Why is superdeterminism not the universally accepted explanation of nonlocality?

In summary, the conversation discusses the concept of nonlocality and entanglement in a deterministic universe, where the information about instantaneous transfer is known to the universe. The conversation also touches upon the idea of superdeterminism, which some people reject due to its conspiratorial nature and lack of a concrete scientific theory. The possibility of interpreting nonlocality as an answer rather than a problem is also mentioned, as well as the importance of keeping beliefs aligned with measured reality. The conversation concludes with the suggestion that it may be better to believe in the existence of random and non-local phenomena rather than inventing longer explanations.
  • #281
ThomasT said:
Sure there is. There's circuitry that matches detection attributes which operates according to calculations based on the photon emission source and the distance between the polarizers.
They're a consequence of matching individual detection attributes wrt calculated coincidence intervals.
But these are just contingent facts about experimental design. Consider an idealized experiment where one photon pair is sent out every hour by a source which is exactly at the midpoint between two polarizers, which catch every single photon with perfect accuracy. In that case all each experimenter has as far as data goes is a list of yes or no answers as to whether the photon went through the polarizer or not. There are no time stamps, distance measurements, coincidence intervals, or anything like that.
Whether coincidental detections are counted 'on the fly' by circuitry built into the experimental design, or after the fact via time stamps, the fact is that the basic datum of entanglement setups (eg., Bell tests) is called coincidental detection, and the rate of coincidental detection varies as a function of θ, the angular difference between the polarizer settings.
No, in the Bell test setup I described above, the basic datum is whether the experimenter sees a photon go through the polarizer or not. I think the word "correlation" is a much better term for what you call the "rate of coincidental detection". It is just the correlation between individual polarization measurements of photons, and as such all its properties are determined by whatever determines the results of individual polarization measurements. And the nonlinear relationship between the correlation and the angle is also entirely determined by whatever determines whether a photon goes through a polarizer or not.
So, given that the rate of individual detection doesn't vary as a function of polarizer setting, then what can you infer from this?
All a local determinist might infer from this is that the decision of whether to go through the polarizer or not is based on some local hidden variable, but we human beings don't know the value of this variable, so to us it seems like an unpredictable 50-50 chance whether it will go through.
No. Incorrect inference. This doesn't follow from the known experimental results.
But the argument is not based on the known data from practical experiments done so far; if you wanted to respond to Bell's theorem in that way you could be like zonde, who believes that Bell tests to date have experimental loopholes, and that quantum mechanics will be disproved as soon as we improve our experimental capabilities. The argument I'm making is more fundamental: it is that it is impossible for a local determinist to believe that all the experimental predictions of quantum mechanics are correct, without regard to the practical difficulties of testing these predictions. It took us a while to do any Bell tests at all, but that did not change the validity of Bell's theorem.
 
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  • #282
lugita15 said:
There is no experimental procedure called "coincidence detection" ...

ThomasT said:
There's circuitry that matches detection attributes which operates according to calculations based on the photon emission source and the distance between the polarizers.
lugita15 said:
... so the term "rate of coincidence detection" is highly misleading. Coincidences aren't "detected" experimentally, they are a consequence of individual detections.
ThomasT said:
They're a consequence of matching individual detection attributes wrt calculated coincidence intervals.
lugita15 said:
But these are just contingent facts about experimental design. Consider an idealized experiment where one photon pair is sent out every hour by a source which is exactly at the midpoint between two polarizers, which catch every single photon with perfect accuracy. In that case all each experimenter has as far as data goes is a list of yes or no answers as to whether the photon went through the polarizer or not. There are no time stamps, distance measurements, coincidence intervals, or anything like that.
But my reply was in reply to your reply that "there's no experimental procedure called 'coincidence detection'. And of course there is an experimental procedure called coincidence detection.

And in reply to that you propose an idealized experiment that has nothing to do with what we're talking about.

The fact of the matter is that wrt Bell tests there are time stamps, distance measurements, and coincidence intervals. So, you're going to have to deal with them.
 
  • #283
ThomasT said:
But my reply was in reply to your reply that "there's no experimental procedure called 'coincidence detection'. And of course there is an experimental procedure called coincidence detection.

And in reply to that you propose an idealized experiment that has nothing to do with what we're talking about.

The fact of the matter is that wrt Bell tests there are time stamps, distance measurements, and coincidence intervals. So, you're going to have to deal with them.
But we're not talking about the practical ability of Bell tests today to definitively disprove local determinism. (There are of course several experimental loopholes to Bell, and people like zonde rely on them to cling onto a local deterministic view, accepting the fact that future experiments may disprove their views.) We're discussing the deeper issue of whether a local determinist can believe that all the experimental predictions of quantum mechanics are true, and that includes what QM has to say about idealized setups like the one I outlined.
 
  • #284
lugita15 said:
... in the Bell test setup I described above, the basic datum is whether the experimenter sees a photon go through the polarizer or not.
That's the basic datum for rate of individual detection. Wrt rate of coincidental detection, the basic datum is coincidental detection.

lugita15 said:
I think the word "correlation" is a much better term for what you call the "rate of coincidental detection".
Rate of coincidental detection has a specific technical meaning. It doesn't, by itself, refer to correlation. It refers to rate of coincidental detection.

lugita15 said:
It is just the correlation between individual polarization measurements of photons, and as such all its properties are determined by whatever determines the results of individual polarization measurements.
That's just incorrect. Rate of coincidental detection certainly does not refer to the correlation between individual polarization measurements of photons.

Bell test correlations refers to the correlation between the angular difference between the polarizers and the rate of coincidental detection.

lugita15 said:
And the nonlinear relationship between the correlation and the angle is also entirely determined by whatever determines whether a photon goes through a polarizer or not.
Also incorrect.

Here's what's known. The rate of individual detection doesn't vary with polarizer orientation. The rate of coincidental detection does vary with the angular difference between polarizer orientation. How can these two different experimental contexts be measuring the same underlying parameter?

lugita15 said:
... the argument is not based on the known data from practical experiments done so far ...
Well, no, your argument isn't. No offense, but from what you've written it doesn't seem that you're all that knowledgeable about Bell tests. Is that the case?

If so, just admit it and then DrC et al. can help you learn about them. They certainly helped me. I'm still more or less quite ignorant ... but a bit less so thanks to their help.
 
  • #285
lugita15 said:
But we're not talking about the practical ability of Bell tests today to definitively disprove local determinism.
Right, we're talking about the practical ability of Bell tests to definitively rule out Bell-type LR models of quantum entanglement, and how that can be explained in a way that still allows the assumptions of locality and determinism.

lugita15 said:
We're discussing the deeper issue of whether a local determinist can believe that all the experimental predictions of quantum mechanics are true, and that includes what QM has to say about idealized setups like the one I outlined.
No, it doesn't include idealized setups like the one you outlined because that idealized setup is a nonsequitur.

I've asked you a specific question, that you still haven't answered, about what you would infer from the experimental facts that, wrt Bell tests, the rate of individual detection does not vary as a function of polarizer orientation, while the rate of coincidental detection does vary as a function of the angular difference between polarizer orientations. So, what might you infer from this?
 
  • #286
ThomasT said:
Right, we're talking about the practical ability of Bell tests to definitively disprove Bell-type LR models of quantum entanglement, and how that can be explained in a way that still allows the assumptions of locality and determinism.
If that's your only point, then you and I have no quarrel. Not only am I willing to concede that the philosophical stance you call local determinism has not been ruled out by experiment, I am also willing to concede that what you call the "Bell-type LR models of quantum entanglement" have not been definitively disproven, due to various kinds of experimental loopholes, and there is reason to believe that we might not be able to do a loophole-free Bell test for the forseeable future.
No, it doesn't include idealized setups like the one you outlined because that idealized setup is a nonsequitur.
Why is it a nonsequitur? What I am trying to argue is that a local determinist must disagree with at least some of the experimental predictions of quantum mechanics. The particular predictions he disagrees with might be difficult or nearly impossible from a practical point of view to test (as in the case of my idealized setup), but the disagreement exists all the same. To answer the OP's question, this is why local determinism is not usually considered an acceptable interpretation of quantum mechanics, unlike the many worlds interpretation or nonlocal deterministic interpretations like Bohmian mechanics. In a (non-superdeterministic) local deterministic universe, there must exist an experiment which disproves quantum mechanics. This is, in my view, the heart of Bell's theorem. Do you disagree with this?
I've asked you a specific question, that you still haven't answered, about what you would infer from the experimental facts that, wrt Bell tests, the rate of individual detection does not vary as a function of polarizer orientation, while the rate of coincidental detection does vary as a function of the angular difference between polarizer orientations. So, what might you infer from this?
I responded to your question in a previous post of mine, but I probably didn't do justice to whatever your intent was:
"All a local determinist might infer from this is that the decision of whether to go through the polarizer or not is based on some local hidden variable, but we human beings don't know the value of this variable, so to us it seems like an unpredictable 50-50 chance whether it will go through." And I'll add that a local determinist would say that the reason a comparison of individual detection results yields a correlation which depends on the relative angle of the polarizers is that both photons contain the same basic hidden variable information, so when we turn our polarizers to different angles we're finding out different parts of this shared information.
 
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  • #287
lugita15 said:
What I am trying to argue is that a local determinist must disagree with at least some of the experimental predictions of quantum mechanics.
And at least one of the things that I'm trying to argue is that a local determinist doesn't have to disagee with any of the experimental predictions of QM.

lugita15 said:
In a (non-superdeterministic) local deterministic universe, there must exist an experiment which disproves quantum mechanics.
Why? QM is in certain respects a nonmechanistic acausal theory, and certainly wrt the quantum entanglements produced via Bell tests. Whether QM is at odds with local determinism is pretty much a matter of interpretation as far as I can tell.

lugita15 said:
This is, in my view, the heart of Bell's theorem. Do you disagree with this?
I think that Bell's theorem showed that an LR model of quantum entanglement encoding certain constraints is necessarily incompatible with standard QM. No more, and no less.

lugita15 said:
I responded to your question in a previous post of mine, but I probably didn't do justice to whatever your intent was ...
It's a straightforward question. Here it is again.

Wrt Bell tests, the rate of individual detection does not vary as a function of polarizer orientation, while the rate of coincidental detection does vary as a function of the angular difference between polarizer orientations.

What might you infer from this?
 
  • #288
lugita15 said:
Demystifer, if pilot waves don't go faster than light, then what explains the nonlocality of entanglement? Does the quantum potential propagate faster than light?
Bohmian mechanics (BM) is not nonlocal because something propagates faster than light. Instead, BM is nonlocal because velocity and acceleration of one particle at a given time depends on the positions of other particles (with which it is entangled) at the same time, no matter haw far these particles are.

lugita15 said:
Also, am I wrong in my impression that a particle's trajectory right now is determined in part by the apparatuses it knows, based on nonlocal interaction, that it's going to encounter later?
In the context of nonrelativistic BM, you are wrong. In the context of relativistic BM, the answer depends on what exactly do you mean by "later".
 
  • #289
Demystifier said:
Bohmian mechanics (BM) is not nonlocal because something propagates faster than light. Instead, BM is nonlocal because velocity and acceleration of one particle at a given time depends on the positions of other particles (with which it is entangled) at the same time, no matter how far these particles are.
So, this isn't nonlocality in the sense of ftl propagations, or nonlocality in the sense of spooky action at a distance. But just nonlocality in a formal sense? Thus, the same sort of nonlocality that might be inferred wrt to the standard QM formalism.? This has been your recent program, right?
 
  • #290
ThomasT said:
So, this isn't nonlocality in the sense of ftl propagations, or nonlocality in the sense of spooky action at a distance. But just nonlocality in a formal sense? Thus, the same sort of nonlocality that might be inferred wrt to the standard QM formalism.? This has been your recent program, right?
Well, not exactly. There is some sense in which BM is "more nonlocal" than orthodox QM. This perhaps is best viewed in the solipsistic hidden-variable interpretation, which interpolates between Bohmian and orthodox interpretation:
http://xxx.lanl.gov/abs/1112.2034
 
  • #291
Demystifier said:
Well, not exactly. There is some sense in which BM is "more nonlocal" than orthodox QM. This perhaps is best viewed in the solipsistic hidden-variable interpretation, which interpolates between Bohmian and orthodox interpretation:
http://xxx.lanl.gov/abs/1112.2034
Thanks for the reply. I have an intuitive grasp of your writings, but some of the technical details are currently beyond me.

But back to the OP. Although it appears as though the OP originator might have gotten temporarily banned. Anyway, what is your opinion of my recent replies to lugita15 and Joncon? Do they make sense to you? Do you think that one can believe that the LR program is ruled out, while still maintaining a belief in locality and determinism?
 
  • #292
ThomasT said:
But back to the OP. Although it appears as though the OP originator might have gotten temporarily banned. Anyway, what is your opinion of my recent replies to lugita15 and Joncon? Do they make sense to you? Do you think that one can believe that the LR program is ruled out, while still maintaining a belief in locality and determinism?
You would help me by pointing to a specific post which you would like me to comment.
 
  • #293
lugita15 said:
First of all, I thought the nonlocal stuff like entanglement was handled through the pilot wave, not the quantum potential.

The difficult and interesting question with respect to Bohm's concept of quantum potential (Q) is specifying which physical object(s) cause this potential and how and why. Bohm argued for an "informational field" interpretation of Q, but this view has been criticized by other "Bohmians" as being very obscure. For instance:
In the context of quantum physics, Bohm and Hiley postulated that ‘active information’ (which is carried by the wave field and represented by the quantum potential) determines a quantum particle’s path and its velocity by using the particle’s own energy. The Active Information Hypothesis opens up a whole host of questions and issues that are extremely problematic. Consider first the difficulties encountered with particle structure. Quantum particles would require complex internal structures with which the ‘active information’ is processed in order that the particle be directed through space. Bohm and Hiley readily acknowledge this: The fact that the particle is moving under its own energy, but being guided by the information in the quantum field suggests that an electron or other elementary particle has a complex and subtle inner structure (e.g., perhaps even comparable to that of a radio) (1993, 37).
Reflections on the deBroglie–Bohm Quantum Potential
http://www.tcm.phy.cam.ac.uk/~mdt26/local_papers/riggs_2008.pdf

For such reasons, some "minimalist" Bohmians (Durr, Goldstein, etc.) try to dispense with Q completely but other problems arise. For example, without Q, are particle trajectories by themselves sufficient to explain quantum phenomena ("problem of trajectories")? Other "Bohmians" attempt to employ the quantum potential concept but dispense with the information field suggesting that "primitive" forces existing on their own in addition to particles (e.g. Belousek):

Energy Content of Quantum Systems and the Alleged Collapse of the Wavefunction
http://arxiv.org/ftp/arxiv/papers/0910/0910.2834.pdf

Formalism, Ontology and Methodology in Bohmian Mechanics
https://springerlink3.metapress.com...oqulc13h34tv0ihv21kj2&sh=www.springerlink.com
 
  • #294
Demystifier said:
Bohmian mechanics (BM) is not nonlocal because something propagates faster than light. Instead, BM is nonlocal because velocity and acceleration of one particle at a given time depends on the positions of other particles (with which it is entangled) at the same time, no matter haw far these particles are.
What is the explanation given in Bohmian mechanics for the dependence of velocity and acceleration on the position of other particles?
 
  • #295
ThomasT said:
And at least one of the things that I'm trying to argue is that a local determinist doesn't have to disagee with any of the experimental predictions of QM.
OK, now the discussion is getting back on track. So consider again the idealized setup I described earlier, since we are trying to deal with the issue of whether local determinists must disagree with the predictions of QM in principle, not whether practical considerations make it difficult to test this disagreement. For this setup, which of the following do you disagree with:
1. The only experimental data collected is the results of individual detection events, so all the experimenter records is a yes or no answer as to whether a given photon went through the polarizer or not.
2. What you call the "rate of coincidental detection" in this case is just a correlation of individual detection results from the two experimenters.
3. Thus, explaining any properties, like θ-dependence, of the correlation between individual detection results involves no more and no less than explaining the results themselves.
4. It is an experimental prediction of QM that there is perfect correlation between detection results if the polarizers are set to the same angle.
5. You are a local determinist who agrees with all the predictions of QM, so you conclude that the particles are not communicating with each other faster-than-light, but rather that the two photons in a pair are using the same function P(θ) to decide whether to go through the polarizer oriented at an angle θ or not, where they go through the polarizer if P(θ)=1 and they don't go through if P(θ)=0.

I hope you agree with these five points.
It's a straightforward question. Here it is again.

Wrt Bell tests, the rate of individual detection does not vary as a function of polarizer orientation, while the rate of coincidental detection does vary as a function of the angular difference between polarizer orientations.

What might you infer from this?
I don't really have a very interesting answer to your question, but here goes. A local determinist, based on my 5 points above, would say that the two photons are consulting the same function P(θ), but humans don't know the details of this function, so it seems like it's a random 50-50 thing whether a photon goes through or not. However, if we make individual measurements on both photons, then we an find out the values of the function P at two different angles, so looking at the results of both measurements make things look a bit less random, and we can draw more inferences about the function P.
 
  • #296
lugita15 said:
What is the explanation given in Bohmian mechanics for the dependence of velocity and acceleration on the position of other particles?
BM does not provide such an explanation. Instead, it POSTULATES the existence of such dependence and shows that such a postulate can explain all measurable quantum phenomena.
 
  • #297
lugita15 said:
2. What you call the "rate of coincidental detection" in this case is just a correlation of individual detection results from the two experimenters.
I have to disagree with this the way it's stated. What's called "rate of coincidental detection" (not just by me, but in all of the literature on Bell tests afaik) isn't "just a correlation of individual detection results from the two experimenters", because that implies that what's being correlated in the joint (entanglement) context is the individual detection results. But that's not what's being correlated in that context. Rather, what's being correlated in the joint context is the rate of coincidental detection wrt the angular difference between the polarizers. The angular difference between polarizer settings is a different measurement parameter than the angular setting of one polarizer, and the rate of coincidental detection is a different detection statistic than the rate of individual detection.

lugita15 said:
3. Thus, explaining any properties, like θ-dependence, of the correlation between individual detection results involves no more and no less than explaining the results themselves.
First of all, a point wrt notation. θ, that is, capital Theta, usually refers to the angular difference between polarizer settings. θ isn't correlated with individual detection results. It's correlated with coincidental detection results. So, a phrase like " ... θ-dependence, of the correlation between individual detection results ...", is contrary to both the predictions and the experimental results in that there are only three combined settings (that is, angular differences, ie., θ) where individual detection results are correlated, afaik. They are 0, 45 and 90 degree angular differences between polarizers. Other than at those θ, individual detections aren't correlated.

lugita15 said:
5. You are a local determinist who agrees with all the predictions of QM, so you conclude that the particles are not communicating with each other faster-than-light, but rather that the two photons in a pair are using the same function P(θ) to decide whether to go through the polarizer oriented at an angle θ or not, where they go through the polarizer if P(θ)=1 and they don't go through if P(θ)=0.
This is just the wrong way to frame it, imho. I don't know what else to say. The function that determines whether or not a photon is transmitted by an individual polarizer should not be inferred to be the same function that determines coincidental detection. And this is, afaik, a reasonable inferential distinction to make wrt the extant experimental results. Why? Because coincidental detection varies as a function of θ, the global or joint measurement parameter, which suggests that it's a function of an underlying constant, and is not varying as a function of the, presumably, randomly varying underlying parameter that, presumably, determines individual detection.
 
  • #298
ThomasT said:
I have to disagree with this the way it's stated. What's called "rate of coincidental detection" (not just by me, but in all of the literature on Bell tests afaik) isn't "just a correlation of individual detection results from the two experimenters", because that implies that what's being correlated in the joint (entanglement) context is the individual detection results. But that's not what's being correlated in that context. Rather, what's being correlated in the joint context is the rate of coincidental detection wrt the angular difference between the polarizers. The angular difference between polarizer settings is a different measurement parameter than the angular setting of one polarizer, and the rate of coincidental detection is a different detection statistic than the rate of individual detection.
ThomasT, I feel like we're arguing semantics. Let me just ask you this: do you agree that in the idealized setup I described, there is no experimental procedure called "coincidence detection", only individual detection events?
First of all, a point wrt notation. θ, that is, capital Theta, usually refers to the angular difference between polarizer settings. θ isn't correlated with individual detection results. It's correlated with coincidental detection results. So, a phrase like " ... θ-dependence, of the correlation between individual detection results ...", is contrary to both the predictions and the experimental results in that there are only three combined settings (that is, angular differences, ie., θ) where individual detection results are correlated, afaik. They are 0, 45 and 90 degree angular differences between polarizers. Other than at those θ, individual detections aren't correlated.
OK, I think this is more semantics. In the terminology that I've seen more often used, if you have an angle at which an individual detection result for one photon completely determines the individual detection result for the other photon, we say that there is perfect correlation (or perfect anticorrelation as the case may be). If there is not perfect correlation, there can still be correlation, described by a correlation coefficient. If the photons are doing the exact same thing, as occurs when both polarizers are at the same angle, the correlation is 100%. If you turn the polarizers 45 degrees apart, you get a 50% correlation, meaning that given the information of what one photon has done you can predict what the other one will do with 50% certainty. Etc.

So we turn each polarizers at various angles, and we record data like "Photon 1 in pair 55 went through detector 1 turned at an angle of 40 degrees." (Remember, I'm talking about the idealized setup I described.) So at the end, for each individual angle setting the experimenter has written a long list of yes or no answers as to whether each photon went through or not. As he looks through the list, he sees no apparent pattern; regardless of what angle he turns the polarizer to, it seems like half of the photons go through, and the other half do not. Then the two experimenters have a meeting and compare their results, and for each angle pair (θ1,θ2) they calculate the correlation coefficient R(θ1,θ2). They find that R(θ1+C,θ2+C)=R(θ1,θ2) for all C, so they conclude it's not the absolute angles that are most important, only the difference θ=|θ1-θ2|, so we can just say R(θ).

Now do you agree or disagree that in my idealized setup, R(θ) is determined entirely by whatever determines the individual detection results? I really don't know how you can disagree with this, because the yes's and no's the experimenters recorded were entirely based on the individual results, and the calculation of R(θ) was done entirely be analyzing those yes's and no's.

Once we're agreed on this, we can discuss the more substantive issues, such as the point even zonde (who is a local determinist) agreed with, that once you accept that there is perfect correlation at identical polarizer settings, as a local determinist you MUST believe that the universe obeys Bell's inequality (even if you believe that this Bell inequality is too difficult to test for practical purposes).
 
  • #299
Demystifier said:
BM does not provide such an explanation. Instead, it POSTULATES the existence of such dependence and shows that such a postulate can explain all measurable quantum phenomena.
OK, in which of the two real differential equations does this dependence occur? (I'm probably asking a really obvious question.)
 
  • #300
lugita15 said:
OK, in which of the two real differential equations does this dependence occur? (I'm probably asking a really obvious question.)
You seem to need a brief course in Bohmian mechanics. See e.g.
http://xxx.lanl.gov/pdf/quant-ph/0611032.pdf
In particular, the answer to your question above is Eq. (1). But please, before asking further trivial questions, read the WHOLE paper first!

For a complementary bottom-up introduction to Bohmian mechanics you may also see
Sec. 2 "Essential and inessential aspects of Bohmian interpretation" of
http://xxx.lanl.gov/pdf/1112.2034.pdf
In this case, the answer to your question is given by the LAST equation (rather than first), Eq. (18).
 
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  • #301
lugita15 said:
ThomasT, I feel like we're arguing semantics.
Partly, yes. Clarifying semantics is an important part of any discussion.

lugita15 said:
Let me just ask you this: do you agree that in the idealized setup I described, there is no experimental procedure called "coincidence detection", only individual detection events?
Yes, I agree. And that's why your idealized setup is a non sequitur wrt the considerations posed in this thread.

If you're not going to look at the actual setups, or some idealization thereof, then what I'm saying won't make any sense to you. So, we can just agree to disagree on this.
 
  • #302
bohm2 said:
The difficult and interesting question with respect to Bohm's concept of quantum potential (Q) is specifying which physical object(s) cause this potential and how and why. Bohm argued for an "informational field" interpretation of Q, but this view has been criticized by other "Bohmians" as being very obscure. For instance:

Reflections on the deBroglie–Bohm Quantum Potential
http://www.tcm.phy.cam.ac.uk/~mdt26/local_papers/riggs_2008.pdf

For such reasons, some "minimalist" Bohmians (Durr, Goldstein, etc.) try to dispense with Q completely but other problems arise. For example, without Q, are particle trajectories by themselves sufficient to explain quantum phenomena ("problem of trajectories")? Other "Bohmians" attempt to employ the quantum potential concept but dispense with the information field suggesting that "primitive" forces existing on their own in addition to particles (e.g. Belousek):

Energy Content of Quantum Systems and the Alleged Collapse of the Wavefunction
http://arxiv.org/ftp/arxiv/papers/0910/0910.2834.pdf

Formalism, Ontology and Methodology in Bohmian Mechanics
https://springerlink3.metapress.com...oqulc13h34tv0ihv21kj2&sh=www.springerlink.com
Again you identify a difficult consideration and provide some helpful references wrt the consideration. Nice work. You present really hard questions/considerations.

One of the reasons that it's difficult for me to label BM as a realistic theory is because of the quantum potential, because I don't understand how it can be interpreted realistically.

Thanks for the references.
 
  • #303
Demystifier said:
BM does not provide such an explanation. Instead, it POSTULATES the existence of such dependence and shows that such a postulate can explain all measurable quantum phenomena.
Your contributions, wrt your view of BM, have been most helpful.
 
  • #304
ThomasT said:
Yes, I agree. And that's why your idealized setup is a non sequitur wrt the considerations posed in this thread.
But the point I've been trying to make is that a local determinist cannot believe in all the experimental predictions of quantum mechanics. That includes all possible experiments, including ones like my idealized setup which may be too difficult to carry out in practice. If all you want to argue is that practical Bell tests make it hard to rule out local determinism, you and I have no quarrel. But do you believe that in the case of my idealized setup, a local determinist would be able to believe that all the predictions of QM are correct?
 
  • #305
ThomasT said:
Your contributions, wrt your view of BM, have been most helpful.
Thanks! :smile:
 
  • #306
lugita15 said:
... do you believe that in the case of my idealized setup, a local determinist would be able to believe that all the predictions of QM are correct?
Your idealized setup doesn't address the OP. Your idealized setup only has to do with individual detecions. Bell showed that LR models of individual detections are compatible with QM.
 
  • #307
ThomasT said:
Your idealized setup doesn't address the OP. Your idealized setup only has to do with individual detecions. Bell showed that LR models of individual detections are compatible with QM.
So it's your assertion that in any experiment in which the only measurements done are individual detections, such as my idealized setup, local determinism is entirely compatible with the predictions of quantum mechanics? I think that is demonstrably false, and I think I demonstrated it in a previous post in this thread. Which of the following do you disagree with, in the case of my idealized setup?
lugita15 said:
1. Pretend you are a local determinist who believes that all the experimental predictions of quantum mechanics is correct.
2. One of these experimental predictions is that entangled photons are perfectly correlated when sent through polarizers oriented at the same angle.
3. From this you conclude that both photons are consulting the same function P(θ). If P(θ)=1, then the photon goes through the polarizer, and if it equals zero the photon does not go through.
4. Another experimental prediction of quantum mechanics is that if the polarizers are set at different angles, the mismatch (i.e. the lack of correlation) between the two photons is a function R(θ) of the relative angle between the polarizers.
5. From this you conclude that the probability that P(-30)≠P(0) is R(30), the probability that P(0)≠P(30) is R(30), and the probability that P(-30)≠P(30) is R(60).
6. It is a mathematical fact that if you have two events A and B, then the probability that at least one of these events occurs (in other words the probability that A or B occurs) is less than or equal to the probability that A occurs plus the probability that B occurs.
7. From this you conclude that the probability that P(-30)≠P(30) is less than or equal to the probability that that P(-30)≠P(0) plus the probability that P(0)≠P(30), or in other words R(60)≤R(30)+R(30)=2R(30).

And just for everyone else's reference, here is my idealized setup again:
lugita15 said:
Consider an idealized experiment where one photon pair is sent out every hour by a source which is exactly at the midpoint between two polarizers, which catch every single photon with perfect accuracy. In that case all each experimenter has as far as data goes is a list of yes or no answers as to whether the photon went through the polarizer or not. There are no time stamps, distance measurements, coincidence intervals, or anything like that.
 
  • #308
ThomasT said:
One of the reasons that it's difficult for me to label BM as a realistic theory is because of the quantum potential, because I don't understand how it can be interpreted realistically.
Bohm and Hiley felt that the quantum potential can be "seen" but only indirectly through its manifestations in the motion of particles. If one takes a "realistic" stance (as they do), how else can one explain interference effects, superconductivity, etc? They argue, that it's unlike fields or forces though because it can only affect a one-particle or a many-particle quantum system. Because of it's representation in configuration space, they regarded it more akin to a "field of information" versus a field of force. But it isn't 'information for us'; rather, it is some form of objective information that is independent of the observer:
Firstly, it must be said that in the many-particle system, the Schrodinger wave is no longer capable of being represented in the ordinary three-dimensional space. Rather, it has now to be thought of in a multidimensional space, called configuration space, in which there are three dimensions for each particle. A single point in this multi-dimensional space corresponds to a certain configuration of the entire system of particles-hence the name, configuration space. It is not possible directly to imagine such a configuration space. However, if we recall that the essential significance of the wave in the one-particle system was that it determines a kind of information, then the interpretation can readily be extended to the many-particle system. For it is well known that information, being a highly abstract sort of thing, can be organized and understood in any number of dimensions. This is a natural development of the idea that the Schrodinger wave is not to be regarded as a field of force, but rather as a field of information.

A more careful analysis of the mathematics for this case shows that the whole set of particles is now subject to a generalized sort of quantum potential. This depends on the Schrodinger field of the entire many-body system. So we have an extension of this interpretation to the many-body system, in which each particle is self-active. However, the form of its action may now depend on a common pool of information belonging to the whole system.
Meaning and Information
http://www.implicity.org/Downloads/Bohm_meaning+information.pdf

Hiley describes this view further:
How do we think about the quantum potential? It describes a field of energy so can it be regarded as producing a force on the particle? There are some problems with this view. Firstly, as we have already remarked above, the quantum potential has no external source so that there is nothing for the particle to 'push against'. The energy is internal so clearly there is something more subtle involved. Here it is more like the role the gravitational field plays in general relativity where the gravitational energy curves space-time itself...

But how are we to understand these puzzling features physically? Because there is nothing to push against we should not regard the quantum potential as giving rise to an efficient cause, ('pushing and pulling') but it should be regarded more in the spirit of providing an example of Aristotle’s formative cause. That is the quantum potential gives new form to the evolution of the trajectories, in a way that is very reminiscent of the morphogenetic fields proposed by Waddington (1956) and Thom (1975) in biology. The form is provided from within but it is, of course, shaped by the environment. Thus the quantum potential reflects the experimental conditions. Close one slit and the quantum potential changes and the subsequent evolution of the particle is different. There seems to be a kind of 'self organisation' involved. Now self-organisation requires the notion of information to be active. In the case of a biological system, this information is clearly provided by the environment, soil conditions, lack of moisture etc. In a quantum system I want to suggest that the information is provided by the experimental conditions, its environment. But this information is not passive. It is active and causes the internal energy to be redistributed between the kinetic (pB) and potential (Q) parts. Thus the quantum process is literally 'formed from within'.
From the Heisenberg Picture to Bohm: a New Perspective on Active Information and its relation to Shannon Information.
http://www.bbk.ac.uk/tpru/BasilHiley/Vexjo2001W.pdf
 
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  • #309
It should be noted that, as I was discussing earlier with Demystifier, Bohmians are only realist with respect to the position observable; the Kochen Specker theorem leads them to reject the reality of other observables.
 
  • #310
lugita15 said:
It should be noted that, as I was discussing earlier with Demystifier, Bohmians are only realist with respect to the position observable; the Kochen Specker theorem leads them to reject the reality of other observables.
Realism and contextualism are not incompatible:
What is challenging about quantum physics is not that there are no objects, but that the properties of quantum objects are remarkably different from the properties that classical physics considers. For instance, in any case of quantum entanglement, conceived as a relation among quantum objects, there are no intrinsic properties of the objects concerned on which the relation of entanglement obtains. The fact, however, that quantum objects cannot be individuated, in the classical sense, does not imply their inexistence. In other words, the non-individuality of quantum objects is not and cannot be tantamount to pronouncing their non-existence.
Realism and Objectivism in Quantum Mechanics
http://philsci-archive.pitt.edu/9042/1/Realism_and_Objectivism_in_Quantum_Mechanics.pdf
 
  • #311
bohm2 said:
Realism and contextualism are not incompatible
But Demystifier said the Kochen-Specker theorem places some distinction between position and (say) angular momentum, because position operators commute with one another whereas angular momentum operators do not commute with one another. What conclusion do Bohmians draw from this?
 
  • #312
I don't think anybody can explain why position (Q) assume pre-existence in BM while everything else is contextual: spin, energy, and other non-position “observables”. It does make it easier though to describe the macroscopic physical objects that we are normally acquainted with: chairs, people, planets, etc. without necesitating collapse. From a realist perspective, a wave function existing in configuration space, by itself, seems like not the right kind of stuff to describe everyday physical objects we are acquainted with in 3-D space, I think. Either way, Bohmian is fine with KS theorem. From the link provided by Demystifier:
Thus, in general, measurements do not measure anything in the closer meaning of the term. The only exception being of course position measurements, and, in some sense momentum-measurements. The latter do indeed measure the asymptotic (Bohmian) velocities. Hence, the only properties of a Bohmian particle are its position and its velocity. Just as ψ is no classical field, the Bohmian particles are not classical particles, i.e. they are no bearers of properties other than position. Therefore a physical object like e.g. an electron should not be confused with the Bohmian particle at position Qi. It is represented by the pair (ψ,Qi). Agreed, this is a radical departure from the classical particle concept. However, within the de Broglie-Bohm theory this move is not only natural (recall that e.g. momentum and energy are concepts which arise in 2nd order Newtonian mechanics while the guidance equation of the de Broglie-Bohm theory is 1st order) but allows for an elegant circumvention of the Kochen-Specker no-go theorem, directed against hidden variable theories (see e.g. Mermin (1990). This theorem demonstrates, that a consistent assignment of possessed values to all observables for a quantum mechanical state is not possible. However, if you allow for contextuality as the de Broglie-Bohm theory does you do not expect such an assignment to exist at all.
 
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  • #313
@ lugita15,

In your post #266 in this thread you wrote:
lugita15 said:
But a "coincidental detection" is ... nothing more than performing "individual detections" on each of the two particles. So definitionally, what determines the result of a coincidental detection is just what determines the results of individual detections.

In your post #271 in this thread you wrote:
lugita15 said:
Since there is no such thing as coincidence detection, and correlation is nothing but correlation of individual detections, an analysis of entanglement cannot consist, even in principle, of anything other than asking what determines the results of individual detection.

There's an experimental procedure for combining the individual data streams, and it produces a datum (called coincidental detection) that's different from individual results and that's correlated to a different measurement parameter and a different underlying parameter than individual results are.

The correlation coefficient calculated wrt any Bell test refers to the correlation between θ (the angular difference between polarizers) and the rate of coincidental detection. This is what entanglement refers to. It does not refer to a correlation between individual detection attributes at A and B.

Your idealized setup confuses things because it doesn't describe Bell tests. From the results of Bell tests, it can be inferred that the underlying parameter that determines coincidental detection can't be varying from pair to pair. So, this underlying parameter (that determines coincidental detection) must be different than the underlying parameter that's inferred to be varying from pair to pair and determining individual detection.
 
  • #314
ThomasT, regardless of whether you think my idealized setup is a good representation of Bell tests, just answer me this: for this setup, in which there are only individual detection results, do you or do you not believe that it is possible for a local deterministic theory to be compatible with all the predictions of QM? If your answer is yes, my followup would be: which of the seven points quoted in post #307 do you disagree with and why? (And when reading that post, please keep in mind that when I say the word correlation I mean correlation between individual detections, not correlation coefficient of the rate of coincidental detection and theta.)
 
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  • #315
Ahha, so this thread was already foretold?
As well as any answers naturally.

So all discussion must then become meaningless.

"All your resistance will be futile" as the Borg says :)

Free will?
 
<h2>1. Why is superdeterminism not the universally accepted explanation of nonlocality?</h2><p>Superdeterminism is not the universally accepted explanation of nonlocality because it goes against the widely accepted principle of free will. Superdeterminism suggests that all events, including human decisions, are predetermined and therefore there is no true randomness or free will in the universe. This goes against our understanding of human agency and the ability to make choices.</p><h2>2. What evidence supports the rejection of superdeterminism as an explanation for nonlocality?</h2><p>One of the main pieces of evidence against superdeterminism is the violation of Bell's inequality, which suggests that there is a limit to how much information can be hidden from an observer. If superdeterminism were true, this limit would not exist and the observed correlations in nonlocal systems would not be possible.</p><h2>3. Are there alternative explanations for nonlocality other than superdeterminism?</h2><p>Yes, there are alternative explanations for nonlocality that do not rely on the concept of superdeterminism. Some theories suggest that there are hidden variables or hidden information that can explain the observed correlations in nonlocal systems without resorting to predetermined events.</p><h2>4. What implications would accepting superdeterminism have on our understanding of the universe?</h2><p>If superdeterminism were to be accepted as the explanation for nonlocality, it would have significant implications on our understanding of the universe. It would mean that all events, including our thoughts and actions, are predetermined and there is no true randomness or free will. This would challenge our understanding of causality and the role of human agency in shaping our reality.</p><h2>5. Is there ongoing research and debate surrounding the concept of superdeterminism and its relation to nonlocality?</h2><p>Yes, there is ongoing research and debate surrounding the concept of superdeterminism and its relation to nonlocality. Scientists continue to explore alternative explanations for nonlocality and gather evidence to support or refute the concept of superdeterminism. This is an active area of study in the field of quantum mechanics and there is no consensus yet on the ultimate explanation for nonlocality.</p>

1. Why is superdeterminism not the universally accepted explanation of nonlocality?

Superdeterminism is not the universally accepted explanation of nonlocality because it goes against the widely accepted principle of free will. Superdeterminism suggests that all events, including human decisions, are predetermined and therefore there is no true randomness or free will in the universe. This goes against our understanding of human agency and the ability to make choices.

2. What evidence supports the rejection of superdeterminism as an explanation for nonlocality?

One of the main pieces of evidence against superdeterminism is the violation of Bell's inequality, which suggests that there is a limit to how much information can be hidden from an observer. If superdeterminism were true, this limit would not exist and the observed correlations in nonlocal systems would not be possible.

3. Are there alternative explanations for nonlocality other than superdeterminism?

Yes, there are alternative explanations for nonlocality that do not rely on the concept of superdeterminism. Some theories suggest that there are hidden variables or hidden information that can explain the observed correlations in nonlocal systems without resorting to predetermined events.

4. What implications would accepting superdeterminism have on our understanding of the universe?

If superdeterminism were to be accepted as the explanation for nonlocality, it would have significant implications on our understanding of the universe. It would mean that all events, including our thoughts and actions, are predetermined and there is no true randomness or free will. This would challenge our understanding of causality and the role of human agency in shaping our reality.

5. Is there ongoing research and debate surrounding the concept of superdeterminism and its relation to nonlocality?

Yes, there is ongoing research and debate surrounding the concept of superdeterminism and its relation to nonlocality. Scientists continue to explore alternative explanations for nonlocality and gather evidence to support or refute the concept of superdeterminism. This is an active area of study in the field of quantum mechanics and there is no consensus yet on the ultimate explanation for nonlocality.

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