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

[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.

 

[audioloop]

...but rather a framework of material phenomena = reality

......:zzz:

 

[harrylin]

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.

There is a colossal difference between "greater than c" (which conforms with "LR") and infinite speed (which does not conform with "LR"). I searched but could not find a claim by Newton that the speed of gravity is infinite (I can imagine that he overlooked it, or that he assumed it to be so great as not to matter), and I don't know of any philosopher of around 1900 who did think that such a proposition is no problem. Can you cite one? (I only ask for one, no need for all).

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 [..]

I find Einstein's own formulation, "spooky action at a distance" much better: for it relates to the implausible infinite speed of QM as well as to the implausible infinite and unfailing working range of QM, independent of distance. Can the De Broglie's model account for that??

[..] 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. [..].

Yes, I agree. All experiments that I looked into so far may be understood to work by exploiting loopholes (or even big holes). By now I regard a "loophole free" experiment in the same way as an experiment that "breaks the PoR" - I won't wait for it.

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

It remains a hot topic; but perhaps this thread is getting to long... Need for an index!

 

[jambaugh]

......:zzz:

Just because you can use (at the classical scale) a reality model as your framework of material phenomena doesn't mean it is the best/only framework.

Phenomena = acts and actions (including e.g. observations measurements dynamic evolutions, system projection/preparation interaction et al.). Only with the algebra of actions is categorical is an object model appropriate.

The point to understand is that there is a class of languages broader than nominative languages. You can use Whitehead's nomenclature of object language and process language, but I prefer to say action language. We use an object language classically but we can recognize quantum mechanics as a action language. The semantic atoms are acts rather than objects.

Now there is a clear means of expressing objects in an action language by means of identities (in the sense of category theory). But to express actions in an object language you must restrict yourself to actions mapping object to object. This is a problem (as with Zeno's paradox). Action languages are a proper superset of object languages. There are more meaningful statements you can make in an action language (at the same level of abstraction) than you can make in an object language. (one can always construct a object language one higher level of abstraction up, objectifying the reference to acts, e.g. "running" as a noun. Note that this is what happens when we reify the wave function and it is a form of Platonism.)

What this boils down to (and where it is relevant to this topic) is that recognizing quantum mechanics as an action language we need no further interpretation when we interpret the symbolism in terms of phenomenological acts. "prepare system, dynamically evolve, selectively detect, measure", "compose actions" <--> "bra" "U" "ket", "X", "AB=C".
It is the person trapped in object language thinking that must insist that these actions only terminate in objective states.

The "reality" in QM is relativized. You can work in a perfectly valid classical logic of states if you restrict your actions to only include a commuting subset of observables. Changing to a distinct subset of observables defines an alternative transformed "reality frame", just as you transform between moving observers and get a different "now" frame in SR. Just as with SR the transition in thinking from absolute to relative is difficult and many become intransigent insisting it is just wrong because they can't let go of their intuition of absolutes.

You see this in the various "disproofs of einstein" which demonstrate that we can get Einstein's predictions by overlaying a whole set of unobservable structure namely the aether.
Einstein rejected the aether because the predictive theory showed it to be fundamentally unobservable.

Reality qua reality is fundamentally unobservable. We observe through acts of measurement not immediate intimate clairvoyance into the state of reality as it is. This barrier is the same as the barrier in SR of observing distant events only through propagating intermediate causal phenomena (light or gravity or bouncing balls or something). In imagining a birds eye view of distant phenomena we imagine and develop an intuition of absolute simultaneity when we must deduce simultaneity from the phenomena of causal signals. Similarly we must deduce states of reality (at the classical scale) from the phenomena of measurements we make. When we push it to the extreme observables significantly fail to commute just as in SR the boosts fail to commute and we can no longer thing of velocities as additive (+ being a commuting product).

When in an action language actions fail to commute we loose the presumption that the quantities they change add. In QM it is the probabilities that cease to be an additive measure over a state space. You get Bell inequality violation which can only be resolved satisfactorily by rejecting the underlying absolute structure. With SR it was the fiber bundle of spatial universe fibers over the base of times, (the spatial universes being the set of simultaneous events in the universe), and we reject the underlying absolute structure of universal time. In QM you loose the fiber-bundle structure of logical values over the base of possible states of reality. In both cases you get a relativity principle and a unified composite structure. In SR it is unified space-time and in QM it is a unified manifold of possibilities. In SR we see mixing of space and time as we change frames and in QM we see the mixing of "reality" and "logic" that becomes probability and is though of as quantum uncertainty. It is a mixing of "reality" and "possibility" which manifests as probability.

What you must then learn to deal with is a limited "relative reality" and a whole lot more which doesn't fit into anyone reality frame just as in SR you have to deal with relative simultaneity and a whole lot of events that are neither unambiguously in the past nor in the future of a given event. In SR one ultimately stops thinking of "simultaneous" as meaningful and rather speaks of space-time separation (time-like, space-like, and light-like). In QM one should ultimately stop thinking of "real" as meaningful and rather speak of forbidden transitions, assured transitions and the in-between probabilistic transitions. Those transitions not being transitions between states of reality but transitions between equivalence classes of acts of determination.

OK, got on a tear. My overall theme is that one is in error holding onto the old ontological language of classical science. It is obstructive (not just in understanding QM). I assert the same error is made in social sciences where the subject under study is incorrectly objectified. One assumes people have "states of mind" and sees the explosion of diagnosed syndromes in psychology and psychiatry. One tries to act on "the economy" as if one need only move the observables around to match their values when it was "in a good state".

These are systems which like physical systems in QM cannot be reduced to objective states because the nature of the acts of observation are either intrinsically or as a matter of pragmatic necessity, intimate. The act of measurement is an interaction. The act of observing affects the observed as well as the observer.

 

[akhmeteli]

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.

It looks like your logic can be used equally well to prove that there is no contradiction between classical mechanics and thermodynamics. Nevertheless, classical mechanics is reversible, and thermodynamics is not. You may say that this contradiction is not practically important, but this is still a contradiction. In the same way, unitary evolution cannot produce irreversibility or turn a pure state into a mixture, and the projection postulate does just that. A contradiction is a contradiction.

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!

I try to avoid discussing philosophy here – first, it requires a lot of time, second, it is not very appropriate here. Let me just note that this thread is not about local realism (LR) being correct or wrong, it’s about LR being or not being ruled out. I am not trying to convince anybody that there is reality out there. I am trying to argue that LR is logically and experimentally possible right now, however prevalent the opposite opinion is.

 

[akhmeteli]

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

I tend to agree with harrylin’s comment (post 777 in this thread). In my book, mediation with infinite speed is no mediation.

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.

If you don’t “want to wait for loophole-free experimental tests of Bell inequalities - fine, I have no problem with this.”:-)

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.

If loophole-free evidence of violations of the Bell inequalities appears tomorrow, I’ll certainly have to reconsider the entire situation. As I wrote in this thread though, I cannot promise that I won’t choose superdeterminism, for example:-). But I do think it is a bit early to speculate “what if”. We exist here and now, and I discuss the current situation in this thread. Mind you, I am not asking you about the consequences of possible absence of violations in loophole-free experiments:-)

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.

In my book, there is no positive evidence of violations. Let me note however that the majority both believes in violations and does not like de Broglie – Bohm interpretation (dBB), and this does not bode well for universal acceptance of dBB:-) But again, while I am not enthusiastic about dBB, I am not its enemy either. Furthermore, my results have applications to dBB.

 

[akhmeteli]

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?

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

I am not sure but I suspect we have two different things in mind. Einstein causality means the speed of causal influence is limited. On the other hand, there is also EPR's reasoning, which I do not accept - for example, I don't question the uncertainty principle and am not enthusiastic about noncontextual hidden variables. One more thing. Let us consider the EPR-Bohm experiment. If initially we have two particles in a singlet state and then the spin projection of one of the particles is measured to be +1, the projection postulate demands that the two particles are in such a state that the spin projection of the first particle is +1, whereas that contradicts unitary evolution, so I have to reject either unitary evolution or the projection postulate as a precise law. My choice is to reject the projection postulate as a precise law.

If the above does not answer your question, let me know, and sorry about that - I did not try to study PBR in detail as I don't mind their conclusion:-)

 

[akhmeteli]

Yes, I agree. All experiments that I looked into so far may be understood to work by exploiting loopholes (or even big holes). By now I regard a "loophole free" experiment in the same way as an experiment that "breaks the PoR" - I won't wait for it.

Thank you. Let me just note that it is a mainstream opinion that there has been no loophole-free experimental evidence of violations so far. I gave quotes confirming that in this and other threads.

 

[Ilja]

There is a colossal difference between "greater than c" (which conforms with "LR") and infinite speed (which does not conform with "LR").

I agree, and thank you for the evidence that the naming "local realism" is misleading. What can be proven by loophole-free experiments is always only "greater than v", with some velocity v, which may be much greater c, but not infinite. But, once there are no interesting known theories with critical velocities v>c, the only interesting point is that such observations can rule out "greater than c". A maximal speed v < ∞ can never be ruled out by observation. Thus, your notion of LR is simply a wrong one - not the one used by the mainstream. But I agree that it is suggested by naming it local realism instead of Einstein-causal realism.

I searched but could not find a claim by Newton that the speed of gravity is infinite

I didn't even search, the point is that it is obvious. The gravitational force is defined by the positions of all other masses at the same moment of time.

I find Einstein's own formulation, "spooky action at a distance" much better: for it relates to the implausible infinite speed of QM as well as to the implausible infinite and unfailing working range of QM, independent of distance. Can the De Broglie's model account for that??

It contains it. As in Newtonian theory, the speed of a particle depends on the positions of all other particles of the universe.

Just because you can use (at the classical scale) a reality model as your framework of material phenomena doesn't mean it is the best/only framework.

Yes, but it is a very simple one, so Ockham's razor is waiting for the alternatives. And you should obtain this simple model in the classical limit (a criterion which rules out MWI and similar phantasies if taken seriously).

The point to understand is that there is a class of languages broader than nominative languages. You can use Whitehead's nomenclature of object language and process language, but I prefer to say action language. We use an object language classically but we can recognize quantum mechanics as a action language. The semantic atoms are acts rather than objects.

I would suggest to name this the "Orwellian interpretation" - changing the language so that one can no longer talk about reality Ok, you argue that it is a superset, that one can formally construct an object language on the top. But looking at your example, "running" as a noun, it is or artificial, or a triviality: I use "existing" as a noun.

What this boils down to (and where it is relevant to this topic) is that recognizing quantum mechanics as an action language we need no further interpretation when we interpret the symbolism in terms of phenomenological acts. "prepare system, dynamically evolve, selectively detect, measure", "compose actions" <--> "bra" "U" "ket", "X", "AB=C".
It is the person trapped in object language thinking that must insist that these actions only terminate in objective states.

Sorry, but I'm not trapped at all. I recognize very well that the minimal interpretation of QM is a useful instrumental device. Realism is, in my opinion, a restriction for physical theories, a restriction, which, as any other restriction (existence of a Lagrange formalism, conservation laws and so on) is useful because it adds predictive power.

That it really adds predictive power we have seen: Realism + Lorentz invariance gives Bell inequalities, without realism not.

The "reality" in QM is relativized. You can work in a perfectly valid classical logic of states if you restrict your actions to only include a commuting subset of observables. Changing to a distinct subset of observables defines an alternative transformed "reality frame", just as you transform between moving observers and get a different "now" frame in SR. Just as with SR the transition in thinking from absolute to relative is difficult and many become intransigent insisting it is just wrong because they can't let go of their intuition of absolutes.

Again, reality is relativized only in particular interpretations of QM. In dBB it exists absolutely in full beauty.

The preference for relativised approaches in modern physics is a nasty side effect of positivism. Once we cannot observe the absolutes, but observe only the relative things, positivists prefer relativistic theories, even if they usually are much more complicate.

Here we have to use Ockham's razor. The cost for relativizing absolute simultaneity is to introduce a whole spacetime into existence, where in classical theory future and past "exist" only in a much weaker sense, and it is sufficient to consider only what exists now as really existing.

In gauge theory the relativised existence becomes even more problematic, and you have to use factorspaces or artificial loop spaces already for the appropriate definition, where in the absolute version a simple gauge potential is sufficient.

And in gravity the problem of the relative approach becomes so complex that there is not even a quantum theory for it.

You see this in the various "disproofs of einstein" which demonstrate that we can get Einstein's predictions by overlaying a whole set of unobservable structure namely the aether.
Einstein rejected the aether because the predictive theory showed it to be fundamentally unobservable.

The "disproofs of Einstein" show something different: Uneducated people with normal intuitions consider the Lorentz ether as being much more reasonable. Being uneducated, they have only an intuitive feeling that the justification for the spacetime interpretation is wrong, and their arguments against it, partially provoced by the standard argumentation ("the preferred frame is unobservable", as if this really matters) appear nonsensical.

Reality qua reality is fundamentally unobservable. We observe through acts of measurement not immediate intimate clairvoyance into the state of reality as it is.

Correct. And this is, and should be, adequately described by the language. So the language has to represent reality as the fundamental hypothesis, and the actions (of measurement and so on) as derived, usually in a quite complex way, from these fundamentals.

This is how a realistic theory is presented. We start with defining what "is", what "exists". Only after this, we define the basic actions of these entities - how they move, how they interact. And only in the last step we care about the much more complex observations. And, what is essential, there is no step where we have to "derive" something from observations - the basic nonsense of positivism.

In imagining a birds eye view of distant phenomena we imagine and develop an intuition of absolute simultaneity when we must deduce simultaneity from the phenomena of causal signals.

I wrote it down, and in the next line you present an example. No, there is no necessity at all for deduction of scientific theories. That's positivism. Scientific theories are hypotheses, they are not and cannot be deduced from observations.

When in an action language actions fail to commute we loose the presumption that the quantities they change add.

I would say we loose a very reasonable criterion for distinguishing scientific theories from nonsense like astrology. What is the main difference between science and astrology? Ok, positivists tend to tell us that it is that the predictions of science are really accurate, but the predictions made by astrology are not. My grandmother possibly disagrees, and knows a lot of examples where astrological predictions have been successful. And I think we all remember a lot of examples where scientific statistics have miserably failed.

I nonetheless agree that, in the long run, it is decisive that scientists are able to present the better predictions. But I also think there is a reason for this - and this reason is the other, far more obvious difference between science and astrology. Science presents theories which not only predict, but also explain why.

You get Bell inequality violation which can only be resolved satisfactorily by rejecting the underlying absolute structure.

Feel free to prefer such mystical interpretations of QM, but the "only" is wrong - it is your free decision to reject the straightforward realistic interpretation of QM - dBB.

BTW, about the analogy between relativism vs. realism in SR vs. Lorentz ether and Kopenhagen vs. dBB we are in agreement. I would simply summarize this in another way: it is the same error of positivistic relativization.

What you must then learn to deal with is a limited "relative reality" and a whole lot more which doesn't fit into anyone reality frame just as in SR you have to deal with relative simultaneity and a whole lot of events that are neither unambiguously in the past nor in the future of a given event. In SR one ultimately stops thinking of "simultaneous" as meaningful and rather speaks of space-time separation (time-like, space-like, and light-like). In QM one should ultimately stop thinking of "real" as meaningful and rather speak of forbidden transitions, assured transitions and the in-between probabilistic transitions.

"Stop thinking" - the Orwellian approach to modern science. SCNR.

If loophole-free evidence of violations of the Bell inequalities appears tomorrow, I’ll certainly have to reconsider the entire situation. As I wrote in this thread though, I cannot promise that I won’t choose superdeterminism, for example:-).

Superdeterminism is a stupid choice. If you would take it seriously, you could even reject a working FTL phone line as evidence against Einstein causality. With superdeterminism no falsification of Einstein causality is possible.

In other words, if you would accept an FTL phone line between Earth and Mars as a falsification of Einstein causality, you should reject superdeterminism.

But I do think it is a bit early to speculate “what if”. We exist here and now, and I discuss the current situation in this thread. Mind you, I am not asking you about the consequences of possible absence of violations in loophole-free experiments:-)

I don't think it is early. Last but not least, the only theory we have in the quantum domain predicts it. I would be happy if we find evidence violating quantum theory, that would open the door to subquantum theory. But there is not even a reasonable candidate for a general subquatum theory which would not predict a violation of Bell's inequalities but predict the observed outcome of all the experiments which have been already done.

Let me note however that the majority both believes in violations and does not like de Broglie – Bohm interpretation (dBB), and this does not bode well for universal acceptance of dBB:-)

That's indeed the great mystery of modern science.

At the current moment, I have only sociological explanations for this: Special relativity can be understood already in school, and those who start studying physics are, therefore, people fascinated by it. What they learn in the university does not change this. So relativity is already, from a sociological point of view, a belief as deep as religious beliefs, and experience tells us that people who change their religious beliefs are only rare exceptions.

One would hope, of course, that the situation in science is different. But there is yet another sociological problem with modern science - that it does no longer support independent thinking sociologically. In the past, scientists have been university teachers, and even without any scientific success they had a safe job as a teacher. Today they have short-time jobs connected with grants, and have to search for a new job every two-three years, and their changes of finding such a job depend on their accepted publications in mainstream journals. From a sociological point of view I would name this an extremal mainstream dependence.

Sorry for the off-topic, SCNR.

 

[akhmeteli]

Superdeterminism is a stupid choice. If you would take it seriously, you could even reject a working FTL phone line as evidence against Einstein causality. With superdeterminism no falsification of Einstein causality is possible.

In other words, if you would accept an FTL phone line between Earth and Mars as a falsification of Einstein causality, you should reject superdeterminism.

I don’t need to defend superdeterminism. I just tried to give an honest answer to your question.

I don't think it is early. Last but not least, the only theory we have in the quantum domain predicts it. I would be happy if we find evidence violating quantum theory, that would open the door to subquantum theory. But there is not even a reasonable candidate for a general subquatum theory which would not predict a violation of Bell's inequalities but predict the observed outcome of all the experiments which have been already done.

I am not sure standard quantum theory truly predicts violations, as to “predict” them, it uses its mutually contradicting components – unitary evolution and the theory of measurement (e.g., the projection postulate). That’s not what I call “prediction". I’d say this is another reason it may be too early to discuss the consequences of loophole-free violations – I think standard quantum theory should sort out its own problems first. Let me also note that LR theories of my work reproduce unitary evolution of quantum field theories.

That's indeed the great mystery of modern science.

At the current moment, I have only sociological explanations for this: Special relativity can be understood already in school, and those who start studying physics are, therefore, people fascinated by it. What they learn in the university does not change this. So relativity is already, from a sociological point of view, a belief as deep as religious beliefs, and experience tells us that people who change their religious beliefs are only rare exceptions.

One would hope, of course, that the situation in science is different. But there is yet another sociological problem with modern science - that it does no longer support independent thinking sociologically. In the past, scientists have been university teachers, and even without any scientific success they had a safe job as a teacher. Today they have short-time jobs connected with grants, and have to search for a new job every two-three years, and their changes of finding such a job depend on their accepted publications in mainstream journals. From a sociological point of view I would name this an extremal mainstream dependence.

One can always find some sociological explanations, but we are still left with the fact that the majority does not think dBB is as “nice” as you think. Your conclusion seems to be that we need a better majority, I suspect we need a better dBB as well.

 

[harrylin]

[..] We observe through acts of measurement not immediate intimate clairvoyance into the state of reality as it is. This barrier is the same as the barrier in SR of observing distant events only through propagating intermediate causal phenomena (light or gravity or bouncing balls or something). In imagining a birds eye view of distant phenomena we imagine and develop an intuition of absolute simultaneity when we must deduce simultaneity from the phenomena of causal signals. Similarly we must deduce states of reality (at the classical scale) from the phenomena of measurements we make. When we push it to the extreme observables significantly fail to commute just as in SR the boosts fail to commute and we can no longer thing of velocities as additive (+ being a commuting product).

That has been discussed several times in the relativity forum. What you probably meant was that we may no longer confound velocity transformations with velocity differences. SR may seem like magic for some (as it used to for me), but in fact it contains no magic. QM still seems like magic to me, but if you can propose a non-magical interpretation of the related phenomena then I'm all ears.

When in an action language actions fail to commute we loose the presumption that the quantities they change add. In QM it is the probabilities that cease to be an additive measure over a state space. You get Bell inequality violation which can only be resolved satisfactorily by rejecting the underlying absolute structure. [..] In QM you loose the fiber-bundle structure of logical values over the base of possible states of reality. In both cases you get a relativity principle and a unified composite structure. In [..] QM it is a unified manifold of possibilities. In SR we see mixing of space and time as we change frames and in QM we see the mixing of "reality" and "logic" that becomes probability and is though of as quantum uncertainty. It is a mixing of "reality" and "possibility" which manifests as probability. [..]

The interpretation of mixing up conceptually different things has no appeal to me - that is just the kind of "magic" that I reject. For SR phenomena it is not necessary and I expect that it will also be found unnecessary for QM phenomena. At least it has not been experimentally disproved (insofar as I understand the experiments!).

in QM [..] the nature of the acts of observation are either intrinsically or as a matter of pragmatic necessity, intimate. The act of measurement is an interaction. The act of observing affects the observed as well as the observer.

Surely everyone agrees on that!

 

[harrylin]

[..] I didn't even search, the point is that it is obvious. [..]

The contrary is for me obvious, because I deem Newton as having been sound of mind, based on what he did express; and since neither of us has proof of what Newton really thought on this matter, we only have our personal estimations about his thinking on this.

[De Broglie's theory] contains [the "implausible infinite and unfailing working range of QM, independent of distance"]. As in Newtonian theory, the speed of a particle depends on the positions of all other particles of the universe.

I'm afraid that you did not understand my question which is not about speed. The usual discussions are only about half of the "spookiness". How does De Broglie's theory explain that an action on a particle at one end of the universe can have an undiminished effect on another particle at the other end of the universe? What physical mechanism did he propose for that? Note that if it requires a long answer, I'll start it as a new topic.

[..] I would suggest to name this the "Orwellian interpretation" - changing the language so that one can no longer talk about reality [..]

I just (finally) read 1984 - and it is even more applicable on some of these discussions than had imagined before I read it. Indeed, there is too much Newspeak going on.

 

[Ilja]

I am not sure standard quantum theory truly predicts violations, as to “predict” them, it uses its mutually contradicting components – unitary evolution and the theory of measurement (e.g., the projection postulate). That’s not what I call “prediction".

I'm sure, because I use the dBB interpretation, and in the dBB interpretation there is no such contradiction.

The collapse of the wave function in dBB is described by the unitary evolution of the wave function of the object itself together with the apparatus, and the evolution of the object and the apparatus themself (by the guiding equation). One can combine the full wave function ψ_full(o,a,t) with the trajectory of the apparatus a(t) to define an effective wave function of the object ψ_o(o,t) = ψ_full(o,a(t),t). The evolution equation for this effective wave function is, during the measurement, not unitary, because unitary interaction holds only for closed systems or systems which at least are not interacting with their environment. Before and after the measurement, that means if there is no longer any interaction of o with something else, it is unitary. This easily follows from the unitary evolution for the full system.

One can always find some sociological explanations, but we are still left with the fact that the majority does not think dBB is as “nice” as you think. Your conclusion seems to be that we need a better majority, I suspect we need a better dBB as well.

There is room for improvement for the presentation of dBB - it is quite typical to use many particles, while, in the light of QFT, it would be much more reasonable to use a general configuration space, which can be, as well, a field.

But the main reason for not liking dBB is obvious - it is the strong belief into fundamental relativity. And here improvements are impossible - any realistic interpretation of QM has to violate fundamental relativity.

This is not a problem of physics - effective relativity is not a problem at all for dBB, the first model for the EM field was part of the first paper by Bohm. It is a problem of philosophy - the belief into fundamental relativity, or the spacetime interpretation, in comparison with effective relativity, which is compatible with the Lorentz ether.

 

[akhmeteli]

I'm sure, because I use the dBB interpretation, and in the dBB interpretation there is no such contradiction.

The collapse of the wave function in dBB is described by the unitary evolution of the wave function of the object itself together with the apparatus, and the evolution of the object and the apparatus themself (by the guiding equation). One can combine the full wave function ψ_full(o,a,t) with the trajectory of the apparatus a(t) to define an effective wave function of the object ψ_o(o,t) = ψ_full(o,a(t),t). The evolution equation for this effective wave function is, during the measurement, not unitary, because unitary interaction holds only for closed systems or systems which at least are not interacting with their environment. Before and after the measurement, that means if there is no longer any interaction of o with something else, it is unitary. This easily follows from the unitary evolution for the full system.

As far as I know, it is impossible to prove violations in dBB without using some assumptions beyond unitary evolution, otherwise such a proof could be transferred to standard quantum theory. If you disagree, could you please give a reference to such a proof?

There is room for improvement for the presentation of dBB - it is quite typical to use many particles, while, in the light of QFT, it would be much more reasonable to use a general configuration space, which can be, as well, a field.

But the main reason for not liking dBB is obvious - it is the strong belief into fundamental relativity. And here improvements are impossible - any realistic interpretation of QM has to violate fundamental relativity.

This is not a problem of physics - effective relativity is not a problem at all for dBB, the first model for the EM field was part of the first paper by Bohm. It is a problem of philosophy - the belief into fundamental relativity, or the spacetime interpretation, in comparison with effective relativity, which is compatible with the Lorentz ether.

I gave my reasons to think that fundamental relativity has not been ruled out - absence of loophole-free demonstrations of violations and absence of contradiction-free proof of violations in quantum theory.

 

[Ilja]

The contrary is for me obvious, because I deem Newton as having been sound of mind, based on what he did express; and since neither of us has proof of what Newton really thought on this matter, we only have our personal estimations about his thinking on this.

My point was not about Newton's thinking, but about the equations. The link http://plato.stanford.edu/entries/Newton-philosophy/#ActDis has been already postet here and shows that Newton was aware that there is an action at a distance in the equations, and has considered the lack of mediation as a problem.

I'm afraid that you did not understand my question which is not about speed. The usual discussions are only about half of the "spookiness". How does De Broglie's theory explain that an action on a particle at one end of the universe can have an undiminished effect on another particle at the other end of the universe? What physical mechanism did he propose for that? Note that if it requires a long answer, I'll start it as a new topic.

dBB does not give any answer, and does not even try to give one. So the situation is quite similar to Newtonian gravity, where the formulas do not tell us anything about an explanation for gravity.

And, similarly, I think this is an interesting open problem and can be a hint for developing some subquantum theories. A theory which, for example, restricts the maximum speed of this spooky action should violate quantum theory.

This would be a second hint for subquantum theory, the first being that QM fails for very small values of ψ. That's because around ψ(q)=0 the dBB velocity becomes infinite, even if only in a quite harmless way (increasingly fast rotation around the 0).

 

[bohm2]

And, similarly, I think this is an interesting open problem and can be a hint for developing some subquantum theories. A theory which, for example, restricts the maximum speed of this spooky action should violate quantum theory.

Not sure if Gisin's experiment was posted in this thread but his group suggested that the speed of this non-local connection must be is at least 10,000 times the speed of light:

For instance, if such a privileged reference frame exists and is such that the Earth's speed in this frame is less than 10^-3 that of the speed of light, then the speed of this spooky influence would have to exceed that of light by at least 4 orders of magnitude.

Testing spooky action at a distance
http://arxiv.org/pdf/0808.3316v1.pdf

 

[harrylin]

Not sure if Gisin's experiment was posted in this thread but his group suggested that the speed of this non-local connection must be is at least 10,000 times the speed of light:

Testing spooky action at a distance
http://arxiv.org/pdf/0808.3316v1.pdf

Nice find! I'll read it.
Note that your Arxiv link is a version of a reviewed publication:
http://www.nature.com/nature/journal/v454/n7206/full/nature07121.html

PS. a quick question: I quickly looked over it but I could not immediately "get" the idea behind it.
What is in a nutshell their method for determining the minimal speed of "spooky action at a distance? They mention two-photon interference, which sounds somewhat like MMX (even more like KTX). Where is "Bell" in all that?

 

[akhmeteli]

Not sure if Gisin's experiment was posted in this thread but his group suggested that the speed of this non-local connection must be is at least 10,000 times the speed of light:

Testing spooky action at a distance
http://arxiv.org/pdf/0808.3316v1.pdf

Let me just note that the article in question does not claim simultaneous elimination of both the detection and the locality loopholes (probably, the detection loophole still exists, as is customary for all experiments with photons), so, strictly speaking, their experiment does not even demonstrate violations of the Bell inequalities.

 

[Ilja]

Nice find! I'll read it.
Note that your Arxiv link is a version of a reviewed publication:
http://www.nature.com/nature/journal/v454/n7206/full/nature07121.html

PS. a quick question: I quickly looked over it but I could not immediately "get" the idea behind it.
What is in a nutshell their method for determining the minimal speed of "spooky action at a distance? They mention two-photon interference, which sounds somewhat like MMX (even more like KTX). Where is "Bell" in all that?

The idea is that if there is another, greater limiting speed, say 100c, then there has to be a corresponding superlight cone and there will be space-like separated event pairs for this superlight cone too. And for such event pairs the Bell inequalities should hold. So one has to test the violation of Bell inequalities for large enough sets of event pairs so that there will be no place for the 100 c superlight cone.

The next idea was that there is a reasonable hypothesis for the place of the superlight cone - one can guess that the time of the rest frame for the background radiation will be time-like in the superlight cone too. So there is no need to rule out all those skew superlight cones, and all one needs is to care about the much smaller set of superlight cones compatible with the background radiation rest frame. So, one only has to look for event pairs which have approximately equal time in the CMBR frame.

 

[harrylin]

The idea is that if there is another, greater limiting speed, say 100c, then there has to be a corresponding superlight cone and there will be space-like separated event pairs for this superlight cone too. And for such event pairs the Bell inequalities should hold. So one has to test the violation of Bell inequalities for large enough sets of event pairs so that there will be no place for the 100 c superlight cone.

The next idea was that there is a reasonable hypothesis for the place of the superlight cone - one can guess that the time of the rest frame for the background radiation will be time-like in the superlight cone too. [..]

Ok, thanks - it's starting to dawn on me now.
I have the impression that in that last paper they tried to be so general as not to need the CMBR hypothesis.

Anyway, I now find my hunch that such an interferometer experiment is unlikely to yield anything "spooky" supported by an old discussion on this forum (keyword I searched with was "Franson"):

https://www.physicsforums.com/showthread.php?t=229393

However, there is for me not enough explanation there ...

 

[bohm2]

This has been posted here before but was just published in Nature Physics. It argues that barring loopholes, if the non-local effects observed in Bell-type experiments propagate at any finite speed, then non-locality could be exploited for superluminal communication:

The new hidden influence inequality shows that the get-out won't work when it comes to quantum predictions. To derive their inequality, which sets up a measurement of entanglement between four particles, the researchers considered what behaviours are possible for four particles that are connected by influences that stay hidden and that travel at some arbitrary finite speed. Mathematically (and mind-bogglingly), these constraints define an 80-dimensional object. The testable hidden influence inequality is the boundary of the shadow this 80-dimensional shape casts in 44 dimensions. The researchers showed that quantum predictions can lie outside this boundary, which means they are going against one of the assumptions. Outside the boundary, either the influences can't stay hidden, or they must have infinite speed.

Looking Beyond Space and Time to Cope With Quantum Theory
http://www.sciencedaily.com/releases/2012/10/121028142217.htm

Quantum non-locality based on finite-speed causal influences leads to superluminal signalling
http://www.nature.com/nphys/journal/vaop/ncurrent/full/nphys2460.html

Full article posted in arxiv:
http://arxiv.org/pdf/1110.3795v1.pdf

 

[bohm2]

I know this isn't likely to sway any opinions but for completion and future reference this is a follow-up piece by Gisin to the J. D. Bancal et al. Nature Physics paper linked above that was just posted on arxiv:

We investigate possible explanations of quantum correlations that satisfy the principle of continuity, which states that everything propagates gradually and continuously through space and time. In particular, following [J.D. Bancal et al, Nature Physics 2012], we show that any combination of local common causes and direct causes satisfying this principle, i.e. propagating at any finite speed, leads to signalling. This is true even if the common and direct causes are allowed to propagate at a supraluminal-but-finite speed defined in a Newtonian-like privileged universal reference frame. Consequently, either there is supraluminal communication or the conclusion that Nature is nonlocal (i.e. discontinuous) is unavoidable.

Quantum correlations in Newtonian space and time: arbitrarily fast communication or nonlocality
http://lanl.arxiv.org/pdf/1210.7308.pdf

 

[bohm2]

Lecture from lead author JD Bancal from Perimeter Institute:

The experimental violation of Bell inequalities using spacelike separated measurements precludes the explanation of quantum correlations through causal influences propagating at subluminal speed. Yet, it is always possible, in principle, to explain such experimental violations through models based on hidden influences propagating at a finite speed v>c, provided v is large enough. Here, we show that for any finite speed v>c, such models predict correlations that can be exploited for faster-than-light communication. This superluminal communication does not require access to any hidden physical quantities, but only the manipulation of measurement devices at the level of our present-day description of quantum experiments. Hence, assuming the impossibility of using quantum non-locality for superluminal communication, we exclude any possible explanation of quantum correlations in term of finite-speed influences.

http://pirsa.org/displayFlash.php?id=11110145

 

[harrylin]

Lecture from lead author JD Bancal from Perimeter Institute:

"[...] we exclude any possible explanation of quantum correlations in term of finite-speed influences"
http://pirsa.org/displayFlash.php?id=11110145

That reminds me of De Raedt et al who more than agreed with that.
As a reminder:

A violation of the Extended Boole-Bell inequalities cannot be attributed to influences at a distance

- https://www.physicsforums.com/showthread.php?t=499002

 

[akhmeteli]

The point here is that this thread appears to indicate that even IF all the loopholes are closed (and I will make MY prediction here that in the near future, say within 3 years, ALL the loopholes will be closed in one single experiment), the intrinsic nature of the theory will STILL not falsify local realism.

Three years have passed. As far as I know, all the loopholes have not been closed in one single experiment. For example, reporting some further progress in a recent article http://arxiv.org/abs/1212.0533 , Zeilinger e.a. still admit that “The realization of an experiment that is free of all three assumptions – a so-called loophole-free Bell test – remains an important outstanding goal for the physics community”.

I am writing this without any Schadenfreude. I do appreciate that a loophole-free experiment can be performed any moment now. It looks like the race to conduct the first experiment of this kind is really fierce. E.g., the following quote is interesting (SCIENCE, VOL 331, P. 1380 (2011)): “Zukowski thinks the race to close all the loopholes simultaneously will soon be over. “Conservatively, it could take another 5 years to complete, but it could also be done tomorrow,” he says. “We’re at the stage where everyone is scared to read their competitors’ papers, in case they find they have been beaten. The only real question is: Who will win?””

I also had this impression of a fierce race listening to talks on quantum foundations experiments at several conferences last year. On the other hand, some experimentalists admitted (typically, not in their official talks:-) ) that they encounter some formidable challenges.

So I am just trying to say that these three years since the start of this thread have demonstrated again that it is extremely difficult to demonstrate violations of the genuine Bell inequalities. Will they be demonstrated by the fiftieth anniversary of the Bell’s article next year? Or ever? My prediction is “no”. But I may be mistaken.

 

[Peter Morgan]

The point is that particles in a singlet state have, both theoretically and experimentally, a higher correlation than you seem to allow (or expect) in your work.

I guess you're just bashing your response out, so this is not intended to be a substantive criticism, but it's not a correlation that's higher, it's a sum of absolute values of a sum and a difference between four different correlations $|A-B|+|C+D|$ (at least, that's what it is in the CHSH formulation, in no case is the difficulty for local realism that a correlation coefficient simpliciter is too high).

 

[akhmeteli]

The point is that particles in a singlet state deliver, both theoretically and experimentally, a higher expectation value* than you seem to allow (or expect) in your work.

Dear Gordon Watson,

I tried to explain in my post 753 in this thread why I cannot agree with you.

 

[akhmeteli]

OK; disagreeing with me is no big deal. BUT I'm NOT aware of any rational quantum physicist that agrees with you:

"... that there are some reasons to believe Bell inequalities cannot be violated either in experiments or in quantum theory." [Cited above.]​

So Santos, Marshall, nightlight are not rational quantum physicists, in your book. They are in mine. Let me add that I gave those "reasons" and properly published them (although I just repeated other people's arguments, as far as those "reasons" are concerned).

Another thing: "the foundations of quantum mechanics ... remain hotly debated in the scientific community, and no consensus on essential questions has been reached." (Schlosshauer, Kofler, Zeilinger, http://arxiv.org/abs/1301.1069 ). So disagreement is a "new normal" for quantum foundations.

 

[nanosiborg]

Using your terms to conclude re my position (vis-a-vis yours), I am satisfied that:

1. Bell inequalities are repeatedly violated by experiment.

2. Bell inequalities are certainly violated by quantum theory.

3. Except for their motivation toward better experiments, the remaining loopholes are of no consequence.
..

Agree. 1 and 2 are facts, and 3 seems to me to be a much more reasonable position than that taken by the loophole people.

 

[akhmeteli]

Using your terms to conclude re my position (vis-a-vis yours), I am satisfied that:

You are satisfied, I'm not.

1. Bell inequalities are repeatedly violated by experiment.

Not unless you ignore the loopholes.

2. Bell inequalities are certainly violated by quantum theory.

Not unless you use as assumptions mutually contradictory postulates of standard quantum theory, such as unitary evolution and the projection postulate. However, if you use mutually contradictory assumptions, you can get any conclusion, however absurd.

3. Except for their motivation toward better experiments, the remaining loopholes are of no consequence.

This is an opinion, not a fact.

 

[harrylin]

[..] position [..] taken by the loophole people.

Who are such "loophole people"? It is suggestive of people who stick to an opinion against all odds, and I would be surprised if anyone here identifies with such a position - in which case it's just a strawman (it's a derogative term, used to indicate a means of escape or evasion).