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

[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.

 

[Frame Dragger]

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.

A question answered with a question devoid of any SEMBLANCE of new thinking or information? Oh wait, it was said in the MAXIMUM (ok, near max) number of words possible... what a shock.


Tell you what, since you're repeating yourself, go back and re-read the last few question Dr. Chinese has asked you, and answer them in order. As for leaving physics, I think it's a given you were never there based on your lack of responses, and the simple fact that if this is how you comported yourself, you would have been beaten to death by nerds.

 

[akhmeteli]

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?

DrChinese, thank you for your time and your letters, I do appreciate them. Actually, they are quite helpful.

Unfortunately, I cannot answer all your questions immediately. I'll try to do it later, but let me start somewhere. So here's the reference:

E. Santos, "Bell’s theorem and the experiments: Increasing empirical support for local realism?", Studies in History and Philosophy of Modern Physics, 36 (2005) 544–565. It's mostly Section 7.

Some quotes:

"According to the traditional formulation, quantum mechanics consists of two quite different ingredients: the formalism (including the equations) and the theory of measurement, both of which are postulated independently. (Actually the two ingredients are to some extent contradictory, because the quantum evolution is continuous and deterministic except during the measurement, where the ‘‘collapse of the wavefuction’’ is discontinuous and stochastic. Thus the modern approach tends to remove any postulated theory of measurement...)."

"The point is that standard proofs of ‘‘Bell’s theorem’’ rest upon the theory of measurement (and preparation of states)."

Santos then mentions other elements of the measurement theory than PP, but you do need PP to calculate the correlations for quantum mechanics: say, you measure a spin projection of one particle of the entangled pair, say, you get value +1, then you use PP to state that after the measurement the system has a definite spin projection of the first particle, then you use UE to state that, due to conservation of angular momentum, the spin projection of the other particle on the same axis is -1, and only then you use the Born rule to find the probability of the other particle having a certain projection of spin on another axis. As the two measurements are spatially separated, it does not matter if you conduct one measurement earlier than the other, later, or simultaneously.

So you cannot take the Malus law from nowhere. It cannot appear in the proof of the Bell's theorem as an experimental law, it can appear there only as a derived result of quantum mechanics, otherwise you cannot say that quantum mechanics predicts nonlocality. And to derive the Malus law in quantum mechanics, you need the theory of measurement, e.g., PP (as I described above).

 

[DrChinese]

DrChinese, thank you for your time and your letters, I do appreciate them. Actually, they are quite helpful.

Unfortunately, I cannot answer all your questions immediately. I'll try to do it later, but let me start somewhere. So here's the reference:

E. Santos, "Bell’s theorem and the experiments: Increasing empirical support for local realism?", Studies in History and Philosophy of Modern Physics, 36 (2005) 544–565. It's mostly Section 7.

Some quotes:

"According to the traditional formulation, quantum mechanics consists of two quite different ingredients: the formalism (including the equations) and the theory of measurement, both of which are postulated independently. (Actually the two ingredients are to some extent contradictory, because the quantum evolution is continuous and deterministic except during the measurement, where the ‘‘collapse of the wavefuction’’ is discontinuous and stochastic. Thus the modern approach tends to remove any postulated theory of measurement...)."

"The point is that standard proofs of ‘‘Bell’s theorem’’ rest upon the theory of measurement (and preparation of states)."

...

A poor reference indeed. You may as well be quoting yourself. Santos is a sad figure (in my personal opinion), whose grand contribution is to convince a few good people that "all loopholes should be closed simultaneously" (a questionable conclusion).

His referenced result is not generally accepted any more than Santos' stochastic mechanics hypotheses, all of which have been soundly critiqued. Gosh, they were published too! You'll have to do a lot better than this.

 

[SpectraCat]

DrChinese, thank you for your time and your letters, I do appreciate them. Actually, they are quite helpful.

Unfortunately, I cannot answer all your questions immediately. I'll try to do it later, but let me start somewhere. So here's the reference:

E. Santos, "Bell’s theorem and the experiments: Increasing empirical support for local realism?", Studies in History and Philosophy of Modern Physics, 36 (2005) 544–565. It's mostly Section 7.

Some quotes:

"According to the traditional formulation, quantum mechanics consists of two quite different ingredients: the formalism (including the equations) and the theory of measurement, both of which are postulated independently. (Actually the two ingredients are to some extent contradictory, because the quantum evolution is continuous and deterministic except during the measurement, where the ‘‘collapse of the wavefuction’’ is discontinuous and stochastic. Thus the modern approach tends to remove any postulated theory of measurement...)."

"The point is that standard proofs of ‘‘Bell’s theorem’’ rest upon the theory of measurement (and preparation of states)."

Santos then mentions other elements of the measurement theory than PP, but you do need PP to calculate the correlations for quantum mechanics: say, you measure a spin projection of one particle of the entangled pair, say, you get value +1, then you use PP to state that after the measurement the system has a definite spin projection of the first particle, then you use UE to state that, due to conservation of angular momentum, the spin projection of the other particle on the same axis is -1, and only then you use the Born rule to find the probability of the other particle having a certain projection of spin on another axis. As the two measurements are spatially separated, it does not matter if you conduct one measurement earlier than the other, later, or simultaneously.

So you cannot take the Malus law from nowhere. It cannot appear in the proof of the Bell's theorem as an experimental law, it can appear there only as a derived result of quantum mechanics, otherwise you cannot say that quantum mechanics predicts nonlocality. And to derive the Malus law in quantum mechanics, you need the theory of measurement, e.g., PP (as I described above).

Ok, so I think I finally understand why it has been to hard to understand your point of view here, at least in my case. You are actually challenging the foundations of the standard formulation of quantum mechanics, by attacking one of the core postulates. This is of course fine, but it would have been helpful if you constructed your arguments in that context from the beginning, rather than focusing on the Bell theorem, which is actually just collateral damage from your primary attack.

In truth, there is nothing wrong with Bell's theorem, because he simply takes for granted the postulates that are part and parcel of SQM ... that is what one is *supposed* to do with postulates, when working within a theoretical framework. On the other hand, you refuse to accept one of those postulates, as you have stated consistently from the beginning, and of course this is the really the only logical grounds on which to challenge an otherwise correct mathematical proof/derivation.

EDIT: As I said above, this is fine, but it is hardly mainstream in this case. While the "measurement problem" has been debated long and hard in quantum mechanics, I think most people would still concede that this has not so far proved to be a practical problem for either measurements, or for theoretical predictions derived from the accepted postulates.

Your challenges on the experimental side of things are also hard for me to accept, but as we have already realized, that is because I tend to accept the fair sampling assumption as valid, while you do not. We have each stated our case, and I guess neither has been convinced by the other ... we will simply have to wait for improved detection efficiencies to resolve this matter I guess.

So, while I tend to view your challenge to SQM as rather quixotic, who is to say that I am correct? All I can say is that the postulates of SQM have served us rather well to this point, and there are no clear-cut cases where they have been found to be false. Perhaps there is a point to be made that they are somehow self-contradictory, but so far that is not a widely held view. I have no problem "rationalizing away" the seeming contradiction that you raise, because the unitary evolution postulate pertains to the microscopic quantum system, whereas the measurement postulate pertains to the interaction of the quantum system with a macroscopic detector. Thus the apparent irreversibility that seems to be the focus of your concerns could in my view just be an "effective irreversibility" resulting from entropic effects as the quantum system interacts with the (effectively) continuous distribution of states represented in the macroscopic detector. I think that if this is correct (and I am not claiming that it is), it would be provide a nice symmetry with classical physics, where temporal irreversibility is also just an "effective" phenomenon resulting from the tendency of natural systems to seek states of high entropy.

 

[DrChinese]

... This is of course fine, but it would have been helpful if you constructed your arguments in that context from the beginning, rather than focusing on the Bell theorem, which is actually just collateral damage from your primary attack.

In truth, there is nothing wrong with Bell's theorem, because he simply takes for granted the postulates that are part and parcel of SQM ... that is what one is *supposed* to do with postulates, when working within a theoretical framework. On the other hand, you refuse to accept one of those postulates, as you have stated consistently from the beginning, and of course this is the really the only logical grounds on which to challenge an otherwise correct mathematical proof/derivation.
...

I don't follow your assessment of the relationship of sQM and Bell. All Bell depends upon is the prediction of sQM - nothing else. It does not assume that prediction is correct. There is nothing about a Bell test, either, that assumes QM is correct. Maybe it isn't.

Either way, the point of Bell was to demonstrate that the Local Realistic view and the QM views are not compatible. After 1935, it was widely believed that they might be.

 

[SpectraCat]

I don't follow your assessment of the relationship of sQM and Bell. All Bell depends upon is the prediction of sQM - nothing else. It does not assume that prediction is correct. There is nothing about a Bell test, either, that assumes QM is correct. Maybe it isn't.

Either way, the point of Bell was to demonstrate that the Local Realistic view and the QM views are not compatible. After 1935, it was widely believed that they might be.

Right, and the prediction of sQM follows from the postulates of sQM, that is all I am saying with the above. If one of those postulates were incorrect, as akhmeteli has hypothesized, then the prediction of sQM could be "wrong", which would then obviously impact the Bell theorem as well. Of course, as I have written, I find akhmeteli's characterization highly suspect ... I accept both the postulates of sQM and the Bell theorem as valid. However at least I now understand where he is coming from ...

 

[MaxwellsDemon]

The postulates were chosen in accordance with experimental observations...basically because they work. Personally I think it would be nice if we could replace the highly abstract and mathematical postulates of QM with postulates that still make the same predictions but are more more physically intuitive aesthetically pleasing...more "human". When studying QM, I always get the feeling that I'm starting with Fermat's Last Theorem as an axiom and trying to prove that 2+2=4.

On a side note, I haven't been on this forum for a while...I'm amazed to see that this thread is still active! I thought the matter seemed settled on the first couple pages last I checked.

Oh, and I thought I'd mentioned that I really like beer. I think it tastes great. Nothing like beer and pizza...or beer and burgers...or beer and ____. :D

"Beer is proof that God loves us and wants us to prosper" - Ben Franklin

 

[DrChinese]

Right, and the prediction of sQM follows from the postulates of sQM, that is all I am saying with the above. If one of those postulates were incorrect, as akhmeteli has hypothesized, then the prediction of sQM could be "wrong", which would then obviously impact the Bell theorem as well. Of course, as I have written, I find akhmeteli's characterization highly suspect ... I accept both the postulates of sQM and the Bell theorem as valid. However at least I now understand where he is coming from ...

So I think we are in sound agreement: Wrong postulates COULD possibly lead to bad predictions; bad predictions would lead to experimental falsification. But regardless, that has NO IMPACT at all on the incompatibility of QM and LR which Bell's Theorem addresses.

Ergo, bad postulates do not invalidate Bell's Theorem. Bell's Theorem in no way says "IF LR is wrong, then QM is true" or vice versa. They could both be false.

 

[DrChinese]

Oh, and I thought I'd mentioned that I really like beer. I think it tastes great. Nothing like beer and pizza...or beer and burgers...or beer and ____. :D

"Beer is proof that God loves us and wants us to prosper" - Ben Franklin

SpectraCat still owes me a couple of beers and refuses to pay up.

 

[Frame Dragger]

So, at what point do you accuse someone of being a crackpot who talks endlessly without producing meanginful citations, of being ATM in the thread; relentlessly and annoyingly? (ahkmeteli)

I realize this is a largely civil forum, but I feel that many pages have been wasted in an interesting discussion so that one indivudual could disagree with SQM without saying so. Can we just move on? DrChinese has stated what I believe all relevant members of this discusson agree on, and we can continue. We don't even need to agree with SQM, or Bells Theorem. Surely nothing could be simpler.

 

[ThomasT]

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.

Let's try again.

At the outset of a run in an idealized, two-photon, optical Bell test the detection rate probabilities are:

for individual detection

P(A) = P(B) = 1/2


and for joint detection

P(A,B) = cos²Θ .


A and B are sets of time-ordered, random-valued, individual detection attributes -- unpredictable sequences of 1's and 0's.

The individual detection rates at A and B aren't correlated to each other, or to Θ, or to λ, or to a or b (the polarizer settings at A and B, respectively). They never vary from 1/2.

However, due to the assumption of common properties imparted to counter-propagating disturbances via emission, then if the value of Θ is known to be 0 or π/2, then if the attribute at A is known then the attribute at B for the pair can be deduced (and vice versa).


The set (A,B) is constructed by pairing the members of A with the members of B wrt detection times. The values of the members of (A,B) also occur randomly.

P(A,B), or the number of pairs containing identical detection attributes is correlated to Θ, and varies as cos²Θ.

Ok so far?

... 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?

Yes. See above.

You still haven't (in fact nobody has) said what you think about the argument against the usual interpretation of the meaning of Bell's theorem and violations of Bell inequalities. I've restated it many times. It has simply to do with the contradiction between the factorability of a Bell LHV joint probability representation and Bell test experimental designs, as well as the contradiction between this factorability and QMs nonfactorable joint (entangled) state representation.

 

[SpectraCat]

Let's try again.

At the outset of a run in an idealized, two-photon, optical Bell test the detection rate probabilities are:

for individual detection

P(A) = P(B) = 1/2

Just to be clear here, in a standard Bell test, *both* polarization components are measured at A and B. So, as long as you are not equating 0 with "no detection event", then I agree with your statement. What the value of 1/2 signifies to me is that, at detector A, a result of "H" is observed half the time, and "V" is observed for the other half of the events; they are never observed simultaneously. Here "H" and "V" refer to two orthogonal polarization directions.

and for joint detection

P(A,B) = cos²Θ .

Again, just to be clear, this is the case for an entangled source only ... the cos²Θ relationship will not hold for unentangled particles. If you use your earlier example of two independent, randomly polarized counter-propagating beams, then for *any* choice of measurement angles at A and B, you will observe P(A,B)=P(A)P(B)=1/4 (that is, paired detection events satisfying any particular choice of "H" and "V" at both A and B will be observed one quarter of the time).

Furthermore, you can make the polarization relationship between the two *independent* beams whatever you like, and while the overall analysis will become more complicated, Alice will still observe that the probability of observing a particular result at A remains independent of the choice of detection settings at B. That is how she can tell whether or not Bob is using an entangled source or not in the thought experiment I have described in my last few posts.

A and B are sets of time-ordered, randomly occurring individual detection attributes -- unpredictable sequences of 1's and 0's.

The individual detection rates at A and B aren't correlated to each other, or to Θ, or to λ, or to a or b (the polarizer settings at A and B, respectively). They never vary from 1/2.

Agreed ... and perhaps my phrasing was somehow unclear, but I never claimed anything different from this. What I have been saying is that for entangled particles, the likelihood of obtaining a coincidence between paired results at A and B depends in a predictable and non-random way on the relative choice of detection angles, which we have been calling Θ. (Note that it is only the relative value of theta that matters ... the absolute settings in the lab frame at A and B are irrelevant.) For unentangled particles, there is no general dependence of the coincidence rate on the choice of Θ, period.

However, due to the assumption of common properties imparted to counter-propagating disturbances via emission, then if the value of Θ is known to be 0 or π/2, then if the attribute at A is known then the attribute at B for the pair can be deduced (and vice versa).

I would phrase this differently. I would say that, in any setup, one can attempt to make a prediction of a measurement result at detector B, based on the observed result at A and the relative detection angle Θ. In the case of entangled particles, one will find upon comparing paired measurements that the chance that their prediction was correct is either cos²Θ, or 1 - cos²Θ, depending on particular type of entanglement. (As you say, these values become 0 and 1 for the choices of Θ you have been focusing on.) In the case of unentangled particles, one would find that the chance of their prediction being correct is independent of the choice of Θ.

But please consider what happens in both of our pictures when we change Θ by an infinitesimal amount from one of these values (0 or π/2). In my case, the chance of the prediction being correct changes by an infinitesimal amount .. in your case the results become "completely random", to use your words.

The set (A,B) is constructed by pairing the members of A with the members of B wrt detection times, and is also a random sequence.

I think the use of "random" is too vague here. I agree that the results of any particular pair cannot be predicted with certainty in the general case, however the likelihood of a coincidence is given by cos²Θ, so it is not purely random either. That is why I choose the term "correlated" ... I would use "perfectly correlated" or "perfectly anti-correlated" to describe the situation at Θ=0 and Θ=π/2.

P(A,B), or the number of pairs containing identical detection attributes is correlated to Θ, and varies as cos²Θ.

Again, I emphasize that P(A,B)=cos²Θ is only obtained for entangled particles. If you are restricting your statement to that case, then I agree.

 

[SpectraCat]

You still haven't (in fact nobody has) said what you think about the argument against the usual interpretation of the meaning of Bell's theorem and violations of Bell inequalities. I've restated it many times. It has simply to do with the contradiction between the factorability of a Bell LHV joint probability representation and Bell test experimental designs, as well as the contradiction between this factorability and QMs nonfactorable joint (entangled) state representation.

Sure I have ... I have said that I thought that such arguments make no sense for the reasons that we have been discussing. The whole Alice and Bob thought experiment I have devised is intended to show that the "inherent contradiction" you mention regarding the experimental design of Bell tests does not exist. (DrChinese has also made similar points.) You have yet to understand the crux of my arguments, but that may be because I have not yet communicated my points clearly ... thus I keep trying.

 

[DrChinese]

1. The individual detection rates at A and B aren't correlated to each other, or to Θ, or to λ, or to a or b (the polarizer settings at A and B, respectively). They never vary from 1/2.

2. However, due to the assumption of common properties imparted to counter-propagating disturbances via emission, then if the value of Θ is known to be 0 or π/2, then if the attribute at A is known then the attribute at B for the pair can be deduced (and vice versa).

1. Not exactly sure what you are saying here. I think you are saying that the values are random no matter where across 360 degrees you place the settings. There IS a correlation for Theta, although the values themselves are still random.

2. I think you are re-stating the QM rule used to get the prediction of cos^2(theta). I guess you could call it an assumption used to make the prediction, but that is really simply saying it is part of the theory (or theory application). It is not an assumption of Bell. It is more part of EPR.

 

[SpectraCat]

SpectraCat still owes me a couple of beers and refuses to pay up.

Heh! I haven't conceded that I actually lost those beers yet ... but I can only carry on so many arguments at one time ... I hope to pick up ours again later.

Still, if ever I make it to Texas, I will look you up and buy you a couple brews, just to keep you quiet!