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

[akhmeteli]

No, I don't think so. If you look at the actual equation they give for the Born rule in section 3.4, the equation is giving a probability of getting a given eigenvalue, not a given eigenstate/eigenvector. The verbal discussion in the paragraph preceding that equation is a bit confusing because they assume the Born rule is always coupled with the collapse postulate, so that the probability of getting a given eigenvalue would be the same as the probability of collapsing to the corresponding eigenstate, but the two assumptions are logically separable, and the article follows every other source I've seen in defining the Born rule in terms of the probability of getting a particular eigenvalue (which is understood as a possible measurement result).

It is not obvious that b_i is an eigenvalue, not an eigenstate. While b_i was defined earlier in the text, it was defined as an expansion coefficient, not as an eigenvalue. And the narrative suggests that the author is talking about the probability of the eigenstate. But anyway, let’s use your definition.

I don't understand what you mean by "nothing in" them "about" measurement records. Unitary evolution and the Born rule apply the same way to all quantum systems, they don't give specific rules for pointer states so I guess in that sense you could say there is "nothing in" them about pointer states, but nor do they give specific rules for electrons going through a double-slit or for any other particular quantum system, would you say "there is nothing in unitary evolution or in the Born rule about electrons"? The point is that unitary evolution and the Born rule can be applied in exactly the same way to any quantum system you like, so why not apply them to the macroscopic measuring devices and their records/pointer states in just the way you'd apply them to microscopic systems?

I mean the Born rule is not about “records”, either observable or not, it is about the final results of observation (please advise if you disagree). These are two different things, as, for example, "records” are never final.

Who said they had to be permanent? The point is just to pick some time T shortly after all the experiments have been done, and apply the Born rule at T to find the probabilities of observing different measurement records at T. Maybe in the distant future all records of this experiment will be lost and no one will remember what the actual results were, but so what? This is just a procedure for making predictions about empirical results in the here-and-now.

As I said, this procedure can be satisfactory for one purpose and unsatisfactory for another one. We are talking about the Born rule as applied to Bell experiments. In this case your procedure should be as follows: you have to take the records of measurements for two spatially separated particles and observe them simultaneously to obtain the input to the correlation. If you observe the records simultaneously (and that means in the same place), you cannot do that fast enough to eliminate the possibility of subluminal signaling (i.e. to close the locality loophole). On the other hand, you cannot be sure the records were the same at the time of the measurement, as the records are not permanent.

Don't know what you mean by that. Any time you use a theoretical model to make predictions about a real-world experiment, the model is always simplified, you couldn't possibly model the precise behavior of every single particle involved in the experiment, so in that sense all models are "abstract", but they are nevertheless highly useful in making predictions about real-world experiments, otherwise we'd just be doing pure math and not physics!

I mean the following. You cannot apply the Born rule in a specific form to an arbitrary measurement. For example, you cannot apply the Born rule defining the probability of the system having certain coordinates to a momentum measurement. In the same way, if you apply the Born rule for spin projections of two spatially separated particles, strictly speaking, the measurement should be designed to measure the two spin projections simultaneously, so perhaps you need some nonlocal measurement arrangement (nightlight said something to this effect). That’s not what happens in Bell experiments, where you measure the spin projections separately, and then combine the results. As I said above, this is something different.

I think you need to review the links I gave you earlier about von Neumann's procedure for calculating probabilities (see post #706 in particular). Again, there is no problem with measurements being made prior to the moment we apply the Born rule, it's just that each measurement is modeled as causing the measuring-device to become entangled with the system being measured exactly as you'd expect from unitary evolution, with no attempt to talk about probabilities at that point. Then at some time T after all measurements have already been performed, the Born ruler is applied to the pointer states of all the measuring devices. Obviously in the a real Bell experiment, at some point all the data will be collected in one place so scientists can review it, what's wrong with waiting until then to apply the Born rule to find the probability that a scientist will see different combinations of results on their computer screen?

I disagree that “there is no problem” – “at some time T after all measurements have already been performed” you cannot close the locality loophole, as “all the data will be collected in one place”, and you cannot state with certainty that the records have not changed. And that is “what's wrong with waiting until then”.

How so?

On the one hand, the probability of nonzero sum of spin projections is zero, according to the Born rule. On the other hand, according to unitary evolution, the spin projection measurement cannot turn the superposition into a mixture, so the spin projection measurement on the second particle can yield any value, so, according to the Born rule, the probability of nonzero sum of spin projections is not zero.

But von Neumann's approach doesn't involve multiple successive applications of the Born rule, just a single one after all the experiments have been completed.

But Bell experiments involve independent measurements on the two spatially separated particles.

You haven't really explained why you think it contradicts unitary evolution. Many advocates of the many-worlds interpretation have tried to argue that the Born rule would still work for a "typical" observer in that interpretation, despite the fact that in the MWI unitary evolution goes on forever and thus each experiment just results in a superposition of different versions of the same experimenter seeing different results.

See above

Also, have a look at the paper at http://www.math.ru.nl/~landsman/Born.pdf which I found linked in wikipedia's article on the Born rule, the concluding paragraph says "The conclusion seems to be that no generally accepted derivation of the Born rule has been given to date, but this does not imply that such a derivation is impossible in principle."

I am not trying to say that the Born rule per se contradicts unitary evolution (I am not sure about that), it’s the Born rule as applied for Bell experiments that contradicts unitary evolution (see above).

Besides, you talk as though "unitary evolution" were a sacred inviolate principle, but in fact all the empirical evidence in favor of QM depends on the fact that we can connect the abstract formalism of wavefunction evolution to actual empirical observations via either the Born rule or the collapse postulate--without them you can't point to a single scrap of empirical evidence in favor of unitary evolution!

My reasoning is as follows: yes, a local realistic theory cannot produce all the predictions of standard quantum mechanics, however, the postulates of standard quantum mechanics are mutually contradictory, so you cannot blame local realistic theories for failing to reproduce all predictions of standard quantum theory. So if you question unitary evolution, you also question standard quantum mechanics, therefore you cannot reasonably blame local realistic theories for failing to reproduce all predictions of standard quantum theory. And I can use unitary evolution with the Born rule for just one observable as an operational rule to get empirical evidence in favor of unitary evolution.

Of course if unitary evolution + collapse/Born rule produces a lot of successful predictions, then on the grounds of elegance there seems to be a good basis for hoping that the same unitary evolution that governs interactions between particles between measurements also governs interactions between particles and measuring devices (since measuring devices are just very large and complex collections of particles)...that's why my hope is that a totally convincing derivation of the Born rule from the MWI will eventually be found. But to just say "the Born rule and the collapse postulate violate the sacred principle of unitary evolution, therefore they must be abandoned", and to not even attempt to show how "unitary evolution" alone can yield a single solitary prediction about any empirical experiment ever performed, seems to be turning unitary evolution into a religious creed rather than a scientific theory.

See above

If the predictions of "quantum mechanics" are understood in von Neumann's way, then we can say that local realism is incompatible with the predictions of "quantum mechanics", and that "quantum mechanics" has a perfect track record so far in all experimental tests that have been done (including Aspect-type experiments, although none so far have done a perfect job of closing all loopholes).

You see, thermodynamics also “has a perfect track record so far in all experimental tests that have been done”, however, irreversibility is at odds with dynamics, be it classical or quantum dynamics

If on the other hand you choose to define "quantum mechanics" as unitary evolution alone, then unless you have some argument for why the Born rule should still work as MWI advocates do, your version of "quantum mechanics" is a purely abstract mathematical notion that makes no predictions about any real-world empirical experiments whatsoever.

Again, you can use unitary evolution with the Born rule for just one observable, as an operational rule.

 

[yoda jedi]

100% detection efficiency?
(If you already did it on some post above, you can only write the post number.)

not yet.

There have been experiments that closed the detector efficiency loophole

wrong.



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

..."detection-loophole-freeBell experiment seems possible in the near future"...

 

[akhmeteli]

Let me add (belatedly) that the article mentioned in post 574 of this thread has just been published (you may wish to look at the postprint of the article and the exact reference to it at http://www.akhmeteli.org/akh-prepr-ws-ijqi2.pdf ).

It should be noted that some results of the article have already been significantly improved. For example, the elimination of the matter field from scalar electrodynamics has been done somewhat cleaner. Furthermore, while the extension to spinor electrodynamics in the article is much less general, some surprising new results suggest that the results for scalar electrodynamics can be fully valid for spinor electrodynamics.

 

[JesseM]

here have been experiments that closed the detector efficiency loophole

wrong.



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

..."detection-loophole-freeBell experiment seems possible in the near future"...

Didn't notice this post before. For some examples of experiments with ions that have already closed the detection loophole (without simultaneously closing the locality loophole, as I noted), see here (pdf file) and here.

 

[yoda jedi]

Photonic.

Phys. Rev. A 83, 032123 (2011)
Detection loophole in Bell experiments: How postselection modifies the requirements to observe nonlocality
http://arxiv.org/pdf/1010.1178
http://pra.aps.org/abstract/PRA/v83/i3/e032123

A common problem in Bell-type experiments is the well-known detection loophole: if the detection efficiencies are not perfect and if one simply postselects the conclusive events, one might observe a violation of a Bell inequality, even though a local model could have explained the experimental results. In this paper, we analyze the set of all postselected correlations that can be explained by a local model, and show that it forms a polytope, larger than the Bell local polytope. We characterize the facets of this postselected local polytope in the Clauser-Horne-Shimony-Holt scenario, where two parties have binary inputs and outcomes. Our approach gives interesting insights on the detection loophole problem.


.

 

[akhmeteli]

Let me make a quick update, as the thread drew a lot of interest.

In post 574 in this thread, I announced some results for scalar electrodynamics published by now in the International Journal of Quantum Information (http://www.akhmeteli.org/akh-prepr-ws-ijqi2.pdf) and relevant to this thread. However, the results of that article for spinor electrodynamics (which is more realistic) were much less general and less satisfactory. Since then I obtained some surprising results for spinor electrodynamics and the Dirac equation: http://arxiv.org/abs/1008.4828 (accepted for publication in the Journal of Mathematical Physics), which opened a way for extension of the results of my previous article to spinor electrodynamics in its entirety.

 

[akhmeteli]

I obtained some surprising results for spinor electrodynamics and the Dirac equation: http://arxiv.org/abs/1008.4828 (accepted for publication in the Journal of Mathematical Physics), which opened a way for extension of the results of my previous article to spinor electrodynamics in its entirety.

So here's the link to the published version of the article - http://akhmeteli.org/wp-content/uploads/2011/08/JMAPAQ528082303_1.pdf , and the abstract:

"Three out of four complex components of the Dirac spinor can be algebraically eliminated from the Dirac equation (if some linear combination of electromagnetic fields does not vanish), yielding a partial differential equation of the fourth order for the remaining complex component. This equation is generally equivalent to the Dirac equation. Furthermore, following Schrödinger [Nature (London), 169, 538 (1952)], the remaining component can be made real by a gauge transform, thus extending to the Dirac field the Schrödinger conclusion that charged fields do not necessarily require complex representation. One of the two resulting real equations for the real function describes current conservation and can be obtained from the Maxwell equations in spinor electrodynamics (the Dirac-Maxwell electrodynamics). As the Dirac equation is one of the most fundamental equations, these results both belong in textbooks and can be used for development of new efficient methods and algorithms of quantum chemistry."

 

[akhmeteli]

Another quick update: the extension to spinor electrodynamics (which is more realistic than scalar electrodynamics) has been described in a short article in Journal of Physics: Conference Series ( http://dx.doi.org/10.1088/1742-6596/361/1/012037 - free access):

"2. After introduction of a complex 4-potential (producing the same electromagnetic field as the standard real 4-potential), the spinor field can be algebraically eliminated from spinor electrodynamics; the resulting equations describe independent evolution of the electromagnetic field.

3. The resulting theories for the electromagnetic field can be embedded into quantum field
theories."

The details can be found in the references of the article.

 

[Gordon Watson]

Another quick update: the extension to spinor electrodynamics (which is more realistic than scalar electrodynamics) has been described in a short article in Journal of Physics: Conference Series ( http://dx.doi.org/10.1088/1742-6596/361/1/012037 - free access):

"2. After introduction of a complex 4-potential (producing the same electromagnetic field as the standard real 4-potential), the spinor field can be algebraically eliminated from spinor electrodynamics; the resulting equations describe independent evolution of the electromagnetic field.

3. The resulting theories for the electromagnetic field can be embedded into quantum field
theories."

The details can be found in the references of the article.

NB: To avoid side-tracking this thread, I've reproduced this post at https://www.physicsforums.com/showpost.php?p=3909153&postcount=289 :- I suggest any discussion-arising should be done there. GW

Hi Andrey, and congratulations on the publication of another advance in your work. However, with respect to the passage copied below AND your concern about breaching Bell inequalities, I suggest that you need to carefully distinguish this dichotomy, imho:

The (1) "violation of a Bell inequality" is NOT the same as (2) "falsifying local realism".

I am certain that valid experiments (and good theory) will continue to deliver (1): a violation of Bell inequalities. I am confident that no experiments will ever falsify (2): local realism (properly defined).

To these ends, and to this latter end in particular, I'd welcome your comments on the breaching of Bell inequalities AND the explicit local realism (and any other matter) in https://www.physicsforums.com/showpost.php?p=3905795&postcount=287

PS: As previously discussed, I believe that the BOLD-ed sentence below greatly weakens your work. Me believing it to be a FALSE hope (as opposed to Bell's positive one, as discussed and delivered in the above link).

With best regards,

Gordon
....

From http://iopscience.iop.org/1742-6596/361/1/012037/pdf/1742-6596_361_1_012037.pdf -- "Of course, the Bell inequalities cannot be violated in such a theory. But there are some reasons to believe these inequalities cannot be violated either in experiments or in quantum theory. Indeed, there seems to be a consensus among experts that “a conclusive experiment falsifying in an absolutely uncontroversial way local realism is still missing” [4]. On the other hand, to prove theoretically that the inequalities can be violated in quantum theory, one needs to use the projection postulate (loosely speaking, the postulate states that if some value of an observable is measured, the resulting state is an eigenstate of the relevant operator with the relevant eigenvalue). However, such postulate, strictly speaking, is in contradiction with the standard unitary evolution of the larger quantum system that includes the measured system and the measurement device, as such postulate introduces irreversibility and turns a superposition of states into their mixture. Therefore, mutually contradictory assumptions are required to prove the Bell theorem, so it is on shaky grounds both theoretically and experimentally and can be circumvented if, for instance, the projection postulate is rejected. [Emphasis added by GW: other issues arising not addressed here.]​

NB: To avoid side-tracking this thread, I've reproduced this post at https://www.physicsforums.com/showpost.php?p=3909153&postcount=289 :- I suggest any discussion-arising should be done there. GW

 

[akhmeteli]

NB: To avoid side-tracking this thread, I've reproduced this post at https://www.physicsforums.com/showpost.php?p=3909153&postcount=289 :- I suggest any discussion-arising should be done there. GW

Dear Gordon Watson,

Thank you for your comment. I think it is relevant to this thread as well.

Hi Andrey, and congratulations on the publication of another advance in your work.

Thank you

However, with respect to the passage copied below AND your concern about breaching Bell inequalities, I suggest that you need to carefully distinguish this dichotomy, imho:

The (1) "violation of a Bell inequality" is NOT the same as (2) "falsifying local realism".

I guess this statement is technically correct, as, for example, violations of the Bell inequalities cannot exclude superdeterministic theories.

I am certain that valid experiments (and good theory) will continue to deliver (1): a violation of Bell inequalities.

With all due respect, this is just your opinion, not a fact. For example, there is no loophole-free experimental evidence of violations. I am not ready to concede this point, sorry.

I am confident that no experiments will ever falsify (2): local realism (properly defined).

I would also be surprised to hear about such experiments falsifying local realism, but who knows...

To these ends, and to this latter end in particular, I'd welcome your comments on the breaching of Bell inequalities AND the explicit local realism (and any other matter) in https://www.physicsforums.com/showpost.php?p=3905795&postcount=287

I will look at that thread, but I am not sure I will be able to comment - these are difficult and sometimes controversial issues.

PS: As previously discussed, I believe that the BOLD-ed sentence below greatly weakens your work. Me believing it to be a FALSE hope (as opposed to Bell's positive one, as discussed and delivered in the above link).

From http://iopscience.iop.org/1742-6596/361/1/012037/pdf/1742-6596_361_1_012037.pdf -- "Of course, the Bell inequalities cannot be violated in such a theory. But there are some reasons to believe these inequalities cannot be violated either in experiments or in quantum theory. Indeed, there seems to be a consensus among experts that “a conclusive experiment falsifying in an absolutely uncontroversial way local realism is still missing” [4]. On the other hand, to prove theoretically that the inequalities can be violated in quantum theory, one needs to use the projection postulate (loosely speaking, the postulate states that if some value of an observable is measured, the resulting state is an eigenstate of the relevant operator with the relevant eigenvalue). However, such postulate, strictly speaking, is in contradiction with the standard unitary evolution of the larger quantum system that includes the measured system and the measurement device, as such postulate introduces irreversibility and turns a superposition of states into their mixture. Therefore, mutually contradictory assumptions are required to prove the Bell theorem, so it is on shaky grounds both theoretically and experimentally and can be circumvented if, for instance, the projection postulate is rejected. [Emphasis added by GW: other issues arising not addressed here.]​

[/B]

Again, with all due respect, you offer your opinion, not your reasons.

 

[Gordon Watson]

Dear Gordon Watson,

Thank you for your comment. I think it is relevant to this thread as well.

Thank you

Thanks Andrey, I'm happy to discuss it here, and in detail. [That suggestion came from the concern that a focus on classical probability theory and Malus' Method (i.e., on what is essentially high-school maths and logic; with little more required) would distract from the maths that you're working with in your papers.]

Now, wrt this statement: The (1) "violation of a Bell inequality" is NOT the same as (2) "falsifying local realism", you say:

I guess this statement is technically correct, as, for example, violations of the Bell inequalities cannot exclude superdeterministic theories.

However, understanding the point at issue, you would NOT be able to offer this response; imho!

[EDIT: this emphasised above to clearly identify that the response's reference to "I guess ... technically correct ... cannot exclude super deterministic theories" is inadequate in the face of what can be clearly shown: that a DEFINITE local realistic formulation demolishes your escape clause. That is "I guess ... " to a TRUISM is not acceptable. Agree; or refute the truism, please. /EDIT]

For it can be clearly shown, with neither mystery nor complication, that a DEFINITE local realistic formulation demolishes your escape clause. MOREOVER, the formulation is right in line with Bell's hope: It begins with the acceptance of Einstein-locality (EL). It continues with Bell's hope:

"... the explicit representation of quantum nonlocality [in 'the de Broglie-Bohm theory'] ... started a new wave of investigation in this area. Let us hope that these analyses also may one day be illuminated, perhaps harshly, by some simple constructive model. However that may be, long may Louis de Broglie continue to inspire those who suspect that what is proved by impossibility proofs is lack of imagination," (Bell 2004: 167). "To those for whom nonlocality is anathema, Bell's Theorem finally spells the death of the hidden variables program.³¹ But not for Bell. None of the no-hidden-variables theorems persuaded him that hidden variables were impossible," (Mermin 1993: 814). [All emphasis and [.] added by GW; see https://www.physicsforums.com/showpos...&postcount=287]

Bell (2004): Speakable and Unspeakable in Quantum Mechanics; 2nd edition. CUP, Cambridge.

Mermin (1993): Rev. Mod. Phys. 65, 3, 803-815. Footnote #31: "Many people contend that Bell's Theorem demonstrates nonlocality independent of a hidden-variables program, but there is no general agreement about this."
​

So, this suggests that you are up against a proven fact (and not just an opinion ); this TRUISM:

"The (1) "violation of a Bell inequality" is NOT the same as (2) "falsifying local realism."

... reinforcing a conclusion held by many, for many years.

Next, in response to: "I am certain that valid experiments (and good theory [including current QM]) will continue to deliver (1): a violation of Bell inequalities," you say:

With all due respect, this is just your opinion, not a fact. For example, there is no loophole-free experimental evidence of violations. I am not ready to concede this point, sorry.

The point is this (if you seek to down-play the good theories): VALID EXPERIMENTS already violate Bell's Theorem (with loopholes for the desperate)! Moreover, such loopholes are being reduced almost daily! Why then would better experiments reverse that trend AND suddenly NOT-violate Bell's Theorem? AGAINST the whole history of VALID QM experimentation? Especially WHEN the idealised maths (that you're to examine) show that ideal experiments WILL continue the violation!

To put the position clearly: You will one day concede this point; imho. So why not see what needs be adjusted in your work NOW to avoid this later capitulation with its consequent complications?

I would also be surprised to hear about such experiments falsifying local realism, but who knows...

Good! Do we agree then, that Einstein-locality remains at the core of our personal world-views?

I will look at that thread, but I am not sure I will be able to comment - these are difficult and sometimes controversial issues.

Thanks; that's all that is asked! In an attempt to be helpful wrt to your work; with any and all critiques of my work most welcome.

You write: "But there are some reasons to believe these inequalities cannot be violated either in experiments or in quantum theory." AGAINST which, in effect, the message is: "Please, abandon this false hope!" You respond:

Again, with all due respect, you offer your opinion, not your reasons.

Please: Reasons are clearly given, at the level of high-school maths and logic, here: https://www.physicsforums.com/showpos...&postcount=287

With best regards, Gordon

 

[lugita15]

Gordon, do you agree or disagree with akhmeteli's point that the only way you can have viable local hidden-variable model in the face of a Bell inequality violation (with no experimental loopholes) is if your hidden-variable model is superdeterministic, i.e. violates the no-conspiracy condition?

 

[lugita15]

Hi lugita, DISAGREE: on the understanding that by "super-determinism" you mean "NO free-will on the part of Alice and Bob."

As to "violating the no-conspiracy condition" -- best you spell that out for me, please.

The no-conspiracy condition, which is one of the assumptions used in Bell's proof, states that the result Alice observes by measuring her photon is independent of the angle setting at which Bob measures his photon. This assumption rules out several possibilities at once:
1. The Universe conspires to make Alice and Bob make the exact measurement decisions needed to make Bell's inequality appear violated when it would really not be if Alice and Bob's measurement decisions were totally random.
2. The universe tells the photons what Alice and Bob are going to do, so that the photons can plan their strategy to anticipate the measurement decisions

Etc. Someone who believes in local hidden variables but denies no-conspiracy is called a superdeterminist. Given this, are you one?

Concerning your "classical challenge", I think your time may be better spent trying to understand the core of Bell's reasoning, which is only a few steps of simple logic, rather than focusing on the gory details of his original proof, which discusses things like factorization of conditional probability and integrating over lambda. Why don't you take a look at Herbert's version of Bell's proof, which is simpler by leaps and bounds than Bell's original paper and can thus allow us to identify the locus of your disagreement with Bell.

EDIT: Sorry, I forgot the link:

http://quantumtantra.com/bell2.html

 

[akhmeteli]

Gordon, do you agree or disagree with akhmeteli's point that the only way you can have viable local hidden-variable model in the face of a Bell inequality violation (with no experimental loopholes) is if your hidden-variable model is superdeterministic, i.e. violates the no-conspiracy condition?

Dear lugita15,

I am afraid I have to disagree with your interpretation of my words in the answer to Gordon Watson. I only agreed with GW that

"violation of a Bell inequality" is NOT the same as (2) "falsifying local realism"

, and I mentioned superdeterminism just as an example to explain why I had to agree with GW's statement. I did not say that superdeterminism is "the only way you can have viable local hidden-variable model in the face of a Bell inequality violation (with no experimental loopholes)". I may have conceded this point elsewhere for the sake of argument, but I don't want to take sides on this issue - I just don't know enough about it.

 

[lugita15]

Dear lugita15,

I am afraid I have to disagree with your interpretation of my words in the answer to Gordon Watson. I only agreed with GW that

, and I mentioned superdeterminism just as an example to explain why I had to agree with GW's statement. I did not say that superdeterminism is "the only way you can have viable local hidden-variable model in the face of a Bell inequality violation (with no experimental loopholes)". I may have conceded this point elsewhere for the sake of argument, but I don't want to take sides on this issue - I just don't know enough about it.

Sorry for putting words in your mouth, akhmeteli! Let me state that as my point, then.

 

[akhmeteli]

Sorry for putting words in your mouth, akhmeteli! Let me state that as my point, then.

OK, no problem

 

[akhmeteli]

Now, wrt this statement: The (1) "violation of a Bell inequality" is NOT the same as (2) "falsifying local realism", you say:

However, understanding the point at issue, you would NOT be able to offer this response; imho! For it can be clearly shown, with neither mystery nor complication, that a DEFINITE local realistic formulation demolishes your escape clause. MOREOVER, the formulation is right in line with Bell's hope: It begins with the acceptance of Einstein-locality (EL). It continues with Bell's hope:
So, this suggests that you are up against a proven fact (and not just an opinion ); this TRUISM:

"The (1) "violation of a Bell inequality" is NOT the same as (2) "falsifying local realism."

... reinforcing a conclusion held by many, for many years.

Dear Gordon Watson,

I am afraid I am royally confused :-( I actually AGREED with your TRUISM in my previous post (745), so what are you talking about?

Next, in response to: "I am certain that valid experiments (and good theory [including current QM]) will continue to deliver (1): a violation of Bell inequalities," you say:

The point is this (if you seek to down-play the good theories): VALID EXPERIMENTS already violate Bell's Theorem (with loopholes for the desperate)!

You believe that loopholes are “for the desperate”, but I am afraid this is just your opinion, and I don’t have to agree with such an opinion. For example, even Zeilinger, who is no fan of local theories, calls the loopholes “essential” (you can find the quote in this post: https://www.physicsforums.com/showpost.php?p=1705826&postcount=65 ).

As for “good theory [including current QM]”, I explained in the very first post in this thread why I have problems with this THEORETICAL argument. Briefly: the proof of the possibility of violations of the Bell inequalities in quantum mechanics (which proof is an important part of the Bell theorem proof) typically uses two major assumptions of standard QM: unitary evolution and theory of measurements (e.g., the projection postulate). However, these assumptions are mutually contradictory, as unitary evolution, unlike the projection postulate, cannot provide irreversibility or turn a pure state into a mixture.

Moreover, such loopholes are being reduced almost daily! Why then would better experiments reverse that trend AND suddenly NOT-violate Bell's Theorem? AGAINST the whole history of VALID QM experimentation?

I explained why such reasoning does not impress me in post 34 in this thread: “what’s wrong with the following reasoning: planar Euclidian geometry is wrong because it predicts that the sum of angles of any triangle is 180 degrees, whereas experiments demonstrate with confidence of 300 sigmas or more that the sums of angles of a quadrangle on a plane and a triangle on a sphere are not equal to 180 degrees. Or do you think there is nothing wrong with it? In both cases we are talking about a theorem, remember? If you have not made sure that all assumptions of the theorem are fulfilled simultaneously, you cannot demand that the statement of the theorem hold true.” So, up to now, experiments demonstrate violations only when the assumptions of the Bell theorem are not fulfilled. Until loophole-free violations are demonstrated, I don’t buy your conclusion on violations, sorry.

Especially WHEN the idealised maths (that you're to examine) show that ideal experiments WILL continue the violation!

If you are talking about standard QM, see above (starting with “As for “good theory [including current QM]””). If, however, you are talking about your own model… OK, let us assume for the sake of argument that your model is indeed local and predicts violations. Does this prove that violations are for real? No way, as the status of your model is unknown – I don’t know if your model is correct or not. If your model has the same predictions for all experiments as standard QM, it means it is also self-contradictory. If, however, your model’s predictions are different from those of QM, the experimental status of your model is dubious in the best case.

To put the position clearly: You will one day concede this point; imho. So why not see what needs be adjusted in your work NOW to avoid this later capitulation with its consequent complications?

Maybe I’ll concede this point in the future, for example, if and when new experiments provide results that I do not expect. But right now I don’t see valid reasons to concede it or adjust my work.

Good! Do we agree then, that Einstein-locality remains at the core of our personal world-views?

If you mean locality of special theory of relativity, then yes, if you mean locality of EPR, then perhaps no.

You write: "But there are some reasons to believe these inequalities cannot be violated either in experiments or in quantum theory." AGAINST which, in effect, the message is: "Please, abandon this false hope!" You respond:

Please: Reasons are clearly given, at the level of high-school maths and logic, here: https://www.physicsforums.com/showpos...&postcount=287

I did not study that post in detail, but it looks like you use Malus law as an assumption. I cannot accept this law as a precise one for reasons given in post 41 in this thread (PP and UE there stand for “projection postulate” and “unitary evolution”, respectively.)

 

[akhmeteli]

Dear akhmeteli: Sorry for any confusion on my part. (I've now added to my remark in an attempt to be very clear). Your " I guess ... " response was so highly and incorrectly conditional that I saw no AGREEMENT of the KIND warranted by the data that I referred you to! It is a TRUISM, so please: AGREE unconditionally, or reject it (with grounds)! That's what I was talking about. The days of your response being seen as in any way relevant are passed, imho. That's all that was meant; and REMAINS!

Dear Gordon Watson,

I just don't want to say more about your statement than I said. As for your data, I have looked at it and decided against studying it in detail, as, on the one hand, that would require quite some time, and I have other priorities (I have a day job and three different physics projects on my hands), on the other hand, the data does not look properly published (with all due respect, Physics Essays is not a source I would rely on). Looks like mentors agree, as they have just closed your thread. Again, I don't comment on correctness or incorrectness of your model, but, with all due respect, if you cannot publish it properly, it's not my problem.The world of physics is ruthless.

I stand by my opinion.

No problem. But again, it's just your opinion, not a fact.

OK; so you "dismiss" current QM. That's fine; I simply re-interpret it in the light of the "good theory" that remains: The one that you leave unaddressed and thus intact. The one that is the sole basis for my suggestion that you need to "tweak" your theory and correct (or remove) references to the items that I highlighted.

I dismiss the projection postulate, as it contradicts unitary evolution anyway, but I fully adopt unitary evolution. And I agree, I leave your theory unaddressed (for the above reasons) and intact (as I don't comment on its correctness). Again, even assuming that your theory is correct as a theory, that would not mean that I have to adjust my work, as the experimental status of your theory is unknown (unless its predictions coincide with those of standard QM, in which case your theory is also self-contradictory).

Sorry? But if you do not examine the free data; the data that I suggest leaves these OLD arguments of yours behind; the data THAT STARTS WITH Bell's primary assumptions fulfilled ... well, "sorry" doesn't seem to cut it. A suggestion re "avoidance" would fit the situation better.

As I said, Bell's primary assumptions are mutually contradictory, so if you START with them, your conclusions cannot impress me. And yes, I do avoid studying your theory in detail for reasons given above.

If I sincerely offer a model that might help you correct errors in your papers (as I have done sincerely, and privately, from the start), MAYBE you should revisit high-school maths and logic and check it out. For that's the hint I gave; assuring you it was not very heavy-duty analysis: JUST heavy-duty conclusions .. and heavy-duty consequences for some of your statements.

Again, I tried to explain why I don't see how your material can affect my work. If you don't accept my explanations, just tell me: do experimental predictions of your model fully coincide with those of standard QM?

Just study that data that I offered, please. IT IS certainly beyond your expectations thus far, in our discussions to-date. It is not beyond your ability; nor, as I see it, is it beyond the direction that your research is taking you. (That's the why of why-I'm-here.)

See above.

I mean Einstein-locality. Please: HOW does that differ from (your once again) seeming conditional hedge? Please elaborate on the "locality of EPR" -- for I may have missed something there.

I just don't think we need noncontextual variables.

If I send you some data and you do not study it IN ANY meaningful WAY, what more can I say?

Just this, perhaps:

Every phrase emBOLDed (by me) is wrong, irrelevant or lazy. Which hardly seems fair comment on a model that delivers on Bell's hope for a simple constructive model: one that is (as he surmised) perhaps harshly illuminative.

You may call my phrases wrong and irrelevant, but, with all due respect, you're not my boss, so my laziness is none of your business. As I said, I have other priorities and obligations. Again, I fail to see how your model can affect my work. As for fairness... I owe fairness to my co-authors, who expect me to contribute to our mutual work in a timely manner.

PS: Re Zeilinger: "Expecting that any improved experiment will also agree with quantum theory, a shift of our classical philosophical positions seems necessary. Among the possible implications are nonlocality or complete determinism or the abandonment of counterfactual conclusions. Whether or not this will finally answer the eternal question: “Is the moon there, when nobody looks?” ... is certainly up to the reader’s personal judgement. [Emphasis by GW.]"

The bold-emphasised piece agrees with me. The shift in "classical philosophical positions" is delivered, courtesy of Malus' Method, in the data to which you were directed. It's worth a good hard read.

I cannot reasonably expect "that any improved experiment will also agree with quantum theory" as some assumptions of standard quantum theory (unitary evolution and the theory of measurements) flatly contradict each other. As for your data... I am of no consequence anyway, whereas mentors do not believe your data belongs here. Publish your data properly, then discuss it here. I know first-hand that it is not always easy to publish your work, but nobody else can do that for you. If people are not enthusiastic about our work, it's our problem, not theirs.

 

[akhmeteli]

LOL! The experimental status of my work is exactly that of QM = my work and QM share the same predictions! (I am NOT so radical as to dispute valid experiments and theory. NB: My focus is on Bell's Theorem, which (AFAIK) is NOT a property of quantum theory; Peres text-book (1995: 162) and I in agreement on this point. AND THAT's why I'm encouraging you to reassess your published statements about BT and its impact on your theory. You are bringing into your physics an issue that ... ... ... me leaving you to complete the sentence.)

Self-contradictory? Sorry, not so. That 30 minutes got to be looking like a good investment.

Make it 25 minutes: You might be surprised to see (so-called) "projection" and "unitary evolution" united in my simple equations!

Amazing. In your terms: What you're allowed to say versus what I'm not allowed to question!

Let me STRESS this important point: I am on Bell's side in this matter: and vice-versa, AFAIK. And, to be clear about my advocacy for Bell and QM: I'll back him against your colleagues, supervisors, etc; me taking the view (not lightly) that I am one of Bell's keenest 'disciples', disagreeing (AFAIK) only with a supplementary assumption that he made in arriving at his 'theorem'. An assumption that is not included in the excellent (imho) "primary" assumptions that he began with.

That is: NO contradiction arises if you take Bell's primary assumptions to be: Bell (1964: eqns (1), (2), (3), (12), (13), (14))! And, Yes; I do start with them: for I'm not playing games -- AND I accept Einstein-locality as my starting point, as did Bell (e.g., 1964).



Of course! Fully! As shown in equations (9) and (10). Make it 20 minutes; you've just been told, to the best of my ability.



Andrey: it is well known that any result you like can be drawn from a contradiction. I suggest that the (SEROUS) contradiction that you see (and cite) ARISES from an erroneous interpretation of mathematical terms. I suggest that the reason that I see NO contradiction is that my own work gives me access to a very different (physically significant) interpretation.

So, in closing: the essence of my intended-to-be-helpful message to you (from day one) is this:

1. IF your theory requires you to take the stance on Bell's Theorem that you do, THEN:

2. Imho, your theory is defective. BUT:

3. Imho, it may equally be the case, from my experience, that such a defect might be readily and easily remedied.

4. That's it; that's all; still wishing you the best of good luck with every project,
​

PS: Excuse any fun above; it was late; I tend to mix fun and physics; and I love wrestling with, and very much appreciate, your feisty spirit.

Dear Gordon Watson,

Thank you for your reply.

You did clarify your position. If I understood you correctly, you believe that

1) your theory's experimental predictions fully coincide with those of standard quantum mechanics;

2) your theory is not self-contradictory and unites "projection" and "unitary evolution".

Let me tell you what. I wrote nothing or almost nothing original about the Bell theorem in my published articles. I just had to define my position, as the issue of the Bell theorem would have arisen anyway.

In particular, I wrote, following other authors, that:

1) Unitary evolution and quantum theory of measurements (e.g., the projection postulate) are mutually contradictory.

2) Both unitary evolution and the projection postulate are used to prove that the Bell inequalities can be violated in standard quantum mechanics (SQM).

Neither of these points is new or belongs to me. If your theory adopts both unitary evolution and the projection postulate of SQM, but not its contradiction, then you seem to have solved the 80-year-old measurement problem of quantum mechanics ( http://plato.stanford.edu/entries/qt-measurement/ and published work cited there, such as Albert's, or Bassi/Ghirardi's ). I congratulate you with this achievement, and suggest that you don't waste time on me (I was dead serious saying that I am of no consequence anyway) and publish your result (it does not matter if I see contradiction or not; what matters is that the measurement problem in quantum mechanics is generally recognized as such, no matter if I am dead or alive). Until properly published, your great result does not belong here, and, with all due respect, on the one hand, I don't believe your claims, on the other hand, I don't want to and don't have to check your derivation.

Let me assure you that I have no intention to offend you. Let me emphasize that I am not an expert in the Bell theorem. If I had more time to go into details, I would have started with reading (more) published articles of other people who defend local realism against the Bell theorem :-). Somehow they are able to publish their work, although, in general, local realism is not very popular:-).

 

[lugita15]

Unitary evolution and quantum theory of measurements (e.g., the projection postulate) are mutually contradictory.

Why do you think they're mutually contradictory? They have been used together for nearly a century, and have produced amazing theoretical and experimental results. Now you may believe that the combination of the two is philosophically problematic, because of the measurement problem, but logically they seem to go together just fine. There are a variety of interpretations of QM that embrace or explain these two features of quantum mechanics: Copenhagen, de Broglie-Bohm, Many Worlds, etc. Are you saying that all of these views are inconsistent/incoherent?

 

[scijeebus]

There isn't much of a violation of anything, things in quantum mechanics aren't really causally related, they are related via correlation. Because of this, entanglement doesn't have to violate that things are independent from us, because before measurement the particles are still entangled, otherwise we wouldn't be able to disentangle them. When we disentangle particles, there is no causality of information being sent between points. When particles are entangled, the plural form is meaningless, they are the same particle by the properties of correlation, and it is this same correlation that breaks the entanglement, for when particles become dis-entangled, all that is really happening is their probabilities adjust to correlate to specific but different values, and that's it. This same property of correlation also explains the quantum erasure. Paths aren't ever destroyed, the probability of an electron in a double slit experiment just correlates to that of a single path upon measurement.
Of course, there we can't be 100% sure of anything in the first place because we aren't ever even observing photons, we are observing the electrical impulses in our brain.
But, because things aren't causally connected, there isn't a causation that can be violated. This leaves room for the principal of locality but also for realism because things can still be logically correlated to show a sequence of events.

 

[akhmeteli]

Why do you think they're mutually contradictory?

Because, for example, unitary evolution cannot provide irreversibility or turn a pure state into a mixture, whereas the projection postulate mandates just that.

They have been used together for nearly a century, and have produced amazing theoretical and experimental results.

Thermodynamics has been used for much longer than a century and has produced amazing theoretical and experimental results. However, there is a contradiction between themodynamics and its underlying theories - classical or quantum mechanics: for example, unitary evolution cannot provide irreversibility, which is a basic assumption of thermodynamics.

Furthermore, the Bell theorem drives the assumptions of standard quantum mechanics to their extremes, which are currently inaccessible in experiment - loophole-free experiments are not possible right now (I am not saying that they won't be possible tomorrow, or in a year, or in ten years from now) - so that may be a reason why the theorem's conclusions have not been disproved experimentally yet. I do appreciate that loophole-free experimental demonstration of violations of the Bell inequalities can be achieved in the future, but we are living and discussing right now. As they say, it is difficult to make forecasts, especially for the future:-)

Now you may believe that the combination of the two is philosophically problematic, because of the measurement problem, but logically they seem to go together just fine.

I did not say anything about philosophical problems, and logically they are mutually contradictory (see above). I am not trying to sell you something that I invented or something that was invented yesterday - the contradiction has been recognized 80 years ago by von Neumann - see more details at http://plato.stanford.edu/entries/qt-measurement/ or at http://en.wikipedia.org/wiki/Measurement_problem and references there.

There are a variety of interpretations of QM that embrace or explain these two features of quantum mechanics: Copenhagen, de Broglie-Bohm, Many Worlds, etc. Are you saying that all of these views are inconsistent/incoherent?

Not exactly. I am saying that standard quantum mechanics is indeed inconsistent (there are many versions of Copenhagen interpretation, so I cannot be sure this is true for all of its versions).

In de Broglie-Bohm interpretation, the projection postulate (PP) is just an approximation (see, e.g., Demystifier's post https://www.physicsforums.com/showpost.php?p=2167542&postcount=19 - he wrote dozens of articles on dBB interpretation. If you need, I think I'll be able to find other quotes confirming that). If it's an approximation, not a rigorous result, on the one hand, I cannot say that dBB is inconsistent, on the other hand, I don't need to waste my breath trying to prove that PP is, strictly speaking, incorrect.

As for Many Worlds, although some people state that the measurement problem has been solved in that interpretation, this statement is not generally recognized, as far as I understand. While there is no wave function collapse in that interpretation, "There is a serious difficulty with the concept of probability in the context of the MWI." (plato.stanford.edu/entries/qm-manyworlds ).

 

[akhmeteli]

I believe (1), (2) and (3). That is:

(1) the theory's experimental predictions fully coincide with those of standard quantum mechanics;

(2) the theory is not self-contradictory;

(3) the theory unites "projection" and "unitary evolution".

I am certain re (1) and (2). However (3) uses terms that are not mine.

Yeah, and (3) has some nasty implications. I emphasized in this thread that (3) immediately introduces nonlocality: let us consider two particles in a singlet state; however far apart they are, as soon as you measure a spin projection of one of them, the spin projection of the second particle immediately becomes definite. I don't think this can be compatible with locality (if you assume free will). So maybe you should not accept the projection postulate - it is not compatible with unitary evolution anyway.

As for formal publication in a recognised journal: I've given up on that and will now direct my efforts toward on-line publication via sites that give such as me a go. Where helpful people engage with you in the strongest possible terms; and there are no concerns re loss of face, etc.

People make different decisions and take different approaches, depending on their circumstances. Nobody knows which approach is right or wrong. For example, nightlight apparently decided against trying to publish his results, but those results outlined in forums were extremely important for me, and I cited in my articles.

PS: My first supporter, a Russian-born physicist in USA, told me: "You'll never be published; you have no sponsor; someone to get the credit for discovering you." This was the truth for 9 years. But under his terms, my "sponsor" from 1998 is a former student and close associate of Louis de Broglie! A nicer person you should never expect to meet; I trust there's one in your work somewhere.

I don't have any "sponsor" (as far as I know:-) )

I wish you every success

 

[akhmeteli]

Andrey, I'm confident that you and I (and Penrose; and any others in your camp) can come to a NICE resolution of seeming differences. I am certain that you and I will come to agreement: the form of that agreement maybe depending on your definition of the terms in "contradiction"...!

SO, please, to ensure there's no misunderstanding:

Please complete these sentences in adequate detail (referring to sound QM text-book sources** at least once, if possible) to ensure that we start on the same page. If you refer to a "state" please be sure to explain what you mean by that term.

PP: "By the 'projection postulate' I mean ... ... ."

UE: "By 'unitary evolution' I mean ... ... ."

I expect to show that there's a very simple resolution of the "apparent" contradiction: via that eqn (11) = (11a) for Alice + (11b) for Bob. The emphasised bits above being reminders of what I'll be fixing.

A big claim? Maybe; but we'll see: We cannot both be right; I'm here to learn; and it just might help you remove those "offending" (imho) comments from your future papers.


** I thought I might help, from Peres textbook (1995) but look at this: Subject Index, Page 442: projection postulate 442!


With best regards, Gordon

Dear Gordon Watson,

Unfortunately, I just don’t have time to write the exact definitions for you. Shortly (and cutting some corners, which is important),

1) The projection postulate states that after a measurement of some observable the system is in an eigenstate of that observable with the same eigenvalue.

2) Unitary evolution is the standard evolution of a quantum system described, e.g., by the Schroedinger equation.

I don’t need to define what “state” is because the following is actually important (again, I am cutting some corners): according to the projection postulate, if one measurement gave a certain result, another measurement conducted immediately after the first one will give the same result with probability 1. And this is incompatible with unitary evolution.

If you are not happy with the above, let me offer the following. I agree with the more precise definitions on the first two pages of the article by Bassi/Ghirardi (Phys. Lett., A275 (2000) p.373). You may find it at http://arxiv.org/abs/quant-ph/0009020 as well (it’s 3 pages there). However, what I call “projection postulate”, they call “packet reduction postulate”, and what I call “unitary evolution”, they call “quantum evolution” or simply “Schroedinger equation”. They explain in this article how these two assumptions of standard quantum mechanics are mutually contradictory (although this contradiction was discussed by von Neumann 80 years ago). The Bassi/Ghirardi article is well-known and respected (see, e.g., http://plato.stanford.edu/entries/qt-measurement/ ).

In general, nothing that I am saying about this contradiction is new or belongs to me. If you claim there is no such contradiction, you may publish a refutation of Bassi/Ghirardi and von Neumann. However, with all due respect, I am not ready to read your unpublished texts with such claim. If, however, you quote some reputable source with such refutation, I'll try to look at it, if that does not require too much time.

 

[Ilja]

I believe you’ll agree that elimination of LR is an extremely radical idea. You may also agree that the burden of proof is much higher for extremely radical ideas. We are not talking about a 40-dollar parking ticket. This idea turns philosophy upside down.

I disagree. Philosophy can, without any problem, go back to their state of 1900. At this time, no philosopher had a problem with the speed of Newtonian gravity being greater than c.

It is the naming convention "local realism" which is highly misleading here. It strongly suggests that one should give up realism. Then, the second alternative, named "local", also sounds as if there has to be given up something which was always assumed to be true, if in fact it is only Einstein causality which has to be given up, which can be done without any philosophical problem simply by accepting a preferred frame and good old Lorentz ether.

And a simple and nice interpretation of quantum theory is also available with de Broglie-Bohm theory.

 

[audioloop]

.


of course, just there is no reality......:zzz:

 

[Ilja]

As I mentioned at the end of post #581, there is a theoretical loophole in Bell's proof due to the implicit assumption that each measurement yields a unique outcome, so with a many-worlds-type interpretation you could have a local model consistent with observed violations of Bell inequalities in experiments with all the experimental loopholes closed:

Of course Bell uses common sense and probability theory in its standard meaning. In MWI, I do not see that probability theory makes any sense.

Why this mysticism is named realistic is beyond my understanding. Whatever the realistic theory, it should be clear for me that I really exist. But I see no way to identify myself with a wave function defined over the space of all possible configurations of the whole universe - or, more accurate, over some unspecified space, because naming points of this space "configurations" does not make sense.

 

[jtbell]

Uh... Ilja, did you notice the dates on the posts that you replied to?

 

[akhmeteli]

I disagree. Philosophy can, without any problem, go back to their state of 1900. At this time, no philosopher had a problem with the speed of Newtonian gravity being greater than c.

Let me just note that even Newton "had a problem with the speed of Newtonian gravity being greater than c" - http://plato.stanford.edu/entries/Newton-philosophy/#ActDis

It is the naming convention "local realism" which is highly misleading here. It strongly suggests that one should give up realism. Then, the second alternative, named "local", also sounds as if there has to be given up something which was always assumed to be true, if in fact it is only Einstein causality which has to be given up, which can be done without any philosophical problem simply by accepting a preferred frame and good old Lorentz ether.

You think Einstein causality has to be given up, I am just saying this is a strong statement, which needs very definite experimental proof. My understanding there is no such proof yet, as there is no evidence of faster-than-light communication or loophole-free evidence of violations of the Bell inequalities.

And a simple and nice interpretation of quantum theory is also available with de Broglie-Bohm theory.

I could agree with simple, but not with "nice". Of course, "nice" is subjective, but it looks like the majority does not think it's "nice". Mind you, I highly value the de Broglie - Bohm interpretation, as, correct or wrong, it shows us that some no-go theorems have unreasonable assumptions.

 

[jambaugh]

Cough! Sneeze! (Pardon me, it's just the dust from opening up this old thread.)
Some points.

If you look at the unitary evolution of a composite system wherein two components interact in such a way as to become correlated (entangled) then consider the partial trace over one component system the density operator for the other system will appear to have evolved non-unitarily. Indeed it will have shown an entropy change. The whole system evolved unitarily and yet when you consider only part of the system you must use a non-unitary description of the part. This is by no means a "contradiction" or a mystery. The act of observing a system is an act of interacting with the system via an episystemic element not represented in the dynamics, the observer mechanism is by its nature correlated with the system (the physical record of the measurement is correlated (entangled) with the system itself.) What is more the nature of measurement is thermodynamic, there is of necessity entanglement of other variables with a heat dump.

There is no "gotcha!" contradiction in the disparate descriptions of unitary evolution between measurements and non-unitary description of measurements.

As far as rejecting local realism is concerned, there is a tendency to assume rejecting "reality" somehow a great leap when it is in fact the acceptance of reality which is the leap, the extraordinary assertion requiring extraordinary proof. Specifically the acceptance of the assumption of an objective state of reality.

The alternative is not a nihilistic unreality but rather a framework of material phenomena which does not require the platonic idealism of a universe of objects. Things actually happen whether we are here to see them or not. Since we are here we describe them as phenomena, formulate a theory of cause and effect, utilize probabilistic descriptions of outcomes given the impossiblity of our omniscience, and update our descriptions (discontinuously) when we update our knowledge (discontinuously) through observation...
and when phenomena occur in sufficiently large aggregate form we can build a functionally useful symbolic model we call objective reality. Indeed our brains evolved the means to imagine a state of reality because it was functionally useful for day to day interactions at our scale of experience. But it is hubris in the extreme to insist that the actuality around us must conform in its fundamental nature to the objective reality we model in our minds.

Start with the definition of science as an epistemological discipline and you will see what is fundamental, the empirical observation not the objective state. Now formulate a theory of nature based on this fundamental action, what we may observe and how observations correlate. Maximize our ability to represent knowledge, even partial knowledge by expressing probabilistic correlations between outcomes of measurements. Quantum mechanics is such a theory. There is no contradiction nor ambiguity of meaning in this framework.

It is only when one insists that we can go beyond science and give meaning to objective models beyond their link to scientific knowledge in the form of successful prediction that one finds contradiction. There is a fork in the road, one way leads to classical reality with its infinite precision and the other way leads to more accurate predictions of quantum actuality. Pick your path but do not insist that the roads must meet up further down the line.

The format of a theory which best fits observed phenomena and best holds to the principles of science is one of local actuality, QM with Copenhagen ["lack of further ontological"] Interpretation. Reality be damned!

 

[Ilja]

Let me just note that even Newton "had a problem with the speed of Newtonian gravity being greater than c" - http://plato.stanford.edu/entries/Newton-philosophy/#ActDis

That's about a completely different issue - it is the "without a mediation" which is problematic there, not the speed of the mediation.

You think Einstein causality has to be given up, I am just saying this is a strong statement, which needs very definite experimental proof. My understanding there is no such proof yet, as there is no evidence of faster-than-light communication or loophole-free evidence of violations of the Bell inequalities.

If you want to wait for loophole-free experimental tests of Bell inequalities - fine, I have no problem with this. In this point, I'm in agreement with the mainstream and don't wait myself for them, but that's clearly a personal choice.

So what is worth to be discussed are only the consequences of violations of Bell inequalities. If you agree that in this case Einstein causality has to be given up, fine. If not, explain.

I could agree with simple, but not with "nice". Of course, "nice" is subjective, but it looks like the majority does not think it's "nice". Mind you, I highly value the de Broglie - Bohm interpretation, as, correct or wrong, it shows us that some no-go theorems have unreasonable assumptions.

I think the majority does not like it because it destroys Lorentz covariance, which is highly valued by the majority. If one accepts that it is dead on the fundamental level, and survives only for observables, if Bell's inequalities are violated, then the situation looks quite different. Then the most non-beautiful element seems that the whole wave function is part of the ontology.

 

[Ilja]

and when phenomena occur in sufficiently large aggregate form we can build a functionally useful symbolic model we call objective reality. Indeed our brains evolved the means to imagine a state of reality because it was functionally useful for day to day interactions at our scale of experience. But it is hubris in the extreme to insist that the actuality around us must conform in its fundamental nature to the objective reality we model in our minds.

Of course, the model in our mind is not the reality itself, but only a hypothesis how it might be, which is, moreover, extremely simplified.

But the scientific principle of realism, that a theory which gives a realistic model of what happens is preferable to a pure tool which makes predictions without explanations is worth to be defended.

Start with the definition of science as an epistemological discipline and you will see what is fundamental, the empirical observation not the objective state.

I disagree. The ability to predict observation may be the motivation, the point which makes science a useful tool for survival and scientific thinking an advantage in evolution. And observation is an important tool for testing theories.
But none of this is fundamental to the scientific method. The fundamental thing in the scientific method is the theory - a hypothesis which is not derived from something else, but is a base for deriving everything else, and even for interpretating observations.

Now formulate a theory of nature based on this fundamental action, what we may observe and how observations correlate. Maximize our ability to represent knowledge, even partial knowledge by expressing probabilistic correlations between outcomes of measurements. Quantum mechanics is such a theory. There is no contradiction nor ambiguity of meaning in this framework.

But it is not satisfactory. By the way, every scientific theory is much more than knowledge about observed correlations - it is the general hypothesis that some essential properties of these past observations will be repeated in future observations as well.

It is only when one insists that we can go beyond science and give meaning to objective models beyond their link to scientific knowledge in the form of successful prediction that one finds contradiction. There is a fork in the road, one way leads to classical reality with its infinite precision and the other way leads to more accurate predictions of quantum actuality. Pick your path but do not insist that the roads must meet up further down the line.

There is no such fork. Quantum theory is compatible with classical realism. And it is not the aim of classical realism to reach infinite precision.

 

[bohm2]

You think Einstein causality has to be given up, I am just saying this is a strong statement, which needs very definite experimental proof. My understanding there is no such proof yet, as there is no evidence of faster-than-light communication or loophole-free evidence of violations of the Bell inequalities.

I'm sort of confused. Irrespective of Bell's, doesn't PBR rule out any Einstein-type psi-epistemic model? The PBR theorem does make a few assumptions (e.g. no superdeterminism, etc.). So what are the particulars why you disagree with Leifer's point here below regarding the implications of PBR? Do you think this PBR no-go theorem also has some unreasonable assumptions?

As emphasized by Harrigan and Spekkens, a variant of the EPR argument favoured by Einstein shows that any psi-ontic hidden variable theory must be nonlocal. Thus, prior to Bell's theorem, the only open possibility for a local hidden variable theory was a psi-epistemic theory. Of course, Bell's theorem rules out all local hidden variable theories, regardless of the status of the quantum state within them. Nevertheless, the PBR result now gives an arguably simpler route to the same conclusion by ruling out psi-epistemic theories, allowing us to infer nonlocality directly from EPR.

PBR, EPR, and all that jazz
http://www.aps.org/units/gqi/newsletters/upload/vol6num3.pdf

 

[jambaugh]

Of course, the model in our mind is not the reality itself, but only a hypothesis how it might be, which is, moreover, extremely simplified.

But the "reality that is"is fundamentally unknowable in and of itself. You can utilize clairvoyance to "see reality" you can only observe phenomena. So any assertion you make about reality including its "reality" is an article of faith, outside the scope of science, or is understood as a tentative model, not to be taken too seriously. That is not to say that "reality as a model" is not a very useful means to encapsulate systems of coherent phenomena on the larger scale. (I have hardwood floors, red oak to be specific.) But again as I said, in science the empirical act is more fundamental (that is fundamental in a definitional sense, if you adopt an ontological bias then you of course define "fundamental" ontologically.)

But the scientific principle of realism, that a theory which gives a realistic model of what happens is preferable to a pure tool which makes predictions without explanations is worth to be defended.

Preferable by whom? Science is a discipline not a moral code. You may prefer realism but I find that it contradicts QM + locality. Locality of causal actions can be expressed in a language of actions without invocation of objective states, (excepting of course the pragmatic state language of the classical scale instruments of measurement.)

What we have heuristically sought in scientific theories are theories which reduce the number of free assumptions. One can see how this typically follows from invoking of relativity principles. Relativity of time gives us SR and GR and space-time unification. Relativity of reality gives us QM and a subtle unification of dynamics and logic(information).

I disagree. The ability to predict observation may be the motivation, the point which makes science a useful tool for survival and scientific thinking an advantage in evolution. And observation is an important tool for testing theories.

It is more than just an important tool, it is the only arbiter of correctness of theories. Given this then the only components of a scientific theory are those necessary to formulate predictions. The luminiferous aether was a component for theories of light and had its final form in Maxwell's mechanical model. It however is unnecessary to the theory and so Einstein dispensed with it reformulating the theory sans aether.

Now we could formulate a theory in the form of a catalog of past predictions and contexts and simply predict based on pattern matching. That would be a perfectly valid scientific theory (like alchemists with recipes for producing effects). However the better theory builds up a structure of composite phenomena, equivalences of actions, all too based on our empirical experience. We trim down the multiplicities of catalogued context/predictions into principles. (and at the classical scale a reality model is ideal, but it is the virtue of that model which defines the classical scale!)

But none of this is fundamental to the scientific method. The fundamental thing in the scientific method is the theory - a hypothesis which is not derived from something else, but is a base for deriving everything else, and even for interpretating observations.

So I can theorize all day and I'm doing science? No. Science occurs in the laboratory, or at the very least in the "gedankin lab" where we consider the potentially observable predictions.

But it is not satisfactory.

Its failure to satisfy you is not relevant. Please explain what other value system than your personal aesthetic needs to be satisfied.

By the way, every scientific theory is much more than knowledge about observed correlations - it is the general hypothesis that some essential properties of these past observations will be repeated in future observations as well.

Yes quite right but saying an observation will be repeated is asserting a correlation (over time).

There is no such fork. Quantum theory is compatible with classical realism. And it is not the aim of classical realism to reach infinite precision.

Is not! (Is to!) Is not! (Is too!)...
Ok, then let me explain. 1. Assert a classical realism underlying quantum phenomena, 2. Assert the predictions of QM, 3. Assert there are two systems of observables that can be kept causally isolated by suitable control of the environment (dynamics), 4. QM asserts, (and prescribes how) you can entangle these two independent systems, let them evolve in the asserted isolation and then observe Bell inequality violation upon multiple repetition of this procedure. Since you can derive Bell's inequality purely from the assumption of objective a-priori states you have a contradiction. The RAA proof is that it is absolutely impossible to ever isolate two systems (or QM's predictions must be violated.) It doesn't matter whether you are using the locality hypothesis as the means of isolation. Not two degrees of freedom can every be independently measured unless you reject the reality component of Bell's local reality hypothesis. To retain reality one must assert that every measurement of every observable can causally affect the measurement of every other observable. Try to retain reality (and QM's predictions) and one is no longer measuring the state of objective systems and reality (as something connected to what we empirically experience) breaks down anyway.

There is a third alternative to objective states vs nihilism. I am not preaching nihilism (nothing really exists). There is an actuality, a universe of acts and actions, of "happenings" out there independent of our minds. But I assert that it is an error to invoke "state of reality" format thinking i.e. classical realism a priori when describing this actuality. It is appropriate at the macro scale but not at the micro scale of elementary phenomena.

 

[Ilja]

But the "reality that is"is fundamentally unknowable in and of itself. You can utilize clairvoyance to "see reality" you can only observe phenomena. So any assertion you make about reality including its "reality" is an article of faith, outside the scope of science, or is understood as a tentative model, not to be taken too seriously.

Agreement so far - our models are tentative.

Preferable by whom? Science is a discipline not a moral code. You may prefer realism but I find that it contradicts QM + locality. Locality of causal actions can be expressed in a language of actions without invocation of objective states, (excepting of course the pragmatic state language of the classical scale instruments of measurement.)

Feel free to prefer what you like - I will not object if you prefer astrology or believe in invisible pink unicorns. I will also not object if you prefer things which can be expressed in "a language of action". In my opinion, the last will be preferred by revolutionary activists. But I don't see any connection between a language of action and the scientific method.

The central object of the scientific method are scientific theories. Even if they are always only hypotheses. But you cannot do anything in science without relying on theories. You have no idea which experiments may be interesting - the interesting ones are those which allow to test some theories. You cannot make any predictions without theories. You cannot even interpret what you see without a lot of different theories.

What we have heuristically sought in scientific theories are theories which reduce the number of free assumptions. One can see how this typically follows from invoking of relativity principles. Relativity of time gives us SR and GR and space-time unification. Relativity of reality gives us QM and a subtle unification of dynamics and logic(information).

It is nice that you recognize that there are other criteria than observation to prefer some theories - the number of free assumptions, for example. But your examples are quite strange. SR has not been given by any relativity principle, the relativity principle was only part of one particular formulation of SR. SR and GR are useful theories even outside the spacetime interpretation, which is only one possibility to interpret them. QM also has not been given by any "relativity of reality". It was only the popularity of positivism at that time which has made the positivistic Kopenhagen interpretation the most popular one. And there is no unification of dynamics and logic.

It is more than just an important tool, it is the only arbiter of correctness of theories.

If at all, they are the arbiter of incorrectness. But there are other such arbiters - logical inconsistencies, infinities in the predictions, the failure to make testable predictions, and the introduction of unnecessary entities.

Given this then the only components of a scientific theory are those necessary to formulate predictions. The luminiferous aether was a component for theories of light and had its final form in Maxwell's mechanical model. It however is unnecessary to the theory and so Einstein dispensed with it reformulating the theory sans aether.

Einstein has recognized very well that constructing such mechanical models is very useful. His argument was that this construction has not been successful, and that's why should be given up.

It was the failure of the attempts to construct reasonable models of the ether which was the only difference to similar constructions in atomic theory of matter.

Now we could formulate a theory in the form of a catalog of past predictions and contexts and simply predict based on pattern matching. That would be a perfectly valid scientific theory (like alchemists with recipes for producing effects).

But nonetheless only a hypothetical theory, based on the quite nontrivial hypothesis that some accidentally observed pattern is not accidental.

But none of this is fundamental to the scientific method. The fundamental thing in the scientific method is the theory - a hypothesis which is not derived from something else, but is a base for deriving everything else, and even for interpretating observations.

So I can theorize all day and I'm doing science? No. Science occurs in the laboratory, or at the very least in the "gedankin lab" where we consider the potentially observable predictions.

Of course, not every theorizing is science. But, with this in mind, yes you can. Some of the greatest scientists have never made experiments. That's simply subdivision of labor.

Its failure to satisfy you is not relevant. Please explain what other value system than your personal aesthetic needs to be satisfied.

I'm not a moralist, feel free to believe in unicorns or the language of action.

Its my personal preference that I like to do science. And I think that realism is a basic principle of science, and certainly much more fundamental than a particular symmetry of some particular scientific theory.

Of course, a particular symmetry is very useful for developing other theories - if, by accident, the known symmetry of an already well-known theory appears to be the same as that of a yet unknown theory, the guess that the symmetry will be the same is extremely helpful for developing that theory. Last but not least, if the symmetry of a theory has been correctly guessed, this gives very much.

Realism in itself does not give that much for the particular design of a single theory - it is not very restrictive, leaves too much freedom in the construction of particular theories. But what will be the consequence of giving it up? It means to give up the search for the real causes of the observed phenomena. Science will be reduced to the level of astrology - if the predictions of astrology would be a little bit more successful, it would be completely fine as science. The difference between astrology and science - that science gives realistic explanations - would disappear.

1. Assert a classical realism underlying quantum phenomena, 2. Assert the predictions of QM, 3. Assert there are two systems of observables that can be kept causally isolated by suitable control of the environment (dynamics), 4. QM asserts, (and prescribes how) you can entangle these two independent systems, let them evolve in the asserted isolation and then observe Bell inequality violation upon multiple repetition of this procedure. Since you can derive Bell's inequality purely from the assumption of objective a-priori states you have a contradiction. The RAA proof is that it is absolutely impossible to ever isolate two systems (or QM's predictions must be violated.) It doesn't matter whether you are using the locality hypothesis as the means of isolation. Not two degrees of freedom can every be independently measured unless you reject the reality component of Bell's local reality hypothesis. To retain reality one must assert that every measurement of every observable can causally affect the measurement of every other observable. Try to retain reality (and QM's predictions) and one is no longer measuring the state of objective systems and reality (as something connected to what we empirically experience) breaks down anyway.

Given that with dBB there exists a quite simple realistic interpretation of QM, which has far less conceptual problems than other interpretations, your problem is clearly exaggerated. To reach independence is, of course, a little bit more problematic once you accept that in entangled states there exists the possibility of causal influences faster than light. But so what? Conceptually the situation was not better in Newtonian gravity.

There is a third alternative to objective states vs nihilism. I am not preaching nihilism (nothing really exists). There is an actuality, a universe of acts and actions, of "happenings" out there independent of our minds. But I assert that it is an error to invoke "state of reality" format thinking i.e. classical realism a priori when describing this actuality. It is appropriate at the macro scale but not at the micro scale of elementary phenomena.

Feel free to develop a reasonable mathematical model for this. That means, something which allows to distinguish theories which follow your scheme from astrology.

Or, alternatively, embrace astrology as a reasonable scientific theory, which has only one minor problem, that its statistical predictions have not been corroborated by observations - a point where, by the way, many people disagree.