Local realism ruled out? (was: Photon entanglement and )

[Demystifier]

This is strange. My understanding was nonlocality was not proven, e.g., in SQM, using just UE, and you have not stated the opposite before (your article is not at all categorical on this point, moreover, you are saying there that you don't have (yet) a proof of your conjecture). Maybe you misread my question? Or maybe you could give me a reference to such proof (using just UE) for SQM or dBB?

Or maybe you have not read my paper? Nonlocality (where the word "nonlocality" is defined in the algorithmic sense explained in the paper) is proven in any definite formulation/interpretation of QM. When I say that nonlocality is not proven, I mean that it is not proven that there does not exist another (yet unknown) formulation/interpretation which can avoid algorithmic nonlocality. All that is explained in the paper, for those who want to read it.

Furthermore, independent on my conjecture on "algorithmic" nonlocality that I haven't proven, Bell has already proven "realistic" nonlocality. My unproven "algorithmic" nonlocality is a generalization of the Bell's proven "realistic" nonlocality.

 

[Frame Dragger]

@Akhmeteli: Did you even skim the paper? They address EXACTLY your concerns, and lay them to rest in all but a rhetorical sense. They begin in the last portion of page 3 and conclude with:

However, we emphasize that this is true
only if these hidden-variable formulations really are observationally
equivalent to the local formulation. In this
regard, we note that some variants of the Bohmian interpretation
may, under certain circumstances, observationally
differ from other formulations. The examples of
such circumstances are the early universe [26] and certain
relativistic conditions [27].

If you didn't read it, or can't grasp it then just say that. There's nothing wrong with that on an educational website, with a science advisor (Demystifier) who's bending over backwards trying to help you.
And yes... now I'm having a field day.

 

[akhmeteli]

Or maybe you have not read my paper? Nonlocality (where the word "nonlocality" is defined in the algorithmic sense explained in the paper) is proven in any definite formulation/interpretation of QM. When I say that nonlocality is not proven, I mean that it is not proven that there does not exist another (yet unknown) formulation/interpretation which can avoid algorithmic nonlocality. All that is explained in the paper, for those who want to read it.

Furthermore, independent on my conjecture on "algorithmic" nonlocality that I haven't proven, Bell has already proven "realistic" nonlocality. My unproven "algorithmic" nonlocality is a generalization of the Bell's proven "realistic" nonlocality.

Demystifier,

To be frank, I am completely confused...

I asked you about nonlocality of non-standard interpretations of QM, such as dBB. You told me: yeah, sure, their nonlocality can be proven using UE only. Now you're telling me you had in mind YOUR VERY OWN definition of locality... And what definition it is!

My take on your article is as follows. Actually, you implicitly introduce at least two definitions.

One of them is as follows: "A theory is local if and only if there exists an FI [formulation/interpretation] of the theory in which all irreducible elements are local." Actually, I could live with such a definition. But you do not have a proof of nonlocality under such definition for QM, it's just your conjecture.

The other (implicit) definition is actually for FI, not theories, and it requires that all its irreducible elements are local. Under this definition you do prove that all known FI of quantum theory are not local (say, because they contain such elements as psi(x,y)). However, under this definition even the Hamilton-Jacobi formulation of classical mechanics is not local, as far as I can see. Some definition indeed...

As for Bell's proof, it requires something beyond UE, such as PP.

 

[Demystifier]

I don't understand what exactly you are confused about. That there are different inequivalent definitions of nonlocality? It's often the case in discussions on various stuff that the source of disagreement lies in the unrecognized fact that people have in mind different definitions of the same word. Thus, saying explicitly that there are different definitions is often the first and sometimes crucial step towards achieving agreement.

So, when you say that you believe in locality, what exactly your definition of that word is?

 

[DrChinese]

As for Bell's proof, it requires something beyond UE, such as PP.

As we keep telling you, it does NOT require such. You do NOT need to accept QM to rule out local realism. You only need to accept the cos^2(theta) experimental prediction. Which of course is incompatible with LR.

Please quit repeating what has already been pointed out as false. Whether you accept the experimental results of Bell tests or not, there is no sense in which Bell depends on one's acceptance of QM itself. And as such, your (also ridiculous) assessment of QM as "wrong" is completely meaningless.

P.S. All theories are "wrong" in some sense. A model is not reality. Please see my tag line.

 

[Frame Dragger]

As we keep telling you, it does NOT require such. You do NOT need to accept QM to rule out local realism. You only need to accept the cos^2(theta) experimental prediction. Which of course is incompatible with LR.

Please quit repeating what has already been pointed out as false. Whether you accept the experimental results of Bell tests or not, there is no sense in which Bell depends on one's acceptance of QM itself. And as such, your (also ridiculous) assessment of QM as "wrong" is completely meaningless.

P.S. All theories are "wrong" in some sense. A model is not reality. Please see my tag line.

Why do I think that akhmeteli would not be familiar with GS? Someone that enamoured with words in a physical discipline is obviously not concerned about GIGO in relation to their brain.

To follow that semantic thread... would it be better to say that all theories are incomplete representations of reality, and potentially misleading if taken as more? To me the terms "right and wrong" are polar opposites, not open to degrees. I'm open to correction on this point.

To Ahkmeteli: If you do reject the results of the Bell tests, I would be very interested to hear your defense of that unenviable position.

 

[akhmeteli]

I don't understand what exactly you are confused about. That there are different inequivalent definitions of nonlocality? It's often the case in discussions on various stuff that the source of disagreement lies in the unrecognized fact that people have in mind different definitions of the same word. Thus, saying explicitly that there are different definitions is often the first and sometimes crucial step towards achieving agreement.

So, when you say that you believe in locality, what exactly your definition of that word is?

This thread is about the assumptions of the Bell theorem and experimental tests of the theorem, at least that’s how the thread started. Of course, the topic can change with time, but, on the one hand, I asked you the following questions about non-standard variants of QM:

"Do they predict any experimental results incompatible with any LR models, as is the case for standard quantum mechanics? If you say they do (for example, I am not even sure if this is the case for dBB), then my second question is: Does the relevant proof (an analog of the proof of the Bell theorem in SQM) uses the projection postulate or something like that?",

and you yourself mentioned that non-standard versions of QM "predict violation of Bell inequalities for the (ideal) case of detectors with perfect efficiency", so I had all reasons to assume that you also had in mind the nonlocality as it is defined in the Bell theorem. Then you told me that nonlocality can be proven in, say, dBB using UE only. If you had in mind a new definition of nonlocality, would not it have been appropriate to warn me and other readers of your posts, the more so as you did not use some generally recognized definition, but your own one? That was one source of my confusion.

The other source of confusion was that the specific definition of nonlocality you used was downright unreasonable, as even the Hamilton-Jacobi formulation of classical mechanics satisfies it. You reproached me for not reading your article carefully enough, but I just could not imagine you took that definition seriously (let alone the fact that I was under no obligations to learn the article by heart).

As for your question on the definition of locality that I believe in, it would be more precise to talk about the definition of nonlocality that I don't believe in - existence of violation of the Bell inequalities.

So my question again is: can violations of the Bell inequalities be proven in dBB using UE only, and if yes, I wonder if you could possibly give a reference.

 

[akhmeteli]

As for Bell's proof, it requires something beyond UE, such as PP.

As we keep telling you, it does NOT require such. You do NOT need to accept QM to rule out local realism. You only need to accept the cos^2(theta) experimental prediction. Which of course is incompatible with LR.

You seem to be reproaching me for not listening to what you're saying, but it looks like you're not listening. Indeed, you mentioned the Malus law before in this thread, and I replied that "as far as I understand, in the context of the Bell experiment, the Malus law and PP give the same result, therefore, strictly speaking, the Malus law is in contradiction with UE. Indeed, UE cannot turn a superposition into a mixture of states." I have not seen any critique of this statement from you (and I repeated that statement replying to SpectraCat). Therefore I stand by what I said: "As for Bell's proof, it requires something beyond UE, such as PP."

You see, the Malus law may be a great approximation, but it's just an approximation. The Coulomb law is a great approximation, but it breaks exactly where it predicts nonlocality.

Please quit repeating what has already been pointed out as false.

If you pointed out that something is false, that does not necessarily mean it is indeed false. I believe I answered your critique, so I guess we just disagree on what is false and what is correct.

Whether you accept the experimental results of Bell tests or not, there is no sense in which Bell depends on one's acceptance of QM itself.

I emphasized that the proof of the Bell theorem uses as assumptions the mutually contradictory elements of standard quantum mechanics - UE and PP, so the problem of QM does indeed become a problem for the Bell theorem.

And as such, your (also ridiculous) assessment of QM as "wrong" is completely meaningless.

OK, so you think this assessment is ridiculous. The problem is I substantiated this assessment: UE and PP are mutually contradictory, because the former cannot destroy a superposition or introduce irreversibility, and PP does that. And this makes the assessment meaningful.

P.S. All theories are "wrong" in some sense. A model is not reality. Please see my tag line.

That does not mean theories cannot be improved.

 

[Demystifier]

As for your question on the definition of locality that I believe in, it would be more precise to talk about the definition of nonlocality that I don't believe in - existence of violation of the Bell inequalities.

Good! Let's then talk only about this definition of locality and ignore other definitions.

So my question again is: can violations of the Bell inequalities be proven in dBB using UE only, and if yes, I wonder if you could possibly give a reference.

Yes it can.

The reference is the classic 1952 Bohm paper (part II, section entitled "Theory of quantum measurements" or something like that). There it is shown that ALL probabilistic predictions are the same as those of standard QM with a collapse, even though there is no collapse in dBB. In fact, the role of this quantum theory of measurements is to explain why we can, for all practical purposes, use collapse as an effective description of measurements, despite the fact that, in dBB, the collapse does not really exist.

This is the classic reference, but even a better explanation of the same stuff can be found in many reviews of dBB. My favored one is the Holland book, chapter "Quantum theory of measurements".

 

[Frame Dragger]

Good! Let's then talk only about this definition of locality and ignore other definitions.


Yes it can.

The reference is the classic 1952 Bohm paper (part II, section entitled "Theory of quantum measurements" or something like that). There it is shown that ALL probabilistic predictions are the same as those of standard QM with a collapse, even though there is no collapse in dBB. In fact, the role of this quantum theory of measurements is to explain why we can, for all practical purposes, use collapse as an effective description of measurements, despite the fact that, in dBB, the collapse does not really exist.

This is the classic reference, but even a better explanation of the same stuff can be found in many reviews of dBB. My favored one is the Holland book, chapter "Quantum theory of measurements".

Demystifier is a kind individual. It goes without SAYING that dBB satisfies the predictions of QM; this is why it's around when all of the LHV theories died; because dBB is NON-Local HV Theory. It's not a matter of reference, but a matter of the very definition of why dBB isn't dead, but rather no longer a shooting offense to teach.

Akhmeteli: You do realize you now have pages of your writing that boils down to, "I'M the sane one, it is all of THEM who are are mad *insane laughter"? No need to respond, I know you think you have your pride.

Edit @ Akhmeteli: I do believe you've annoyed DrChinese... which is a first I've seen. Why the insistance on rhetoric and not just a stand for what you believe? Do you even KNOW what it is you believe? I get the sense that maybe you're just blowing smoke here, and don't believe anything in particular, which you should also come out and say clearly.

 

[DrChinese]

You seem to be reproaching me for not listening to what you're saying, but it looks like you're not listening. Indeed, you mentioned the Malus law before in this thread, and I replied that "as far as I understand, in the context of the Bell experiment, the Malus law and PP give the same result, therefore, strictly speaking, the Malus law is in contradiction with UE. Indeed, UE cannot turn a superposition into a mixture of states." I have not seen any critique of this statement from you (and I repeated that statement replying to SpectraCat). Therefore I stand by what I said: "As for Bell's proof, it requires something beyond UE, such as PP."

2. That does not mean theories cannot be improved.

1. Arrgh! Bell does NOT require you to believe ANYTHING other than the idea that QM predicts (rightly or wrongly) that there is a cos^2(theta) relationship. It does NOT matter how QM gets that prediction or whether it is observed in experiments (which it is). There is NO other prediction from QM other than the cos^2(theta) relationship (despite your absurd claims that QM is "wrong" whatever that means in this context). So WHAT ARE YOU TALKING ABOUT? Bell is not dependent on the correctness of QM in any way. That was Bell's point actually, that QM and LR are mutually incompatible.

There is no controversery to what I am saying. What you are saying not only makes NO SENSE, but is not accepted by anyone I have ever talked to or read. Forum rules require that you identify personal theories which are not generally accepted as such, and to back up your statements with references when challenged - and you are being challenged. Or better, acknowledge that it is a personal theory with no support other than your belief and stick to discussion points that are appropriate. In this forum, continuing to push points that have been discredited - as yours have - is poor etiquette. We have already covered this ground before in this thread!

2. I couldn't agree more - you can improve on theories. But theories should NOT be judged according to whether they are "right" or "wrong", but rather according to their utility. For example, Newtonian gravity is actually a better theory than General Relativity for many applications (it has fewer variables). You will see that the next time you calculate the velocity an apple drops from a tree.

 

[akhmeteli]

Good! Let's then talk only about this definition of locality and ignore other definitions.

Very well, thank you.

So my question again is: can violations of the Bell inequalities be proven in dBB using UE only, and if yes, I wonder if you could possibly give a reference.

Yes it can.

The reference is the classic 1952 Bohm paper (part II, section entitled "Theory of quantum measurements" or something like that). There it is shown that ALL probabilistic predictions are the same as those of standard QM with a collapse, even though there is no collapse in dBB. In fact, the role of this quantum theory of measurements is to explain why we can, for all practical purposes, use collapse as an effective description of measurements, despite the fact that, in dBB, the collapse does not really exist.

This is the classic reference, but even a better explanation of the same stuff can be found in many reviews of dBB. My favored one is the Holland book, chapter "Quantum theory of measurements".

I am afraid we've run into one of the problems that I anticipated in my post 273 in this thread. If your following statement were precise: "ALL probabilistic predictions are the same as those of standard QM with a collapse", then dBB would have inherited the internal contradictions of standard quantum mechanics and would have been, strictly speaking, wrong. However, this statement is not a precise result in dBB. How do I know that? Just because you told me in another thread that the projection postulate is an approximation in dBB (https://www.physicsforums.com/showpost.php?p=2167542&postcount=19 ).

Therefore, I suspect that violations of the Bell inequalities cannot be proven in dBB using UE only, you need some additional assumptions (or approximations, if you like).

 

[ThomasT]

SpectraCat, to revisit your last comments:

From your previous statements, you appear to agree that for source P, the sets A and B will show a statistical dependence, and for source Q they will not.

The data sets A and B don't, by themselves, show anything. They're just random sequences of detection attributes.

Therefore, simply from her observations, and without communicating with Bob, Alice can determine which source is being used, based on her measured coincidence statistics.

The matched data wrt Q won't show entanglement correlations no matter how you match it, while appropriately matched data wrt P will. P(A,B) can deviate from P(A)P(B) if there's some common cause connection between paired photons produced by Q. But only wrt setup P will rate of coincidental detection be cos²Θ .

My point here is that it doesn't matter what the experimenters are *trying* to do with the source, because the detection scheme allows for the possibility that their design would fail, as I argued above.

How the counter-propagating optical disturbances are produced, how they're filtered, how they're detected and how the resulting data is processed all matters.

Am I missing your point?

 

[ThomasT]

I really don't get what you are saying.

Just that:

1. The factorability of the LHV form for Bell test joint probabilities is what makes this form incompatible with QM and entanglement experiments.
2. This factorability represents statistical dependence between A and B.
3. Statistical dependence between A and B doesn't require flt propagation between them.
4. Therefore, violation of Bell inequality doesn"t imply nonlocality.

The fact is, local realists deny that entanglement is a state.

A state is just a mathematical representation of an experimental setup.

If you mean that they deny that the QM representation is the correct one, then, while this might be a fitting characterization in general, such a denial isn't required in order to be a local realist.

They say it is all coincidence, and there is a common cause.

Of course. And because there's a common cause the rate of coincidental detection wrt angular difference is predictable.

So it is true that Bell tests - which demonstrate entanglement as a state - will always violate LR.

I don't think this is why LHV formulations have so far been incompatible with Bell tests.

Bell tests show that entangled photons operate in a different spacetime view than the local realist would envision.

Not necessarily, In fact the QM prediction, P(A,B) = cos2Θ , is what a local realist might expect for experiments in which counter-propagating optical disturbances emitted by the same atom are analyzed by crossed polarizers.

 

[SpectraCat]

SpectraCat, to revisit your last comments:
The data sets A and B don't, by themselves, show anything. They're just random sequences of detection attributes.

The matched data wrt Q won't show entanglement correlations no matter how you match it, while appropriately matched data wrt P will. P(A,B) can deviate from P(A)P(B) if there's some common cause connection between paired photons produced by Q. But only wrt setup P will rate of coincidental detection be cos²Θ .

How the counter-propagating optical disturbances are produced, how they're filtered, how they're detected and how the resulting data is processed all matters.

Am I missing your point?

Yes, because without knowing about the source, and by applying a consistent treatment to the data, based only on a consistent definition of what construes a coincident detection event, Alice can use the data sets A and B to determine empirically if Bob is using the entangled source P, or the unentangled source Q. That is why the results of Bell tests are valid, because the measurement and data analysis *can distinguish* between entangled and unentangled pairs based on the coincidence counting. Note that the results will not necessarily be random if Bob uses an unentangled source, they will just fail to violate a Bell inequality, because the two measurement sets will not show a statistical dependence.

Finally, your assertion that the data sets are only correlated at the two relative measurement angles of 0 and pi/2 seems false to me. The fact is that more coincidences are observed when the angle is closer to pi/2 and fewer are observed when it is closer to 0. So yes, the correlation of any particular pair of measurements is fundamentally unknowable, but the probability of observing a coincindence will be given by Malus's law based on the *difference between the measurement angles at A and B* when an entangled source is used. If an unentangled source is used, then the results at detector B will be independent of the measurement angle choice at A, and vice versa. So the correlation between sets A and B for the entangled case is not "perfectly random" except for the two cases of theta=0 and theta=pi/2 as you are claiming, and certainly differs in a measurable way from the correlation in the unentangled case.

I know that the above is somewhat repetitive, but I don't know how else to explain it. I hope this makes it clearer

 

[DrChinese]

If you mean that they deny that the QM representation is the correct one, then, while this might be a fitting characterization in general, such a denial isn't required in order to be a local realist.

Of course. And because there's a common cause the rate of coincidental detection wrt angular difference is predictable.

...

Not necessarily, In fact the QM prediction, P(A,B) = cos2Θ , is what a local realist might expect for experiments in which counter-propagating optical disturbances emitted by the same atom are analyzed by crossed polarizers.

Now, if you are a local realist, you say there is a common cause. And yet you cannot construct a dataset in which the cos^2 relationship holds. So what is all the deal about separability? Just show me the dataset for 0, 120 and 240 degrees and we will have something meaningful to discuss. I don't follow all your comments about Bell tests being biased from inception when you cannot do something this simple (because it is impossible).

And entanglement is not so easy to explain these days with some of the newer experiments. EPR is completely lost on these. Please explain, for example, how photons become entangled when they are not in each other's light cones - and never have been - and originate from different lasers. Meanwhile, QM can.

I just do not understand technical objections against Bell when it seems as if the entire point of Bell is lost. Bell is a road map to understanding that local realism is incompatible with the predictions of QM. No matter what the local realistic theory looks like, I can use the Bell thinking to disprove it when compared to experiment. Now, it matters not at all if my map has a small misprint or other minor issue as long as I can get where I need to go.

 

[ThomasT]

Yes, because without knowing about the source, and by applying a consistent treatment to the data, based only on a consistent definition of what construes a coincident detection event, Alice can use the data sets A and B to determine empirically if Bob is using the entangled source P, or the unentangled source Q. That is why the results of Bell tests are valid, because the measurement and data analysis *can distinguish* between entangled and unentangled pairs based on the coincidence counting.

Ok ...

Note that the results will not necessarily be random if Bob uses an unentangled source, ...

Right, but P(A,B) won't be cos2Θ.

... they will just fail to violate a Bell inequality, because the two measurement sets will not show a statistical dependence.

There will still be a statistical dependence between A and B if the (unentangled) counter-propagating disturbances have a common cause and the data are matched wrt this criterion. For example, where setup Q has (emitter - polarizer 1 - polarizer 2 - detector) on both sides, and polarizers 1 are aligned and the setting is changing rapidly and randomly so as to produce identical random polarization for each counter-propagating pair.

Finally, your assertion that the data sets are only correlated at the two relative measurement angles of 0 and pi/2 seems false to me.

These are the only two settings wrt which you can predict B given A, and vice versa.

The fact is that more coincidences are observed when the angle is closer to pi/2 and fewer are observed when it is closer to 0.

In the ideal, when Θ = 0 then P(A,B) = 1 (detection attributes for A and B are always identical), and when Θ = 90 degrees then P(A,B) = 0 (detection attributes for A and B are always opposite).

If an unentangled source is used, then the results at detector B will be independent of the measurement angle choice at A, and vice versa.

This is true even wrt an entangling source.

So the correlation between sets A and B for the entangled case is not "perfectly random" except for the two cases of theta=0 and theta=pi/2 as you are claiming ...

Actually, it is. To illustrate:

The polarizers at A and B are misaligned but not by 90 degrees. A has just registered a detection. Will B also register a detection wrt this pair or not?

 

[ThomasT]

Now, if you are a local realist, you say there is a common cause. And yet you cannot construct a dataset in which the cos^2 relationship holds.

Right, not if the LHV joint probability has to be expressed in factorable form.

So what is all the deal about separability?

It entails that local realist models can be formulated as nonseparable states.

I don't follow all your comments about Bell tests being biased from inception when you cannot do something this simple (because it is impossible).

I agree that it's impossible. That's the point of departure for the argument. The question, then, is why is it impossible. One answer is that it has to do with the factorability of the LHV representation of the joint probability.

Assuming that it has to do with this factorability, then the argument goes ... this factorability was meant to represent locality. Instead it merely represents statistical independence.

However, one might notice, Bell tests are designed to produce statistically dependent data sets, and this statistical dependence doesn't require nonlocal interactions/transmissions.

Hence, violation of Bell inequality doesn't mean that locality or realism has been contradicted, because the violation is simply due to a formal misapplication.

Please explain, for example, how photons become entangled when they are not in each other's light cones - and never have been - and originate from different lasers.

Different lasers can produce the same light, indistinguishable photons.

 

[akhmeteli]

1. Arrgh! Bell does NOT require you to believe ANYTHING other than the idea that QM predicts (rightly or wrongly) that there is a cos^2(theta) relationship.

I respectfully disagree. I think this is factually incorrect. Indeed, you need SOMETHING else to prove the Bell theorem, namely, conservation of angular momentum (otherwise how can you be sure that after you measured polarization of one photon of the entangled pair you definitively know polarization of the other one?) And conservation of angular momentum is a consequence of unitary evolution of QM. That is why I repeat that the proof of the Bell theorem requires both UE and PP, which contradict each other.

It does NOT matter how QM gets that prediction or whether it is observed in experiments (which it is). There is NO other prediction from QM other than the cos^2(theta) relationship (despite your absurd claims that QM is "wrong" whatever that means in this context). So WHAT ARE YOU TALKING ABOUT?

Again, I respectfully disagree. The cos^2(theta) relationship is not the only prediction from QM. Indeed, if the system was initially in a superposition, there is no way you can get destruction of this superposition or irreversibility, unless you reject unitary evolution for the entire system, including the instrument (and an observer, if you wish). So, if there is no irreversibility, that means that no measurement is ever final, in the first place. You want to know what this prediction is exactly? I cannot write the exact prediction, not within a reasonable time frame, but this is not just my opinion. Other people took the trouble to study the process of quantum measurement using a rigorously solved model and showed how the standard results we all are accustomed to arise as approximations, not as precise results, how the projection postulate evolves as a result of irreversibility, which irreversibility, strictly speaking, does not exist, e.g. due to the quantum recurrence theorem. I quoted this published work several times: arXiv:quant-ph/0702135 (Phys. Rev. A 64, 032108 (2001), Europhys. Lett. 61, 452 (2003), Physica E 29, 261 (2005)). Again, you don't need to believe me or Allahverdyan and coauthors. You are a knowledgeable person with profound understanding of quantum mechanics, you are fully aware of the measurement problem in quantum mechanics (and I gave you all the references), so I suspect you fully understand that UE and destruction of superposition are incompatible. Nevertheless, you keep saying something like "C'mon, you're nit-picking, nobody's perfect, so why pick at QM? Be a sport". Sorry, DrChinese, a spade is a spade.

Bell is not dependent on the correctness of QM in any way.

Yes, it is, as the Bell theorem proof requires both elements of QM as assumptions - UE and PP, which are mutually contradictory.

That was Bell's point actually, that QM and LR are mutually incompatible.

I agree. However, as I said, standard quantum mechanics is also incompatible with standard quantum mechanics, so if you believe your (or Bell's) statement rules out LR, it also means it rules out standard QM.

There is no controversery to what I am saying. What you are saying not only makes NO SENSE, but is not accepted by anyone I have ever talked to or read.

I am not sure this is technically correct:-), as I mostly follow nightlight's reasoning, and you criticized nightlight's opinions many times, so I guess you read them:-). Of course, that does not mean that nightlight's opinions or my opinions are correct, but that means that you have been exposed to such opinions.

Forum rules require that you identify personal theories which are not generally accepted as such, and to back up your statements with references when challenged - and you are being challenged. Or better, acknowledge that it is a personal theory with no support other than your belief and stick to discussion points that are appropriate. In this forum, continuing to push points that have been discredited - as yours have - is poor etiquette. We have already covered this ground before in this thread!

Again, what is it that I state? It's actually three statements:

1. There have been no loophole-less experimental demonstration of violations of the Bell inequalities.
2. The proof of the Bell theorem requires both unitary evolution (UE) and the projection postulate (PP) as assumptions.
3. UE and PP, strictly speaking, contradict each other.

and a conclusion:

The Bell theorem is on shaky grounds both experimentally and theoretically.

Statement 1 is the mainstream, and I gave all the references to Shimony, Zeilinger, Genovese.

For statement 2 I indicated where UE and PP are used in the proof of the Bell theorem (to use conservation of angular momentum and to calculate the QM correlations, respectively).

I gave the references to statement 3 (in the form of the problem of measurement in QM) - to von Neumann, Albert, Bassi.

So where is my personal theory? In the conclusion? I believe this conclusion immediately follows from Statements 1-3.

You state that my points were discredited. I reject your statement. I believe I gave adequate answers to the objections. You disagree. That does not mean you're correct and I am wrong or vice versa.

2. I couldn't agree more - you can improve on theories. But theories should NOT be judged according to whether they are "right" or "wrong", but rather according to their utility. For example, Newtonian gravity is actually a better theory than General Relativity for many applications (it has fewer variables). You will see that the next time you calculate the velocity an apple drops from a tree.

This is an excellent example. The problem is it proves my point, not yours. Indeed, Newtonian gravity is very useful. However, it is nonlocal (same as the Coulomb law), whereas general relativity is local, and wherever predictions of these theories differ, the predictions of the latter are correct. I highly respect Newtonian gravity, let alone quantum theory, which is a monumental achievement. But useful theories are not always sufficient to prove such notions as locality or nonlocality, which are important not just for physics, but also for philosophy.

Another example of this kind is thermodynamics. It's an extremely successful and useful theory, but more fundamental theories, such as mechanics or quantum mechanics, strictly speaking, do not allow any irreversibility, which is an integral part of thermodynamics.

 

[Frame Dragger]

You state that my points were discredited. I reject your statement. I believe I gave adequate answers to the objections. You disagree. That does not mean you're correct and I am wrong or vice versa.

True, that's for staff to decide, but since "what naturally follows..." is that you reject Bell Theorem and that, believe me, is YOUR theory. Your view that UE and PP are contradictory have been addressed, and I suppose, "rejected" by you.

So, you've finally made yourself (mostly) clear. Now it's time for you to cite like crazy to support such an ATM view here.

 

[SpectraCat]

Ok ...

Right, but P(A,B) won't be cos2Θ.

There will still be a statistical dependence between A and B if the (unentangled) counter-propagating disturbances have a common cause and the data are matched wrt this criterion. For example, where setup Q has (emitter - polarizer 1 - polarizer 2 - detector) on both sides, and polarizers 1 are aligned and the setting is changing rapidly and randomly so as to produce identical random polarization for each counter-propagating pair.

These are the only two settings wrt which you can predict B given A, and vice versa.

In the ideal, when Θ = 0 then P(A,B) = 1 (detection attributes for A and B are always identical), and when Θ = 90 degrees then P(A,B) = 0 (detection attributes for A and B are always opposite).

This is true even wrt an entangling source.

Actually, it is. To illustrate:

The polarizers at A and B are misaligned but not by 90 degrees. A has just registered a detection. Will B also register a detection wrt this pair or not?

None of what you are saying makes any sense .. in one breath you say that for entangled particles, the coincidence rate between A & B depends on cos²theta, and in the next breath you say that A & B are "completely random" for any choices of theta besides zero and pi/2. These statements are mutually contradictory. Of course I agree that except for those choices one cannot predict with certainty the outcome at B, given A. However, you can notice that the coincidence rate depends on theta, and that means that the results are not 'completely random". Look at it this way ... in my Alice & Bob example, if Bob used a type-II PDC for source P, and Alice measures compares measurements at theta=30º and theta=60º (theta here is the difference between the polarizer settings), then she will see coincidence rates of 25% and 75%, respectively. If he uses your randomly polarized example for source Q, Alice will see the same results for any value of theta.

Finally, it is a bit of a semantic point, but there is no way to get theta values of exactly zero and pi/2 experimentally .. there will always be at least a finite error. So by your argument, all of the A & B data sets in all the Bell test experiments ever carried out are "completely random" or "uncorrelated", or whatever you call it. Do you really believe that is true?

 

[DrChinese]

1. I respectfully disagree. I think this is factually incorrect. Indeed, you need SOMETHING else to prove the Bell theorem, namely, conservation of angular momentum (otherwise how can you be sure that after you measured polarization of one photon of the entangled pair you definitively know polarization of the other one?) And conservation of angular momentum is a consequence of unitary evolution of QM. That is why I repeat that the proof of the Bell theorem requires both UE and PP, which contradict each other.

2. Again, I respectfully disagree. The cos^2(theta) relationship is not the only prediction from QM. Indeed, if the system was initially in a superposition, there is no way you can get destruction of this superposition or irreversibility, unless you reject unitary evolution for the entire system, including the instrument (and an observer, if you wish). So, if there is no irreversibility, that means that no measurement is ever final, in the first place. You want to know what this prediction is exactly? I cannot write the exact prediction, not within a reasonable time frame, but this is not just my opinion. Other people took the trouble to study the process of quantum measurement using a rigorously solved model and showed how the standard results we all are accustomed to arise as approximations, not as precise results, how the projection postulate evolves as a result of irreversibility, which irreversibility, strictly speaking, does not exist, e.g. due to the quantum recurrence theorem. I quoted this published work several times: arXiv:quant-ph/0702135 (Phys. Rev. A 64, 032108 (2001), Europhys. Lett. 61, 452 (2003), Physica E 29, 261 (2005)). Again, you don't need to believe me or Allahverdyan and coauthors. You are a knowledgeable person with profound understanding of quantum mechanics, you are fully aware of the measurement problem in quantum mechanics (and I gave you all the references), so I suspect you fully understand that UE and destruction of superposition are incompatible. Nevertheless, you keep saying something like "C'mon, you're nit-picking, nobody's perfect, so why pick at QM? Be a sport". Sorry, DrChinese, a spade is a spade.

3. Yes, it is, as the Bell theorem proof requires both elements of QM as assumptions - UE and PP, which are mutually contradictory.

4. I am not sure this is technically correct:-), as I mostly follow nightlight's reasoning, and you criticized nightlight's opinions many times, so I guess you read them:-). Of course, that does not mean that nightlight's opinions or my opinions are correct, but that means that you have been exposed to such opinions.

5. Again, what is it that I state? It's actually three statements:

1. There have been no loophole-less experimental demonstration of violations of the Bell inequalities.
2. The proof of the Bell theorem requires both unitary evolution (UE) and the projection postulate (PP) as assumptions.
3. UE and PP, strictly speaking, contradict each other.

and a conclusion:

The Bell theorem is on shaky grounds both experimentally and theoretically.

Statement 1 is the mainstream, and I gave all the references to Shimony, Zeilinger, Genovese.

For statement 2 I indicated where UE and PP are used in the proof of the Bell theorem (to use conservation of angular momentum and to calculate the QM correlations, respectively).

I gave the references to statement 3 (in the form of the problem of measurement in QM) - to von Neumann, Albert, Bassi.

So where is my personal theory? In the conclusion? I believe this conclusion immediately follows from Statements 1-3.

You state that my points were discredited. I reject your statement. I believe I gave adequate answers to the objections. You disagree. That does not mean you're correct and I am wrong or vice versa.

6. This is an excellent example. The problem is it proves my point, not yours. Indeed, Newtonian gravity is very useful. However, it is nonlocal (same as the Coulomb law), whereas general relativity is local, and wherever predictions of these theories differ, the predictions of the latter are correct. I highly respect Newtonian gravity, let alone quantum theory, which is a monumental achievement. But useful theories are not always sufficient to prove such notions as locality or nonlocality, which are important not just for physics, but also for philosophy.

Another example of this kind is thermodynamics. It's an extremely successful and useful theory, but more fundamental theories, such as mechanics or quantum mechanics, strictly speaking, do not allow any irreversibility, which is an integral part of thermodynamics.

What is wrong with you?

1. Bell points out about perfect correlations, which is also present in EPR. This does not require any further discussion, it is an experimental fact and accepted by all: entangled particles exhibit this, and no assumption is required. UE and PP are irrelevant to Bell, and I challenge you to produce a reference otherwise.

2. Do you not read anything I (or anyone else) says? I said that QM predicts the cos^2(theta) relationship for entangled particles. It does not predict otherwise. So who cares how that is arrived at if you think QM is wrong (an embarassing position by the way)? Bell says QM conflicts with LR, really, how hard is that for you to understand? It is absurd to repeat the same statements over and over in post after post. You don't have to agree with QM to know this is the prediction and there is no other (if so, what is it?). You don't have to be a genius to figure out that LR must respect Bell's Inequality once Bell's Theorem is considered. And that is different than QM.

3. Again, reference please.

4. nightlight? You must be kidding, right? He never said this that I recall. And I disagreed with almost everything he said. nightlight is a diehard local realist who ignores Bell test results and disagreed with Bell, as I recall. But never did I hear a comment that QM was "wrong" because of mutually contradictory elements. But perhaps you can correct me on that point, I would welcome that.

5. Laughable! You completely mischaracterize the nature of Zeilinger et al's position on loopholes by quoting out of context. It is true that Zeilinger would like to see a "loophole-free" demonstration of a Bell test, but that is for significantly different reasons than you describe. Zeilinger has already ruled out local realism in numerous OTHER experiments, need I re-reference these? GHZ is a good starter, and there are plenty of others. So it is not about LR being viable or not to him!

Further: the measurement problem - which I acknowledge freely - is hardly a flaw in QM. May as well say GR is wrong too at a singularity because of division by zero. You clearly like to turn back the clock hands with meaningless semantic diversions. How about a little useful science to go with your words? Noone - least of all me - claims QM answers all questions about all things. It is a model, and it is a very useful one. You have only to lay on the table a model that matches and exceeds it to get my attention. Short of that, you are nothing but HOT AIR.

Again, references for your claim that Bell assumes theoretical elements of QM. It ONLY requires knowledge of the predictions of QM, not how those predictions are arrived at.

6. Newtonian gravity IS a useful theory. The subject is theory utility, not theory correctness. Theories may be more or less useful, and they may be disproven as well. All you need to do is provide a more useful theory than QM and we can then discuss that. In the meantime, you again are saying nothing other that "I am right".

--------------------------

You manage to write a lot of words and make a lot of empty claims. I am certainly glad you agree with yourself, very impressive that. Meanwhile, quit making unsupported claims. Where is there a paper which says that Bell assumes UE or PP? HOW ABOUT A BONA FIDE DIRECT REFERENCE FROM A RESPECTED SOURCE?

 

[Demystifier]

Therefore, I suspect that violations of the Bell inequalities cannot be proven in dBB using UE only, you need some additional assumptions (or approximations, if you like).

Oh, now I see. When you say "proof", you mean a rigorous mathematical-logical Proof (with capital "P"), not an approximative natural-science proof. Well, I must disappoint you. When applied to the real world without idealizations and approximations, physics cannot Prove anything. It can prove a lot, but it can Prove nothing. Nonlocality of QM is not an exception. You should either find a way to live with it, or leave physics entirely.

 

[Demystifier]

... but rather no longer a shooting offense to teach.

English is your native language, right? Unfortunately, that's not the case with me. That's why I often have problems with understanding your beautiful phrases like the one above.
What do you mean by that?

 

[jtbell]

Re: "shooting offense"

I think it's an expression from the cowboy days of the Wild West, where people walked around with guns strapped to their hips, and some were likely to shoot you if you did something that gave them serious offense.

[off-topic aside] I once watched a Western movie on TV in which the mountains looked strange, with bare rounded tops and rounded rock outcroppings. Yet they also looked familiar. It turned out that the movie had been filmed in Croatia, about which I had seen a travel program not long before!

 

[Frame Dragger]

English is your native language, right? Unfortunately, that's not the case with me. That's why I often have problems with understanding your beautiful phrases like the one above.
What do you mean by that?

I apologize if I was confusing. "A shooting offense" is probably... mid-century (1900s) American Idiom. It's intentional exaggeration meaning that once people were dismissed or punished offhand for 'x' act. In modern parlance, it's often an intentional device used to point out how reactionary people were regarding a given subject at a period in history.

I believe, for the record, that back in the day (in the USA) when executions in the west were mostly hangings and shootings... well... you get the idea. Not a lot of "Due Process" in the old west.

In this context, I was (trying) to be dry, based on a conversation I once had with Zenith. In essence she made the point that not very long ago, it was not allowed to teach dBB in many respected universities. Now that dBB has survived and managed to hold its own, I was reflecting with some measure of sarcasm on a period in our history when the theory was treated like something criminal to be stamped out.

It's not an insult to the theory, but rather the system that is so judgemental of groups and not individuals.

EDIT:
@jtbell: Well, something lik that. I did a little checking when I saw you posted. It turns out it WASN'T the old west! They saved their bullets, and hanged you. ouch. It was a much more "civilized" notion, describing the point at which a crime became a capitol offense.

EDIT: Croatia?! Wow... now I want to see that movie! I've seen a drinking show that made the place look wonderful, another travel show which did the same, and a friend (in Ireland) went to a party there for a week, and thought the people were amazing, the architecture stunning, the food damned good, and the weather fine.

I wouldn't mind sipping something cool while looking at ancient architecture.

 

[Demystifier]

EDIT: Croatia?! Wow... now I want to see that movie! I've seen a drinking show that made the place look wonderful, another travel show which did the same, and a friend (in Ireland) went to a party there for a week, and thought the people were amazing, the architecture stunning, the food damned good, and the weather fine.

As someone who lives in Croatia for (almost) the whole life, I can only confirm that.
Well, except for the architecture. I wouldn't call it amazing, but perhaps that's because I'm used to it.

 

[Frame Dragger]

As someone who lives in Croatia for (almost) the whole life, I can only confirm that.
Well, except for the architecture. I wouldn't call it amazing, but perhaps that's because I'm used to it.

Oh! Well, from the US, hello! I live on the east coast with very VERY British architecture. It's lovely, but after a while... eh. I love travel, as most countries have significantly longer and more diverse histories than the european history in the americas. For me, the architecture is great!

By the way... have you had Bermet? I've only ever heard of it, or seen it on television, but it sounds very interesting.

 

[Demystifier]

By the way... have you had Bermet? I've only ever heard of it, or seen it on television, but it sounds very interesting.

It's an alcohol drink, right? Actually, I don't drink alcohol at all. (It's not a matter of principle, I simply don't like it. Well, except in some chocolate products.)

 

[Frame Dragger]

It's an alcohol drink, right? Actually, I don't drink alcohol at all. (It's not a matter of principle, I simply don't like it. Well, except in some chocolate products.)

It is, and same here, although I can't claim to even enjoy the chocolate varieties. My friends still laugh at me (over decade later I should add) that my first words upon tasting my first beer were, "Thbbbppptt, what the ****?! Isn't this supposed to be sweet?? This is so bitter it's, ecchhhhh." And so forth. :shy:

 

[Demystifier]

It is, and same here, although I can't claim to even enjoy the chocolate varieties. My friends still laugh at me (over decade later I should add) that my first words upon tasting my first beer were, "Thbbbppptt, what the ****?! Isn't this supposed to be sweet?? This is so bitter it's, ecchhhhh." And so forth. :shy:

I see we have a lot in common.

 

[DrChinese]

Oh, now I see. When you say "proof", you mean a rigorous mathematical-logical Proof (with capital "P"), not an approximative natural-science proof. Well, I must disappoint you. When applied to the real world without idealizations and approximations, physics cannot Prove anything. It can prove a lot, but it can Prove nothing. Nonlocality of QM is not an exception. You should either find a way to live with it, or leave physics entirely.

akhmeteli: I guess your policy is to pick and choose what to accept or reject in QM. I have never seen you comment about any other aspect of QM as wrong. Yet I wonder why you bother with anything in quantum physics if it is all wrong.

So here are my challenges to you, please address any you are able:

1. Post a solid reference to paper that says Bell's Theorem is dependent on the theoretical constructs within QM (rather than the predictions, as most believe). You have so far failed to do this, instead posting references to the QM measurement problem which is hardly the same thing.

2. Provide a dataset for polarization values for 0, 120 and 240 degrees which match experimental statistics. You should be able to supply this if the Bell road map is invalid.

3. Provide an explanation of how particles can become entangled which have never met. Zeilinger and others have performed an entire series of experiments in the past 5+ years around this subject. I would think this would give pause to a local realist. Unless, of course, you simply disregard evidence going against your entrenched position.

 

[Frame Dragger]

akhmeteli: I guess your policy is to pick and choose what to accept or reject in QM. I have never seen you comment about any other aspect of QM as wrong. Yet I wonder why you bother with anything in quantum physics if it is all wrong.

So here are my challenges to you, please address any you are able:

1. Post a solid reference to paper that says Bell's Theorem is dependent on the theoretical constructs within QM (rather than the predictions, as most believe). You have so far failed to do this, instead posting references to the QM measurement problem which is hardly the same thing.

2. Provide a dataset for polarization values for 0, 120 and 240 degrees which match experimental statistics. You should be able to supply this if the Bell road map is invalid.

3. Provide an explanation of how particles can become entangled which have never met. Zeilinger and others have performed an entire series of experiments in the past 5+ years around this subject. I would think this would give pause to a local realist. Unless, of course, you simply disregard evidence going against your entrenched position.

I would add this codicile: Do all of that in the minimum number of words required to do so.

 

[DrChinese]

I would add this codicile: Do all of that in the minimum number of words required to do so.

Thank you!

 

[akhmeteli]

Oh, now I see. When you say "proof", you mean a rigorous mathematical-logical Proof (with capital "P"), not an approximative natural-science proof. Well, I must disappoint you. When applied to the real world without idealizations and approximations, physics cannot Prove anything. It can prove a lot, but it can Prove nothing. Nonlocality of QM is not an exception. You should either find a way to live with it, or leave physics entirely.

Demystifier,

I am happy you understood me. Thank you.

So now the question is whether mathematical rigor is relevant to our discussion.

You see, I can live with nonlocality, no problem at all. I'm just curious: why should I?

You mentioned the real world. However, there is no signal nonlocality in the real world, no experimental demonstration of violations of the genuine Bell inequalities. So we are left with no-go theorems, such as the Bell theorem. But if it uses approximations as assumptions, that opens a hole for locality. Is this hole wide enough or too narrow? I don't know. Do you?

Quantum theory is mature and astonishingly precise, so we can and should judge it to the highest standards. Classical mechanics also was mature and astonishingly precise (and nonlocal, by the way, what with Newton gravity and things like that). But it had problems with birth control, so relativity and quantum theory were born. So is the Bell condom good enough to avoid the trouble of locality? I don't know. The only thing I know it has holes, both experimental and theoretical.

As for my leaving or not leaving physics... You see, physics is a very wide area, there is enough place there both for approximations and for rigorous results, for the Boltzmann equation and for Poincare recurrence theorem. You were very kind to call one of my ideas "interesting", and I am grateful to you, but that idea was based on a rigorous result. Actually, we all do what we can, not what we want.