be a common local cause when there is no common light cone overlap?

 

[martinbn]

3. Of course swapping adds to the mystery. And it certainly rules out some types of candidate theories. How can there be a common local cause when there is no common light cone overlap?

Can you clarify. How can there be no common overlap? Any two past lightcones overlap.

 

[DrChinese]

...I just wanted to defend Deutsch's reputation and point out that DrChinese did not address the argument in the article. I considered his response quite rude, given that I just argued based on a legit article by a legit researcher. The article contains detailed calculations, so one could just point to a mistake if there was one.

I read the 1999 Deutsch article, and unfortunately it did not map to my 2012 reference. There is actually no reason it should (or would), as the experiment had not been conceived at that time.

As I mentioned in another post, Deutsch's reputation does not need defending. However, I would not agree that his well-known positions on MWI should be considered as representing generally accepted science. Some are, and some are not, and I certainly think it is fair to identify positions as "personal" vs "generally accepted" when it is relevant. There is nothing wrong with having personal opinions that are contrary to orthodox science, but I believe those should be identified.

Show me where Zeilinger (or any of the authors of similar papers) says there are local explanations for the kind of swapping I describe, and we'll be on to something. From the paper: "The observed quantum correlations manifest the non-locality of quantum mechanics in spacetime." I just don't see how SD can get around this: it is supposed to restore realism and locality to QM.

 

[Nullstein]

1. Relevant here if he is stating something that is not generally accepted (and the part in quotes was actually from another physicist). Local explanations of swapping are not, and clearly that is the tenor of the paper. Deutsch is of course a respected physicist (and respected by me), that's not the issue.

Have you conducted a representative survey or how do you know what's generally accepted? I'm not aware of a rebuttal to Deutsch's paper, so his argument must be taken to be the current state of our knowledge. It's well written and explicit and doesn't rely on vague formations, so it should be quite easy to point at a mistake if there was one.

2. I specifically indicated how your citation differed from swapping using independent sources outside of a common light cone (which does not occur in Deutsch's earlier paper).

Deutsch's argument is completely independent of the spatial and temporal order. He just tracks down the flow of information in a general entanglement swapping setting and shows that everything is perfectly local.

There are no "local" explanations for how 2 photons that have never existed within a common light cone manage to be perfectly correlated (entangled) a la Bell. That you might need information from a classical channel to postselect pairs is irrelevant. No one is saying there is FTL signaling or the like.

3. Of course swapping adds to the mystery. And it certainly rules out some types of candidate theories. How can there be a common local cause when there is no common light cone overlap?

The particles are only entangled after Alice and Bob have received Carol's information through the classical, sub light speed channel and adjust their states locally based on that information, so there is a common event in the intersection of the backwards light cones. There is just no common cause for the correlations of the original Bell pairs. Entanglement swapping just propagates this unexplained quantum correlation through this classical channel (at $v<c$). As Deutsch puts it: The ability of quantum information to flow through a classical channel in this way, surviving decoherence, is also the basis of quantum teleportation, a remarkable phenomenon to which we now turn.

I read the 1999 Deutsch article, and unfortunately it did not map to my 2012 reference. There is actually no reason it should (or would), as the experiment had not been conceived at that time.

Entanglement swapping was known long before 2012 and Deutsch discusses it in full generality in his paper. Your paper is not about a new phenomenon, but just an experimental verification of the phenomenon of entanglement swapping, which was known long before. It contains no new theory.

As I mentioned in another post, Deutsch's reputation does not need defending. However, I would not agree that his well-known positions on MWI should be considered as representing generally accepted science. Some are, and some are not, and I certainly think it is fair to identify positions as "personal" vs "generally accepted" when it is relevant. There is nothing wrong with having personal opinions that are contrary to orthodox science, but I believe those should be identified.

Show me where Zeilinger (or any of the authors of similar papers) says there are local explanations for the kind of swapping I describe, and we'll be on to something.

This is again an argument based on reputation and not on math. Zeilinger doesn't decide what's wrong or right. If there was a mistake in Deutsch's paper, one should be able to point it out. It's written in a very clear language and exposes all the calculations.

From the paper: "The observed quantum correlations manifest the non-locality of quantum mechanics in spacetime." I just don't see how SD can get around this: it is supposed to restore realism and locality to QM.

In the literature, "quantum non-locality" just means violating Bell's inequality. Nobody denies that Bell's inequality is violated by this experiment. The mechanism is what's puzzeling.

(By the way, I don't even believe in superdeterminism. I just think the common criticism is unfair and doesn't hold water.)

 

[PeterDonis]

I'm not aware of a rebuttal to Deutsch's paper, so his argument must be taken to be the current state of our knowledge.

This is not a valid argument. There are many papers that never get rebuttals but are still incorrect.

If there was a mistake in Deutsch's paper, one should be able to point it out.

This is not a valid argument either; many papers have had mistakes that are not easily pointed out. Nor is it relevant to what @DrChinese is saying. @DrChinese is not claiming there is a mistake in Deutsch's paper. He is saying he doesn't see how Deutsch's paper addresses the kind of experiment he is talking about (entanglement swapping) at all. If you think Deutsch's paper does address that, the burden is on you to explain how.

 

[Nullstein]

This is not a valid argument. There are many papers that never get rebuttals but are still incorrect.

Maybe, although a paper by a famous physicist like Deutsch is much more likely to get a rebuttal if it is false, than a paper by a random PhD candidate. But as you say, the objective should be to point at a mistake in the paper and not to fight about missing rebuttals. If DrChinese claimed that it was wrong, he should be able to point at a mistake. Since I quoted that paper, the actual argument in the paper has not been addressed. We have only been arguing about reputation and rebuttals so far.

@DrChinese is not claiming there is a mistake in Deutsch's paper. He is saying he doesn't see how Deutsch's paper addresses the kind of experiment he is talking about (entanglement swapping) at all. If you think Deutsch's paper does address that, the burden is on you to explain how.

Entanglement swapping is a special case of quantum teleportation. Deutsch discusses the general quantum teleportation framework in his paper (section 5, "Information flow in quantum teleportation"), so his paper also applies to the special case of entanglement swapping.

 

[PeroK]

"Quantum nonlocality" is just another word for Bell-violating, which is of course accepted, because it has been demonstrated experimentally and nobody has denied that. The open question is the mechanism and superdeterminism is one way to address it.

It's perhaps not a fair question but what odds would you give on SD being that mechanism? Would you bet even money on this experiment proving QM wrong? Or, 10-1 against or 100-1 against?

I wonder what Hossenfelder would be prepared to bet on it?