I Local mechanism for nonlocal anticorrelations inside spin theory

[iste]

TL;DR Summary

Recent theory of spin implies localized elliptical polarization in fields. In field media with an underlying microscopic particle theory available, this is mediated by the elliptical orbit of classical particles. It then seems logically possible - and easily visualizable - for those particles to evince nonlocal correlations (albeit not all aspects of photon polarization correlations) given that they share the same fundamental description. Importantly, this mechanism is entirely local.

Spin (and therefore photon circular polarization) can be constructed generically in terms of intrinsic rotations on vector fields, whether describing classical and quantum physical systems: e.g.

https://scholar.google.co.uk/scholar?cluster=14889979702374754652&hl=en&as_sdt=0,5

Building on this kind of construction, a relatively recent model ascribes the cause of spin to elliptical polarization localized to individual points within those fields. This elliptical polarization is proportional to the local spin density that is integrated over the field to get the total spin: e.g.

https://scholar.google.co.uk/scholar?cluster=15022687356306265602&hl=en&as_sdt=0,5&as_vis=1
(sections 5 & 6)

The kinds of rotational motion implied by this localized polarization are experimentally observable. It also resolves a paradox regarding the spin of plane waves, and explains the enigmatic "virtual" properties of spin that distinguish it from orbital angular momentum (i.e. how there is spin current without probability density transport). Due to how the construction of spin is so generic, this localized polarization has been formulated for a number of systems such as electromagnetic waves, water, acoustic waves, electron plasma and the electron quantum state (spinning probability current). It then implies localized elliptical orbits of particles whenever such a microscopic theory is available; for water, the predicted trajectories have been observed via probe particles (depiction in paper below).

https://scholar.google.co.uk/scholar?cluster=5115823896615614796&hl=en&as_sdt=0,5&as_vis=1

https://scholar.google.co.uk/scholar?cluster=2602243500647624252&hl=en&as_sdt=0,5&as_vis=1

https://scholar.google.co.uk/scholar?cluster=17892291218685033829&hl=en&as_sdt=0,5&as_vis=1

Importantly, the local elliptical polarization possesses the same properties as any classical or quantum descriptions of photon / light polarization, regardless of what medium is being described. For instance, local circular polarization at a point in space can be described in terms of two interfering orthogonal components that are ±90° phase-shifted, instantiable by circular orbits of particles. If we then additionally have a ±90° phase shift between the rotations of two separate particles, they would clearly display similar kinds of anti-correlations as entangled photons in virtue of the periodicity of their respective orbits. When one particle is experiencing the vertical part of its motion, it would imply that the other particle is in the midst of a horizontal part and vice versa (or when comparing any other two perpendicular pairs of directions). You could fix the phase relation at some initial source and then this correlation could be maintained without communication so long as the two particles keep orbiting in the same way undisturbed, even if they travel very far apart. Because of the continual orbiting, any measurement of particle direction would obviously not be pre-defined at source despite the anti-correlations. This then suggests that it is at least logically possible for nonlocal correlations of classical particles to be mediated by a mechanism that is entirely local. The particles don't even need to have locally interacted so long as the appropriate phase relation can be set.

In a paper by Jung:

https://www.frontiersin.org/journals/physics/articles/10.3389/fphy.2020.00170/full

They derive polarization correlations entirely in classical optics from a phase shift for circularly polarized light + Malus Law. From this, it seems that, though the orbital motions of particles obviously could not explain superposition or probabilistic aspects of measurement which would be connected to the local Malus Law aspect, this mechanism does seem to be able to account for the entire non-local aspect of these correlations.

 

[iste]

Obviously, the description that has been given of polarization correlations with orbiting particles is nowhere near laying out some kind of full model of photon polarization correlations but it suggests the logical possibility of mediating non-local correlations via a local mechanism. I think the most interesting application for this would be to fit it into an existing interpretation / formulation such as stochastic mechanics. Markovian stochastic mechanics can reproduce all quantum predictions through classical microscopic particles moving randomly on continuous trajectories. The theory is overtly non-local, not so dissimilarly to Bohmian mechanics. However, it has been shown before that this non-locality disappears if you use non-Markovian diffusions, first by Edward Nelson in his book Quantum Fluctuations, and then in Levy and Krener's reformulation of stochastic mechanics using reciprocal diffusions:

https://web.math.princeton.edu/~nelson/papers.html

https://www.google.com/search?q=Stochastic+mechanics+of+reciprocal+diffusions+pdf

Levy and Krener's analysis identifies the cause of non-locality in stochastic mechanics with the inability for Markovian diffusions to satisfy the Schrodinger evolution without corrections to their potentials, something not required in the non-Markovian subclass they constructed (dubbed "Quantum diffusions"). The Markovian assumption may plausibly be an artificial idealization with non-locality as a byproduct that is ultimately not veridical. A possible local mechanism for photon correlations then gives further reason to take this idea seriously. Stochastic mechanics may take care of the rest of the limitations of the mechanism. The stochasticity may take care of the Malus Law aspect of correlations unaccounted for in this mechanism (e.g. non-commutativity / uncertainty relations can be derived from stochastic trajectories) and the non-dissipative, conservative nature of the diffusion accounting for maintaining the periodic orbits similar to how circularly rotating light can just keep on rotating.

Edit:

Its also interesting to note that the recent explicitly non-Markovian stochastic formulation of quantum theory by Barandes (subject of a post some time ago) explains non-local entanglement through the ability of the non-Markovian transition matrix to remember correlations from local interactions in the past (and implying that a Markovian counterpart could not do this). This explanation actually seems quite reminiscent of the idea that a phase shift is set at source and maintained or remembered over time until measured / decohered.

 

[DrChinese]

Obviously, the description that has been given of polarization correlations with orbiting particles is nowhere near laying out some kind of full model of photon polarization correlations but it suggests the logical possibility of mediating non-local correlations via a local mechanism. …

The Jung paper includes a fantastic list of references on various tests of entanglement and closing of loopholes. However, there is a huge hole in the discussion of local explanations of quantum nonlocality. Specifically: experimental entanglement of systems that have never interacted or existed in a common light cone, including delayed choice versions.

https://arxiv.org/abs/0809.3991

This experiment (and many others like it) completely invalidates your hypothesis (of a local explanation). Which is why it is missing as a reference, I guess.

In my reference, an entangled photon pair is created that have never been close to each other. The choice to entangle them or not is freely decided and executed by a remote experimenter. There is no local interaction to tie the entangled photons to each other.

I really miss the point of the attempts being made to re-introduce classical locality into QM when there are well-accepted counter examples from nearly 20 years ago. An author putting forth such hypothesis must start with the most difficult challenge, not an easier one. And this has not been done.

 

[iste]

In my reference, an entangled photon pair is created that have never been close to each other. The choice to entangle them or not is freely decided and executed by a remote experimenter. There is no local interaction to tie the entangled photons to each other.

It doesn't matter whether they ever contacted. If you look at the pair of graphics of rotating waves in this wikipedia section on Handedness conventions:

https://en.wikipedia.org/wiki/Circular_polarization#Handedness_conventions

I am pretty sure the little arrows on both graphics are rotating at a constant rate in a way that when one is pointing in a certain direction the other is always pointed in another direction, displaying a phase shift. That is the kind of correlation. Clearly they don't need to communicate to be in-synch and there is no reason why they need to be in physical contact for different people to independently calibrate the rotation of either of the little hands so that they both are in-synch. It simply doesn't matter if the pair were ever in local contact if you can set the correct phase relation somehow. Regarding the delayed choice? No entanglement experiments, with or without delay, will work unless the phase shift and coherence is preserved throughout the whole experiment, something which it seems experimentalists take great care in trying to achieve in their set ups to avoid the destruction of the entanglement; messing about with the paths in interferometers can affect the phase, for instance, as you would expect. So such delayed entanglements would still imply that the phase relation, the synchronized nature of orbits or rotations is still totally preserved. Once this has been set in a way that it is preserved in the set up, any kind of delay in the measurements doesn't matter in principle. The correlation is fully accounted for by the phase regardless of which photon gets measured first or the time between their measurement because the experiment has been set up in a way that their synchronization (e.g. of the little hands in the graphics of the rotating waves above) up to measurement has been pre-set without needing to invoke spooky collapse.

 

[DrChinese]

It doesn't matter whether they ever contacted. If you look at the pair of graphics of rotating waves in this wikipedia section on Handedness conventions:

https://en.wikipedia.org/wiki/Circular_polarization#Handedness_conventions

I am pretty sure the little arrows on both graphics are rotating at a constant rate in a way that when one is pointing in a certain direction the other is always pointed in another direction, displaying a phase shift. That is the kind of correlation. Clearly they don't need to communicate to be in-synch and there is no reason why they need to be in physical contact for different people to independently calibrate the rotation of either of the little hands so that they both are in-synch. It simply doesn't matter if the pair were ever in local contact if you can set the correct phase relation somehow. Regarding the delayed choice? No entanglement experiments, with or without delay, will work unless the phase shift and coherence is preserved throughout the whole experiment, something which it seems experimentalists take great care in trying to achieve in their set ups to avoid the destruction of the entanglement; messing about with the paths in interferometers can affect the phase, for instance, as you would expect. So such delayed entanglements would still imply that the phase relation, the synchronized nature of orbits or rotations is still totally preserved. Once this has been set in a way that it is preserved in the set up, any kind of delay in the measurements doesn't matter in principle. The correlation is fully accounted for by the phase regardless of which photon gets measured first or the time between their measurement because the experiment has been set up in a way that their synchronization (e.g. of the little hands in the graphics of the rotating waves above) up to measurement has been pre-set without needing to invoke spooky collapse.

In my cited experiment, they are created fully independently and distant from each other. So none of what you mention applies. They are not correlated in any way to begin with. It takes a remote action to cause them to become entangled. If that action does not occur, they are not entangled. And every piece of the process is distant and nonlocal.

 

[martinbn]

It seems that there two things people try to do when they cannot accept the validity of Bell's theorem. One is to look for some local mechanism, a local interaction that will explain the results. This of course is stupid because the theorem says that it is impossible. The second is to try to find some nonlocal mechanism, some kind of action at a distance. This is also stupid. It is an attempt to find a classical explanation. QM is the explanation and needs nothing more, unless you cannot accept QM and desperately cling to classical worldview.

 

[Demystifier]

It seems that there two things people try to do when they cannot accept the validity of Bell's theorem. One is to look for some local mechanism, a local interaction that will explain the results. This of course is stupid because the theorem says that it is impossible. The second is to try to find some nonlocal mechanism, some kind of action at a distance. This is also stupid. It is an attempt to find a classical explanation. QM is the explanation and needs nothing more, unless you cannot accept QM and desperately cling to classical worldview.

So you say that it is stupid to ask whether predictions of QM can be explained by a classical worldview. But Bell obtained his theorem precisely by asking such a question. So are you telling that the Bell theorem has been obtained by asking a stupid question, and yet that the theorem itself is not stupid?

 

[martinbn]

So you say that it is stupid to ask whether predictions of QM can be explained by a classical worldview.

No, I said that it is stupid to look for such an explanation. You can ask the question if there is such an explanation.

But Bell obtained his theorem precisely by asking such a question. So are you telling that the Bell theorem has been obtained by asking a stupid question, and yet that the theorem itself is not stupid?

No again. I didn't say that it is a stupid question to ask if such an explanation exists. I said that it is stupid to look for such an explanation. In view of the theorem it is even more stupid to try that.

 

[DrChinese]

The second is to try to find some nonlocal mechanism, some kind of action at a distance. This is also stupid. It is an attempt to find a classical explanation. .

I wouldn’t call a nonlocal mechanism “classical”. And considering the number of experiments that demonstrate some form of quantum nonlocality (probably over 1000), that seems like a good place to look.

 

[martinbn]

I wouldn’t call a nonlocal mechanism “classical”.

By classical I meant non quantum.

And considering the number of experiments that demonstrate some form of quantum nonlocality (probably over 1000), that seems like a good place to look.

They demonstrate nonlocality in the sense of violating Bell's inequality, not in the sense of action at a distance. They couldn't demonstrate action at a distance because QM has no such action but predicts all the experiments so far.

 

[Demystifier]

No, I said that it is stupid to look for such an explanation. You can ask the question if there is such an explanation.

No again. I didn't say that it is a stupid question to ask if such an explanation exists. I said that it is stupid to look for such an explanation. In view of the theorem it is even more stupid to try that.

So are you saying that such an explanation of QM, with a classical worldview, does not exist? Isn't Bohmian mechanics a counterexample?

 

[PeterDonis]

Isn't Bohmian mechanics a counterexample?

Not by the definition of "classical" that @martinbn is using per post #10, which explicitly rules out Bohmian mechanics as "classical" since it is a quantum theory.

 

[martinbn]

So are you saying that such an explanation of QM, with a classical worldview, does not exist? Isn't Bohmian mechanics a counterexample?

Well, I didn't say that such an explanation doesn't exist. Only that it is not a good idea to look for such explanations.

 

[Demystifier]

Well, I didn't say that such an explanation doesn't exist. Only that it is not a good idea to look for such explanations.

And why is it not a good idea?

 

[martinbn]

And why is it not a good idea?

That's obvious.

 

[DrChinese]

They demonstrate nonlocality in the sense of violating Bell's inequality, not in the sense of action at a distance. They couldn't demonstrate action at a distance because QM has no such action but predicts all the experiments so far.

Of course there is explicit nonlocality in QM. The quantum expectation value of measurements on entangled systems is dependent on the nature of distant measurements, and nothing else. For example: for spin/polarization, it is the difference between 2 distant angle settings (usually called theta) made independently. That is straight out (quantum) nonlocality.

 

[martinbn]

Of course there is explicit nonlocality in QM. The quantum expectation value of measurements on entangled systems is dependent on the nature of distant measurements, and nothing else. For example: for spin/polarization, it is the difference between 2 distant angle settings (usually called theta) made independently. That is straight out (quantum) nonlocality.

Yes, of course, and this is not in any way contrary to what i said.

 

[PeterDonis]

The quantum expectation value of measurements on entangled systems is dependent on the nature of distant measurements

No, the correlations are dependent on the nature of distant measurements. But the expectation values of individual measurements taken in isolation are not. If Alice and Bob each measure an entangled qubit, Bob's expectation value for a given measurement (i.e., a given angle he chooses for his measuring device to measure the spin of the qubit), taken in isolation, i.e., without any knowledge of Alice's measurement, is the same regardless of what measurement Alice chooses to make on her qubit. The entanglement only shows up in the correlations between the two measurements when the results from both are analyzed together.

 

[DrChinese]

No, the correlations are dependent on the nature of distant measurements. But the expectation values of individual measurements taken in isolation are not. If Alice and Bob each measure an entangled qubit, Bob's expectation value for a given measurement (i.e., a given angle he chooses for his measuring device to measure the spin of the qubit), taken in isolation, i.e., without any knowledge of Alice's measurement, is the same regardless of what measurement Alice chooses to make on her qubit. The entanglement only shows up in the correlations between the two measurements when the results from both are analyzed together.

Seriously, you are simply mincing words.

The quantum expectation value OF THE CORRELATIONS is strictly dependent on distant settings. There is no classical situation where this is true. Of course there is no distance involved in a single measurement.

Was your comment really necessary?

 

[martinbn]

Seriously, you are simply mincing words.

The quantum expectation value OF THE CORRELATIONS is strictly dependent on distant settings. There is no classical situation where this is true. Of course there is no distance involved in a single measurement.

Was your comment really necessary?

So you agree with me? "There is no classical situation where that is true."

 

[Morbert]

In my reference, an entangled photon pair is created that have never been close to each other. The choice to entangle them or not is freely decided and executed by a remote experimenter. There is no local interaction to tie the entangled photons to each other.

Any mainstream interpretation that accounts for conventional EPRB experiments with local interactions can account for the creation of entanglement between photons that have never been close to each other with local interactions.

 

[DrChinese]

Any mainstream interpretation that accounts for conventional EPRB experiments with local interactions can account for the creation of entanglement between photons that have never been close to each other with local interactions.

No, there are no such explanations I have ever seen or heard of - and I’ve seen a lot. What there are a lot of are *claims* of such, and usually they focus on demonstrating equivalence to QM mathematically. A full remote swapping context features 2 separated measurements (violating a Bell inequality) and a third remote spot where a decision can be made (with the free will of the experimenter) to create entanglement or not.

Anyone who can pitch that as local action successfully would be of great interest to me. Just show me a paper with a diagram. :)

 

[PeterDonis]

The quantum expectation value OF THE CORRELATIONS

Which is not what the post I was responding to said. The claim that post made said "measurements", which is much more general than "correlations". That's why I clarified it.

 

[PeterDonis]

Any mainstream interpretation that accounts for conventional EPRB experiments with local interactions

What do you mean by "local interactions"? Depending on how you interpret that phrase, it could apply to all interpretations, or none.

 

[iste]

In my cited experiment, they are created fully independently and distant from each other. So none of what you mention applies. They are not correlated in any way to begin with. It takes a remote action to cause them to become entangled. If that action does not occur, they are not entangled. And every piece of the process is distant and nonlocal.

True, but I think the time-synchronization required for the independent sources is kind of analogous in that it is required to obtain the new entanglement state through coherence.

As said before, this mechanism in original post doesn't account for all aspects of photon polarization correlation but it seems to me it can produce correlations analogous to entanglement swapping.

For two "entanglements" of orbiting particle pairs (e.g. photons 1 & 2 vs. photons 3 & 4), there could be initially no overall correlation between the pairings when you consider that the outcomes in photons 1 & 2 are independently random from those of photons 3 & 4 so that all possible pairs of outcomes for 2 & 3 (or 1 & 4 respectively) are possible.

But when you consider coincidence detection or measurement at 2 & 3 and condition on the outcomes, then it seems natural that the photons 1 & 4 must be correlated because if 3 is always precisely correlated to 4 and 1 is always precisely correlated to 2, then a definite relationship between 2 & 3 by measurement is clearly enough to establish a definite relationship between 1 & 4. This relationship would go away when you consider all of the possible outcomes at the same time, but statistical conditioning (which afaik is all that projective collapse implies on a formal level) unveils the underlying correlations which would show entanglements in 1 & 4.

This is a similar kind of description as the "entanglement through measurement" section suggests here:

https://scholar.google.co.uk/scholar?cluster=17666541244192212757&hl=en&as_sdt=0,5&as_vis=1

I think this would seem to suggest that what is strange about entanglement swapping is nothing above what is strange about conventional entanglement.

 

[iste]

It seems that there two things people try to do when they cannot accept the validity of Bell's theorem. One is to look for some local mechanism, a local interaction that will explain the results. This of course is stupid because the theorem says that it is impossible. The second is to try to find some nonlocal mechanism, some kind of action at a distance. This is also stupid. It is an attempt to find a classical explanation. QM is the explanation and needs nothing more, unless you cannot accept QM and desperately cling to classical worldview.

Such a mechanism wouldn't contradict Bell's theorem because it isn't saying outcomes are determined from the source, nonetheless the correlation is determined from source and kind of 'remembered' by both particles so it wouldn't require spooky communication. It would still be non-local in the Bell sense; I mean't spooky action at a distance.

There is an interesting example of a kind of memory of correlations in a model of a classical hydrodynamic system here:

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

Because the fluid bath exhibits non-Markovian behavior, droplets surfing on the bath continue to remember correlations between themselves even though a physical barrier has been put up that prevents them from communicating in any way at all. Sort of like entanglement.

Also I might add that a model of quantum mechanics does exist that is constructed purely from classical (but stochastic) assumptions and can in principle reproduce all of the behaviors of quantum mechanics (like Bohmian mechanics can). It is maybe just not very well known:

https://en.wikipedia.org/wiki/Stochastic_quantum_mechanics

 

[PeterDonis]

the correlation is determined from source and kind of 'remembered' by both particles

Yes, proposing such a mechanism would contradict Bell's theorem, since it is precisely the kind of mechanism that Bell's theorem applies to. What you call "determined from source and kind of 'remembered' by both particles" is what is called "hidden variables" in Bell's theorem.

 

[PeterDonis]

There is an interesting example of a kind of memory of correlations in a model of a classical hydrodynamic system here

Classical models are irrelevant here, since no such model can produce correlations that violate the Bell inequalities.

 

[PeterDonis]

a model of quantum mechanics does exist that is constructed purely from classical (but stochastic) assumptions

No, it isn't. The fact that "stochastic quantization" is given as one of the assumptions in the Wikipedia article you reference should be a huge red flag to you that your claim here is not valid.

 

[Fra]

I'm not defending those particular papers but...

It seems that there two things people try to do when they cannot accept the validity of Bell's theorem. One is to look for some local mechanism,

There is a third option: Accept Bell's theorem as such, but that claims it's premises are not valid in the situation, because one seeks not a local mechanism for explaning the results, but just to explain the correlation.

Bell's theorem proves that no explanation of the correlation that builds on "hidden values" will work, but it does not reject a theory that may have a mechanism, but only correlations of unknown values are required. I think this type of explanation need not be (or probably even can't be) "classical".

QM is the explanation and needs nothing more, unless you cannot accept QM and desperately cling to classical worldview.

QM, describes it but the I think the idea that there is no way to improve the understandin and causal mechanism of QM, without cling onto an outdated worldview, is something I do not share.

QM is the best theory we have, but that doesn't mean it has nothing left to wish for.

/Fredrik

 

[PeterDonis]

There is a third option: Accept Bell's theorem as such, but that claims it's premises are not valid in the situation, because one seeks not a local mechanism for explaning the results, but just to explain the correlation.

Bell's theorem proves that no explanation of the correlation that builds on "hidden values" will work, but it does not reject a theory that may have a mechanism, but only correlations of unknown values are required. I think this type of explanation need not be (or probably even can't be) "classical".

Do you have any references for these claims? Please bear in mind that, even in this forum, personal speculation is not permitted.

 

[iste]

Yes, proposing such a mechanism would contradict Bell's theorem, since it is precisely the kind of mechanism that Bell's theorem applies to. What you call "determined from source and kind of 'remembered' by both particles" is what is called "hidden variables" in Bell's theorem.

The memory thing isn't a hidden variable like that because it is the correlation that is determined from source and remembered, not the outcomes. The mechanism also already exists in quantum experiment and formalism in the sense that all that is being talked about is a phase shift. You can see in the Jung paper of original post that the phase that determines the correlation from source is something they have gotten from previous influential papers. You can find an interferometric version of this phase in papers by Horne et al. from late 80s/early 90s. Dr. Chinese posted an entanglement paper in a circular polarization thread not long ago that also mentions the phase at source and how changing it can change from vv hh correlations to vh hv correlations. The issue is physically interpretating some mechanism that already exists in quantum mechanics rather than adding some distinctly novel mechanism that may or may not reproduce the correct behavior - so I don't think it would contradict Bell.

Classical models are irrelevant here, since no such model can produce correlations that violate the Bell inequalities.

Well the same type of classical hydrodynamic system as the last paper has been shown to be able to violate Bell inequalities in the case where there is no barrier. The authors are I believe looking at the barrier case so that is an open question I think.

https://scholar.google.co.uk/scholar?cluster=9229154603514546961&hl=en&as_sdt=0,5&as_vis=1

No, it isn't. The fact that "stochastic quantization" is given as one of the assumptions in the Wikipedia article you reference should be a huge red flag to you that your claim here is not valid.

I think this is a case of two different things with the same name. The assumptions in stochastic mechanics come from what you would ordinarily think of as classical stochastic process.

 

[DrChinese]

True, but I think the time-synchronization required for the independent sources is kind of analogous in that it is required to obtain the new entanglement state through coherence.

As said before, this mechanism in original post doesn't account for all aspects of photon polarization correlation but it seems to me it can produce correlations analogous to entanglement swapping.

For two "entanglements" of orbiting particle pairs (e.g. photons 1 & 2 vs. photons 3 & 4), there could be initially no overall correlation between the pairings when you consider that the outcomes in photons 1 & 2 are independently random from those of photons 3 & 4 so that all possible pairs of outcomes for 2 & 3 (or 1 & 4 respectively) are possible.

But when you consider coincidence detection or measurement at 2 & 3 and condition on the outcomes, then it seems natural that the photons 1 & 4 must be correlated because…

What you are suggesting cannot be true, and the papers themselves say the same thing: there are no correlations between 1 & 4 unless and until the decision is made to execute a swap. Let me know if you need a quote/reference on that. Monogamy of Entanglement prevents that, for one thing.

But you are missing a critical point in your use of the word “correlations”. They are *perfect* correlations, which are only possible with entangled systems. On the other hand, in a coherent laser beam, photons are correlated but only have the same polarization at 4 angles. Big difference, right! There cannot be any deeper correlation even between photons from the same source, and certainly not from independent (but phase-locked) sources.

And the most important element is yet again bypassed: The perfect correlations only appear if the decision to execute the swap is made. This is dependent on whether the 2 & 3 photons are indistinguishable (leading to entanglement) or not. That decision and its execution occur remotely. Where is the local mechanism to address this?

As I say: claims of a local mechanism to explain entanglement are often made, but application to modern swapping experiments is sadly lacking. (Hand-waving does not count in light of experimental evidence to the contrary.)

 

[PeterDonis]

The issue is physically interpretating some mechanism that already exists in quantum mechanics

There is no "mechanism" in QM. That's why there is not one single generally accepted interpretation of QM. People can "explain" a given QM result with different interpretations that use completely different, inconsistent, and incompatible "mechanisms".

 

[iste]

There is no "mechanism" in QM. That's why there is not one single generally accepted interpretation of QM. People can "explain" a given QM result with different interpretations that use completely different, inconsistent, and incompatible "mechanisms".

Well, what I mean by 'mechanism' is just something in quantum mechanics regardless of quantum mechanics.

 

[PeterDonis]

what I mean by 'mechanism' is just something in quantum mechanics

Which makes this discussion pretty pointless; basically you're saying "quantum mechanics is quantum mechanics". True, but hardly worth discussion.

 

[martinbn]

What you are suggesting cannot be true, and the papers themselves say the same thing: there are no correlations between 1 & 4 unless and until the decision is made to execute a swap.

And even then there is no correlation. There is correlation of the results of a subset of the trials.

 

[Fra]

There is no "mechanism" in QM. That's why there is not one single generally accepted interpretation of QM.

Agreed. Or rather there ia no known mechanism behind QM that helps deep understanding of QM weirdness.

But that isnt the same as to say its meaningless to look for one. For some of us a least, the reward at the end of this path of inquiry is not just another "pure interpretation" that makes no difference, but the hope of an interpretation that will guide us into the real open questions regarding unification of forces. This is very different that looking for a "Bell class" HV explanation.

/Fredrik

 

[PeroK]

Well, what I mean by 'mechanism' is just something in quantum mechanics regardless of quantum mechanics.

It's worth noting that the idea of a fundamental mechanism isn't sustainable in physics generally. Newton's second law, to some extent, allows the concept of a mechanism in each case. But, Newton's law of gravity - by Newton's own admission - is purely a mathematical relationship that has no possible underlying mechanism. Likewise, GR has no "mechanism" for the stress-energy tensor determining the geometry of spacetime. And, Maxwell's mathematics, again not a specific mechanism, drives the propagation of EM radiation etc. I believe that 19th physicists were slow to accept Maxwell's EM theory because it wasn't mechanical enough. They, like you, wanted a mechanism; not just mathematics.

And, in general, if we are using a Lagrangian or Hamiltonian approach, then we have a mathematical, rather than a mechanical description of nature at all scales, from the microscopic to the cosmological.

You could argue that QM takes this a stage further, but you are never going to find a mechanism in any sense of the word, with microscopic cogs and wheels and levers, at the core of modern physics.

 

[Fra]

It's worth noting that the idea of a fundamental mechanism isn't sustainable in physics generally.

Agreed, this is one of the arguments in favour of ABM (agent based models) instead of the "Newtoian Scheme" System dynamics. Both are mathematical models, and both paradigms can often model the same phenomenan, but they offert perspectives.

In system dynamics, of course there is no "mechanism" we just have evolution laws on system level.
In Agent based interactions, the mechanism is at the focus, and system dyanmics is emergent.

This point is I think also at the root of Smolin path of inquiry where he argues - against the prevailing paradigm in physics - that we need a paradigm change. Sometime he received also plenty of critique for (not too surprisingly!)

/Fredrik

 

[Morbert]

What do you mean by "local interactions"? Depending on how you interpret that phrase, it could apply to all interpretations, or none.

I mean the same that @DrChinese means: If A and B are spatially distant, an external influence on A cannot have an immediate effect on B.

 

[Morbert]

No, there are no such explanations I have ever seen or heard of - and I’ve seen a lot. What there are a lot of are *claims* of such, and usually they focus on demonstrating equivalence to QM mathematically. A full remote swapping context features 2 separated measurements (violating a Bell inequality) and a third remote spot where a decision can be made (with the free will of the experimenter) to create entanglement or not.

Anyone who can pitch that as local action successfully would be of great interest to me. Just show me a paper with a diagram. :)

Do you take issue with accounts for conventional EPR experiments with local interactions? E.g.

As to the EPRB setup, consider an analogous classical situation: a bomb, initially at rest, explodes into two fragments carrying opposite angular momenta. Alice and Bob, far away from each other, measure arbitrarily chosen components J1 and J2 [...]

The distribution of bomb fragments is given by a Liouville function in phase space. When Alice measures J1, the Liouville function for J2 is instantly altered, however far Bob is from Alice. No one finds this surprising, since it is universally agreed that a Liouville function is only a mathematical tool representing our statistical knowledge. Likewise, the wave function ψ, or the corresponding Wigner function (Wigner, 1932) which is the quantum analogue of a Liouville function, are no more than mathematical tools for computing probabilities.

The essential difference [...] is that the classical Liouville function is attached to objective properties that are only imperfectly known. On the other hand, in the quantum case, the probabilities are attached to potential outcomes of mutually incompatible experiments, and these outcomes do not exist “out there” without the actual interventions. Unperformed experiments have no results.

https://arxiv.org/abs/quant-ph/0212023

A similar exercise can be carried out for your systems of interest, where entanglement is established between photons that have never been close together. You have not accepted such exercises in previous threads, so I think your issue with local accounts is larger than swapping experiments.

 

[DrChinese]

1. Do you take issue with accounts for conventional EPR experiments with local interactions? E.g. https://arxiv.org/abs/quant-ph/0212023

2. A similar exercise can be carried out for your systems of interest, where entanglement is established between photons that have never been close together. You have not accepted such exercises in previous threads, so I think your issue with local accounts is larger than swapping experiments.

1. Of course I take issue with Peres’ description, which he of all people should have known better. First, that’s an old reference (2002) and I keep specifying modern experiments. They didn’t even start those until about 2002. Peres certainly knew of the appropriate theory though at that time, and specifically he well knew of delayed choice options. So I would criticize his description in particular.

Second, that is once again ignoring what I am challenging. Which is: remote swapping.

2. No, claiming a “similar exercise” without detailing further is merely hand waving. The devil is in the details, let’s see those. If this were class, I’d say “show your work”.

 

[physika]

You could argue that QM takes this a stage further, but you are never going to find a mechanism in any sense of the word, with microscopic cogs and wheels and levers, at the core of modern physics.

...what limited language.

Mechanism:
Process by which something takes place by a set of rules/law etc.
(Obviously, describable by mathematics).

....

 

[iste]

there are no correlations between 1 & 4 unless and until the decision is made to execute a swap

Yes, I say this in the post, literally in what you quote. There is no correlation unless you condition on the outcomes via measurement and I explain why that is in the quote.

They are *perfect* correlations, which are only possible with entangled systems.

Yes, the correlations from this model are perfect. Again, This mechanism isn't accounting for everything about photon polarization correlations but they are perfect. If you have two particles, each traveling on orbital motions where they rotate at the rate and the phase shift between them is fixed (e.g. 90 degrees), then you can get perfect anti-correlations in the sense that if you measure one polarized vertically the other one is always going to be horizontal and vice versa, or for any other direction of motion. You can then get two particles moving away from each other, doing their little orbiting spiralling motions as they go and so long as their rotations are not interrupted, you should always gets the same correlations even if they are very far apart. If you do a phase shift by 0 or 180 degrees, then it will always be horizontal-horizontal, vertical-vertical, matched diagonals etc etc.

Where is the local mechanism to address this?

Its just statistical conditioning. If there are perfect anticorrelations (just looking at regular entanglement swapping in general here) then if 2 is H and 3 is H, then 1 and 4 must both be V and there is a perfect relationship between 1 and 4 too. 2 is H, 3 is V? Then 1 is V and 4 is H so there will be another perfect anticorrelation. If you dont condition then 1 & 4 can take on all possible combinations of HH, VV, HV, VH and so you wont see any correlation unless you condition on outcomes of 2 & 3 - then they suddenly become perfect just because you have conditioned statistically on those outcomes. Obviously, experimentally you need to ensure that you can get the correct coincidences.

 

[iste]

There is no "mechanism" in QM. That's why there is not one single generally accepted interpretation of QM. People can "explain" a given QM result with different interpretations that use completely different, inconsistent, and incompatible "mechanisms".

Well, what I mean by 'mechanism' is just something in quantum mechanics regardless of quantum mechanics.

Woops, I meant regardless of interpretation.

 

[iste]

Which makes this discussion pretty pointless; basically you're saying "quantum mechanics is quantum mechanics". True, but hardly worth discussion.

Woops, I didn't even see this.

No, not at all. For instance, you can derive the Schrodinger equation and reproduce all of quantum mechanics from stochastic processes according to stochastic mechanics. Because what is being derived is identical to quantum mechanics, it will not contradict it in anyway and it won't contradict Bell, hence how Stochastic mechanics has been shown recently to be able to reproduce electron spin correlations and Bell violations. However, despite being clearly equivalent, there is the addition of a different underlying interpretation.

So you can analogously give an underlying interpretation of quantum mechanical formalism and experiment, of the phase which is established at source and is important to the eventual measured correlations.

 

[iste]

It's worth noting that the idea of a fundamental mechanism isn't sustainable in physics generally. Newton's second law, to some extent, allows the concept of a mechanism in each case. But, Newton's law of gravity - by Newton's own admission - is purely a mathematical relationship that has no possible underlying mechanism. Likewise, GR has no "mechanism" for the stress-energy tensor determining the geometry of spacetime. And, Maxwell's mathematics, again not a specific mechanism, drives the propagation of EM radiation etc. I believe that 19th physicists were slow to accept Maxwell's EM theory because it wasn't mechanical enough. They, like you, wanted a mechanism; not just mathematics.

And, in general, if we are using a Lagrangian or Hamiltonian approach, then we have a mathematical, rather than a mechanical description of nature at all scales, from the microscopic to the cosmological.

You could argue that QM takes this a stage further, but you are never going to find a mechanism in any sense of the word, with microscopic cogs and wheels and levers, at the core of modern physics.

Personally, I think this is too quick. For me, the existence of stochastic mechanics, the derivation of quantum mechanics from stochastic processes suggests that a kind of mechanistic construction of quantun mechanics is possible in principle.

 

[DrChinese]

Yes, I say this in the post, literally in what you quote. There is no correlation unless you condition on the outcomes via measurement and I explain why that is in the quote.

Yes, the correlations from this model are perfect. Again, This mechanism isn't accounting for everything about photon polarization correlations but they are perfect. If you have two particles, each traveling on orbital motions where they rotate at the rate and the phase shift between them is fixed (e.g. 90 degrees), then you can get perfect anti-correlations in the sense that if you measure one polarized vertically the other one is always going to be horizontal and vice versa, or for any other direction of motion. You can then get two particles moving away from each other, doing their little orbiting spiralling motions as they go and so long as their rotations are not interrupted, you should always gets the same correlations even if they are very far apart. If you do a phase shift by 0 or 180 degrees, then it will always be horizontal-horizontal, vertical-vertical, matched diagonals etc etc.

Its just statistical conditioning. If there are perfect anticorrelations (just looking at regular entanglement swapping in general here) then if 2 is H and 3 is H, then 1 and 4 must both be V and there is a perfect relationship between 1 and 4 too. 2 is H, 3 is V? Then 1 is V and 4 is H so there will be another perfect anticorrelation. If you dont condition then 1 & 4 can take on all possible combinations of HH, VV, HV, VH and so you wont see any correlation unless you condition on outcomes of 2 & 3 - then they suddenly become perfect just because you have conditioned statistically on those outcomes. Obviously, experimentally you need to ensure that you can get the correct coincidences.

Sorry, virtually everything you are saying involves claiming there are local hidden variables. Bell tells us otherwise, which is generally accepted by the physics community.

To be clear: there is no connection whatsoever between 1 and 4 regardless of the polarization measurements of 2 & 3. The only way you get entanglement between 1 & 4 is for 2 & 3 to interact indistinguishably. No interaction - distant to 1 & 4 and optionally delayed - there are no perfect correlations.

Again I say: address an actual experiment all the way though, not via hand waving generalities.

High-fidelity entanglement swapping with fully independent sources
Kaltenback et al (2008)
https://arxiv.org/pdf/0809.3991

See figure 1, noting that distances in this setup are arbitrary. And please, how about addressing my point: there can be no “information update” unless a remote physical interaction occurs between 2 & 3. So obviously something physical does happen remotely, and it’s not simply an information update. Which is why it cannot be statistically conditioned on the outcome at 2 & 3, which can be performed later. Whether there are perfect correlations or not is strictly dependent on whether that physical interaction occurs.

Again: the 2 & 3 outcomes are the same - HH, HV, etc. - regardless of whether that physical interaction occurs. But if it does not occur, there are no perfect correlations. So that is the difference, and why your explanation cannot work.

I ask that you not fall back to old descriptions that do not work for modern experiments. There cannot be the kind of locality you envision given these experiments from the past 15 years or so. Trace through it carefully and you will see what I’m saying is correct. I still have no idea what the mechanism is that underlies this process. But it is just basic QM, and really should not be anything surprising to anybody.

 

[Morbert]

1. Of course I take issue with Peres’ description, which he of all people should have known better. First, that’s an old reference (2002) and I keep specifying modern experiments. They didn’t even start those until about 2002. Peres certainly knew of the appropriate theory though at that time, and specifically he well knew of delayed choice options. So I would criticize his description in particular.

Before we tackle modern experiments, I want to know if you take issue with such accounts of simpler EPR experiments. E.g. Alice and Bob are spatially distant and perform joint measurements on entangled 2-particle systems. The outcomes exhibit Bell-inequality violating correlations. Without worrying about more sophisticated experiments yet, do you believe these simpler experiments cannot be accounted for with local interactions?