I A new realistic stochastic interpretation of Quantum Mechanics

[Fra]

I think one reason this is hard to understand is because we implicitly but repeatedly confuse normative/guiding P of possibilities and descriptive P of what actually happened historically.

Histories don't interfere. Interference lies in how guiding probabilities account for possibilities and uncertainties of the future.

In inference its important to not mix the concepts. This is closely related to what barandes label the "category error" or "category problem".

Ie. If you keep thinkning of the transition probabilites as descriptive, it gets wrong. But if you think of them as guiding P for an agent taking stochastic actions, it makes more sense.

The flawed application of common cause in bells ansatz is easier to spot if you think in terms of guiding probabilities of agent/observer - which of course, like barandes thinks, is a physical system. One just have to not confuse this with thinking that means there is an exteral view of all this. It is beacause it does not, that makes the guiding view of P more fundamental.

/Fredrik

 

[Fra]

calling it an interpretation is flawed at this stage, it is like calling a Wick rotation an interpretation.

I partly agree with this. But I think he highlights important things, and changing stance that can make future development eaiser. He points out the obvious flaw in bells ansatz, that was there all along but which few speak of. Its in the talk RUTA posted way back in the thread sa well.

/Fredrik

 

[pines-demon]

In two of Barandes' papers he mentions the mechanism for entanglement being the fact that correlations induced by local interactions between two different stochastic systems are remembered over time until the system is later disturbed (e.g. by measurement devices), after which it basically forgets what had happened in the past at the original local interaction. This is purely because the indivisible transition matrix is non-Markovian - divisibility or division events means it no longer has these memory properties. There is no superdeterminism because the correlation is solely due to the local interaction. Any correlations in the measurement devices are solely due to the fact that the correlation from the original local interaction is remembered; the devices do not causally influence each other over distances independently of this. It is very general though. His entanglement examples I don't think give strong insight to entangled polarization / spin experiments.

You say it is not superdeterminism but as you put it, it sounds like it is. You say that measurement devices do not necessarily interact with each other instantaneously (so it is not some nonlocal faster-than-light interaction), but it is more of like past event thing

There is no superdeterminism because the correlation is solely due to the local interaction. Any correlations in the measurement devices are solely due to the fact that the correlation from the original local interaction is remembered

Does that means that all measurement devices interacted once in the past so measurements are not independent [a.k.a aka superdeterminism]? If it is not this, what is it? Is there a way I can think about it aside from "indivisible non-Markovianity"?

 

[Fra]

"Not statistically independent" does not imply superdeterminism. Superdeterminism is a special extremal case.

Just as in bell experiments, the "memory" explains the correlation - it does not determine the full results, because they involve detector settings too.

So the full interaction is then conceptually an interaction between
1. a system (that is remebers a relation to its correlates partner)
2. The detector that is ignorant about this, and thus acts stochastically based on "preparation info" only - which is "public"

The combination fo this will have elements of chance; and be influenced by detector choices; but also partially influenced by the "memory" of incoming system.

For me this is conceptually quite clear. What is missing is the mathematical modell of this from that perspective.

IMO, what prevents superdeterminism conceptually is that the memory of systems are limited; thus over time some model with lossy retention seems required. Only maybe an observer beeing a black hole can retain most without loss by growing mass.

But this is all future possible developments not lined out by Barandes. But de does say thar he thinks there may be link to this and future QG. It is in the same talk in rutas post.

/Fredrik

 

[pines-demon]

I partly agree with this. But I think he highlights important things, and changing stance that can make future development eaiser. He points out the obvious flaw in bells ansatz, that was there all along but which few speak of. Its in the talk RUTA posted way back in the thread sa well.

/Fredrik

I rewatched that part today and now I am more skeptic. To get Bell's inequality one needs several ingredients, mainly statistical independence (violations lead to superdeterminism) and factorizability. There are several ways to get factorizability. Bell had two different ways, one appears in Bell's later work and is called local causality. The other is indeed Reichenbach's common cause principle (not used by Bell). Either way, standard quantum mechanics violates this factorizability.

Barandes finds that his theory also violates this factorizability and claims that it is a violation of Reichenbach principle (it could very well be). But it could be very well that it is a violation of local causality making Barandes' interpretation nonlocal (in the Bell way, like in the case of Bohmian mechanics). In his lecture he conflates the Bell's local causality with Reichenbach' common cause (saying that is what Bell used) so I do not think he is into something there.

 

[pines-demon]

"Not statistically independent" does not imply superdeterminism. Superdeterminism is a special extremal case.

It is kind of the definition. That comment was aimed at iste who claimed that the correlations result from the the interactions of the detectors in the past . This is usually what superdeterminism claims (maybe iste did not meant that but to say interactions between the entangled particles instead).

 

[Fra]

It is kind of the definition. That comment was aimed at iste who claimed that the correlations result from the the interactions of the detectors in the past . This is usually what superdeterminism claims

Determinism means the future is predetermined. At least in principle - modulo deterministic chaos. Superdetermimism take this to include even choices of experimenters.

That is not what the memory thing implies. The problem with bells ansatz lmo does NOT(edit) save determinism.

/Fredrik

 

[pines-demon]

Determinism means the future is predetermined. At least in principle - modulo deterministic chaos. Superdetermimism take this to include even choices of experimenters.

While superdeterminism does imply determinism it is not exactly that what is meant by that term. At least in this context it is a statistical property, statistical independence (no superdeterminism) it is the ability to average out any correlations between the measuring devices (make many trials, create the measuring devices in different factories, put them far apart, make the setting dependent on nuclear random number generators). It is important in science because that's why experiments can be repeated. Mathematically, superdeterminism means that a representative distribution of your hidden parameters $\lambda$ depend on the settings $x,y$ of your measuring devices, i.e.
$$\rho(\lambda|x,y)\neq\rho(\lambda).$$
It is called superdeterminism because all measuring devices of the observable universe interacted at some point in the past if not in the Big Bang, so the correlations would be set from early in the past (conspiracy).
Edit: funny enough there are Bell tests that put constraints to superdeterministic theories by deciding the settings of the measurement devices based on thermal radiation from very distant galaxies.

 

[iste]

You say it is not superdeterminism but as you put it, it sounds like it is. You say that measurement devices do not necessarily interact with each other instantaneously (so it is not some nonlocal faster-than-light interaction), but it is more of like past event thing

Does that means that all measurement devices interacted once in the past so measurements are not independent [a.k.a aka superdeterminism]? If it is not this, what is it? Is there a way I can think about it aside from "indivisible non-Markovianity"?

No, measurement devices didn't interact in past. Particles interact in the past before they are measured, causing a correlation between them which is preserved when the particles are separated and subsequently measured. Measurement devices don't interact with each other or anything else before the measurement of the particles. But obviously this doesn't incorporate measurement settings so maybe it is missing something that could account for what you are possibly thinking about.

Barandes finds that his theory also violates this factorizability and claims that it is a violation of Reichenbach principle

From the paper, he seemed to suggest that its not so much that Reichenbach's principle is violated but it isn't applicable to the stochastic description because the third variable needed to formulate it doesn't exist in the stochastic description, even though the straightforward analysis is that the correlation between the particles can be directly attributed to an initial local interaction between the particles that is subsequently remembered even when they are moved far apart, purely because of the non-markovianity of the indivisible transition matrix.

I actually mentioned a source earlier that seems to display this mechanism in a completely different classical hydrodynamical model:

https://journals.aps.org/prfluids/abstract/10.1103/PhysRevFluids.7.093604

Droplets interact in the same fluid bath and become correlated so that their dynamics are nonseparable. A barrier is erected which isolates the particles so they can no longer communicate in any way. But despite their isolation, their behavior still maintains correlations between them which can be attributed to the fact that they have been remembered by the now-isolated respective particle-bath systems. This description models quite closely to Barandes' description of entanglement only here it is expicit that there is no non-local communication because its a classical model of just a droplet in a bat which you could build an experiment about. Its not mentioned in the abstract I think but if you look at other sources for these pilot-wave hydrodynamic systems, the reason they have these quantum-like behaviors is that they are non-Markovian and retain memory of the past.

 

[iste]

They are only constrained by their initial and final points. It is in fact somewhat wrong to think about them as paths. They are functions $x(t)$, a function can be totally weird, like $x(t)=0$ for rational $t$ and $x(t)=1$ for irrational $t$. The "path" integral is really the functional integral, i.e. the integral over all functions.

What does weird mean here in terms of paths?

 

[pines-demon]

No, measurement devices didn't interact in past. Particles interact in the past before they are measured, causing a correlation between them which is preserved when the particles are separated and subsequently measured. Measurement devices don't interact with each other or anything else before the measurement of the particles. But obviously this doesn't incorporate measurement settings so maybe it is missing something that could account for what you are possibly thinking about.

Thanks for clarifying what you meant, I quoted a previous text of yours that seemed to suggest the opposite.

From the paper, he seemed to suggest that its not so much that Reichenbach's principle is violated but it isn't applicable to the stochastic description because the third variable needed to formulate it doesn't exist in the stochastic description, even though the straightforward analysis is that the correlation between the particles can be directly attributed to an initial local interaction between the particles that is subsequently remembered even when they are moved far apart, purely because of the non-markovianity of the indivisible transition matrix.

That does not cut it for me. He does not have factorizability that is fine, he can argue about Reichanbach principle all day, but Reichbach vs Bell causal locality is not settled. So he could also just have nonlocality built into it without knowing it. I mean again I would sell his work as a duality, it needs to be worked into an interpretation that can provide a picture of the phenomena.

I actually mentioned a source earlier that seems to display this mechanism in a completely different classical hydrodynamical model:

https://journals.aps.org/prfluids/abstract/10.1103/PhysRevFluids.7.093604

Droplets interact in the same fluid bath and become correlated so that their dynamics are nonseparable. A barrier is erected which isolates the particles so they can no longer communicate in any way. But despite their isolation, their behavior still maintains correlations between them which can be attributed to the fact that they have been remembered by the now-isolated respective particle-bath systems. This description models quite closely to Barandes' description of entanglement only here it is expicit that there is no non-local communication because its a classical model of just a droplet in a bat which you could build an experiment about. Its not mentioned in the abstract I think but if you look at other sources for these pilot-wave hydrodynamic systems, the reason they have these quantum-like behaviors is that they are non-Markovian and retain memory of the past.

This for me would do the work [if understood], in the sense that if he can come up with a SIMPLE classical picture of his phenomena he would be able to provide an interpretation. However I cannot access or assess this paper and I would not be too surprised if real fluid systems have weird non-linear effects lead to wrong conclusions. That's why I think a toy model with a single qubit could clarify the situation.

 

[Demystifier]

What does weird mean here in terms of paths?

The $x$ attains only two values, 0 and 1, without ever attaining any value in between. Moreover, it jumps from 0 to 1 and back infinitely often. The velocity $dx/dt$ is not defined at any $t$.

 

[pines-demon]

The $x$ attains only two values, 0 and 1, without ever attaining any value in between. Moreover, it jumps from 0 to 1 and back infinitely often. The velocity $dx/dt$ is not defined at any $t$.

Just to be clear here the derivative is not defined but has some instantaneous momentum right?

 

[WernerQH]

Droplets interact in the same fluid bath and become correlated so that their dynamics are nonseparable.

But do these experiments produce anything resembling Bell-type correlations? Classical correlations have been understood for ages. It is misleading to wave your hands and talk about "nonseparable" dynamics.

 

[iste]

But do these experiments produce anything resembling Bell-type correlations? Classical correlations have been understood for ages. It is misleading to wave your hands and talk about "nonseparable" dynamics.

The Barandes entanglement example is very rudimentary. I was just implying that given the description of entanglement he gives, there is no need to add any underlying non-local influence; the paper then is an example since it is equally rudimentary. I see that someone may not be as convinced with regard to actual quantum experiments, or even that the indivisibility could be achieved without something else funny going on.

I would not be too surprised if real fluid systems have weird non-linear effects lead to wrong conclusions.

I do note in post #247 that these hydrodynamic models are superficially similar to the interpretation given by Nelson's stochastic mechanics, which is a predecessor that shares the same stochastic interpretation as Barandes' model. But yes, Barandes' model is agnostic of what kind of mechanisn would cause the non-Markovianity... or how weird the mechanism would be. I guess there could be an underlying non-local mechanism but to me it feels like that is like overkill in terms of parsimony by doubling the mechanisms in the picture.

 

[iste]

The $x$ attains only two values, 0 and 1, without ever attaining any value in between. Moreover, it jumps from 0 to 1 and back infinitely often. The velocity $dx/dt$ is not defined at any $t$.

And this is a discontinuous path? I guess it would not be  identical to the stochastic mechanical paths. In the Hiley paper I linked though, they seem to imply they are only considering continuous paths?

 

[pines-demon]

The Barandes entanglement example is very rudimentary. I was just implying that given the description of entanglement he gives, there is no need to add any underlying non-local influence; the paper then is an example since it is equally rudimentary. I see that someone may not be as convinced with regard to actual quantum experiments, or even that the indivisibility could be achieved without something else funny going on.



I do note in post #247 that these hydrodynamic models are superficially similar to the interpretation given by Nelson's stochastic mechanics, which is a predecessor that shares the same stochastic interpretation as Barandes' model. But yes, Barandes' model is agnostic of what kind of mechanisn would cause the non-Markovianity... or how weird the mechanism would be. I guess there could be an underlying non-local mechanism but to me it feels like that is like overkill in terms of parsimony by doubling the mechanisms in the picture.

Just for clarification the first quote is not mine but of WernerHQ. As for the second comment, i have nothing left to add I only hope that this agnosticism is because he is working out the details.

 

[Demystifier]

Just to be clear here the derivative is not defined but has some instantaneous momentum right?

I don't know how to define momentum in this case.

 

[Demystifier]

In the Hiley paper I linked though, they seem to imply they are only considering continuous paths?

They do. In fact, the integral over all paths/functions is mathematically ambiguous (because the limit $\epsilon\to 0$ is ambiguous, where $\epsilon$ is associated with the discretized time), so people define it differently in different contexts.

 

[Fra]

While superdeterminism does imply determinism it is not exactly that what is meant by that term. At least in this context it is a statistical property, statistical independence (no superdeterminism) it is the ability to average out any correlations between the measuring devices (make many trials, create the measuring devices in different factories, put them far apart, make the setting dependent on nuclear random number generators). It is important in science because that's why experiments can be repeated. Mathematically, superdeterminism means that a representative distribution of your hidden parameters $\lambda$ depend on the settings $x,y$ of your measuring devices, i.e.
$$\rho(\lambda|x,y)\neq\rho(\lambda).$$
It is called superdeterminism because all measuring devices of the observable universe interacted at some point in the past if not in the Big Bang, so the correlations would be set from early in the past (conspiracy).
Edit: funny enough there are Bell tests that put constraints to superdeterministic theories by deciding the settings of the measurement devices based on thermal radiation from very distant galaxies.

I have a feeling you miss details and mix up causal influence and determinism. It this another case where bell community reinvent meaning of established words? We know they did to "locality".

Also non-deterministic causality does not logically imply deterministic p- distributions evolution. In standard QM there is determinism at distribution level, but this is not the general case, its excludes reinforced emergence or evolutionary emergence.

How we label things does not bother me but ignoring these logical possibilities makes the analysis meaningless.And if we redfine words to mean something different we only fool ourselves.

/Fredrik

 

[pines-demon]

I have a feeling you miss details and mix up causal influence and determinism. It this another case where bell community reinvent meaning of established words? We know they did to "locality".

Also non-deterministic causality does not logically imply deterministic p- distributions evolution. In standard QM there is determinism at distribution level, but this is not the general case, its excludes reinforced emergence or evolutionary emergence.

How we label things does not bother me but ignoring these logical possibilities makes the analysis meaningless.And if we redfine words to mean something different we only fool ourselves.

/Fredrik

I think we are mixing different arguments into a mesh of partial arguments that lead nowhere. The mathematics of each assumption in the Bell theorem are clear, so any misunderstanding of the assumptions can be solved by writing them mathematically. Is superdeterminism for you some other mathematical assumption? As for determinism, if quantum mechanics or Barandes theory is deterministic is a topic that I have not discussed yet.

 

[Fra]

I think we are mixing different arguments into a mesh of partial arguments that lead nowhere. The mathematics of each assumption in the Bell theorem are clear, so any misunderstanding of the assumptions can be solved by writing them mathematically.

if I just look at the math (decompose and label as one wish), the key mathematical asssumptions of bells ansatz is IMO flawed and simplistic. Bells theorem litteraly disproves a simple "naive" form of hidden variables. Its been a dead horse for me for 25 years.

As for the less naive version bells theorem is of course,correct - it is a mathematical theorem - it just does not apply, and for this is clear. No conspiracya of determinism has anything to dp with that.

Is superdeterminism for you some other mathematical assumption?

Yes it is. It is for me the ultimate determinstic conspiracy. It an sense, if you belive in determinism, then why not superdeterminism? (Then you are at least consistent over complexity scales)

I subscribe to neither however.

/Fredrik

 

[iste]

Just to be clear here the derivative is not defined but has some instantaneous momentum right?

I'll just note that none of the continuous, non-differentiable paths have a well-defined instantaneous momentum either. If you look at the first link to the Hiley paper in #287 they talk about it a bit; its not well-defined becauae generally momenta going into a point and momenta leaving it are not the same and its completely ambiguous which one you would choose if you wanted to define instantaneous momentum - so when they calculate the average path integral trajectory momentum at some point, they have to consider both. And they have a nice picture.

 

[pines-demon]

if I just look at the math (decompose and label as one wish), the key mathematical asssumptions of bells ansatz is IMO flawed and simplistic. Bells theorem litteraly disproves a simple "naive" form of hidden variables. Its been a dead horse for me for 25 years.

That’s on you. You are the one not assigning the usual terminology by not engaging with the usual derivations of the theorem.

As for the less naive version bells theorem is of course,correct - it is a mathematical theorem - it just does not apply, and for this is clear. No conspiracya of determinism has anything to dp with that.

If you are not using the usual terminology it is hard to agree or disagree with you. Please define the assumptions you think are useful mathematically.

Yes it is. It is for me the ultimate determinstic conspiracy. It an sense, if you belive in determinism, then why not superdeterminism? (Then you are at least consistent over complexity scales)

I subscribe to neither however.

/Fredrik

Again if you or I want to believe in it or not it is not the issue. The topic at hand is what Barandes interpretation means, if somebody say it implies X but you disagree thinking that X means Y, then you are going to talk past each other.

The topic of superdeterminism in relation to Barandes was directed at a phrase of another user and that user has now clarified that he did not mean that. So we can move past that topic of superdeterminism. Alternatively you can open a post to discuss what superdeterminism means.

 

[Fra]

Again if you or I want to believe in it or not it is not the issue. The topic at hand is what Barandes interpretation means

Agreed, lets get back to the topic.
Whatever we call it, he points out the issue in the ansatz here,
I posted this link in an older post in thread as well.

What I thought we were going, is to conceptually elaborate on this - it to find a conceptual interpretation of the math. But as we diverged in terminology-disagreement. The question is what perspective to take, that can make the issue barandes points out, more intuitive to understand? The only reasons I like barandes papers and talk, is because I am already tuned in to perspectives which harmonize well with his new perspective. But I also agree that I think he doesn't "explain" in clear enough to convey those not already tune into this. This is what I can't stop wondering what future stuff Baranders has up his sleeves to take this to the next nevel, perhaps relating to unification. If he can show a glipse of that, perhaps the reason for this change of perspective would be easier to accept.

/Fredrik

 

[Fra]

what Barandes interpretation means

As I wrote before I'm not sure I would call it an interpretation either at this point, but his "change of view" from hilbert space to simply transition probabilities, might be more "natural" for certain interpretations, for example my own qbist inspired one. This is why it makes sense to me. I think the hilbert space formalism, is a clever way to make compact math, after all linear algebra is quite "clean" and nice. But it may conceptually obscure the mapping onto the preferred ontology.

/Fredrik

 

[Lord Jestocost]

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......

From the conclusion of the paper “Is quantum mechanics equivalent to a classical stochastic process?” by H. Grabert, P. Hänggi and P Talkner (Phys. Rev. A 19, 2440 (1979)):

“In this paper we have analyzed the relations between the theory of stochastic processes and the statistical interpretation of quantum mechanics. We have shown that the Schrödinger evolution is not equivalent to a Markovian process, as claimed in several papers. Possible relations to a non-Markovian process have been investigated, and we have shown that the various correlation functions used in quantum theory do not have the properties of the correlations of a classical stochastic process. This leads to the conclusion that quantum mechanics has little if anything to do with the theory of stochastic processes.” [Bold by LJ]

 

[WernerQH]

From the conclusion of the paper “Is quantum mechanics equivalent to a classical stochastic process?” by H. Grabert, P. Hänggi and P Talkner (Phys. Rev. A 19, 2440 (1979)):

This leads to the conclusion that quantum mechanics has little if anything to do with the theory of stochastic processes.

I don't think that the Grabert et al. paper has ruled out all conceivable stochastic processes. What saves Barandes' papers is that they present more an abstract framework. He hasn't really defined a specific stochastic process.

 

[Fra]

I don't think that the Grabert et al. paper has ruled out all conceivable stochastic processes. What saves Barandes' papers is that they present more an abstract framework. He hasn't really defined a specific stochastic process.

Conceptually I would say the difference must be the "constraints" on stochastic in configuration space the barandes transition probabilities impose on the "stochastic process", to replace the normal physical laws, as this is his take on how "the micrcophysical law" is encoded. If I remember correctly he put it like something like that in one of the talks or paper.

To get some more explanatory value I would expect some mechanis that explaines where this comes from; otherwise they are just as finetuned and unexplained as the hamiltonian. (My personal vision is that they are emergent in bigger picture, but it is not clear what Baranders thinks, I think he just leaves this unresolved which I don't blame hime for, because that is a big question, not quickly resolved I think).

/Fredrik

 

[iste]

From the conclusion of the paper “Is quantum mechanics equivalent to a classical stochastic process?” by H. Grabert, P. Hänggi and P Talkner (Phys. Rev. A 19, 2440 (1979)):

“In this paper we have analyzed the relations between the theory of stochastic processes and the statistical interpretation of quantum mechanics. We have shown that the Schrödinger evolution is not equivalent to a Markovian process, as claimed in several papers. Possible relations to a non-Markovian process have been investigated, and we have shown that the various correlation functions used in quantum theory do not have the properties of the correlations of a classical stochastic process. This leads to the conclusion that quantum mechanics has little if anything to do with the theory of stochastic processes.” [Bold by LJ]

I'm pretty sure the Barandes indivisible process doesn't satisfy the assumptions used in the last section either!

 

[DrChinese]

... Particles interact in the past before they are measured, causing a correlation between them which is preserved when the particles are separated and subsequently measured.

... even though the straightforward analysis is that the correlation between the particles can be directly attributed to an initial local interaction between the particles that is subsequently remembered even when they are moved far apart, ...

Droplets interact in the same fluid bath and become correlated so that their dynamics are nonseparable. A barrier is erected which isolates the particles so they can no longer communicate in any way. But despite their isolation, their behavior still maintains correlations between them which can be attributed to the fact that they have been remembered by the now-isolated respective particle-bath systems. This description models quite closely to Barandes' description of entanglement ...

And if you go back to comments I made in the first page of this thread (March 5!), you will see my specific objection to the Barandes' paper. Namely, that he does NOT address modern experiments that rule out his approach. Specifically, experiments such as this from 2008:

High-fidelity entanglement swapping with fully independent sources
Rainer Kaltenbaek, Robert Prevedel, Markus Aspelmeyer,
and Anton Zeilinger (shared a Nobel for this and other works)

Now, I realize this is the Interpretations subforum. If an interpretation contains the same math/predictions as garden variety QM, then it should cover experiments such as this. I don't think it does! But more importantly, your statements above (presumably echoing Barandes at some level) are flat out contradicted by my citation of a well-accepted experiment.

There is NO requirement that that entanglement correlations between 2 particles must follow from an earlier interaction which is "remembered". In the cited experiment, the entangled particles have never existed in a common light cone, and have never interacted in any way. They are created from different sources. Via entanglement swapping, they test "the entanglement of the previously uncorrelated photons 1 and 4".

In the "Experimental Delayed Choice" version (2012), the choice to entangle the 2 particles is freely chosen at a 3rd location - after 1 and 4 are detected. Clearly, nothing is "remembered". This is standard QM theory, and these are factual counterexamples to any variation of an assertion that entanglement requires a past interaction of any kind.

Any interpretation/explanation/belief that contradicts established experiment must be rejected out of hand, of course.

-DrC

 

[Fra]

There is NO requirement that that entanglement correlations between 2 particles must follow from an earlier interaction which is "remembered". In the cited experiment, the entangled particles have never existed in a common light cone, and have never interacted in any way. They are created from different sources. Via entanglement swapping, they test "the entanglement of the previously uncorrelated photons 1 and 4".

In the "Experimental Delayed Choice" version (2012), the choice to entangle the 2 particles is freely chosen at a 3rd location - after 1 and 4 are detected. Clearly, nothing is "remembered".

But there is a requirement is that you have two pairs of prepared correlated particles - each pair might "remember" the relation to it's partner. And then via the clever swapping measuremenent, this allows "transferring" the correlation to 1 and 4, by measuring 2&3 via the swapping setup and use that data to extract the relevant 1 & 4 pairs.

So do not see that Baranders idea per see, is a problem for entanglement swapping? Why would it?

/Fredrik

 

[DrChinese]

But there is a requirement is that you have two pairs of prepared correlated particles - each pair might "remember" the relation to it's partner. And then via the clever swapping measurement, this allows "transferring" the correlation to 1 and 4, by measuring 2&3 via the swapping setup and use that data to extract the relevant 1 & 4 pairs.

So do not see that Baranders idea per see, is a problem for entanglement swapping? Why would it?

/Fredrik

Sorry, but this is again factually incorrect. Yes, there is a swap operation (photons 2 & 3). But it is done far away (in terms of the speed of light) from the measurement of the final entangled pair (1 & 4). And in fact can be done long AFTER their entangled measurements, and be done remotely at the free choice of the experimenter. And the swapping can be chained to further confuse the usual concepts of cause/effect (since order of processes does not matter). In fact, the concept of chained swaps is the basis for long distance quantum networks.

So to recap: there is absolutely NO requirement that entangled particles must have interacted in the past, NOR is there any requirement that some other particles have interacted with them as intermediaries prior to measurement. None of that happens in the Delayed Choice version.


PS There are no 1 & 2 pairs that are entangled/Bell correlated with 3 & 4 pairs initially. This is canonical (look up Monogamy of Entanglement).

 

[PeterDonis]

there is absolutely NO requirement that entangled particles must have interacted in the past, NOR is there any requirement that some other particles have interacted with them as intermediaries prior to measurement. None of that happens in the Delayed Choice version.

I think one caveat is appropriate here, though: the two photons that do interact in the delayed choice experiment (photons 2 & 3) do share an initial preparation with the photons that end up entangled without ever having interacted (photons 1 & 4). AFAIK it is not possible to have two photons (or quantum systems in general) become entangled if they do not meet at least one of four conditions, the first two of which are the ones you mentioned, which are not met in delayed choice experiments:

(1) They have directly interacted with each other;

(2) They have interacted with intermediary systems;

(3) They share a common preparation;

(4) They have shared a common preparation with intermediary systems.

I include (3) just for completeness; it is of course obvious, but is also not met in delayed choice experiments, which is why it has not been mentioned in this or other discussions of them.

Note that (4) is even more indirect than (2): there is no single intermediary system that shares a common preparation with both photons 1 & 4. Rather, there are two separate intermediary systems, photons 2 & 3, each of which shares a common preparation with only one of photons 1 & 4, and then those two intermediary systems interact.

But I don't know of any case where all of the above conditions are not met, but there is still entanglement produced.

 

[PeterDonis]

at least one of four conditions

I think one could formulate a single condition that covers all four cases, by drawing a graph of any experiment involving entanglement as follows:

Draw a node for each event, where "event" means one of these: preparation, interaction, measurement. In the delayed choice experiment under discussion, there would be two preparation nodes, for photons 1&2 and photons 3&4, one interaction node, for photons 2&3 at the BSM, and two measurement nodes, one for photon 1 and one for photon 4.

If a quantum system is involved in both of a pair of events, draw a line from one to the other, marked with that system's identifier. In the delayed choice experiment, there would be a "photon 1" line from "preparation of photons 1&2" to "measurement of photon 1", a "photon 4" line from "preparation of photons 3&4" to "measurement of photon 4", a "photon 2" line from "preparation of photons 1&2" to "interaction of photons 2&3", and a "photon 3" line from "preparation of photons 3&4" to "interaction of photons 2&3".

Then, if one can find a connected subgraph between two measurement nodes, the measurements at those nodes can show entanglement. In this case, the entire graph is itself a connected subgraph from the "measurement of photon 1" node to the "measurement of photon 4" node.

I don't know if this has ever been formulated in this way in the literature.

 

[gentzen]

The pure formalism presented in the two older papers suffered from an unclear status of causal locality. I have not studied the newest paper in any detail yet, but if it manages to overcome this problem, then it constitutes nice incremental progress for this new formulation.

I read some relevant parts of the "new" paper now. I don't think that "it constitutes nice incremental progress for this new formulation". He does his calculation regarding locality in the normal Hilbert space formulation. I admit that he did his definitions regarding locality both in his formulation and in Hilbert space.

Barandes would do better to put his "new formulation" in the context of "quantum reconstructions" rather than "quantum interpretations". (Then he could check whether his math contains new insights, and also whether he was careful enough to show all "expected" continuity properties of his construction with respect to the time parameter t.) And his "Causally Local Formulation" turns out to be just the well known "no signaling" property of QM, verified with calculations done using normal QM (not his new formulation).

 

[gentzen]

From the conclusion of the paper “Is quantum mechanics equivalent to a classical stochastic process?” by H. Grabert, P. Hänggi and P Talkner (Phys. Rev. A 19, 2440 (1979)):

“In this paper we have analyzed the relations between the theory of stochastic processes and the statistical interpretation of quantum mechanics. We have shown that the Schrödinger evolution is not equivalent to a Markovian process, as claimed in several papers. Possible relations to a non-Markovian process have been investigated, and we have shown that the various correlation functions used in quantum theory do not have the properties of the correlations of a classical stochastic process. This leads to the conclusion that quantum mechanics has little if anything to do with the theory of stochastic processes.” [Bold by LJ]

It would be interesting to also hear in your own words how you would argue against Barandes claims. I don't doubt that you are right, in fact I decided to read parts of his new paper because your and A. Neumaier's reaction indicated to me that it is probably "disappointing".

 

[DrChinese]

I think one caveat is appropriate here, though: the two photons that do interact in the delayed choice experiment (photons 2 & 3) do share an initial preparation with the photons that end up entangled without ever having interacted (photons 1 & 4). AFAIK it is not possible to have two photons (or quantum systems in general) become entangled if they do not meet at least one of four conditions, the first two of which are the ones you mentioned, which are not met in delayed choice experiments:

...

(3) They share a common preparation;

(4) They have shared a common preparation with intermediary systems.

Well, I guess I fail to understand how (3) and (4) would appear in an experiment entitled "High-fidelity entanglement swapping with fully independent sources". Emphasis being on the phrase "fully independent", i.e. no common preparation in the normal usage of the language. It is fair to say that the authors of the paper know what "fully independent" means. Specifically, the initial pairs have never interacted.

Perhaps you mean that the common preparation relates to the laser sources? The lasers are synchronized, true, but clearly there exists no known "local causal" physics to explain why pairs coming from different PDC crystals would become entangled at the whim of an experimenter after the entanglement is measured - just because the source lasers have the same phase.

Or perhaps you mean something else. At any rate, the final 1 & 4 pair does not display any correlation unless the swap is executed with 2 & 3 being indistinguishable - this case was specifically tested. So that means there was no entanglement (correlations) present due to the lasers being phase locked.

 

[PeterDonis]

I guess I fail to understand how (3) and (4) would appear in an experiment entitled "High-fidelity entanglement swapping with fully independent sources".

This is the same experiment that I described and that we have been discussing. (3) does not appear in it, as I said in post #334. (4) appears as the common preparation of photons 1&2, and of photons 3&4. Photon 1 and photon 4 of course do not have a common preparation--that's why (3) does not appear. Photons 2 and 3 are the "intermediary systems" in (4).

Post #335 might help to clarify what I mean by (4). The graph I describe in that post is basically Figure 1 of the paper you cite (but without the post-BSM measurements of photons 2 and 3--not that those aren't relevant, just that they aren't needed to have a connected subgraph from the photon 1 measurement to the photon 4 measurement).

 

[iste]

If an interpretation contains the same math/predictions as garden variety QM, then it should cover experiments such as this. I don't think it does!

If Barandes' proof is not faulty then it should cover experiments like that because what it seeks to do is show that any unitarily evolving quantum system can be translated into an indivisible stochastic one and vice versa. Ofcourse, Barandes may be wrong. And Barandes' theory is completely open and agnostic about what can cause indivisibility or how weird those causes could be.

But addressing why you think Barandes' theory cannot account for entanglement swapping: i.e.

There is NO requirement that that entanglement correlations between 2 particles must follow from an earlier interaction which is "remembered". In the cited experiment, the entangled particles have never existed in a common light cone, and have never interacted in any way. They are created from different sources.

,

i don't think entanglement swapping is anything above ordinary entanglement. The additional swapping aspect is just due to transitivity of correlations unveiled by statistical conditioning, quantum mechanics not especially required. In Barandes' papers, collapse is not a physical event, nothing more than statistical conditioning.

In the "Experimental Delayed Choice" version (2012), the choice to entangle the 2 particles is freely chosen at a 3rd location - after 1 and 4 are detected. Clearly, nothing is "remembered". This is standard QM theory, and these are factual counterexamples to any variation of an assertion that entanglement requires a past interaction of any kind

This is not an issue in Barandes' theory where collapse isn't physically real and measurement results do not communicate.

 

[JC_Silver]

I made an account just to answer here because I feel I have one point to add.

Most of Barandes' newer interviews he has done he doesn't touch on the "interpretation" aspect of his paper instead choosing to focus on the "wavefunction is not a real thing" side and I believe this is because he has possibly realized what some here have too, this is not an interpretation of QM, this is a reformulation of the math instead.

And I think that if what Barandes claims is true (I don't have enough knowledge in non-markovian processes to say if his math is correct), I believe it's worth looking into.

Assuming ALL of Quantum Mechanics is a special case of non-Markovian processes, it could be worthy to look into it to see if we can find fenomena where QM can't seem to find an answer (eg. Gravity) to see if the answer lies outside the Markovian assumptions.

I wouldn't call this an interpretation though, much less say it confirms that Pilot Waves are real.

I say the value of this paper is to argue from a new perspective that wavefunction is a math tool to predict the world and that they are not the real object.

 

[pines-demon]

I made an account just to answer here because I feel I have one point to add.

Most of Barandes' newer interviews he has done he doesn't touch on the "interpretation" aspect of his paper instead choosing to focus on the "wavefunction is not a real thing" side and I believe this is because he has possibly realized what some here have too, this is not an interpretation of QM, this is a reformulation of the math instead.

And I think that if what Barandes claims is true (I don't have enough knowledge in non-markovian processes to say if his math is correct), I believe it's worth looking into.

Assuming ALL of Quantum Mechanics is a special case of non-Markovian processes, it could be worthy to look into it to see if we can find fenomena where QM can't seem to find an answer (eg. Gravity) to see if the answer lies outside the Markovian assumptions.

I wouldn't call this an interpretation though, much less say it confirms that Pilot Waves are real.

I say the value of this paper is to argue from a new perspective that wavefunction is a math tool to predict the world and that they are not the real object.

That seems to be the growing consensus here, if the math is right. In that case, Barandes just found a useful duality between quantum and non-Markovian akin to the Osborn's rule or Wick rotations. If it works as an interpretation some of us are still "agnostic".

Of course some have considered that the mathematics might not be right or well funded either. For example Barandes would have to explain how to avoid the result of paper in post #327.

 

[jbergman]

That seems to be the growing consensus here, if the math is right. In that case, Barandes just found a useful duality between quantum and non-Markovian akin to the Osborn's rule or Wick rotations. If it works as an interpretation some of us are still "agnostic".

Of course some have considered that the mathematics might not be right or well funded either. For example Barandes would have to explain how to avoid the result of paper in post #327.

Right. I need to dive deeper l, but right now I think it's a bit of an Emperor's New Clothes situation in that it doesn't say much about Interpretations. It really comes down to understanding this indivisibility condition on the evolution of the transition matrix, but as far as I can tell that doesn't imply things like local realism.

 

[DrChinese]

1. If Barandes' proof is not faulty then it should cover experiments like that because what it seeks to do is show that any unitarily evolving quantum system can be translated into an indivisible stochastic one and vice versa. Of course, Barandes may be wrong. And Barandes' theory is completely open and agnostic about what can cause indivisibility or how weird those causes could be.

2. i don't think entanglement swapping is anything above ordinary entanglement. The additional swapping aspect is just due to transitivity of correlations unveiled by statistical conditioning, quantum mechanics not especially required. In Barandes' papers, collapse is not a physical event, nothing more than statistical conditioning.

3. This is not an issue in Barandes' theory where collapse isn't physically real and measurement results do not communicate.

1. Again, there is no initial "unitarily evolving quantum system" evolving into a "indivisible stochastic one". It begins as *two* widely separated ones, and does not become an "indivisible" one unless and until a remote irreversible interaction at the BSM creates a swap. This is the experiment, and saying his "proof not is faulty" does not make it cover this experiment as it might otherwise for basic PDC entanglement (without a swap).

You are the one who says: Entanglement is always "directly attributed to an initial local interaction". Either Barandes claims this, or he doesn't. Either way, it is factually incorrect (experimentally falsified).


2. This too is factually incorrect: There is no statistical conditioning. ALL cases in which photons 2 & 3 arrive within the specified narrow time window (indistinguishably) lead to a swap, and are counted - and they show perfect correlations (1). All cases in which photons 2 & 3 arrive at the BSM but are made distinguishable fail to lead to a swap, and are counted. They show only random correlations. The only difference is whether the experimenter chooses to make them distinguishable or not.

Normally: when we see the experimenter is able to change the outcomes at will, we conclude that she has control over a causal variable. That variable is a deliberate action, and again normally we would conclude that there must have been a physical interaction between the 2 & 3 at the BSM. After all, the method they use to fail the swap is to delay either 2 or 3 so both 2 & 3 cannot be in the BSM apparatus at the same time (making them distinguishable).

In normal science, this would be considered a proof there was an interaction, and that it is physical. So rejecting this conclusion without any reasonable basis ("Barandes' interpretation is equivalent to other interpretations") is the very example of hand-waving.


3. My point being: how can the interaction at the BSM *not* be physically real, given the facts per 2.?

 

[JC_Silver]

This might be obvious but I honestly don't know the answer. How does Barandes' (and any other pilot wave interpretation) explain quantum tunneling? There shouldn't be any classical fenomena that allows for it, right?

 

[DrChinese]

Photons 2 and 3 are the "intermediary systems" in (4).

OK, that's what I thought you were aiming at. But... how could that work? Actually, I agree that photons 2 & 3 (when indistinguishable at the BSM) do connect initially separate systems 1&2 and 3&4.

But there is no spacetime region in which (in some versions of the experiment) that connection could possibly influence the previous 1 & 4 measurements - everything is distant in terms of c. We are left with 2 causal problems: a) nonlocality is evident (because the relevant measurements occur in widely separated regions); b) Einsteinian causal order is defied (because the outcomes are not dependent on measurement order).

So it seems that any assumption we make regarding how the mechanism works FAILS if we accept the clear experimental evidence for a) and b) I have provided. Keep in mind, I have no idea how nature performs its tricks. But I know that a) and b) must be true, if you accept the experiment as valid.

 

[PeterDonis]

how could that work?

I'm not trying to say anything about how it might work. I'm only trying to describe the conditions that appear to me to be necessary to have entanglement, without making any hypotheses at all about why those are the necessary conditions. I understand that nobody has a mechanism that could explain why. But that doesn't change the fact that, for example, if we take away the "interaction" node at the BSM (in my graph description), entanglement is no longer present--and as you have said, whether or not there is an "interaction" node at the BSM is under the experimenter's control. Nobody understands how it could be that the experimenter can control whether photons 1 & 4 are entangled by choosing whether or not to let photons 2 & 3 interact at the BSM. But that is, factually, the case, as the experiments show. I'm just trying to describe that factual condition in a way that might help to make it clearer exactly what is required.

 

[pines-demon]

This might be obvious but I honestly don't know the answer. How does Barandes' (and any other pilot wave interpretation) explain quantum tunneling? There shouldn't be any classical fenomena that allows for it, right?

The particle does not need to have enough energy to jump over the barrier because it is not following classical physics, it is just guided by the guiding wave function which can tunnel.

 

[JC_Silver]

I thought Barandes was trying to do away with the wavefunction but I guess I need to study more before understanding it

 

[pines-demon]

I thought Barandes was trying to do away with the wavefunction but I guess I need to study more before understanding it

Whatever Barandes is doing would lead to the particle effectively tunneling and thus not following classical physics either.