I A new realistic stochastic interpretation of Quantum Mechanics

[DrChinese]

1. Nonsense. All signals travel in space and time in the future direction. What you can't do is send a signal to anything other than the causal future.

2. Claiming the arrival event of 2 and 3 is in the causal future of 1 and 4 MEANS that 1 and 4 measurement results can be sent via a classical signal to this event. If they cannot, then the 2 and 3 arrival point is at spacelike separation not timelike, and is NOT in the causal future of 1 and 4.

1. Yes, all signals travel in the future direction at speeds not to exceed c. I didn't make that sufficiently clear, simply because I am not saying any signal can be sent FTL (and I have never implied otherwise).

2. No it does not. There is absolutely no requirement that Chris be close (enough for a classical signal) to Alice and/or Bob when the swap occurs. That's what I keep trying to tell you. This experiment has already been performed. Alice, Bob and Chris can be arbitrarily far apart, and the ordering of the events can be arbitrary without any observable difference. This is exactly as predicted by QM.

Chris can execute the swap in the future of Alice and Bob, while also being far enough away that no signals can be exchanged between any of the 3 before their observations are completed. At the same time, the photons of Alice and Bob need not have ever co-existed in a common light cone.

 

[PeterDonis]

A decision by Chris can entangle - or not - 2 distant photons.

As I have already noted, though, Chris does not have control over all of the relevant factors involved, so his freedom to make a "decision" is limited. Chris can choose to prevent the entanglement swap with certainty, by delaying one of the photons; but Chris cannot choose to make the entanglement swap happen with certainty, because Chris cannot guarantee that, if he does not delay either of the photons, they will both arrive within the required time window and cause a swap. The best Chris can do, if he wants a swap to happen, is to not choose to prevent it.

 

[DrChinese]

As I have already noted, though, Chris does not have control over all of the relevant factors involved, so his freedom to make a "decision" is limited. Chris can choose to prevent the entanglement swap with certainty, by delaying one of the photons; but Chris cannot choose to make the entanglement swap happen with certainty, because Chris cannot guarantee that, if he does not delay either of the photons, they will both arrive within the required time window and cause a swap. The best Chris can do, if he wants a swap to happen, is to not choose to prevent it.

Certainly this is true. Chris could just turn off his station too. So we agree.

But there is a nuance here I’m trying to make. With a specific delay, Chris can insure there is no swap but also could affirmatively say a swap would have occurred without that delay. IFF the timing aligned otherwise. I.e. 3 fold coincidence with the 4th running just behind.

There is another odd twist. Adding the delay does not actually reduce the total number of swaps! It changes the line-up of timings such that differently timed pairs match up. For a swap to occur, there must be overlap in Chris’ beam splitter. Even if there is extra fiber added, the number of overlapping 2 & 3 photons stays the same, on average. In such case, the 4 fold timing would look a bit different, but a swap would occur.

This is easiest to see if you imagine that a “normal” 4 fold detection has all 4 photons traveling the same distance (within experimental accuracy). All 4 time stamps would be within the same coincidence window without adjustment. The 1 &2 photons are therefore created nearly simultaneously as the 3 & 4 photons. But each source creates pairs randomly and independently. The swap is strictly based on the indistinguishable timing of the overlap of 2 & 3, nothing else.

 

[PeterDonis]

With a specific delay, Chris can insure there is no swap but also could affirmatively say a swap would have occurred without that delay.

Is that true? As I understand it, even if there is no artificially imposed delay, it is still possible that the photons do not arrive within the required time window to cause a swap; that is not under the experimenter's control. So there is no way to affirmatively say that a swap must occur if there is no artificially imposed delay.

 

[PeterDonis]

Adding the delay does not actually reduce the total number of swaps! It changes the line-up of timings such that differently timed pairs match up.

Wouldn't this only be true for some very precisely chosen values of the delay timing?

 

[DrChinese]

1. Is that true? As I understand it, even if there is no artificially imposed delay, it is still possible that the photons do not arrive within the required time window to cause a swap; that is not under the experimenter's control. So there is no way to affirmatively say that a swap must occur if there is no artificially imposed delay.

1. If they would have arrived within the BSM's time window without the delay, there would affirmatively be a swap. Suppose as an example, we had the following timings (not realistic) with exactly equal path lengths (also not particularly realistic). Assume no delay added to the photon 3 path unless specified. Check out especially a. versus d.

a. 1 arrives at .200 ms; 2 & 3 (indistinguishably) arrive at .200 ms (i.e. 2 clicks); 4 arrives at .200 ms. A swap occurs. The 1 & 4 times are the same.

b. 1 arrives at .200 ms; 2 arrives at .200 ms; 3 arrives at .400ms; 4 arrives at .400 ms. No swap occurs since 2 & 3 are distinguishable. This is the most common case that Chris sees for 2 & 3, because the creation times for 2 & 3 aren't nearly close enough together. This b. variation might occur 1000 times more often than a.

c. 1 arrives at .200 ms; 2 arrives at .200 ms; 3 arrives at .201ms; 4 arrives at .201 ms. No swap occurs since 2 & 3 are distinguishable even though the difference in arrival times is small. The creation times for 2 & 3 aren't quite close enough together.

Now Chris adds a .001 ms delay to the photon 3 path, sufficient to insure no swap occurs in case d.

d. 1 arrives at .200 ms; 2 arrives at .200 ms; 3 arrives at .201ms (.200 + .001 delay); 4 arrives at .200 ms. No swap occurs since 2 & 3 are distinguishable even though they are close. But note that the 1 & 4 times are the same! That means without the .001 delay of photon 3, there affirmatively would have been a swap. Because there would have been overlap, and proper overlap always leads to a swap.

e. 1 arrives at .201 ms; 2 & 3 (indistinguishably) arrive at .201 ms; 4 arrives at .200 ms. A swap occurs. Notice that the 1 & 4 photons traveled the same length as always, but their arrival times were different. No problem, because them arriving simultaneously is not a requirement. This counts as a 4 fold coincidence.

2. Wouldn't this only be true for some very precisely chosen values of the delay timing?

2. Not at all! The precision timing is the overlap at Chris' beamsplitter (photons 2 & 3). It doesn't matter at all when photon 2 was created relative to photon 3. And the overlap is simply randomly occurring, with the majority of Chris' clicks being a lone 2 or a lone 3 - easily distinguished because there are only 2 of 4 total possible clicks within the time window. When Chris does get 2 clicks within the small time window, the next step will be to associate the click that Alice gets with Chris' double click. Ditto for Bob. Then you have the 4 fold results. From the reference below: "In the BSM, it is critical that the signal photons sent by Alice and Bob arrive at the 50:50 beam splitter (BS) simultaneously."

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Below is from Field test of entanglement swapping over 100-km optical fiber with independent 1-GHz-clock sequential time-bin entangled photon-pair sources
It's just another permutation of these remote setups whereby Alice, Bob and Chris (here named Charlie) are all distant from each other when their respective measurements are performed. Here Alice is located next to source I and Bob is near source II but are delayed by the addition of fiber, so technically the photons each observe are in each others' light cones. Nonetheless, you can see that the positioning (and distances) are arbitrary; Alice, Bob and Charlie (my Chris) can be located further away from each other simply by placing them physically further away from each other with less coiled fiber.

 

[PeterDonis]

If they would have arrived within the BSM's time window without the delay, there would affirmatively be a swap.

But whether they arrive in the time window is not completely controllable by the experimenter, correct? The experimenter can force them not to by imposing a delay, but if the experimenter doesn't do that, it's still not guaranteed that they will arrive within the time window, as I understand it.

The reason I keep harping on this is that, if it is possible for the experimenter (Chris) to guarantee that a swap does happen, then we have the problem @PAllen brought up earlier: in a setup where the 1 & 4 measurement results are in the past light cone of Chris making the decision of what, if anything, to do to photons 2 & 3 before they arrive at the BSM, Chris could wait until he sees a pair of 1 & 4 results that are inconsistent with entanglement (for example, a combination of results that is impossible in the entangled state), and then force a swap to happen at the BSM--which would contradict the predictions of QM, since QM predicts that if the 1 & 4 results show no entanglement, a swap cannot happen. The only way to avoid this contradiction is to not have Chris be able to force a swap to happen--i.e., to have at least some factors involved in determining whether a swap happens be out of Chris's control.

 

[PAllen]

But whether they arrive in the time window is not completely controllable by the experimenter, correct? The experimenter can force them not to by imposing a delay, but if the experimenter doesn't do that, it's still not guaranteed that they will arrive within the time window, as I understand it.

The reason I keep harping on this is that, if it is possible for the experimenter (Chris) to guarantee that a swap does happen, then we have the problem @PeroK brought up earlier: in a setup where the 1 & 4 measurement results are in the past light cone of Chris making the decision of what, if anything, to do to photons 2 & 3 before they arrive at the BSM, Chris could wait until he sees a pair of 1 & 4 results that are inconsistent with entanglement (for example, a combination of results that is impossible in the entangled state), and then force a swap to happen at the BSM--which would contradict the predictions of QM, since QM predicts that if the 1 & 4 results show no entanglement, a swap cannot happen. The only way to avoid this contradiction is to not have Chris be able to force a swap to happen--i.e., to have at least some factors involved in determining whether a swap happens be out of Chris's control.

That is exactly the point I was raising as well. Maybe you meant me, not @PeroK ?

 

[PeroK]

That is exactly the point I was raising as well. Maybe you meant me, not @PeroK ?

It must be. I shot my bolt as far as this thread is concerned many posts ago.

 

[PeterDonis]

That is exactly the point I was raising as well. Maybe you meant me, not @PeroK ?

Oops, yes, fixed now.

 

[DrChinese]

But whether they arrive in the time window is not completely controllable by the experimenter, correct? The experimenter can force them not to by imposing a delay, but if the experimenter doesn't do that, it's still not guaranteed that they will arrive within the time window, as I understand it.

The reason I keep harping on this is that, if it is possible for the experimenter (Chris) to guarantee that a swap does happen, then we have the problem @PeroK brought up earlier: in a setup where the 1 & 4 measurement results are in the past light cone of Chris making the decision of what, if anything, to do to photons 2 & 3 before they arrive at the BSM, Chris could wait until he sees a pair of 1 & 4 results that are inconsistent with entanglement (for example, a combination of results that is impossible in the entangled state), and then force a swap to happen at the BSM--which would contradict the predictions of QM, since QM predicts that if the 1 & 4 results show no entanglement, a swap cannot happen. The only way to avoid this contradiction is to not have Chris be able to force a swap to happen--i.e., to have at least some factors involved in determining whether a swap happens be out of Chris's control.

1. You are correct in that the experimenter has no control over which 2 & 3 pairs will arrive at the BSM such that they overlap indistinguishably - that's strictly random. When the 1 & 4 photons arrive is of course related to the 2 & 3 arrival time(s) at the BSM. But... there aren't any 1 & 4 results that are inconsistent with an entangled state - at least not without considering the 2 & 3 results.

Remember that when it comes to timing and time windows, everything must be adjusted/normalized relative to everything else. And likewise, the 2 independent sources and all observers can be located as close or as far apart relative to each other as desired. No combination of locations/distance (ideal case) changes the observed outcomes.

If you didn't follow the permutations I presented in post #106 (lol), then consider this one instead. All of the sources, detectors and observers are in the same room. The distance to the 1 & 4 detectors from their respective sources is exactly the same. The distance to the 2 & 3 BSM (beamsplitter portion) is the same, plus there is an extra 20 km of fiber rolled up on the floor that the 2 & 3 photons must travel through. The distance from the beamsplitter to the BSM detectors is exactly equal. So Alice and Bob will see their mutual results together, a little before Chris decides to add a bit of delay (or not) to the photon 3 line.

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2. We only consider cases where Alice (photon 1) and Bob (photon 4) both see simultaneous clicks (defined as being within the specified time window, of course). As mentioned, this is simply something that occurs randomly. The basic scenario is as follows with Chris adding no delay, and ideal lossless conditions (and very fast observers LOL):

a) Every outcome has photons 1 & 4 entangled. Every, single one. If 1 & 4 arrive at their detectors simultaneously, so will 2 & 3. That's because 1 & 4 traveled the same distance relative to each other, and so did 2 & 3 relative to each other. So they will all appear in the same adjusted time window.


b) If Alice and Bob are checking photons 1 & 4 at the same angle settings: They can tell Chris the information needed (match or no match) to predict - with certainty - which of 2 Bell states will occur at the BSM. The BSM being in the future of what Alice and Bob just witnessed. If Alice and Bob matched (at same angles), then the BSM can only yield 2 possible outcomes: ψ+ or φ+ entanglement. If Chris got 2 clicks, it's ψ+; if only one click, it's φ+. Which of those occurs is simply random. The total number of clicks is 4 if ψ+/-; or 3 if φ+/-.

Nothing Alice or Bob do can any way affect whether the outcome is ψ+ or φ+, so there is no way to send a signal from Alice and Bob to Chris using the entanglement channel. Even though Alice and Bob can pass information on their results to Chris before Chris knows how many clicks show up at the BSM from the 2 & 3 photons. Keeping in mind that φ+/- outcomes only yield a single click at the BSM - but if Chris knows that Alice and Bob simultaneously matched at the same angles, then the φ- case can be ruled out.

Importantly: When Chris does see see 2 clicks, it will ALWAYS be a BSM combination that indicates ψ+ (if Alice and Bob matched) or ψ- (if Alice and Bob did not match). There are multiple permutations of clicks at the BSM that indicate this. On the other hand: if Chris sees only a single click at the BSM, that is neither proof nor disproof that the appropriate φ+ or φ- case occurred. Because a single click at the BSM cannot distinguish these.


c) If Alice and Bob are checking photons 1 & 4 at the different angle settings (such as for CHSH): They cannot tell Chris the information needed to predict which of 4 Bell states will occur at the BSM. That's because any combination of outcomes that Alice and Bob see is consistent with any of the 4 Bell states. Alice and Bob could provide information to Chris as to what is likely to occur though. Because there are outcomes that are more likely by far. (Typically a bit less than 75% accurate and a bit more than 25% inaccurate in the CHSH angle settings.)

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3. Hopefully everything presented so far makes sense. Now, everything the same as above, but instead: Chris chooses to implement the delay feature before knowing what Alice and Bob saw (match or no match).

d) Every outcome has 1 & 4 NOT entangled. There is no correlation at all with anything that happens at the BSM. Of course, Alice and Bob don't know this. In each and every case, the 2 & 3 photons arrived at the BSM far enough apart in time that Chris can pick out the 2 photon as the one arriving earlier, and the 3 photon as the one arriving later. Since they are distinguishable, there cannot be a swap.

Regardless of the clicks that Chris sees, there will be absolutely 0 correlation between those clicks (i.e. what they would otherwise indicates as to which Bell state occurred - and whether Alice and Bob matched or not.

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4. I would say that Chris' decision to add the delay time (or not) to photon 3's travel time - which occurs AFTER photons 1 & 4 outcomes are registered - was the "causal factor" in whether or not entanglement was swapped. There is absolutely no other factor involved, as you can clearly see, and the outcome is certain. Chris makes that decision while ignorant of the outcomes that Alice and Bob see, and in fact it wouldn't matter anyway.

Now, most anyone is going to say that Chris' decision to entangle or not - which is 100% demonstrably* a result of that decision - cannot change something that occurred in the past. And certainly, regardless, how to properly explain what happens is interpretation dependent. But what is not interpretation dependent is that Alice, Bob and Chris can literally be anywhere relative to each other - distant in terms of spacetime - and the outcomes will be exactly as I describe. And of course in no known situation can anyone send a signal that would violate signal locality, and no one can cause anything to occur in the past (or future) that would be inconsistent with the present.

-DrC

*If you are unsure about this, compare again cases a) and d) above. Note that the absolute proof can ONLY be seen in cases in which Chris sees 2 clicks at the BSM. 2 BSM clicks, no delay -> 100% correlation. 2 BSM clicks, with delay -> 0% correlation.

 

[PeterDonis]

You are correct in that the experimenter has no control over which 2 & 3 pairs will arrive at the BSM such that they overlap indistinguishably - that's strictly random.

Ok, good. That's what I thought.

When the 1 & 4 photons arrive is of course related to the 2 & 3 arrival time(s) at the BSM.

"Related" only in a very weak sense. Obviously if the 1 & 4 measurements are going to be in the past light cone of the BSM operation, there has to be a significant delay involved with the 2 & 3 photons. But the precise length of that delay is not exactly controllable by the experimenter. So the experimenter also has no exact control over the relationship between the 1 & 4 photon measurement times and the time window required for the BSM to do a swap.

there aren't any 1 & 4 results that are inconsistent with an entangled state - at least not without considering the 2 & 3 results.

Hm. I guess this is because all 4 of the entangled Bell states are possible outcomes of the BSM swap operation--it's just that we don't (at least currently) have any experimental setups that can distinguish all 4 of them. In experiments I remember being discussed in previous threads, the only entangled state that could be distinguished was the singlet state, and of course any pair of 1 & 4 results that give the same outcome for measurements in the same direction is inconsistent with that state. But from what you're saying, that would not mean 1 & 4 could not be entangled at all; it would just mean that if they are entangled, they're not in the singlet state. So as long as whatever 2 & 3 outcomes were measured were consistent with them not being in the singlet state, that would be ok. And the experimenter can't control the outcome of the 2 & 3 operation: even if it is a swap, the experimenter can't dictate that it is a swap into a particular entangled state.

the 2 independent sources and all observers can be located as close or as far apart relative to each other as desired. No combination of locations/distance (ideal case) changes the observed outcomes.

Yes, agreed.

 

[DrChinese]

1. Ok, good. That's what I thought.


2. "Related" only in a very weak sense. Obviously if the 1 & 4 measurements are going to be in the past light cone of the BSM operation, there has to be a significant delay involved with the 2 & 3 photons. But the precise length of that delay is not exactly controllable by the experimenter. So the experimenter also has no exact control over the relationship between the 1 & 4 photon measurement times and the time window required for the BSM to do a swap.


3. Hm. I guess this is because all 4 of the entangled Bell states are possible outcomes of the BSM swap operation--it's just that we don't (at least currently) have any experimental setups that can distinguish all 4 of them. In experiments I remember being discussed in previous threads, the only entangled state that could be distinguished was the singlet state, and of course any pair of 1 & 4 results that give the same outcome for measurements in the same direction is inconsistent with that state. But from what you're saying, that would not mean 1 & 4 could not be entangled at all; it would just mean that if they are entangled, they're not in the singlet state. So as long as whatever 2 & 3 outcomes were measured were consistent with them not being in the singlet state, that would be ok. And the experimenter can't control the outcome of the 2 & 3 operation: even if it is a swap, the experimenter can't dictate that it is a swap into a particular entangled state.


Yes, agreed.

1. Yay!


2. Peter, this is not correct. The relationship of the relative timings is extremely precise. And is completely under control of the experimenter - from millimeters apart to kilometers apart. This is in fact demonstrated in almost all swapping experiments, as well as many Bell type experiments. You already know this, but it may have gotten lost with all the back and forth.

Below is the HOM dip, which is measured in picoseconds; while the window is usually measured in nanoseconds. These are 4 fold coincidences. Obviously, the experiments I am citing are typically 10-15 years old. Recent advances are moving timings into much greater resolution, such as this from 2018: Attosecond-Resolution Hong-Ou-Mandel Interferometry.

In delayed choice variations, where the BSM is performed in the future of photons 1 & 4: usually that delay to the future is relatively short - exactly as you imagine - on the order of 100 meters (about 500 ns) as in here. After all, there is no specific theoretical difference between 100 meters and 100 times that. Of course, swapping itself has been demonstrated over distances of as much as 100 km (here and here*) without the delayed choice version. Since there is no particular open question related to the many delayed choice quantum experimental variations - all confirming the predictions of QM - I am not sure there is much experimental interest in setting new records for one particular version.

*From the reference: "As shown in Fig. 2, the typical peak-to-peak delays between arrival times of photons from Alice and Bob changes are 200 ps, 500 ps, and 1000 ps in rainy days, cloudy days, and sunny days, respectively, which are much larger than the coherent time of signal photons (∼ 110 ps). We use the difference between the arrival times of signal photons from Alice and Bob as error signals and feed them into a delay line to suppress the relative delay to 6 ps under all weather conditions, which is <<∼ 110 ps to ensure high interference visibility."


3. Yes and no. Assuming 1 & 4 are measured at the same angles when entangled, the results (match or mismatch) reduces the possible Bell states to 2 (which occur randomly). But only 1 of those can be discerned explicitly by the BSM. When doing the CHSH inequality, you are correct: any of the 4 Bell states would be compatible with any individual 1 & 4 result. And only 2 of those 4 can be discerned.

In some experiments, it is easier for the experimenter to look for a single specific Bell state with the BSM (what you can the singlet). So it depends what the experimenter is looking to do (in the particular paper) that determines whether to consider 1 or 2 of the 4 Bell states. If they are looking for 2 Bell states: it is possible to discern ψ+ or ψ- (most common), or φ+ or φ- (less common). But in no scenario does it make any difference to the scientific conclusion. Keep in mind that the experimenters know perfectly well that each Bell state occurs randomly and very nearly equally. If there were any hint otherwise, that would be a major issue.


4. Yay again

 

[PeterDonis]

he typical peak-to-peak delays between arrival times of photons from Alice and Bob changes are 200 ps, 500 ps, and 1000 ps in rainy days, cloudy days, and sunny days, respectively, which are much larger than the coherent time of signal photons (∼ 110 ps)

This was the sort of thing I was thinking of in what you labeled as item 2.

We use the difference between the arrival times of signal photons from Alice and Bob as error signals and feed them into a delay line to suppress the relative delay to 6 ps under all weather conditions

So this looks like the experimenters are correcting for the issue above. That looks like a key factor that I was missing.

 

[AndreasC]

Don't we have enough interpretations already?

Well it's not like we pay tax on them.

 

[Fra]

The point is Conceptual clarity.

At first I would agree but this is apparently one of the most relative notions ever invented. What is clear to you may well be hazy to someone else. So I think the discriminator is still whatever makes progress on open questions easier, clear or not.

/Fredrik

 

[Fra]

I skimmed some of

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

I skimmed these but I lack any for me preferred new conceptual grip, it seems mainly descriptive as I find no references to the observer or the context.

In the last paper he writes...

"At the level of dynamics, the microphysical laws consist of conditional or transition probabilities of the form Γij(t) ≡ p(i, t|j, 0) [for i, j = 1, . . .N], (18) each of which supplies the probability for the system to be in its ith configuration at a continuously variable time t..."

Sounds reasonable and these obviously encode the corresponding hamiltonian details, but the question is, what is the process whereby these laws (transition probabilities) are inferred by a real observer. Without this, this seems to be out of taste for me. In principle I can imagine some elaborations where these transition amplities are constructed, but I see no traces of that in this thikning from skimming the papers. without this, this remains pursely descriptive, treating the "observer" as an implicit non-interacting context, just like most other interpretations.

/Fredrik

 

[RUTA]

TL;DR Summary: 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

Here is a talk he gave this month

 

[RUTA]

Well, that's kinda the issue, isn't it? He says here: "one can reformulate quantum theory in terms of old-fashioned configuration spaces together with 'unistochastic' laws. These unistochastic laws take the form of directed conditional probabilities, which turn out to provide a hospitable foundation for encoding microphysical causal relationships. This unistochastic reformulation provides quantum theory with a simpler and more transparent axiomatic foundation, plausibly resolves the measurement problem, and deflates various exotic claims about superposition, interference, and entanglement."

That abstract sounds exotic to me! Superposition and interference are merely "claims? Measurement problem: solved! And entanglement... well I think it is very clear entanglement is a great big target on the back of this formulation. No, you cannot define/redefine the phrase "causal locality" to be different than "local causality", and then expect to dodge GHZ, advanced entanglement issues and the latest no-go's.

That's a far cry from agreeing with the idea that there is signal locality - which as far as I know is disputed by essentially no one. And if in fact you are correct, he has a new mathematical representation: so is it in fact exactly identical (since he drops the standard mathematical methods entirely) ? How would a reader understand that either way? His abstract contains some big claims, and I certainly missed the elements where he convinces of the abstract's claims.

Here is the last sentence of his conclusion, you tell me if he thinks he is onto something different and important. Because it certainly reads to me that the Bell conclusion* (along with GHZ etc.) is being thrown out.

"Remarkably, one therefore arrives at what appears to be a causally local hidden-variables formulation of quantum theory, despite many decades of skepticism that such a theory could exist."


*Which is: "No physical theory of local Hidden Variables can ever reproduce all of the predictions of Quantum Mechanics."-DrC

His last statement is correct, given his redefinition of local causality. But, as many of you have pointed out, changing the semantics will not solve the mystery of quantum entanglement for most people.

 

[Fra]

While I see other problems, not at all addressed by this "new interpretation" (such as constructing the transition matrixes rather than just assume their existence), I appreciate the attempt to clarify the meaning and definition of causality as I think the "nature of causation" is indeed at the heart of the matter, so it might be a more compatible with bayesian interpretations.

As the various traditional bell defintions of terms based on what violates bell inequalities are conceptually entangled with assumptions going into Bells ansatz. But those assumptions I see as a outdate legacy.

His last statement is correct, given his redefinition of local causality. But, as many of you have pointed out, changing the semantics will not solve the mystery of quantum entanglement for most people.

quantum nonlocality are probabilistic, and therefore do not constitute evidence of what might be labeled as "causal" anyway.

I think as long as one refuse to include the observers actions into the physics, we will likely not make progress.

The merit I find in defining causality in terms of conditional probabilities instead of single events is that they are what would be expected to causally influence an agents actions towards it's environment, rather than single events.

The only for me at least conceptually meaningful notion of local causality principle, is that local decisions are influence only by local information. Thus "causality" would then not be a statement of future correlations, but a statement about present actions. It is in this sense I also envision (but maybe differently Barandes) that "hidden variables" CAN explain the correlations in entanglement as per Reichenbach's Principle, while violating bell inequality, because the causal mechanism is not on "outcomes" but on "actions"; so the Reichenbach's keys is still hidden, so the ignorance anzats of Bell cant' be valid. This is the confusion that I always felt is built into the legacty anzats of Bell, as it implies a "ignorance interpretation".

But this conceptual understanding still needs to be realized in reconstructing the interactions (transition matrixes) that would essentiall encode the actions of matter (linking to unification). So a massive task! But I think some simply would see this conceptual possibility until the full theory is explicit. While others(me included) find it a guiding principle - I find no clues of this in his papers though. Which is why I appreciate attacking the nature of causality, but don't yet understand what else it adds.

/Fredrik

 

[iste]

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.

Barandes' formulation will violate local realism and uphold contextuality insofar that you can just describe ordinary quantum mechanics through his formulation. He gets non-local correlations in entanglement like it occurs ordinarily in quantum mechanics. The new paper I think is just denying that correlation is causation which, to my understanding, is not so conceptually different from what people have already said about things like no-signaling. I think the novelty is trying to demonstrate it through causal modeling of the explicit stochastic systems that underlie the quantum formalism in his formulation... or something like that.

The big thing about the formulation is that it does always realize definite, localized outcomes even when there are no measurements going on like during coherent superposition. This doesn't contradict non-locality or contextuality for the simple reason that these definite outcomes don't explicitly exist in orthodox quantum mechanics. All of the kinds of no-go theorems and contextual phenomena are not at the level of the realized outcomes in this formulation. In Barandes' formulation, the wavefunction is clearly not physically real (neither is wave collapse) and just predicts the actual localized outcomes. Obviously someone like yourself might want to explicitly see the following, but in principle, the fact he hasn't given an explicit treatment of GHZ or entanglement swapping doesn't matter because 1) the formulation isn't explicitly proposing any predictions or mathematical machinery explicitly different from ordinary quantum mechanics and 2) the whole point of what he has demonstrated in the first two papers is that any scenario with a unitarily evolving quantum system can be shown to be equivalent to a generalized stochastic system that realizes definite outcomes - doesn't matter the specifics of GHZ or entanglement swapping or anything else. The objects of quantum mechanics are "translated" directly from statistical information in stochastic matrices or vice versa. It's all just statistics except for the actual realized outcomes which are not explicit in the orthodox formalism (in the sense that they even occur when unmeasured), except perhaps in one place - the path integral formulation. People are encouraged to look at the Feynman paths that are summed over as computational tools but actually, they are clearly explicit expressions of stochastic trajectories in the same way you get out of Barandes' formulation or perhaps other stochastic formulations. From the pov of Barandes' formulation, these paths are in the theory because this is exactly what the theory is trying to say happens - it is not an inexplicable tool.

Because contextuality is just context-dependent statistics in lieu of a unique joint probability distribution, there is absolutely no conflict with the notion of definite outcomes as long as their relative frequencies are constituting the statistics being described. Seems to me that only if you interpret the wave-function as a physical object, do you get any conflict.

We then only have to look at Fine's theorem to see where the non-causal correlations come from. Barandes has not mentioned this but it's just a general, notable result in quantum mechanics.

https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.48.291

"It is shown that the following statements about a quantum correlation experiment are mutually equivalent… (3) There is one joint distribution for all observables of the experiment, returning the experimental probabilities. (4) There are well-defined, compatible joint distributions for all pairs and triples of commuting and non-commuting observables. (5) The Bell inequalities hold."

Bell violations are just an indicator of absent joint probability distributions which follow come from the presence of local incompatibility. It doesn't seem to me that there is any indication from this kind of result that it depends on the nature of actual physical events. Similar to how, if I rotate a physical object along different directions, and find that the order I make the rotations in matters for the final result… well this result has nothing directly to do with the physical scenario. It is a formal property that follows from the mathematics of 3D rotations. The physical scenario just has to satisfy the formal conditions, but it is not the physical scenario itself that is the cause of the rotation phenomena when I rotate a book or something. Similarly, Bell violations are just an unintuitive formal consequence of absent joint probability distributions, a connection first discovered by George Boole in the 1800s:

https://arxiv.org/abs/2010.13326

"(Pitowsky quote within paper - For certain families of events the theory stipulates that they are commeasurable. This means that, in every state, the relative frequencies of all these events can be measured on one single sample. For such families of events, the rules of classical probability — Boole’s conditions in particular — are valid. Other families of events are not commeasurable, so their frequencies must be measured in more than one sample. The events in such families nevertheless exhibit logical relations (given, usually, in terms of algebraic relations among observables). But for some states, the probabilities assigned to the events violate one or more of Boole’s conditions associated with those logical relations. - End)

The point we would like to emphasize is that tables such as the Bell table in section 2.1 can — and do — arise from experimental data, without presupposing any particular physical theory."

These absent joint probability distributions are implicit in Barandes' paper. He doesn't talk about it explicitly but his violated Markov property in the first two papers can just be seen as violations of the law of total probability for Markov trajectories. You also see in the papers that quantum interference terms can be constructed from them in the exact same way that follows from violations of total probability in orthodox quantum formulations. So it's safe to say the violated markov property plays the same role as total probability violations in causing quantum behavior from absent joint probability distributions. Classical stochastic trajectories are explicitly characterized in terms of joint probabilities along time points, as you can see through things like Kolmogorov extension theorem / consistency conditions, so these are the kinds of joint probability distributions being implied by the Markov property. Incidentally, the failure of total probability for classical stochastic trajectories have been explicitly characterized in terms of failures of "pre-existing" dynamics or non-invasive measurement, analogously to quantum mechanics:

https://arxiv.org/abs/2012.01894

Stochastic processes also have a unique explanatory value for non-local correlations in that if an individual particle's state trajectory has random dynamics then there is no issue about how particles "knew" what the measurement settings were in a Bell-type experiment, because outcomes are not fixed at source. States are always fluctuating along particle trajectories so that if you think about it, the eventually measured outcomes must have randomly occurred at the point of measurement, and this will be according to a joint probability distribution that depends on the measurement setting. However, none of these context-dependent distributions can be found from marginalization of a unique, context-invariant distribution that underlies them.

Effectively when you combine this latter stochastic advantage with what is implied by Fine's theorem, the mystery of Bell violations can be entirely deflated as a consequence of purely statistical behavior in particles that have definite locations, states, trajectories. Again, this is allowed because these realizations are not explicit in the orthodox quantum formalism; all the usual non-local correlations and contextuality co-exist happily with them. Barandes' papers are just concretely showing this by demonstrating that quantum mechanics corresponds to generalized stochastic systems, which actually do not need to be dressed in the quantum formalism in order to exhibit non-local behavior either.

 

[iste]

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.

I put this next part in a separate post because clearly I was getting carried away but I still want to emphasize the generality of these ideas though maybe it drifts away a bit from my original post.

In recent years, Bell violations have come up in social science too. Not just experiments but even in online data you can find violations of CHSH inequalities:

https://arxiv.org/abs/2012.01894

What is the commonality between quantum mechanics and this kind of online data? I think most parsimoniously, the common factor is that we just have violations of total probability here. Phenomenologically statistical, non-deterministic theories will be able to violate Bell inequalities purely as a formal stipulation, not as a direct consequence of local physical interactions. The great Daniel Kahneman died this week, having won a Nobel prize in economics for a body of work showing that humans are "irrational". Incidentally, this stuff is the exact kind of thing that is now being modeled with quantum probability theory and in which we find phenomena like Bell violations and quantum interference. Why? Because human behavior is context-dependent. There are scenarios where the statistics of human behavior vary with context in ways that were not expected from traditional rational choice theory in economics and so naive applications of classical probability theory failed to model this behavior appropriately. How does this manifest formally? Violations of total probability. Where does this also happen? Quantum contextuality.

Abramsky has shown this absence of joint probability distribution is the fundamental underlying feature that brings us quantum contextuality and non-locality:

https://iopscience.iop.org/article/10.1088/1367-2630/13/11/113036/meta

Which essentially just generalized the result Arthur Fine and various people like him found back in the mid-late 20th century.

Barandes' work reiterates the notion that such statistical phenomena are fundamentally ambivalent to how those statistics are physically instantiated, consequently there is no reason why theories which always have definite, localized outcomes cannot reproduce the same quantum phenomena if they conform to the required statistics. Barandes shows such theories are indeed equivalent to quantum mechanics in his first two papers. Does this mean we have quantum mechanical theories in psychology now? Well, arguably yes, insofar as people are now actually explicitly using quantum theory to model psychology. Not because psychology is weird, mysterious and full of woo - it is just because psychology is sometimes contextual in ways which cannot be modeled by Markov decision processes - non-Markovian just as Barandes explicitly characterizes the generalized stochastic systems in his papers.

 

[DrChinese]

1. Barandes' formulation will violate local realism and uphold contextuality insofar that you can just describe ordinary quantum mechanics through his formulation. He gets non-local correlations in entanglement like it occurs ordinarily in quantum mechanics. The new paper I think is just denying that correlation is causation which, to my understanding, is not so conceptually different from what people have already said about things like no-signaling....

The big thing about the formulation is that it does always realize definite, localized outcomes even when there are no measurements going on like during coherent superposition. This doesn't contradict non-locality or contextuality for the simple reason that these definite outcomes don't explicitly exist in orthodox quantum mechanics.

...Barandes' papers are just concretely showing this by demonstrating that quantum mechanics corresponds to generalized stochastic systems, which actually do not need to be dressed in the quantum formalism in order to exhibit non-local behavior either.

2. All of the kinds of no-go theorems and contextual phenomena are not at the level of the realized outcomes in this formulation. In Barandes' formulation, the wavefunction is clearly not physically real (neither is wave collapse) and just predicts the actual localized outcomes. Obviously someone like yourself might want to explicitly see the following, but in principle, the fact he hasn't given an explicit treatment of GHZ or entanglement swapping doesn't matter because 1) the formulation isn't explicitly proposing any predictions or mathematical machinery explicitly different from ordinary quantum mechanics and 2) the whole point of what he has demonstrated in the first two papers is that any scenario with a unitarily evolving quantum system can be shown to be equivalent to a generalized stochastic system that realizes definite outcomes - doesn't matter the specifics of GHZ or entanglement swapping or anything else.

I'm impressed, quite a defense.

1. Hmmm... so which is it?

a. It will "violate local realism", OK, that's a requirement of Bell. No sound person is really going to accept otherwise. And this paper certainly isn't the one to accomplish that.

b. It will "uphold contextuality" which in essence means it is non-realistic. Statistical outcomes are dependent on a future context, even when the measurement setting are changed midflight and are far distant. That's good, dozens of experiments show this exact point. It also means that particle observables don't have definite values outside of when they have an eigenvalue.

c. There are "non-local correlations in entanglement like it occurs ordinarily in quantum mechanics". Fine, that is generally accepted and is called "quantum nonlocality". There are about 5000 papers with this in the title on arxiv.

d. "The big thing about the formulation is that it does always realize definite, localized outcomes even when there are no measurements going on like during coherent superposition." What?? That is exactly the opposite of b. How can a superposition yield definite values on all bases simultaneously? And even if they could, how do those values appear when measured on a specific basis such that it follows quantum statistics if they are to be called "localized". (Whatever that is supposed to mean in this context, since c. above implies exactly the opposite.)

e. "This doesn't contradict non-locality or contextuality for the simple reason that these definite outcomes don't explicitly exist in orthodox quantum mechanics." Admittedly they don't exist in orthodox QM. After Bell, this is explicitly ruled out! You cannot have such outcomes - well they are even outcomes as they aren't measured - and also say it will agree with the predictions of QM. They call that...hand-waving.

f. "...quantum mechanics corresponds to generalized stochastic systems [or really?], which actually do not need to be dressed in the quantum formalism in order to exhibit non-local behavior either." So stochastic systems exhibit nonlocal behavior but feature no nonlocality? Or what?

Yes, if there is some nonlocal mechanism here that keeps entangled systems synchronized or otherwise in some kind of contact when their spatial extent grows, then all is good and I am satisfied. But that is not what I am reading.


2. How can anyone say with a straight face that they are presenting something novel, it's just like QM only better, and then blatantly ignore the obvious hurdles of things like swapping and GHZ.

a. Swapping: Systems become entangled without ever existing in a common local region. You think that is a "stochastic" result? I don't think that does very far as an argument.

b. GHZ: The assumption that particles have pre-existing values for observables yields predictions that are diametrically opposed to experiment in each and every case?

In stochastic theories, there are supposed to be many unknowns leading to various apparently random outcomes (Wiki: "Stochastic processes are widely used as mathematical models of systems and phenomena that appear to vary in a random manner."). Neither of these apply to a. or b. above.

So yes, I would insist any interpretation explain these. They are a lot more critical than something to be dismissed ("GHZ or entanglement swapping doesn't matter") by saying the basic elements are the same as orthodox QM. Either it's the same, in which it adds nothing, or it posits different elements. We know it posits different elements, because of the items discussed in 1. above.

To be fair: Please note that most "new" interpretations of QM are in the same boat. They have worked so hard to try and get around Bell (1964) by some new twist or variation, but ignore all the incredible theoretical work since: GHZ, PBR*, Kochen-Specker-Bell, Leggett, Hardy, just to name a few. All of these are serious and significant hurdles, and every one should be addressed explicitly in any new work.


*Psi-epistemic is a common term for "the wavefunction is clearly not physically real". Directly disproven by PBR.

 

[DrChinese]

1. In recent years, Bell violations have come up in social science too. Not just experiments but even in online data you can find violations of CHSH inequalities:

https://arxiv.org/abs/2012.01894

What is the commonality between quantum mechanics and this kind of online data? I think most parsimoniously, the common factor is that we just have violations of total probability here. Phenomenologically statistical, non-deterministic theories will be able to violate Bell inequalities purely as a formal stipulation, not as a direct consequence of local physical interactions.

2. The great Daniel Kahneman died this week, having won a Nobel prize in economics for a body of work showing that humans are "irrational".

1. Don't make me laugh at these ridiculous contrived examples. I've seen plenty of attempts to try and parallel classical situations with quantum entanglement, and they all fall woefully short. Because they all fail in one GIANT* manner: They cannot reproduce perfect correlations on bases chosen after the fact. That is of course ignoring the obvious fact that the examples themselves are self-chosen by the author as being "like quantum mechanics". I'll pick the human/classical scenario, let the author find the parallel.

So: How about two independently shuffled decks of cards (not initially correlated in any way) that have been shuffled by Alice and Bob, who have not communicated in any manner? Say: the 30th card in each stack should be the same color. Or the 42nd card in each? Etc. That actually happens in Bell tests featuring swapping**. That is what needs to be handled by any example purporting to show classical violations a la Bell. Think you can find a way to present them as entangled and showing perfect correlations? That's just the beginning of the challenge, good luck. (If you can solve that, we can proceed to the second half.)


2. Wow, I missed that! I am a long-time fan of his and Tversky (also Nisbett and Ross if you are familiar with them, work along similar lines of thinking). After reading your post, I picked up the paper (WSJ) and there was a nice front page article about him.


*And glaring manner. The person inventing the example forgot to consider the lesson of EPR (1935) which features perfect correlations. Bell didn't forget it, that's why his 1964 paper was titled: "On the Einstein Podolsky Rosen paradox".

**See experiments such as: High-fidelity entanglement swapping with fully independent sources

 

[Fra]

1. Don't make me laugh at these ridiculous contrived examples. I've seen plenty of attempts to try and parallel classical situations with quantum entanglement, and they all fall woefully short. Because they all fail in one GIANT* manner: They cannot reproduce perfect correlations on bases chosen after the fact. That is of course ignoring the obvious fact that the examples themselves are self-chosen by the author as being "like quantum mechanics". I'll pick the human/classical scenario, let the author find the parallel.

In recent years, Bell violations have come up in social science too. Not just experiments but even in online data you can find violations of CHSH inequalities:

https://arxiv.org/abs/2012.01894

What is the commonality between quantum mechanics and this kind of online data? I think most parsimoniously, the common factor is that we just have violations of total probability here. Phenomenologically statistical, non-deterministic theories will be able to violate Bell inequalities purely as a formal stipulation, not as a direct consequence of local physical interactions. The great Daniel Kahneman died this week, having won a Nobel prize in economics for a body of work showing that humans are "irrational". Incidentally, this stuff is the exact kind of thing that is now being modeled with quantum probability theory and in which we find phenomena like Bell violations and quantum interference. Why? Because human behavior is context-dependent. There are scenarios where the statistics of human behavior vary with context in ways that were not expected from traditional rational choice theory in economics and so naive applications of classical probability theory failed to model this behavior appropriately.

A conceptual commonality is also that social interactions is explicitly about interacting information processing agents (humans). This is why this analogy makes conceptual sense at least for me, due to my interpretation. This means we can understand "quantum interactions" as something that emerges naturally in systems containing information processing agents or beeing isomorphic to that.

The problem with many models that find that humans are not rational is that the MEASURE of rationality is not as simply to define. Clearly a human beeing is not a money machine, processing emotions is just as information and in principle that is also "information". Even within this way of thinking there are alot of variation.

I quoted tses papers in an old thread

Nashian game theory is incompatible with quantum physics​

"We suggest to look at quantum measurement outcomes not through the lens of probability theory, but instead through decision theory. We introduce an original game-theoretical framework, model and algorithmic procedure where measurement scenarios are multiplayer games with a structure all observers agree on. Measurement axes and, newly, measurement outcomes are modeled as decisions with nature being an action-minimizing economic agent
...
Most significantly, we observe that game theory based on Nash equilibria stands in contradiction with a violation of Bell inequalities. Hence, we propose that quantum physics should be analyzed with non-Nashian game theory, the inner workings of which we demonstrate using our proposed model."
-- https://arxiv.org/abs/1507.07341

​

Quantifying and Interpreting Connection Strength in Macro- and Microscopic Systems: Lessons from Bell’s Approach​

"As a macroscopic example from the financial world, we show how the unfair use of insider knowledge could be picked up using Bell statistics. Finally, in the discussion of realist interpretations of quantum mechanical Bell experiments, cheating strategies are often expressed through the ideas of free choice and locality. In this regard, violations of free choice and locality can be interpreted as two sides of the same coin, which underscores the view that the meaning these terms are given in Bell’s approach should not be confused with their everyday use. In general, we conclude that Bell’s approach also carries lessons for understanding macroscopic systems of which the connectedness conforms to different causal structures."
-- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8947266/

The conceptual association here I mave between "breaking isolation" of entangled particles, and "unfair use of inside information". Just like in a quantum experiment, we can "detect" if the isolation is broken, one might detect the use of inside information as it changes the results of the total game over time.

For me these are just conceptual parallellts, I didn't bother study or nitpick the papers in details as the conceptual analogue is clear to me anyway.

/Fredrik

 

[PeterDonis]

*Psi-epistemic is a common term for "the wavefunction is clearly not physically real". Directly disproven by PBR.

More precisely, PBR disproves "epistemic" models in which the wave function is treated as a distribution over underlying "ontic" states. But that is not the only kind of model in which the wave function is "not physically real" in the sense that it doesn't describe the real physical state of individual quantum systems. For example, PBR says nothing, as far as I can see, that rules out ensemble or statistical interpretations such as Ballentine's, or the thermal interpretation of @A. Neumaier, since those interpretations do not treat the wave function as a distribution over underlying ontic states--but they also don't treat it as describing the physically real state of individual quantum systems.

 

[martinbn]

More precisely, PBR disproves "epistemic" models in which the wave function is treated as a distribution over underlying "ontic" states. But that is not the only kind of model in which the wave function is "not physically real" in the sense that it doesn't describe the real physical state of individual quantum systems. For example, PBR says nothing, as far as I can see, that rules out ensemble or statistical interpretations such as Ballentine's, or the thermal interpretation of @A. Neumaier, since those interpretations do not treat the wave function as a distribution over underlying ontic states--but they also don't treat it as describing the physically real state of individual quantum systems.

Which imterpretations are disproven? I asking for examples.

 

[Fra]

It may be useful to summarize the assumptions that are necessary for the result. Three can be identied
...
The third assumption is that measuring devices respond solely to the physical properties of the systems
they measure. We do not assume underlying determinism. Even given a full specication of , it may only be possible to make probabilistic predictions about the outcome of a measurement.


-- https://arxiv.org/abs/1111.3328v1

Their third assumption is exactly the one that was objectionable to me, even in bells ansatz, it is no different. It assumes that the interaction betwee measurement device and the "quantum system" in a single interaction, depends ONLY on the physical property of the quantum system, namely the hidden variable.

The only for me at least conceptually meaningful notion of local causality principle, is that local decisions are influence only by local information. Thus "causality" would then not be a statement of future correlations, but a statement about present actions. It is in this sense I also envision (but maybe differently Barandes) that "hidden variables" CAN explain the correlations in entanglement as per Reichenbach's Principle, while violating bell inequality, because the causal mechanism is not on "outcomes" but on "actions"; so the Reichenbach's keys is still hidden, so the ignorance anzats of Bell cant' be valid. This is the confusion that I always felt is built into the legacty anzats of Bell, as it implies a "ignorance interpretation".

This is directly contrast to this. By "local information" means expectations on the system, by the measurement device, the opposite of unknown actual states of hidden variables.

The third assumption alone makes no sense for any scenario where the interaction is changed by the mutual EXPECTATION of the physical states. This is exactly what is going on in social interactions too to connect to the analogy, and IMO the reason why "games of expectations" does not fulfill the assumptions that is used in bells theorem, pbr etc. The missing component, is the understnading of causation or interaction in the first place. IF one looks at social interactions, I would argue that it is in fact intuitive that interactions are not depending only on the hidden STATE of the interacting object, but our OWN EXPECTATIONS of does change our response, and thus the whole interaction.

/Fredrik

 

[DrChinese]

More precisely, PBR disproves "epistemic" models in which the wave function is treated as a distribution over underlying "ontic" states. But that is not the only kind of model in which the wave function is "not physically real" in the sense that it doesn't describe the real physical state of individual quantum systems. For example, PBR says nothing, as far as I can see, that rules out ensemble or statistical interpretations such as Ballentine's, or the thermal interpretation of @A. Neumaier, since those interpretations do not treat the wave function as a distribution over underlying ontic states--but they also don't treat it as describing the physically real state of individual quantum systems.

Amazingly, all psi-epistemic interpretations deny the applicability of PBR. Go figure.

Which interpretations are disproven? I asking for examples.

Ditto, all psi-epistemic interpretations deny the applicability of PBR. Of course, there are many others that think they are generally disproven. But being a gentleman, and considering we are talking about interpretations, I try to leave the conclusion to each person.

Their third assumption is exactly the one that was objectionable to me, even in bells ansatz, it is no different. It assumes that the interaction between measurement device and the "quantum system" in a single interaction, depends ONLY on the physical property of the quantum system, namely the hidden variable.

Consider this: What device/detector are we talking about? In a typical Bell test, there are 4 detectors and 2 polarizing beam splitters (PBS). So... is it the beam splitter where your objection arises? Because that implies Alice's beam splitter contains hidden variables that influence the outcome as H> or V>. That result has never been observed - just consider what happens when any pure H> beam goes into a PBS. It comes out one port with nearly perfect consistency/accuracy. So: No relevant hidden variables there. And what about the detectors? The only thing left up to the detector is to click - or not. No chance of a detection by the H> detector causing the V> detector to click, right? Nothing about the measurement apparatus is going to distort any statistical results, and certainly not with the extremely high quality gear today.

But none of that matters. We already know there is nothing material added by any of the measurement devices, and therefore the "third assumption" is valid. The measurement device could not possibly affect the statistical outcomes, unless remote apparati (of Alice and Bob) are themselves entangled with each other - a possibility that is far-fetched in the extreme.

How do we know this? There are perfect correlations at identical angles! If the measurement devices were part of the equation, you would see that clearly - sometimes the measurement would yield a different answer than expected. But no, we get as close to 100% matching as is experimentally feasible. So there can't be some hidden variables residing in one detector - and influencing the result - unless the same hidden variables are present in the other. Let's face it, your objection does not fit with experiment fact.

 

[martinbn]

Amazingly, all psi-epistemic interpretations deny the applicability of PBR. Go figure.

Ditto, all psi-epistemic interpretations deny the applicability of PBR. Of course, there are many others that think they are generally disproven. But being a gentleman, and considering we are talking about interpretations, I try to leave the conclusion to each person.

Can you name some that are disproven, at leaseast according to you or the original PBR paper.

 

[PeterDonis]

all psi-epistemic interpretations deny the applicability of PBR.

The interpretations I described are not "psi-epistemic" by the PBR definition. That's why PBR is not applicable to them.

 

[Fra]

Consider this: What device/detector are we talking about? In a typical Bell test, there are 4 detectors and 2 polarizing beam splitters (PBS). So... is it the beam splitter where your objection arises? Because that implies Alice's beam splitter contains hidden variables that influence the outcome as H> or V>. That result has never been observed - just consider what happens when any pure H> beam goes into a PBS.

Has this really been tested, separating the source and detector, by distance that would required FTL transfer?

It comes out one port with nearly perfect consistency/accuracy. So: No relevant hidden variables there. And what about the detectors? The only thing left up to the detector is to click - or not. No chance of a detection by the H> detector causing the V> detector to click, right? Nothing about the measurement apparatus is going to distort any statistical results, and certainly not with the extremely high quality gear today.

In how I interpret this: each beam splitter is tuned to("informed") the give preparation procedure. The interference pattern IMO is caused by the interaction between the preparation and the splitter. This means I think that splitter actually interacts differently with the beam of particles due to the preparation procedure.

One way to falsify this idea would be if the preparation procedure was prepared in one way, and the beam was equilibrated, then the preparation procedure would suddenly change, faster than the time it will take for light to propagate from preparate device to splitter and without breaking the entanglement. Not sure if it has been done. But if it would be done, and it still gives the interference, it would probably make me sleepless for some time.

Note, the decision of Alice or Bob to change the polarizer angle does not change the preparation and is a different experiment, we know this has been done. But a "decision" to change the preparation procedure at the source, without giving the information to propagate to Alice and Bob in time before the detection, would be very interesting.

If anyone knows if this experiment has been done, I would be very thankful.

/Fredrik

 

[DrChinese]

The interpretations I described are not "psi-epistemic" by the PBR definition. That's why PBR is not applicable to them.

PBR On the reality of the quantum state: "One [assumption] is that a system has a “real physical state” – not necessarily completely described by quantum theory, but objective and independent of the observer. ... Nonetheless, this assumption, or some part of it, would be denied by instrumentalist approaches to quantum theory, wherein the quantum state is merely a calculational tool for making predictions concerning macroscopic measurement outcomes."

So exactly as you say.

Except that's throwing something of a baby out with the bathwater. Denying there is a state that is "objective and independent of the observer" doesn't sound so reasonable if you are saying there is just an update of knowledge via a "calculational tool". But an out is an out.

 

[martinbn]

PBR On the reality of the quantum state: "One [assumption] is that a system has a “real physical state” – not necessarily completely described by quantum theory, but objective and independent of the observer. ... Nonetheless, this assumption, or some part of it, would be denied by instrumentalist approaches to quantum theory, wherein the quantum state is merely a calculational tool for making predictions concerning macroscopic measurement outcomes."

So exactly as you say.

Except that's throwing something of a baby out with the bathwater. Denying there is a state that is "objective and independent of the observer" doesn't sound so reasonable if you are saying there is just an update of knowledge via a "calculational tool". But an out is an out.

So, what are the names of some interpretations that the PBS theorem applies to?

 

[DrChinese]

Has this really been tested, separating the source and detector, by distance that would required FTL transfer?

In how I interpret this: each beam splitter is tuned to("informed") the give preparation procedure. The interference pattern IMO is caused by the interaction between the preparation and the splitter. This means I think that splitter actually interacts differently with the beam of particles due to the preparation procedure.

One way to falsify this idea would be if the preparation procedure was prepared in one way, and the beam was equilibrated, then the preparation procedure would suddenly change, faster than the time it will take for light to propagate from preparate device to splitter and without breaking the entanglement. Not sure if it has been done. But if it would be done, and it still gives the interference, it would probably make me sleepless for some time.

Note, the decision of Alice or Bob to change the polarizer angle does not change the preparation and is a different experiment, we know this has been done. But a "decision" to change the preparation procedure at the source, without giving the information to propagate to Alice and Bob in time before the detection, would be very interesting.

If anyone knows if this experiment has been done, I would be very thankful.

/Fredrik

Not sure what you are asking about, Fredrik. The distance from the Alice's source to Alice's detector cannot be FTL by definition, and ditto for Bob's setup.

What is FTL (I call usually call it "distant" or "remote") and outside of backward light cones is between:

a. Alice's source as compared to Bob's source and Bob's detector.
b. Alice's detector as compared to Bob's source and Bob's detector.

There are a number of experimental realizations of this in a variety of permutations:

These have everything remote:
High-fidelity entanglement swapping with fully independent sources
Experimental delayed-choice entanglement swapping

In this one, the measurement settings are also changed mid-flight:
Experimental loophole-free violation of a Bell inequality using entangled electron spins separated by 1.3 km

 

[PeterDonis]

Denying there is a state that is "objective and independent of the observer" doesn't sound so reasonable if you are saying there is just an update of knowledge via a "calculational tool".

That's not the only kind of interpretation that the PBR theorem doesn't address. Neither of the interpretations I named--the statistical interpretation as described by, for example, Ballentine, and the thermal interpretation published by @A. Neumaier--say that "there is just an update of knowledge". They do talk about "update of knowledge", but that is not the only meaning ascribed to states. The key point is that they do not treat the quantum wave function as an epistemic distribution over underlying ontic states of individual quantum systems.

Note that we had a thread some time ago discussing whether the PBR theorem rules out the Ballentine ensemble interpretation:

https://www.physicsforums.com/threa...ion-inconsistent-with-the-pbr-theorem.998624/

I don't think that thread reached a conclusive answer either way--which just underscores the fact that there are unresolved disagreements in this area, and indeed with regard to QM interpretations in general.

 

[PeterDonis]

Other relevant older threads on the PBR theorem:

https://www.physicsforums.com/threads/is-there-an-additional-assumption-in-the-pbr-theorem.960246/

https://www.physicsforums.com/threads/understanding-pbrs-additional-assumption.961010/

 

[Fra]

Not sure what you are asking about, Fredrik. The distance from the Alice's source to Alice's detector cannot be FTL by definition, and ditto for Bob's setup.

You are right, I did mean what isn't possible but I was too fast.

I was trying to make a quick reply about what could maybe falsify my understanding, but obviously that idea didn't work

/Fredrik

 

[Fra]

Denying there is a state that is "objective and independent of the observer" doesn't sound so reasonable if you are saying there is just an update of knowledge via a "calculational tool".

I see no conflict here.

The conclusion you make seems to make sense if you tink that the "information" is not contextual to the observer, but just a matematical tool that human physicists use, and where the observer is just like an objective bayesian perspective. But it's not the option I think makes most sense anway.

In an interpretation where "information update" is performed by the "observer beeing an agent and part of the universe" and thus constrained by it's physical resources, it clearly is not fundamentally observer independent nor objective.

But is possbility is the there exists an equivalence class of observers and subjective information updates that are consistent. And this symmetry can be either fixed (given from laws of physics in a timeless manner), or "emergent".

/Fredrik

 

[PeterDonis]

that is probably as far as I can go without violating rules

No, you've gone further than that. You have been cautioned before about not having any model to back up your claims. Now you're being cautioned again, and warned and banned from further posting in this thread to boot.

 

[iste]

Apologies late reply and that this is long. I just always want to ensure I am being clear.

What?? That is exactly the opposite of b. How can a superposition yield definite values on all bases simultaneously? And even if they could, how do those values appear when measured on a specific basis such that it follows quantum statistics if they are to be called "localized". (Whatever that is supposed to mean in this context, since c. above implies exactly the opposite.)

Because in Barandes' formulation, the definite outcomes or configurations the system are in do not appear in the traditional objects of quantum mechanics like wave-functions, density matrices, etc.

First, to clarify generally:

For statistical systems you might distinguish 1) the probability space / random variables, which carry statistical information; from 2) the realized outcomes. (I will be repeating these two numbers a lot in this post so these are what I mean when I say them). At any time, a statistical system could be said to produce a definite outcome which is a physical event; like if you roll a dice, you always only get one number at a given time. The long-run behavior of that dice rolling is described by probability spaces and random variables but these just predict the actual realizations when you repeat the scenario indefinitely. The objects of 1) therefore are not the physical events themselves that appear in a particular time or place - probability spaces are abstract constructs for prediction. The actual physical events are the objects of 2), the actual realized outcomes i.e. what happens when you actually throw the dice a single time.

Back to Barandes' formulation:

His papers essentially translate between stochastic matrices and a Hilbert Space representation to dress up a stochastic process in the quantum formalism. Importantly, only 1) is being translated. Virtually all of the traditional objects of quantum mechanics are coming from 1) which do not represent physical events.

All of the fundamental results about non-locality and contextuality are therefore concerning objects of 1) when they have been dressed up in quantum formalism. Now, from Barandes' formulation you can also translate quantum mechanics back into a generalized stochastic framework. So what is going to happen? Well nothing is being changed about the information in quantum mechanics, only the formalism is changed. Therefore contextuality and non-locality are preserved when described in the stochastic framework; but now, in addition, you will have these definite realized outcomes since all that has happened is we have translated quantum objects back into objects of probability spaces / random variables, and these will give realized outcomes that were not explicit in the traditional quantum formalism.

Superpositions will therefore not have definite values on all bases simultaneously like you say - they will be the same as normal quantum mechanics. But they will ALSO realize definite outcomes which can be seen when you translate the quantum system into a stochastic one and are not observable from looking at the objects of quantum mechanics in the same way that I cannot see my realized outcome for rolling a 4 at t5 just by looking at the probabilities for rolling a 4.

In fact, I can talk about probability spaces and random variables without ever explicitly talking about the realized outcomes. The fact I rolled a particular number at t4 and another at t8 is immaterial to the description at the level of random variables and probability spaces. All the things I can prove wrt to probability theory don't rely on specific realized outcomes. So there is no reason why introducing realized outcomes should change anything about the quantum formalism. Its just the fact that you can translate it back into the formalism of a stochastic system implies it has definite outcomes at any particular time which are predicted from probability spaces, though not in as straightforward away as for conventional Markov systems which is the way people tend to think about stochastic systems.

The coherences of superposition in this formulation is information, even if more implicitly, about long-run statistics, not about any actual physical event that exists in a specific time and place. There is therefore no contradiction here in exactly the same way that having a probability distribution for dice rolls does not contradict definite realized outcomes every time we roll a dice. The fact that superposition does not look like a normal classical probability distribution is a red herring because we are talking about a special (well actually, generalized) kind of stochastic system.

Admittedly they don't exist in orthodox QM. After Bell, this is explicitly ruled out! You cannot have such outcomes - well they are even outcomes as they aren't measured - and also say it will agree with the predictions of QM. They call that...hand-waving.

Yes, like I say, this is because quantum mechanics is only about 1) which are not physical events or objects in Barandes' formulation. 2) only becomes apparent when you translate the quantum system into a stochastic one. Everything Bell said applies to this translated stochastic system... because all of these formal results are about 1), which are just statistics. There is therefore no contradiction between the notions of a system displaying both contextuality and non-local statistics in 1), which then also realizes definite outcomes of 2). Nothing Bell says rules out anything about 2).

So stochastic systems exhibit nonlocal behavior but feature no nonlocality? Or what?

The generalized stochastic systems in Barandes' papers and quantum systems will both display non-local behavior in that they are both equivalent to each other.

Yes, if there is some nonlocal mechanism here that keeps entangled systems synchronized or otherwise in some kind of contact when their spatial extent grows, then all is good and I am satisfied. But that is not what I am reading.

Barandes demonstrates that you can get the kind of non-local behavior of quantum mechanics by just constructing a generalized stochastic system. He doesn't explicitly say how, just that it does naturally occur in the generalized stochastic system.

My view is that it can be explained following from results like Fine's theorem. Bell violations are equivalent to the absence of joint probability distributions. From what I can see, the indivisibility condition Barandes' uses as a prominent part of defining a generalized stochastic system does correspond to the absences of joint probability distributions which are directly related to Bell violations. As I noted before, this is of a formal nature and so no special physical mechanisms are required, just the inability to construct a context-invariant joint probability distribution. That doesn't mean the systems are not entirely well-defined, just not on a single probability space.

2. How can anyone say with a straight face that they are presenting something novel, it's just like QM only better, and then blatantly ignore the obvious hurdles of things like swapping and GHZ.

a. Swapping: Systems become entangled without ever existing in a common local region. You think that is a "stochastic" result? I don't think that does very far as an argument.

b. GHZ: The assumption that particles have pre-existing values for observables yields predictions that are diametrically opposed to experiment in each and every case?

Barandes' formulation should be able to recreate all GHZ and entanglement swapping phenomenon because the core of these papers is just a "dictionary" which one can use to translate between quantum and stochastic formalisms whilst retaining all of the same behavior and properties. I don't see why it shouldn't work in the same for these cases even though they may seem particularly strange.

I can't say much else without being too speculative but it maybe worth noting a secondary point that the equivalence between Bell violations and absent joint probability distributions suggests that the crucial factor above all else is just incompatible observables. This paper even suggests that entanglement isn't strictly required for Bell violations:

https://arxiv.org/abs/1907.02702

GHZ, PBR*, Kochen-Specker-Bell, Leggett, Hardy...

*Psi-epistemic is a common term for "the wavefunction is clearly not physically real". Directly disproven by PBR.

Again, Barandes' formulation implies that any quantum scenario displaying behaviors typified by these results can just be translated into a stochastic system. Nothing different to standard quantum mechanics is implied.

From my understanding, the root of all these examples is contextuality as expressed in the absence of joint probability distributions, and this does seem to be a prominent assumption in Barandes' formulation where it is also responsible for quantum interference.

Finally, going back to an earlier point you said:

Statistical outcomes are dependent on a future context, even when the measurement setting are changed midflight and are far distant. That's good, dozens of experiments show this exact point. It also means that particle observables don't have definite values outside of when they have an eigenvalue.

This phenomena is not so weird in stochastic interpretations as implied by Barandes' formulation. The particle is set on a trajectory and its configuration is always randomly changing over. Therefore, at a point in time just before it is measured, it will be in a different configuration to what it will be when the measurement interaction eventually happens. Similarly, the configuration at both these time points will be different to the particle's configuration at the beginning of its trajectory. Its always changing. The particle is always in a definite configuration and has a definite trajectory but the configuration just changes randomly at every time point on the trajectory. Obviously the only configuration seen by the experimenter is the one that is eventually measured. The quantum state, the wavefunction are not physical objects but solely carry statistical information. Because the eventual measured configuration randomly occurs at the point of measurement, it is not correct to say that outcomes depend on a future context in this formulation because that assumes the particle was only ever in one configuration decided at the beginning of its trajectory. At the point of measurement, the observed outcome will occur randomly according to a joint probability distribution that depends on the measurement setting there and then. The absence of context-invariant joint distribution then implies Bell violations under Fine's theorem due to the non-commutativity between measurement settings which is sufficient to preclude a joint distribution even though the measured pairs commute.

 

[iste]

1. Don't make me laugh at these ridiculous contrived examples.

Im not implying these are the same as quantum mechanics, just that Bell-type violations are generic which implies a common cause, and that is the absence of unique joint probability distributions. They may be different in all kinds of different scenarios. For instance, I believe the ones in those papers violate Tsirelson's bound which cannot happen in quantum mechanics.

 

[iste]

For example, PBR says nothing, as far as I can see, that rules out ensemble or statistical interpretations

This is how the Barandes' formulation is treating the Wave function.

"One [assumption] is that a system has a “real physical state” – not necessarily completely described by quantum theory, but objective and independent of the observer. ... Nonetheless, this assumption, or some part of it, would be denied by instrumentalist approaches to quantum theory, wherein the quantum state is merely a calculational tool for making predictions concerning macroscopic measurement outcomes."

I want to emphasize that when I say definite realized outcomes here I am talking in the same way that a random variable can realize a specific outcome, but a single outcome won't tell you anything about the probabilities of a random variable. Only repeating the scenario many times and looking at the frequencies will give you some idea of the probabilities. The quantum state / wavefunction plays the same role as probabilities there. They aren't referring to a specific event, their information can only become apparent empirically over many many repetitions of some scenario.

 

[DrChinese]

1. Apologies late reply and that this is long. I just always want to ensure I am being clear.

Finally, going back to an earlier point you said:

DrChinese: "Statistical outcomes are dependent on a future context, even when the measurement setting are changed midflight and are far distant. That's good, dozens of experiments show this exact point. It also means that particle observables don't have definite values outside of when they have an eigenvalue."


2. This phenomena is not so weird in stochastic interpretations as implied by Barandes' formulation. The particle is set on a trajectory and its configuration is always randomly changing over. Therefore, at a point in time just before it is measured, it will be in a different configuration to what it will be when the measurement interaction eventually happens. Similarly, the configuration at both these time points will be different to the particle's configuration at the beginning of its trajectory. Its always changing. The particle is always in a definite configuration and has a definite trajectory but the configuration just changes randomly at every time point on the trajectory. Obviously the only configuration seen by the experimenter is the one that is eventually measured. The quantum state, the wavefunction are not physical objects but solely carry statistical information. Because the eventual measured configuration randomly occurs at the point of measurement, it is not correct to say that outcomes depend on a future context in this formulation because that assumes the particle was only ever in one configuration decided at the beginning of its trajectory. At the point of measurement, the observed outcome will occur randomly according to a joint probability distribution that depends on the measurement setting there and then. The absence of context-invariant joint distribution then implies Bell violations under Fine's theorem due to the non-commutativity between measurement settings which is sufficient to preclude a joint distribution even though the measured pairs commute.

1. You're good - time's no problem.

2. Sure, I get the idea. They have definite values at all times but are dynamic. That is quite similar to the Bohmian concepts where there are ongoing influences ("pilot waves"). But for everything to work out, there must be contextuality. And that requires FTL influences - and I mean explicit ones - to make sense. There can be no hiding behind the mask of a local stochastic interpretation.

"...its configuration is always randomly changing..." Because that directly conflicts with the idea that you end up with perfect correlations after measurement settings are remotely changed midflight and the entangled particles are distant (considering c) - and have never interacted in any manner.

You can't have it both ways. @Demystifier (our resident Bohmian expert if I've ever seen one) acknowledged that Bohmian Mechanics is contextual. Nonlocal AND contextual. That makes sense to me (although I'm not a Bohmian) because all of the experimental and theoretical evidence points to the idea that QM is both nonlocal AND contextual. There is absolutely nothing that implies otherwise in the entire canon. But clearly, not a logical requirement either.

Give us a specific example of how any local stochastic theory can explain the perfect correlations. And I don't mean by saying X is equivalent to Y, Y is equivalent to Z, so X is equivalent to Z. I mean: How do those entangled photons, previously uncorrelated in any manner whatsoever, demonstrate perfect correlations when a measurement basis is selected midflight and the observers Alice and Bob are far apart?

Admittedly that is not really on you to provide such example; but I cannot extract any concept out of the Barandes paper that implies such is feasible. So if "the wavefunction are not physical objects but solely carry statistical information" as you say, then how do two far distant photons become entangled and then become 100% perfectly correlated? Either there's a nonlocal mechanism at play, or... ???

 

[DrChinese]

I'm not implying these are the same as quantum mechanics, just that Bell-type violations are generic which implies a common cause...

Again, this is arguing both sides of a coin. Bell violations have nothing to do with human behavior whatsoever, and cannot be called "generic" when there is no known similar physical phenomena. If you can demonstrate that no local hidden variable theory can match the predictions of future generally accepted human behavior theory "X", then we'll have something to debate. Because that is what Bell does with QM and local realism.

And whether there are root "causes" or not (for probabilistic behavior) in QM is currently unknown. What is known (as best as can be) is that determinate causes cannot be propagated faster than c. Call that "a causally local formulation of QM" (per Barandes) ? Who cares? Everyone accepts that as far as I can tell, regardless of interpretation. But indeterminate FTL influences ("quantum nonlocality") are clearly within the realm possibility, as hundreds of experiments demonstrate. That's the gold standard.

I actually cannot believe that this is 2024, and anyone is still pushing the idea of a local realistic theory. Barandes should say these words: "Yes, it's nonlocal under the sheets." As I believe I have said previously, I literally have dozens of references for authors claiming "Bell was wrong", there's a hidden assumption, the experiments are tainted, it doesn't work in 10 dimensions or whatever. I had already included Barandes in that list anyway. So *unless* there is a concrete example to discuss/debate as to what I asked in #144, I don't think I have anything further to add of use or interest to anyone in this thread.

 

[Fra]

Again, this is arguing both sides of a coin. Bell violations have nothing to do with human behavior whatsoever,

Yes, just like "observer" in QM has nothing to do with human brains.

The idea is that it however has todo with interacting information processing systems in a more abstract sense. Big difference. Of course, what it REALLY means for an electron to process information about the nucleus is something that needs to be clarified, and noone has yet done it, so this is why I think the explicit examples that you would like to see to be convinced are still not published anywhere. So its fair to be sceptical.

But I think there indeed is a generic phenomena, that exists in certain self-organising complex systems. And self-organisation naturally happens non-trivially when the parts process and act upon information about other parts.

I just watched one of Barandes clips, and I just noticed that the assumption that I find wrong in bells ansatz, and that i called the equiparition assumption, is what he calles "markov divisibility" assumption here.. but its the same thing, and it¨s indeed what prevents the interference patterns; i totally agree with that up to that point.



My only issue with Barandes, is that the big challenge is to see how to construct the transition matrixes that would define the stochastic processes, and I think there is not one stochastic process but many interacting ones... these are not addressed i think in his paper, and this could be what revoulutionize our understanding once we get to understand that more. To leave the marices for some manual fine tuning by physicists is not a good idea. But the way see this, this will be nothing like a simple classical objective stochastic theory, so I think Dr Chineese doesn't need to worry about wether we are in 2024. I think what will come out of this will both clarify some things with quantum mechanics, but at the price of introducing even other proably worse trouble.

/Fredrik

 

[iste]

That is quite similar to the Bohmian concepts where there are ongoing influences ("pilot waves"). But for everything to work out, there must be contextuality. And that requires FTL influences - and I mean explicit ones - to make sense. There can be no hiding behind the mask of a local stochastic interpretation.

I am pretty sure this interpretation evades the criticisms against Bohmian mechanics because it doesn't explicitly write particles into the theoretical machinery and have their trajectories directly determined by a pilot wave or something like that. There are therefore no ongoing influences. It does not strictly describe the behavior of a single particle moving through space, but the statistical behavior if you repeat the scenario a large number of times. And it is fully contextual and non-local by normal quantum mechanics standards. I still don't think you need faster than light influences for contextuality and non-locality.

I still think the idea that Bell violations just follow from incompatibility and/or the absence of joint distributions as a formal relation is sound. I think the fact that Barandes can get non-local correlations from a generalized stochastic system is testament to that, because by its very nature, this implies you don't need other deeper underlying mechanisms to get non-local correlations other than a certain kind of stochastic system with violated Markov properties. Which is strange, because that is in some ways a very un-specific demand for a system. It doesn't seem to be a physical one particularly, in the same way that the equivalence/relationship between Bell violations and absent joint probabilities doesn't seem particularly physical in the sense of depending on whatever physical laws or possibilities that constrain how the world works (e.g. like speed of light).

I still find it plausible that even considering the following:

"...its configuration is always randomly changing..." Because that directly conflicts with the idea that you end up with perfect correlations after measurement settings are remotely changed midflight and the entangled particles are distant (considering c) - and have never interacted in any manner.

Bell violations could still hold purely because they are just a consequence of the absence of a joint probability distribution (and the fact we are talking about probability distributions kind of implies that the relationship must be hold in the midst of random behavior anyway). In the Barandes paper, the violated joint probability distribution is signified by the violated Markov property. The relationship could then be formal in the same way that say the sum of deviations from the mean is always 0. It doesn't matter what sample I am using, where I find it, how far apart they are etc, etc., the sum is always zero because its a formal relationship. Or again, if I rotate objects, it doesn't matter the physical instantiation, those rotations do not commute as a formal requirement. I might make a long quote from a paper shortly to try further to elaborate a response on this.

And to re-emphasize, the mid-flight change in settings will not matter for measurement correlations since all that matters are the setting-dependent joint probability distributions at the point of measurement, this context-dependence being the cause of the joint probability distribution violation that causes Bell violations.

Again, this is arguing both sides of a coin. Bell violations have nothing to do with human behavior whatsoever, and cannot be called "generic" when there is no known similar physical phenomena.

Again, the relationship is formal not physical, which I will try to give an attempt at elaboration from a paper shortly.

And I have to emphasize that Barandes' formulation is arbitrarily as close to standard quantum mechanics as you want. It is as non-local as quantum mechanics is. My line, and I think the line of the latest Barandes paper, is just that these non-local correlations are due to interactions which are entirely local.

 

[Fra]

An attempt to add to the conceptual picture I at least "see" behind this.

Unless the association between stochastic processes and information processing was clear, they way they are connected in my view is simple: Scrambling followed by filtering/selection, can be seen as a natural form of spontanous information processing. This is one conceptual way to view a stochastic process, as a simple kind of information processing. And it needs to be "simple" because as Dr Chinese mentioned, we aren't talking about human infomration processing, but about some abstract seeds for it that we can imagine beeing implemented by simple material systems. This is the link as well to contextual stochastic models and agent perspective. They are not in conflict

What makes this different that a global non-contextal stochastic model, is that that a non-contextual mode is by constructing lacking insight into the internal causal mechanism of "internal interactions". And this is intuitively what causes interferences.

From model theoretic perspective, Agent based models has some conceptual advantages over the more typical differential based approach, even though many problems can be cast in both forms - they are not in conflict per see. But trying to understand that nature of interactions and causation maybe be easier on one form.

I have not excellent example for this exact topic, but a general paper on the comparasion of ABM vs PDE in complex systems is here

This is no ultimate argument or explict suggestion, but Im just trying to help spark seeing the possibiities that I see, and from the responses here I can tell, some does not see this at present. Which is a pity as i think this is really exciting.

Learning differential equation models from stochastic agent-based model simulations​

https://arxiv.org/abs/2011.08255

Thus the vision is that there is a duality between any effective theory of standard model, and a correspnding agent-based formulation and the latter would be more intuitive, and add explanatory value to quantum weirdness and unification and connect how effective theories renormalize, and how agent-based models evolve as you scale the agents.

All this I would label as stochastic models as well, but DIFFERENT stochastic models than simplistic brownian motion which is non-contextual.

/Fredrik

 

[iste]

Woops, this ended up happening later than I said. Second post will quote from different paper.

So I will post quotes from some papers (might as well be one paper by the same author) who look at spin correlations just as a direct consequence of probability distributions. As far as I can see, they are just elaborating on what Fine said:

(might as well re-link from earlier)
https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.48.291
https://pubs.aip.org/aip/jmp/articl.../Joint-distributions-quantum-correlations-and

Bell violations are equivalent to absences of joint probability distributions and absences are a direct consequence of incompatible observables.

Quotes from papers:

https://www.mdpi.com/1099-4300/24/10/1439
(just from abstract)

"The dependence of the spin correlation on conditional probabilities allows for a clear separation between system state and measurement context; the latter determines how the probability space should be partitioned in calculating the correlation. A probability distribution function ρ(φ) is then proposed, which reproduces the quantum correlation for a pair of single-particle spin projections and is amenable to a simple geometric representation that gives meaning to the variable φ"

https://arxiv.org/abs/2108.07869

"Given that we have found a general probability distribution and an appropriate separation of the probability space that accounts for the positive and negative outcomes contributing to the spin correlation, we now explore a possible geometric explanation for this result. With this purpose in mind, let us take a pair of entangled spins and consider the situation in which the sign of the projection of spin 1 onto a has been determined, say α = +1; for simplicity in the discussion take the +z axis along the direction a, and the x axis perpendicular to it. If the bipartite system is in the singlet state, we know for sure that the projection of spin 2 onto the +z axis would give -1. This means that spin 2 lies in the lower half plane, forming any angle φ such that 0 ≤ φ ≤ π, with the origin of φ along the −x axis and φ increasing counterclockwise. Conversely, if the sign of the projection of spin 1 is α = −1, the second spin lies in the upper half plane, forming any angle φ such that 0 ≤ φ ≤ π, with the origin of φ along the x axis. In both cases, A = −1. (The argument is of course reversible, in the sense that the sign of the projection of spin 2 can be defined first, in which case the angle variable φ refers to spin 1.)

In summary, any series of measurements along parallel directions gives perfect anticorrelation, CQ(a, a) = CQ(b, b) = −1.

Consider now a series of measurements carried out to determine the correlation of the spin projections onto directions (a, b) with the +z axis again along a, and b ≠ a. Take first the case α = +1 for spin 1: when spin 2, lying in the lower half plane, is projected onto the direction b forming an angle θab with the +z axis, A will still be negative for any angle φ such that θab ≤ φ ≤ π, whilst it will become positive for 0 ≤ φ ≤ θab. This gives a concrete meaning to Eq. (31). What is it that determines in each instance the specific value of the (random) variable φ is unknown; we only know its probability distribution."

https://arxiv.org/abs/1908.04225

"It is clear from this discussion that an expression that combines eigenvalues Ak, A′k pertaining to different pairs (a, b), (a, b′) is physically meaningless, as it would entail a mixture of elements pertaining to different subdivisions of the ensemble represented by Ψ0; in other words, it would imply the simultaneous use of two partitionings of the probability space which are incommensurable. Yet the procedure of combining under one formula the eigenvalues that correspond to different pairs of directions is central in the derivation of Bell-type inequalities for the bipartite singlet spin state [6]."

"Translated to the experimental domain, this is equivalent to saying that the spin projections (α, β), (α, β′), a.s.o., belong to different series of experiments. Of course the experimentalist may choose to reset the orientation of the apparatus from b to b′ after the first event, and then back to b after the second one. But eventually, after a large number of measurements, the experimental correlation CE (a, b) will be given by the average value of the projection products (αβ)ab, and CE(a, b′) by the average value of the products (αβ′)ab′ ; the experimentalist does not mix the data from the two series of measurements for the calculation of the average values. If different series of measurements are made, for different pairs of directions (a, b), one should expect the experiment to eventually confirm the functional dependence predicted by quantum mechanics; i. e., CE (a, b) = −a · b."

"Our conclusions, carried out entirely within the quantum formalism, finds a counterpart in the literature in the form of the measurement-dependence or contextuality argument. The assumption of noncontextuality (or so-called contextuality loophole) associated with the Bell and CHSH theorems has been pointed out in different ways; for early works see Refs. [8–10]. More recently, it is raised anew by an increasing number of authors (see e.g. [11–15]), stressing that (1) probabilities belong to experiments and not to objects or events per se, and (2) any probability depends at least in principle on the context, including all detector settings of the experiment [12, 13]. In other words, a hidden-variable model suffers from a contextuality loophole if it pretends to describe different sets of incompatible experiments using a unique probability space and a unique joint probability distribution [12, 14]."

And I think if incompatibility is enough for Bell violations like Fine's theorem implies then we have a cause which is local since incompatibility is confined to observables local to particles. The local incompatibility directly leads to the explicit in the partitioning of probability spaces concerning commuting pairs. The local causes then end up leading to non-local correlations. We don't need communication non-locally because what is required for the Bell violations is the inability to construct a context-invariant joint probability distribution, regardless of whether there is some kind of communication between particles or not. Communication may be a cause of loss of joint probability distribution presumably… but so can measurement-dependent statistics - i.e. contextuality without non-local influences - which is pretty much what is identified as the source in these papers and implied by Fine's.

The question of how particles "know" the measurement setting during the experiment is resolved by the fact that particle configurations are always randomly changing. A particle begins its trajectory at t0 and is measured at t8; we can think of it having probability distributions concerning its configuration at every time point. The final measured outcome at t8 then spontaneously appears at the point of measurement, just as a configuration outcome spontaneously occured at t7 or t6 or t2, etc. At t8, it is now in the local vicinity of the measurement setting it depends on and the context-dependent distributions, which are valid precisely for that time point, are what causes the Bell violation in measurement outcomes.

 

[iste]

Again, this is arguing both sides of a coin. Bell violations have nothing to do with human behavior whatsoever, and cannot be called "generic" when there is no known similar physical phenomena. If you can demonstrate that no local hidden variable theory can match the predictions of future generally accepted human behavior theory "X", then we'll have something to debate. Because that is what Bell does with QM and local realism.

And whether there are root "causes" or not (for probabilistic behavior) in QM is currently unknown. What is known (as best as can be) is that determinate causes cannot be propagated faster than c. Call that "a causally local formulation of QM" (per Barandes) ? Who cares? Everyone accepts that as far as I can tell, regardless of interpretation. But indeterminate FTL influences ("quantum nonlocality") are clearly within the realm possibility, as hundreds of experiments demonstrate. That's the gold standard.

I actually cannot believe that this is 2024, and anyone is still pushing the idea of a local realistic theory. Barandes should say these words: "Yes, it's nonlocal under the sheets." As I believe I have said previously, I literally have dozens of references for authors claiming "Bell was wrong", there's a hidden assumption, the experiments are tainted, it doesn't work in 10 dimensions or whatever. I had already included Barandes in that list anyway. So *unless* there is a concrete example to discuss/debate as to what I asked in #144, I don't think I have anything further to add of use or interest to anyone in this thread.

So this is second post with quotes. I am nit sure that the first post was tagged to you. So just in case, just letting you know there is another post above which quotes from paper specifically about spin correlations.

These authors I will quote are appealing to the exact same line of argument implied by Cetto from previous quotes. But this time they are talking about much more general scenarios so not just quantum. This is because Bell inequality is a special case of the inequalities that Boole discovered in the century prior which, like in Fine's paper, is fundamentally about probability spaces, so that violations occur simply because data points cannot be fit onto a single probability space. Obviously the aim of their argument though is about quantum mechanics. Their example starts properly in the 2nd paragraph of the quote.

https://arxiv.org/abs/0907.0767

"Obviously the inequality of Eq. (3) is non-trivial because based on the fact that the value of all products must be ±1 one could only conclude that: Γ(n) ≥ −3. The nontrivial result has the following reason. Boole included into Eq. (2) a cyclicity: the outcomes of the first two products determine the outcomes in the third product. Because all outcomes can only be ±1 the cyclicity gives rise to Eq. (3). Vorob’ev showed precisely 100 years after Boole’s original work in a very general way that it is always a combinatorial-topological cyclicity that gives rise to non-trivial inequalities for the mathematical abstractions of experimental outcomes. Boole pointed to the fact that Eq. (3) cannot be violated. However, in order to come to that conclusion, the [variables] need, in the first place, to be in a one to one correspondence to Boole’s elements of logic that follow the law “aut A = +1 aut A = −1 tertium non datur”. As discussed in the introduction, eternally valid statements about physical experience such as “aut A = +1 aut A = −1 tertium non datur” can usually not be made when describing the physical world without the use of some coordinates. In the example above these coordinates were the places of birth, the places of examination and the numbering of the exams that were randomly taken. All these coordinates when added need to still allow for a cyclicity in order to make Boole’s in-equality non-trivial. Therefore, if we have a violation of a non-trivial Boole inequality, then we must conclude that we have not achieved a one to one correspondence of our variables to the elementary eternally true logical variables of Boole and that we need further “coordinates” that will then remove the cyclicity. In order to illustrate all this by
a simple example, we consider the following second different statistical investigation of the same disease.

We now let only two doctors, one in Lille and one in Lyon perform the examinations. The doctor in Lille examines randomly all patients of types a and b and the one in Lyon all of type b and c each one patient at a randomly chosen date. Note that in this way, all patients of type b receive two examinations. The doctors are convinced that neither the date of examination nor the location (Lille or Lyon) has any influence and therefore denote the patients only by their place of birth. After a lengthy period of examination they find: Γ = ⟨AaAb⟩ + ⟨AaAc⟩ + ⟨AbAc⟩ = −3.

They further notice that the single outcomes of Aa, Ab and Ac are randomly equal to ±1. This latter fact completely baffles them. How can the single outcomes be entirely random while the products are not random at all and how can a Boole inequality be violated hinting that we are not dealing with a possible experience? After lengthy discussions they conclude that there must be some influence at a distance going on and the outcomes depend on the exams in both Lille and Lyon such that a single outcome manifests itself randomly in one city and that the outcome in the other city is then always of opposite sign. Naturally that way they have removed the Vorob’ev cyclicity and we have only the trivial inequality Eq. (6) to obey.

However, there are also other ways that remove the cyclicity, ways that do not need to take recourse to influences at a distance. For example we can have a time dependence and a city dependence of the illness as follows. On even dates we have Aa = +1 and Ac = −1 in both cities while Ab = +1 in Lille and Ab = −1 in Lyon. On odd days all signs are reversed. Obviously for measurements on random dates we have then the outcome that Aa, Ab and Ac are randomly equal to ±1 while at the same time Γ(n) = −3 and therefore Γ = −3.

We need no deviation from conventional thinking to arrive at this result because now, in order to deal with Boole’s elements of logic, we need to add the coordinates of the cities to obtain: Γ = ⟨A1aA2b⟩ + ⟨A1aA2c⟩ + ⟨A1bA2c⟩ ≥ −3. And the inequality is of the trivial kind because the cyclicity is removed.

The date index does not matter for the products since both signs are reversed leaving the products unchanged. However, in actual fact, also this index might have to be included and could be a reason to remove the cyclicity, e.g. Γ = ⟨A1a(d1)A2b(d1)⟩ + ⟨A1a(d2)A2c(d2)⟩ + ⟨A1b(d3)A2c(d3)⟩ ≥ −3, where we now have included the fact that the exams of pairs are performed at different dates d1, d2, d3."

"The mistake here is that Bell and followers insist from the start that the same element of reality occurs for the three different experiments with three different setting pairs. This assumption implies the existence of the combinatorial-topological cyclicity that in turn implies the validity of a non-trivial inequality but has no physical basis. Why should the elements of reality not all be different?"

In the quantum case, the difference in elements is due to incompatibility / non-commutativity with regard to spin.

Of course the examples would be contrived but they are arguing the same perspective as the other quantum papers. Bell violations follow from the absence of probability distributions. There are no additional conditions saying that, e.g. physically x, y, z must hold too or you need x, y, z to occur for this violation to happen. It's just a formal relationship between probability distributions and the violations. If Fine's theorem hadn't pointed to incompatible observables as the cause, I would probably be more skeptical and think that maybe an absent joint distribution in the Bell scenarios requires non-local interactions. But there is no reason why local incompatibility requires non-local interactions to exist.

You can derive non-commutativity from the non-differentiability / stochastic nature of Feynman paths in the path integral formulation and so getting non-commutativity formally doesn't seem to have anything to do with non-locality either. This is especially relevant to a stochastic interpretation as implied by Barandes' formulation because the realized outcomes that occur on trajectories between two points in Barandes' formulation are just the Feynman paths in the path-integral framework, and carry the same non-differentiable nature because of the randomness of the paths.