Questions on Entanglement and Double-Slit Experiment

[ZapperZ]

You're talking about Bohmian Mechanics here, right? You truly don't get it. Bohmian Mechanics and orthodox QM make identical predictions (at least in cases where the predictions of the latter are unambiguous). So it begs the question to just dismiss Bohm's theory as you do here. One could equally well dismiss orthodox QM (i.e., all the idiotic philosophical ramblings of Bohr) on the same basis -- namely, that what Copenhagen adds to the rigorous formulation of the pilot wave approach is just a bunch of used-to-be-trendy positivist, anti-realist, existentialist-motivated philosophical mumbo jumbo whose only function is to make some moron feel better about their anti-scientific philosophical view of the world. If you actually have any serious interest in this issue, you might start by reading Jim Cushing's book "Quantum Mechanics: Historical Contingency and the Copenhagen Hegemony". Or if you don't have any serious interest, maybe you shouldn't discuss them in public.

As to your big challenge that I should publish a rebuttal to Styer's "misconceptions" paper, see section IV of

http://puhep1.princeton.edu/~mcdonald/examples/QM/norsen_ajp_73_164_05.pdf

This is all particularly ironic given the following:

http://tech.groups.yahoo.com/group/undernetphysics/message/857

Who said anything about Bohmian Mechanics in particular? In fact, this IS included in Styer's text.

Again, it is YOU who said that there ARE formulations that make subtle difference in predictions. Bohmian mechanics does this? Yes? No? If it makes "identical predictions", then why are you up in arms here with this one? It is obviously not what YOU included in your original claim. Yet, you're picking it as an example. So you're right, I DON'T get it.

And thank you for your reference. Unfortunately, your paper has more of a problem with Bell's theorem in general rather than Styer's paper itself! You are claiming that Styer didn't have the "misconception", but rather the whole of quantum mechanics community is the one that did. And yes, I thought it was a good paper because it does present a "historical account" of a thought experiment that has been overlooked. That was it, which was essentially what I said when I pointed it out, no?

[BTW, this also falsifies the often-made claim that I only advertize papers that do not challenge the conventional ideas, even when *I* myself don't think is convincing]

Zz.

 

[ttn]

Who said anything about Bohmian Mechanics in particular? In fact, this IS included in Styer's text.

Funny, since he claims in his earlier paper that Bell's Theorem proves it can't exist.

Again, it is YOU who said that there ARE formulations that make subtle difference in predictions.

There are. GRW for example.

Bohmian mechanics does this? Yes? No?

No, as I said in the previous post, Bohm's theory makes the same predictions as orthodox QM wherever the latter is unambiguous.

If it makes "identical predictions", then why are you up in arms here with this one? It is obviously not what YOU included in your original claim. Yet, you're picking it as an example. So you're right, I DON'T get it.

My original claim was that the different versions of QM don't share the same formalism. You keep trying to twist things around and change the subject in order to win this argument. I frankly don't care about who wins; I just wanted to convey to all the reasonable people who read this that they needn't be bullied by your arrogant dismissiveness about foundational questions. I think I've achieved that, and there's no point continuing to argue about whether my "original claim" was true, so the last word is yours.

And thank you for your reference. Unfortunately, your paper has more of a problem with Bell's theorem in general rather than Styer's paper itself! You are claiming that Styer didn't have the "misconception", but rather the whole of quantum mechanics community is the one that did.

Those aren't exactly mutually exclusive. Styer was simply repeating, without real understanding, a misconception that is widely held in the physics community. Does it somehow invalidate my claim because it is targeted more widely than Styer's paper in particular? That makes no sense -- unless your goal is to follow any path, no matter how ridiculous, in order to try to win an argument.

 

[ZapperZ]

Funny, since he claims in his earlier paper that Bell's Theorem proves it can't exist.

There are. GRW for example.
No, as I said in the previous post, Bohm's theory makes the same predictions as orthodox QM wherever the latter is unambiguous.

My original claim was that the different versions of QM don't share the same formalism. You keep trying to twist things around and change the subject in order to win this argument. I frankly don't care about who wins; I just wanted to convey to all the reasonable people who read this that they needn't be bullied by your arrogant dismissiveness about foundational questions. I think I've achieved that, and there's no point continuing to argue about whether my "original claim" was true, so the last word is yours.

Those aren't exactly mutually exclusive. Styer was simply repeating, without real understanding, a misconception that is widely held in the physics community. Does it somehow invalidate my claim because it is targeted more widely than Styer's paper in particular? That makes no sense -- unless your goal is to follow any path, no matter how ridiculous, in order to try to win an argument.

No I'm not, because this thing has become so convoluted, I doubt if anyone else reading this even CARE who said what when.

My original point was, in case you forgot, that the different formulations of QM are simply variations to the SAME set of principles in the SAME way that Newtonian and Lagrangian/Hamiltonian mechanics are in classical mechanics. They may have different approaches and different "philosophical" views, but no one would call them as different classical mechanics. The list provide by Styer is a clear example where different formalism of QM essentially ARE what we ALL call "quantum mechanics" in the standard sense. My evidence? Other than Bohmian mechanics (which is nothing more than QM with an "action"), all those formulations one encounters either in textbooks, or used in various "applications". None of them produce any results that contradict each other. I don't know why this is such a sticky point!

Now you, however, decided to include what I would call non-standard QM and not only that, claim that one can also arrive and a different result using these. So by bastardizing and redefining what I said, you claim that I made a mistake in judgement. I really don't care if you have an affinity to one thing versus the other, but even YOU can see the absurdity if I have to defend something that I never claim. I never brought up bohmian mechanics till you somehow interpreted my claim as referring to it. I never make any claim about non-standard QM until you decided to claim that I did. The FACT that I repeatedly refer to what is being used in the application of QM as a measuring stick of a very mature formalism of QM somehow, according to you, is my "high horse" position. What ELSE is there, as an evidence, for something to be so well-known and well-accepted other than being used for applications?! For some odd reason, you took offense at this!

We ALL know the formalisms being used often and repeatedly in solving problems in physics beyond JUST the field of foundational QM. I cited the FACT that NO papers, theoretical or experimental, that use the non-standard formalism for problem solving/application as evidence that such formalism is still not fully matured nor accepted YET. This ISN'T a criticism of the formalism! As someone who cares more about how to get to the final result, I cannot trust something new and untested to solve my problem when it isn't part of what I care about. Why is this causing you such a problem?

BTW, are you preparing the possible rebuttal to Marcella's preprint?
http://arxiv.org/abs/quant-ph/0606141

.. and I must have missed your response to Shimony's counter argument against' your paper.
A. Shimony AJP 73, 177 (2005).

Zz.

 

[ttn]

No I'm not, because this thing has become so convoluted, I doubt if anyone else reading this even CARE who said what when.

My original point was, in case you forgot, that the different formulations of QM are simply variations to the SAME set of principles in the SAME way that Newtonian and Lagrangian/Hamiltonian mechanics are in classical mechanics. They may have different approaches and different "philosophical" views, but no one would call them as different classical mechanics. The list provide by Styer is a clear example where different formalism of QM essentially ARE what we ALL call "quantum mechanics" in the standard sense. My evidence? Other than Bohmian mechanics (which is nothing more than QM with an "action"), all those formulations one encounters either in textbooks, or used in various "applications". None of them produce any results that contradict each other. I don't know why this is such a sticky point!

Now you, however, decided to include what I would call non-standard QM and not only that, claim that one can also arrive and a different result using these. So by bastardizing and redefining what I said, you claim that I made a mistake in judgement. I really don't care if you have an affinity to one thing versus the other, but even YOU can see the absurdity if I have to defend something that I never claim. I never brought up bohmian mechanics till you somehow interpreted my claim as referring to it. I never make any claim about non-standard QM until you decided to claim that I did. The FACT that I repeatedly refer to what is being used in the application of QM as a measuring stick of a very mature formalism of QM somehow, according to you, is my "high horse" position. What ELSE is there, as an evidence, for something to be so well-known and well-accepted other than being used for applications?! For some odd reason, you took offense at this!

We ALL know the formalisms being used often and repeatedly in solving problems in physics beyond JUST the field of foundational QM. I cited the FACT that NO papers, theoretical or experimental, that use the non-standard formalism for problem solving/application as evidence that such formalism is still not fully matured nor accepted YET. This ISN'T a criticism of the formalism! As someone who cares more about how to get to the final result, I cannot trust something new and untested to solve my problem when it isn't part of what I care about. Why is this causing you such a problem?

Since I promised to give you the last word, I won't respond to this part.

But I will answer the questions you posed:

BTW, are you preparing the possible rebuttal to Marcella's preprint?
http://arxiv.org/abs/quant-ph/0606141

.. and I must have missed your response to Shimony's counter argument against' your paper.
A. Shimony AJP 73, 177 (2005).

If you really want to discuss this topic -- i.e., the validity of the Einstein's Boxes argument for the incompleteness/nonlocality dilemma faced by orthodox QM -- I would be happy to oblige. Why don't you start a new thread and we'll just wipe the slate clean and focus on this topic?

But to answer the specific questions: no, I am not preparing a rebuttal to that paper of Marcella, since it is very poorly done. (He doesn't even understand what the argument is he thinks he's rebutting.) And, for what it's worth, the same is true of Shimony's piece. I would be happy to elaborate further in the other thread if you're interested in discussing it. Maybe you could get the discussion going by briefly summarizing your own objections to the arguments I made in the paper (you suggested before that you didn't find it convincing) and then summarize the alleged rebuttals of Shimony and Marcella and explain why you agree with those (if you do).

 

[ZapperZ]

But to answer the specific questions: no, I am not preparing a rebuttal to that paper of Marcella, since it is very poorly done. (He doesn't even understand what the argument is he thinks he's rebutting.) And, for what it's worth, the same is true of Shimony's piece. I would be happy to elaborate further in the other thread if you're interested in discussing it. Maybe you could get the discussion going by briefly summarizing your own objections to the arguments I made in the paper (you suggested before that you didn't find it convincing) and then summarize the alleged rebuttals of Shimony and Marcella and explain why you agree with those (if you do).

No, I'm not trying to get in the "last word" here, but I want to make an important clarification.

No where in here did I objected to your arguments. Remember what brought this about. You accused Styer's paper as being full of misconception. That was what I questioned. You tried to support my question by producing your paper. I brought up others that also questioned yours.

What was my point in doing this? It is to show you that what you believe to be a "misconception", others find that YOUR work to also be that, a misconception. At some point, till this is worked out, it becomes as matter of opinion.

This is also EXACTLY my point in why we (as in those of us who have to QM to solve things, and NOT just study the "fundamental" aspect of it) will stick to the standard QM, because we know that works! I know you probably put very little importance to such a concept, but the reality is, if people's lives depend on us getting it right, we have to stick to what we know works. I find no higher degree of validity than that. I use that as a test of ANY theories out there.

Zz.

 

[DrChinese]

You're talking about Bohmian Mechanics here, right? ...One could equally well dismiss orthodox QM (i.e., all the idiotic philosophical ramblings of Bohr) on the same basis...

While you are busy trying to diss QM with an ad hominem attack on Bohr, you might consider balancing the equation with some of Bohm's equivalent jewels. "Wholeness and the Implicate Order", perhaps?

Just a minor comment: your genuinely thought provoking ideas are much more cleanly presented when you skip the gratuitous insults.

Besides, if Bohmian Mechanics had come first and paved the way, then PERHAPS the conversation would be reversed. No one gets much credit for being the second to discover something. At this point, it has been about 50 years and we still have nothing novel from this interpretation (BM that is) that I am aware of. But you never know, perhaps the big validation is right around the corner.

 

[ttn]

What was my point in doing this? It is to show you that what you believe to be a "misconception", others find that YOUR work to also be that, a misconception. At some point, till this is worked out, it becomes as matter of opinion.

Well, like I said, I would be delighted to actually work it out in discussion with you. If you're interested, start a thread (so we don't hijack this one any more than we already have).

This is also EXACTLY my point in why we (as in those of us who have to QM to solve things, and NOT just study the "fundamental" aspect of it) will stick to the standard QM, because we know that works! I know you probably put very little importance to such a concept, but the reality is, if people's lives depend on us getting it right, we have to stick to what we know works. I find no higher degree of validity than that. I use that as a test of ANY theories out there.

I don't disagree with any of that. But if you think we can be sure that Copenhagen QM "works", but we aren't or can't presently be sure whether Bohmian Mechanics "works", you still haven't understood what is at issue here. Perhaps that point will come out into the light if we take this up in another thread.

 

[ttn]

While you are busy trying to diss QM with an ad hominem attack on Bohr, you might consider balancing the equation with some of Bohm's equivalent jewels. "Wholeness and the Implicate Order", perhaps?

Yup, Bohm was a loony in his later years. But, like you, I don't think this is relevant. My point wasn't to argue for Bohm by dissing Bohr with some kind of ad hominem. My point was just that any argument of the form "Copenhagen is great because it works, while Bohm just muddies and encumbers things with his pet philosophical bias" is invalid -- because it can trivially be turned around. What actually matters is, as ZZ has said, whether or not a theory "works" -- i.e., whether it makes the right predictions and satisfies time-tested standards for what constitutes a good scientific theory (e.g., that its formulation be clear and precise and its predictions unambiguous).

Besides, if Bohmian Mechanics had come first and paved the way, then PERHAPS the conversation would be reversed. No one gets much credit for being the second to discover something. At this point, it has been about 50 years and we still have nothing novel from this interpretation (BM that is) that I am aware of. But you never know, perhaps the big validation is right around the corner.

Several points here. First, in a very real sense, Bohmian Mechanics *did* come first. De Broglie discovered it before the full orthodox Copenhagen theory was worked out, but (unfortunately) abandoned the ideas in the face of tremendous negative peer pressure from the Copenhagen crowd. See

http://www.arxiv.org/abs/quant-ph/0609184

for an extremely eye-opening, book-length treatment. And by the way, this is quite important because it establishes rather clearly that it *was* philosophical bias which made the community reject the deterministic pilot-wave theory in favor of what emerged as orthodox QM. Which shows the preposterousness of the kind of argument I mentioned above (that one should just accept Copenhagen as a good scientific theory purely on the grounds that it "got its foot in the door", and then reject any alternatives on principle as just "mumbo jumbo motivated by philosophical bias" or whatever).

Second, it's not clear what you mean by "the big validation". Do you mean some experimental result which shows Bohm's theory to be true and Copenhagen to be false? That's not likely since they basically make the same predictions. Of course, you'll want to respond: aha, that just shows that Bohm's theory doesn't add anything new, and so shouldn't be considered. But you see, that's based on the unjustified taking of Copenhagen as somehow better merely because of the foot-in-the-door point. To whatever extent it's really true that Bohm and Copenhagen make identical predictions, there can be no valid argument that some experiment (or lack thereof) is a special problem for one of the theories and/or a reason for support of the other.

Third, you suggest that nothing useful or important has ever come of Bohm's version of quantum theory. But that's definitely wrong. "The most profound discovery of science" (Stapp's description of Bell's Theorem) was directly motivated by Bell's discovery (more than a decade after Bohm published his theory in 1952, and hence several decades after de Broglie had originally advocated the theory) that Bohm had "done the impossible" -- i.e., provided a direct explicit counterexample to von Neumann's so-called "proof" that one couldn't understand the quantum predictions as arising from a normal, causal, underlying physical process. You should actually read what Bell says and does, instead of accepting as gospel the misconceptions of people like Styer (who, remember, claimed that Bell's theorem actually *refutes* the possibility of a theory like Bohm's... quite a miconception since in fact it was Bell's stumbling onto the really-existing Bohm theory that led him to the famous theorem).

 

[JesseM]

Yup, Bohm was a loony in his later years. But, like you, I don't think this is relevant. My point wasn't to argue for Bohm by dissing Bohr with some kind of ad hominem. My point was just that any argument of the form "Copenhagen is great because it works, while Bohm just muddies and encumbers things with his pet philosophical bias" is invalid -- because it can trivially be turned around.

Do you have a response to my counterargument above, then? Again, "Copenhagen" in the logical-positivist sense and not the "wavefunction collapse is real" sense is basically just the shut-up-and-calculate interpretation, and as such you can't turn it around, because this "interpretation" makes no assumptions one way or another about the existence of any physical realities which can't be measured directly, while Bohm's interpretation does.

 

[Careful]

Several points here. First, in a very real sense, Bohmian Mechanics *did* come first. De Broglie discovered it before the full orthodox Copenhagen theory was worked out, but (unfortunately) abandoned the ideas in the face of tremendous negative peer pressure from the Copenhagen crowd.

True, de Broglies theory was even more complicated than Bohm's (actually you could say that Bohm did not do his homework of crosschecking the literature properly). But de Broglie remained in favor of locality for his entire life and would never have agreed with Bohm's opinions about nonlocality. In that context he remarked that accepting Bell's theorem as an absolute truth testified of a lack of imagination - something I deeply agree with.

 

[ttn]

They [i.e., orthodoxy and bohm] aren't really comparable, at least not if "orthodox QM" is taken to mean the ordinary shut-up-and-calculate version (which is basically what the purely positivist version of the Copehagen interpretation is, although some people use 'Copehagen interpretation' to mean the view that the collapse of the wavefunction is a real physical event), which is just a recipe for making predictions about probabilities without any assumptions (one way or another) about hidden variables, other worlds, or any other aspect of reality that can't be tested directly. Of course, you could also use the formalism of Bohmian mechanics as a recipe for making predictions, without any assumptions about the "reality" of hidden variables or the pilot wave, but this isn't what people usually mean by Bohmian mechanics.

Yes, I completely agree. If you take "orthodoxy" to just mean the "shut up and calculate" attitude, then it's true that "orthodoxy" and Bohm are no longer on an equal footing: one is a mere calculational algorithm, while the other is an actual *theory* about physical processes in the world. (But of course, people who support "orthodoxy" in fact *don't* take this attitude seriously, or at least consistently. They invariably accept the very non-positivist claims that the wave function alone provides already a complete description of physical states, contra "hidden variables.")

I also agree that, if one takes a hard-core positivist attitude toward Bohm's theory, one is simply left with a calculational algorithm -- the same one, in fact, that we called "orthodoxy" just above. In other words, if you insist that any theory *just is* its calculational algorithms, you would have a difficult time understanding what all the fuss (in regard to Bohm vs Copenhagen vs this vs that) is about.

Of course, that attitude is just dumb. I mean, seriously, what scientist actually thinks it's *wrong* to try to figure out how things work? What the heck are the string theorists doing then? Or all the astrophysicists trying to figure out exactly what happens during a core collapse supernova? Or basically every other physicist and scientist currently in existence? Sure, it's always useful to figure out what happens first -- to be in a kind of purely descriptive mode -- but then the whole point is to try to dig deeper and ask "what's going on that makes it come out this way?" or "why does it come out this way instead of some other way?" etc. Practically every important discovery in the whole history of science is an example of this. Gases obey PV = const... but *why*, what is going on physically that makes the pressure vary this way? (Then, 200 years later or whatever, "Oh, the kinetic/atomic theory explains this...") Or: Kepler noticed that planets move in ellipses, etc., but *why*? Newton provided a big part of the answer to those questions with his theory of gravitation. Or: some materials exhibit superconducting or superfluid behavior at certain temperatures... but why? So then people come up with a theory which explains that in terms of some deeper facts about the nature of the substances. Asking why (or "how", which amounts to the same thing but some people for some reason make a big deal over this distinction) is *essential* to good science. Indeed, it is practically synonymous with good science.

In other words, to take this positivist attitude seriously is to spit in the face of the whole entire history of science. So it's no wonder the people who advocated this in the 1920's cooked up a big philosophical set of pseudo-arguments for why the case of quantum theory was fundamentally different, why we really had to accept this new attitude not just because of philosophy but because of certain problems inherent to microphysics, etc. etc. But de Broglie and Bohm put the lie to it by showing explicitly that it's all bogus, that it's not impossible to give a coherent physical theory which tells a comprehensible physical story to explain physically why the measurements come out the way the calculation algorithm says they should. In short, they proved by explicit example that the *real* basis for the Copenhagen hegemony was *not* physics discoveries, but, rather, philosophical bias. Hence the irony of contemporary Copenhagen supporters dismissing Bohm on the grounds that his theory is just philosophical bias. In the end, it does come down to philosophical questions (such as: is there an external physical world, and is it the task of physics/physicists to figure out what it's like and how it works), but the right question is not "who is less biased?" but rather "which philosophy is reasonable?" That's why I'm happy and proud to admit that it's because I'm a realist and a scientist that I am "philosophically biased" in favor of Bohm, GRW, etc. as against "shut up and calculate".

 

[NateTG]

If there are experiments for which 'plug and grind' QM is ambiguous, and Bohmian Mechanics makes falsifiable predictions, then the two are clearly distinct from a scientific perspective, and, Bohmian Mechanics can, at least in theory, be tested there. Barring any such scenario, choosing one over the other is a matter of taste.

Bohmian Mechanics is primarily interesting from a philosophical perspective because it AFAICT provides a deterministic realist interpretation of QM, and thus, Bell's Theorem notwithstanding, if we assume a 'big bang', Bohmian Mechanics is a local realist interpretation of QM. (Locality follows readily from common history and determinism.)

 

[ttn]

If there are experiments for which 'plug and grind' QM is ambiguous, and Bohmian Mechanics makes falsifiable predictions, then the two are clearly distinct from a scientific perspective, and, Bohmian Mechanics can, at least in theory, be tested there.

The classic example of this is "tunneling times". Imagine a particle initially in a metastable bound state, out of which it will (asymptotically) tunnel, i.e., emerge with positive energy at some large radius. What does OQM say about (say) the average time you have to wait before the particle appears at some particular radius? It's not clear how to calculate such a thing in OQM -- and indeed not clear that there is any way to do it. Bohm's theory on the other hand can answer such questions unambiguously. Or so it seems. I don't have any interest in discussing this, really, but I just wanted to note the existence of a huge literature on this specific point.

Barring any such scenario, choosing one over the other is a matter of taste.

Sure, "taste". For example, whether one prefers a mathematically precise formulation which is 100% crystal clear about what it says exists and happens, or prefers instead something "unprofessionally vague and ambiguous" (like such-and-such happens whenever there's no "measurement" happening, while so-and-so happens instead when a "measurement" is happening, and with no further clarification or definition about what the heck a "measurement" is). So, yeah, it's merely a matter of taste: as in, whether one prefers the taste of a good theory to a bad theory.

Bohmian Mechanics is primarily interesting from a philosophical perspective because it AFAICT provides a deterministic realist interpretation of QM, and thus, Bell's Theorem notwithstanding, if we assume a 'big bang', Bohmian Mechanics is a local realist interpretation of QM. (Locality follows readily from common history and determinism.)

Bohm's theory is not local. But then, neither is any other theory which agrees with the experimental results violating Bell's inequality. That's what Bell's theorem proves. Nonlocality is a fact of the world which all empirically viable theories are going to have to include (and, so, they do). People who dismiss Bohm's theory on the grounds that it is nonlocal aren't paying attention.

 

[ueit]

Bohm's theory is not local. But then, neither is any other theory which agrees with the experimental results violating Bell's inequality. That's what Bell's theorem proves. Nonlocality is a fact of the world which all empirically viable theories are going to have to include (and, so, they do). People who dismiss Bohm's theory on the grounds that it is nonlocal aren't paying attention.

It is not true that "nonlocality is a fact of the world". A fully deterministic theoy cannot be ruled out by Bell because it denies the possibility of statistical independence between the source and detectors. All classical theories are of this type and they are not therefore eliminated by Bell.

 

[metacristi]

I've promised once that I'll never return on this forum as much as Zapper Z remains moderator here [nothing personal but I don't think that a too strong authoritarianism is a good thing for science, I still maintain that] but seeing, for some time now, the quality exchange of ideas here I cannot resist writing again (at least today :-)).

The main argument of those defending the 'shut up and calculate' stance is indeed not too far from that of logical positivists. According to this point of view - given that the 'interpretations' do not really make novel, potentially testable, predictions (only the standard mathematical formalism does, around which almost all interpretations are constructed) - we cannot accept them (the 'interpretations') as scientific (in short the interpretation part does not really account for the empirical success of the theory and there is under-determination at this level now, possible forever). Not surprisingly then that such positivists label all interpretations as being 'philosophy' not science.

I would not consider the positivistic stance without any merit (in the case of QM) but I think we can safely attack the claim (of some) that this is the only rational stance for the moment. Fact is that all valid compounds 'formalism-interpretation' are capable to account for the observed facts (post hoc is enough) and they are empirically evolving at the moment (for example Bohmian mechanics has been able to account basically for all new experiments so far though sometimes some auxiliary hypothesis are needed; the same is valid for the other valid interpretations).

In this respect the theoretical constructs used by these compounds 'mathematical formalism-interpretation' (even Copenhagen Interpretation does have such constructs) can be seen as necessary to account for the empirical success of the ‘compound’ they are part of; thus we can see, at limit, every such compound 'formalism-interpretation' as forming at least as a valid scientific program deserving to be pursued further.

Of course if we take in account now the other traditional (but weak) requirements of actual scientific methodology (ontological and logical simplicity, capacity to unify things thought previously as being not connected, coherence with other accepted parts of science etc) we can even make a weak distinction between the different existing compounds 'formalism-interpretation'.

Here clearly (though no interpretation is without problems) Bohm's interpretation appears [with its auxiliary assumptions - like Vigier's explanation of why electrons do not fall into nucleus - or the actual absence of a Lorentz invariant relativistic version] on a lower level than the evolutions of Copenhagen Interpretation (the same is valid for MWI or the transactional interpretation, for other reasons of course etc) but we cannot say that these alternatives are ‘dead ends’ (as some argue wrongly; L. Motl among the most vociferous (at least in the case of BM and TI, I wonder why he is not against MWI which after all 'want to modify physics' too with its resort to possible, but untestable, worlds).

The above mentioned ‘weak’ distinction is informative but not prescriptive, it is still fully rational at the moment to pursue such alternative programs in spite of the fact that currently they comply less with the accepted scientific methodologies (the decision to pursue a certain program as the first choice, personal, program does not automatically involve ontological commitments or claims of epistemological privilege). Indeed the history of science teach us that even seemingly degenerative programs at a certain moment can become theoretically and empirically progressive later (when the ‘background’ is prepared for their emergence) so it would be a big mistake to bar still legitimate directions of research (crucial breakthroughs could be lost forever).

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"...even the most obvious connections remain unseen if we are constantly brainwashed that such connections are impossible or meaningless" - K. Popper (paraphrased)

 

[RandallB]

A fully deterministic theoy cannot be ruled out by Bell because it denies the possibility of statistical independence between the source and detectors.

Could you clarify exactly what the “it” is in “it denies” in your point here.
(“A fully deterministic theory” or “Bell”)

I often have trouble following the logic of “local” proponents that do not accept the idea of a theory building a version of local in a non-local way (non-local Bell way). Which is why IMO BM is as viable as QM, and they are both non-local.

Taking an “Occum’s” view of which is better between BM & QM; they may be one, but I can not tell. Any more than trying to define if Leibniz Calculus is better than Newton’s or if it’s just a matter historical preference that the Leibniz method has become preferred by the majority but still not all, just like QM is used and preferred over BM by most. They give the same non-local results, and maybe both have a place. Example interference problems seem to be more easily understood using BM; while application work in particle physics seems to have made the best progress using QM.

 

[MaverickMenzies]

I think the real problem with all of these interpretations is that they are all after the fact. In other words, we discovered the mathematical formalism that could predict the various empirical effects that were observed and then we tried to make sense of the meaning of the formalism. I think that quantum mechanics will only make sense if one can discover a physical principle from which the formalism can be derived.

 

[DrChinese]

All classical theories are of this type and they are not therefore eliminated by Bell.

You can say this 100 times and it is still not true. Classical theories give results that are inconsistent with observation. I.e. they do not follow the cos^2 rule. The reason is: the observer must be taken into account in explaining the result, a mechanism for which classical theories - because they are by definition classical - are unable to do. Specifiying a common prior history answers nothing until you can tell us how it ties in.

 

[NateTG]

You can say this 100 times and it is still not true. Classical theories give results that are inconsistent with observation. I.e. they do not follow the cos^2 rule.

Falsification by experimental result is not the same thing as falsification by Bell's Theorem.

Specifiying a common prior history answers nothing until you can tell us how it ties in.

It's really quite simple, and simultanteously rather unsatisfying:

Let's assume, for a moment, that the universe is deterministic, not necessarily local and has a definite beginning. Since the universe is deterministic, we can write a (not necessarily finite) list of all of the uncertain events that occur in the universe, \vec{h}. Notably, this list is not dependant on time - so we can postulate that it's the local hidden state of the big bang, and has propagated forward locally from there.

Unless the HUP is somehow falsified (not likely) it's impossible to make any determination about mechanisms, so you could readily think of maxwell's demon runnning around and pulling strings if you like.

 

[ueit]

Could you clarify exactly what the “it” is in “it denies” in your point here.
(“A fully deterministic theory” or “Bell”)

I don't use "it" for persons, so the answer is "A fully deterministic theory”.

I often have trouble following the logic of “local” proponents that do not accept the idea of a theory building a version of local in a non-local way (non-local Bell way). Which is why IMO BM is as viable as QM, and they are both non-local.

AFAIK there is no relativistic BM, but we have QED.

1. The only theory we have that deals with the nature of space and time itself (general relativity) says our universe is local.

2. As I said many times on this forum, Bell's theory isn't a problem for local deterministic theories because these theories do not allow for statistical independence between the detectors and source. A local deterministic universe is like a clock. Bell's theorem requires that you turn independently two "wheels" (detector switches) but you just cannot do that without breaking the mechanism. Therefore the assumptions used for the derivation of Bell's theorem are logically incompatible with the assumption that we live in a local deterministic universe. Bell's theorem only proves that the law of non-contradiction is still valid, which is hardly a remarcable fact.

From 1. and 2. we can see that a local theory is to be preferred (Occam’s razor).

I agree however that a non-local explanation is much better than no explanation at all or a non-realistic one.

 

[RandallB]

First off, in the context you used "it" for was not for the person Bell

I don't use "it" for persons, so the answer is "A fully deterministic theory”.

you were referring to the "Bell Theorem" or its application.

And just declaring the "assumption that we live in a local deterministic universe" does show anything beyond establishing a point of faith maybe.
And GR has not be shown to be "local" - plenty to read by Smolin on the requirement for indeterminate background for GR (Non-local IMO) that has not been disproved to any reasonable satisfaction .

And the idea that when setting of two space like separated wheels (detector switches) we a powerless to use free will or judgment to set them differently that what the Big Bang preset deterministic universe has already decided what we will do, is just pointless. Talk about an un-testable theory - it demands that we can only know a proof for it IF it has been predetermined for us to learn it.
If you understand what LOCAL means, you would recognize this as a Non-Local Local theory. It is only local within itself as it reaches out to its preset deterministic values to explain correlations. Just like non-local BM and MWI are local within those theories, using invisible guide-waves and multi-dimensional extended realities to explain correlations within their theory.

A deterministic universe (classical or non) is not a Local (Bell Local) theory, and if you want to apply Occum's to the Non-locals this one IMO falls to the bottom of that list.

Personally I think realty is local and real does not need some kind of strange extended reality; but that is just an opinion, I don't go around declaring it as a fact. But unlike yours I know exactly the tool that is required to turn my opinion to fact, and that is the Bell Theorem itself. And it only need do so once, and all the non-locals will fall including yours. But no individual Non-local theory even has a tool that has an expectation of excluding other theories.
So if you cannot even produce a tool that might provide a proof of your theory at least state it as an opinion or personal preference and do not demand it be accepted as a simple fact.

 

[exeric]

Hi, I've done some study on this problem of non-locality and have reached my own conclusions. I've written a paper with my own plausible explanation for it. But rather than muck things up with my own ideas right off the bat I'd like to pose some questions for people who are not afraid to think outside of the box.

1.The Bell theorem, as I understand it, simply "assumes" that the EPR paper proposed a condition that required local variables. It may be more logically said that John Bell simply couldn't think of any other way of looking at quantum entanglement than in this way. My understanding is that Einstein never explicitly called for local variables but just for local "realism". In 1930 or thereabouts he produced his own theory of "teleparallelism". This theory could be said to have anticipated the results of quantum entanglement but through a different mechanism - namely "torsion".

2. If Einstein himself proposed a theory 5 years earlier in which non-locality of cause and effect could possibly happen then it could be said that what Einstein was more properly saying in the EPR paper is that quantum entanglement can exist, but that we just need to fill in our picture of physics in a way that it makes sense. It's interesting to me that so many physicists seem to ignore the title of the EPR paper: "Can The Quantum Mechanical Description of Physical Reality Be Considered Complete?"

It almost seems that the physics community has just built this straw man of "local variables" that Bell produced to show Einstein didn't know what he was talking about. Clearly he did and the title of the paper neatly summed it up what he was "really" saying.

Eric

 

[lalbatros]

Dear all,

I have asked this several times here and there. Sorry to repeat myself, for those concerned.

My question: how much can we say that entanglement is an absolute concept?

I explain more:

Let's go back to our particle A and particle B.
Particles are "just" states of a quantum field, the electromagnetic field for example when photons are involved.

This leads me to the idea that entanglement depends on the point of view, since it depends on the states that one takes as reference. In other words, a state can be a mixed state in a basis B and it could be a pure state in another basis B'.

Nevertheles, I have the intuitive feeling that entanglement should be something measurable and with a kind of absolute meaning, like the entropy in statistical physics.

What do you know about that, what are your ideas?
Some references welcome.

Thanks,

Michel

 

[ZapperZ]

Dear all,

I have asked this several times here and there. Sorry to repeat myself, for those concerned.

My question: how much can we say that entanglement is an absolute concept?

I explain more:

Let's go back to our particle A and particle B.
Particles are "just" states of a quantum field, the electromagnetic field for example when photons are involved.

This leads me to the idea that entanglement depends on the point of view, since it depends on the states that one takes as reference. In other words, a state can be a mixed state in a basis B and it could be a pure state in another basis B'.

Nevertheles, I have the intuitive feeling that entanglement should be something measurable and with a kind of absolute meaning, like the entropy in statistical physics.

What do you know about that, what are your ideas?
Some references welcome.

Thanks,

Michel

Even with your explanation, I'm not sure what you mean by an "abolute concept".

Take note that the EPR-type experiments are just ONE consequence of the property of entanglement (and Einstein's non-locality). The fact that "entanglement" means, mathematically, that the state function of the entangled property is not separable, indicates that it can have other measurable consequences.

One such consequence is that the entangled objects' property can be thought of to be one "macro" particle. If that is the case, then 2 entangled photons behave as if it is just one "macro" photon with twice the energy, and thus, half the wavelength. What this means is that if you do optical measurement with such photons, you CAN beat the diffraction limit of the original light source!

This has been done[1]! The higher order interference pattern has been seen, and this is completely consistent with the QM prediction. So I don't know if you consider this as an "absolute concept", but it certainly is very real if you base it on emprical evidence so far.

Zz.

[1] P. Walther et al. Nature v.429, p.158 (2004).

 

[lalbatros]

ZapperZ,

The way you formulate it is clearer indeed:

The fact that "entanglement" means, mathematically, that the state function of the entangled property is not separable, indicates that it can have other measurable consequences.

Indeed, what I mean is that the separability depends on the choice of the basis.
This choice actually depends on the experiment to be analysed in tems of entanglement.

Am I right to say that:

a pair of spins analysed as up or down may be in a separable state
while the same state analysed as a pair of spins left or right would not be separable​

However, I belong to the set of people who believe that the measurement postulate is not more than a pedagogical convenience (or maybe a king of closure of the theory). But still it represents -in some way- an interaction process. I skip here more discussions about the entangled state system + observer after the measurement. However this indicates that entanglement will play a role not only in a (possibly EPR) measurement process, but in any interaction.

Therefore, I believe entanglement is a very important thing. Not only because of some EPR paradox, but even more because I think it plays a big role in the quantum evolution. Maybe this is trivial, but I don't know how to highlight that from -say- the Schrödinger equation.

Considering all that, it could make sense that indeed entanglement is a "relative" property of a composite system. It is relative to the basis states considered (like a reference frame!), and in the end these basis states are related to an (EPR) measurement to be performed.

I was asking myself if entanglement could be given an absolute meaning, and therefore an absolute measure of entanglement could be defined. If there was a "preferred basis", then it would be the case.

Any ideas, suggestions, readings ... ?

Michel

 

[MaverickMenzies]

Hi lalbatros,

There has been some work done to attempt to describe the entanglement of quantum states without requiring a recourse to the tensor product decomposition i.e. the decomposition into subsystems. Here are a couple of e-prints that I have found:

quant-ph/0308043, quant-ph/0305023.

I also think that Prof. Vlatko Vedral (at the university of leeds) has some ideas to relate multipartite entanglement in solid state systems to some order parameter of the system.

I hope that this is of some use.

 

[Doc Al]

Am I right to say that:

a pair of spins analysed as up or down may be in a separable state
while the same state analysed as a pair of spins left or right would not be separable​

No. Whether a two-particle state is entangled or not does not depend on the choice of basis states used to describe it. Perhaps you are thinking of the fact that a "spin-up" state can be expressed as a superposition of "spin-left" and "spin-right" states?

 

[ttn]

No. Whether a two-particle state is entangled or not does not depend on the choice of basis states used to describe it. Perhaps you are thinking of the fact that a "spin-up" state can be expressed as a superposition of "spin-left" and "spin-right" states?

...although the number of terms in the quantum state function (which one might loosely think of as a measure of the "amount" of entanglement) can differ from basis to basis. This, by the way, is the source of the so-called "preferred basis problem" which advocates of the Many Worlds Interpretation are forced to worry about since they are sometimes in the business of "counting worlds" to try to derive Born's rule.

Also, repeating what a previous poster said, there are tons of papers on the question of trying to quantify the "amount" of entanglement. (For the reason I just pointed out, the number of terms in the quantum state function is not a good measure of this since it's basis-dependent!) Search, e.g., on arxiv for "entanglement measure" and lots of things will come up.

Finally, I might be wrong about this, but I got a vague sense that lalbatros was raising these questions about entanglement because of a confusion over Bell's argument for non-locality. Just for the record, the argument is *not* of the form: there's a kind of non-locality associated with entanglement, which is a pretty important/ineliminable feature of quantum theory, hence non-locality is a real physical thing. That's not the argument at all. My sense was that lalbatros was worried that maybe people accepted non-locality too easily (based on some argument like this), when, in fact, there is every reason to wonder if "entanglement" is even an absolute ineliminable concept. It is, after all, a feature of a *theory* -- a theory that there is tons of controversy about whether or to what extent it should be taken as providing a literal true description of physical reality.

I'm not sure I'm saying this very clearly. The point is, anyone who believes that nonlocality is a real feature of the physical world *based on the mere fact that orthodox quantum theory says that spatially separated systems can sometimes be in entangled states* is a crazy fool. Bell was no crazy fool. So anyone interested in understanding why Bell (and those who understand and hence follow him) believed nonlocality was a real physical phenomena, should go read Bell's papers where he explains this all very very clearly!

And now, just in case Zapper Z is still reading... I'm still anxiously waiting to hear what part of the argument in Einstein's Boxes you found unconvincing and/or why you thought the criticisms by Shimony and [that other guy whose name I can't remember] made sense...

 

[exeric]

Hi, I've done some study on this problem of non-locality and have reached my own conclusions. I've written a paper with my own plausible explanation for it. But rather than muck things up with my own ideas right off the bat I'd like to pose some questions for people who are not afraid to think outside of the box.

1.The Bell theorem, as I understand it, simply "assumes" that the EPR paper proposed a condition that required local variables. It may be more logically said that John Bell simply couldn't think of any other way of looking at quantum entanglement than in this way. My understanding is that Einstein never explicitly called for local variables but just for local "realism". In 1930 or thereabouts he produced his own theory of "teleparallelism". This theory could be said to have anticipated the results of quantum entanglement but through a different mechanism - namely "torsion".

2. If Einstein himself proposed a theory 5 years earlier in which non-locality of cause and effect could possibly happen then it could be said that what Einstein was more properly saying in the EPR paper is that quantum entanglement can exist, but that we just need to fill in our picture of physics in a way that it makes sense. It's interesting to me that so many physicists seem to ignore the title of the EPR paper: "Can The Quantum Mechanical Description of Physical Reality Be Considered Complete?"

It almost seems that the physics community has just built this straw man of "local variables" that Bell produced to show Einstein didn't know what he was talking about. Clearly he did and the title of the paper neatly summed it up what he was "really" saying.

Eric

I'd still be interested in any responses to what I said above. I realize what I'm saying maybe a little off in right field to some of you but I really think Bell's inequality is just a starting point for understanding quantum entanglement. It just shows that the non-locality of correlative effects exist but in no way addresses Einstein's real question. I think it misses the forest for the trees. Conversely, I think the EPR paper was concentrating on the forest - something which is done rarely in physics, even today. I promise I won't talk about my own ideas about QE if I can just get you guys to engage on this point.

Eric

 

[ZapperZ]

Indeed, what I mean is that the separability depends on the choice of the basis.
This choice actually depends on the experiment to be analysed in tems of entanglement.

Am I right to say that:

a pair of spins analysed as up or down may be in a separable state
while the same state analysed as a pair of spins left or right would not be separable​

I don't understand this part. How do you separate out, for example

|\Psi> = |up>_1|down>_2 + |down>_1|up>_2 ?

There are no unitary transformation to a different basis that you can do that separate them out, are there?

Zz.

 

[exeric]

ZapperZ,



However, I belong to the set of people who believe that the measurement postulate is not more than a pedagogical convenience (or maybe a king of closure of the theory). But still it represents -in some way- an interaction process. I skip here more discussions about the entangled state system + observer after the measurement. However this indicates that entanglement will play a role not only in a (possibly EPR) measurement process, but in any interaction.

Therefore, I believe entanglement is a very important thing. Not only because of some EPR paradox, but even more because I think it plays a big role in the quantum evolution. Maybe this is trivial, but I don't know how to highlight that from -say- the Schrödinger equation.

Considering all that, it could make sense that indeed entanglement is a "relative" property of a composite system. It is relative to the basis states considered (like a reference frame!), and in the end these basis states are related to an (EPR) measurement to be performed.

I was asking myself if entanglement could be given an absolute meaning, and therefore an absolute measure of entanglement could be defined. If there was a "preferred basis", then it would be the case.

Any ideas, suggestions, readings ... ?

Michel

I, myself don't think that quantum entanglement can be considered as something relative to the way that it is measured. It might have been an open question before the vast experimental evidence has built up, but I don't think it can be said anymore. Entanglement is not an "interpretative" event in that respect. And measurement only nails the quantum state of each of entangled composite particles at the instant it is measured.

I think you brought up a very interesting point about composite particles. This is the heart of the phenomena. It has only very recently been broadly realized that entanglement is not a rare event but probably plays a part in all particles that are made from composite particles. In this sense the assymptotic freedom of quarks in a proton could be considered just another aspect of quantum entanglement. In this special case it might be speculated that the binding energy between quarks is just a case where the energy of quantum entanglement equals the energy of the angular velocity of the quarks. So no matter how much energy one puts into a proton that energy divides equally between quantum entanglement energy and the energy of each quarks spin velocity. It would explain a lot about the origin of E=mc^2. Half of the energy in the formation of protons in the first microseconds of the universe occurred exactly at c, i.e.1/2 mv^2 = 1/2mc^2. This is the kinetic energy of the spin angular momentum of quarks. The other half of the energy, also equaling 1/2mc^2, equals the energy involved in quantum entanglement. So no matter how much energy you put into a proton that energy will divide equally between the magnitude of the spin angular velocity and the quantum entanglement energy and quantum entanglement will continue to rigidly confine the quarks.

I think people are starting to wake up to the fact that quantum entanglement plays a part in forming mass in all composite particles. And single photons are the only particles that are not composite particles and thus have no mass. However they do have energy so the 'm' in the kinetic energy of quarks but still be their energy but not in the "mass" sense. But even they can acquire mass through entanglement with other photons.

Eric

 

[ZapperZ]

I, myself don't think that quantum entanglement can be considered as something relative to the way that it is measured. It might have been an open question before the vast experimental evidence has built up, but I don't think it can be said anymore. Entanglement is not an "interpretative" event in that respect. And measurement only nails the quantum state of each of entangled composite particles at the instant it is measured.

I think you brought up a very interesting point about composite particles. This is the heart of the phenomena. It has only very recently been broadly realized that entanglement is not a rare event but probably plays a part in all particles that are made from composite particles. In this sense the assymptotic freedom of quarks in a proton could be considered just another aspect of quantum entanglement. In this special case it might be speculated that the binding energy between quarks is just a case where the energy of quantum entanglement equals the energy of the angular velocity of the quarks. So no matter how much energy one puts into a proton that energy divides equally between quantum entanglement energy and the energy of each quarks spin velocity. It would explain a lot about the origin of E=mc^2. Half of the energy in the formation of protons in the first microseconds of the universe occurred exactly at c, i.e.1/2 mv^2 = 1/2mc^2. This is the kinetic energy of the spin angular momentum of quarks. The other half of the energy, also equaling 1/2mc^2, equals the energy involved in quantum entanglement. So no matter how much energy you put into a proton that energy will divide equally between the magnitude of the spin angular velocity and the quantum entanglement energy and quantum entanglement will continue to rigidly confine the quarks.

I think people are starting to wake up to the fact that quantum entanglement plays a part in forming mass in all composite particles. And single photons are the only particles that are not composite particles and thus have no mass. However they do have energy so the 'm' in the kinetic energy of quarks but still be their energy but not in the "mass" sense. But even they can acquire mass through entanglement with other photons.

Eric

Please re-read the PF Guidelines that you have explicitly agreed to. Pay particular attention to speculative personal theories. Your posts might be deleted and you will be ask to submit your "theories" to the Independent Research forum.

Zz.

 

[DrChinese]

...If Einstein himself proposed a theory 5 years earlier in which non-locality of cause and effect could possibly happen then it could be said that what Einstein was more properly saying in the EPR paper is that quantum entanglement can exist, but that we just need to fill in our picture of physics in a way that it makes sense. It's interesting to me that so many physicists seem to ignore the title of the EPR paper: "Can The Quantum Mechanical Description of Physical Reality Be Considered Complete?"

It almost seems that the physics community has just built this straw man of "local variables" that Bell produced to show Einstein didn't know what he was talking about. Clearly he did and the title of the paper neatly summed it up what he was "really" saying.

I'd still be interested in any responses to what I said above. I realize what I'm saying maybe a little off in right field to some of you but I really think Bell's inequality is just a starting point for understanding quantum entanglement. It just shows that the non-locality of correlative effects exist but in no way addresses Einstein's real question. I think it misses the forest for the trees. Conversely, I think the EPR paper was concentrating on the forest - something which is done rarely in physics, even today. I promise I won't talk about my own ideas about QE if I can just get you guys to engage on this point.

Eric

Einstein did not believe in non-locality. As the inventor of relativity, he essentially took locality as a given.

As to the title of the great EPR paper: perhaps you should refresh yourself with EPR's primary conclusion, which was proven and is generally accepted: If Quantum Mechanics is complete (i.e. there is no better description of the state of the system - my words), then there cannot be simultaneous reality to non-commuting operators. The contranegative is also true: if there is simultaneous reality to non-commuting operators, then Quantum Mechanics is incomplete.

EPR then speculates as follows: a) that there is simultaneous reality to non-commuting operators MUST be true; therefore QM is incomplete; or b) there exists non-local forces (spooky action at a distance). Since Einstein did not believe b) was true, this shows that he believed in a) and ultimately that the predictions of QM could not hold in this case.

This speculation is what ultimately led to Bell's paper, which showed that: if QM is incomplete but otherwise correct in its predictions, then there must exist non-local forces. I would not call Bell's assumptions "straw men". Although some have referred to them as "naive realism" and/or "naive locality", they are taken plenty seriously today. And certainly so by Einstein, although he of course never saw Bell's work. I am quite sure he would have appreciated what Bell did.

 

[exeric]

Please re-read the PF Guidelines that you have explicitly agreed to. Pay particular attention to speculative personal theories. Your posts might be deleted and you will be ask to submit your "theories" to the Independent Research forum.

Zz.

Why don't you let people pick apart what I've said before you delete it. And if people wish to pick apart what I've said it is always a good idea to first debate the concepts presented by the messenger than to debate the quality of the messenger himself. That is one of the first principles of open debate. I've done substantial work on quantum entanglement and do not wish to overpromote myself on this. I can email you privately what my background on this is if you are interested.

 

[ZapperZ]

Why don't you let people pick apart what I've said before you delete it. And if people wish to pick apart what I've said it is always a good idea to first debate the concepts presented by the messenger than to debate the quality of the messenger himself. That is one of the first principles of open debate. I've done substantial work on quantum entanglement and do not wish to overpromote myself on this. I can email you privately what my background on this is if you are interested.

You could be a Nobel Prize winner, and we will still enforce the Guidelines. You know what you are getting yourself into from the very beginning.

If you wish to have people pick apart your ideas, that is exactly that the Independent Research forum is for. We apply this rule to everyone, you included.

This forum is not the place for you to work out your personal theory.

Zz.

 

[exeric]

You could be a Nobel Prize winner, and we will still enforce the Guidelines. You know what you are getting yourself into from the very beginning.

If you wish to have people pick apart your ideas, that is exactly that the Independent Research forum is for. We apply this rule to everyone, you included.

This forum is not the place for you to work out your personal theory.

Zz.

Ok, delete those posts. But don't delete my first two posts to this thread. There is nothing wrong with them being placed here. I think its a very fine line between trying to advance knowledge by challenging accepted theory and quarantining new ideas to a "safe" place, where they can be ignored. I think it is something to be concerned about, don't you? Science cannot be entirely extricated from human impulses for overt social control but it should be at least recognized that it also happens in science just as in non-scientific areas.

Eric

 

[exeric]

What on Earth are you talking about? You first say you have a couple questions – but give none, only opinions. Just what is “this point” ??
And then what do you think Einstein's real question was, if not to claim QM cannot be complete as QM claims itself to be, as it calls for reality to be non-local.

It's hard to know where to begin. The most blatant problem with quantum entanglement is in asking where the energy for quantum entanglement comes from. Do you actually think conservation of energy is not involved in the quantum entanglement process? If you accept that "free lunch" premise then I'm sorry, but you've already drunk the quantum mechanical kool-aid. This is the real essence Einstein was getting at in the question: "Can the quantum mechanical description of physical reality be considered complete?" There are no free lunches and Einstein was just stating the worst example of non-conservation of energy in the EPR paper, which is the energy involved in quantum entanglement. What's so difficult in understanding this is a problem?

Eric

 

[ZapperZ]

Ok, delete those posts. But don't delete my first two posts to this thread. There is nothing wrong with them being placed here. I think its a very fine line between trying to advance knowledge by challenging accepted theory and quarantining new ideas to a "safe" place, where they can be ignored. I think it is something to be concerned about, don't you? Science cannot be entirely extricated from human impulses for overt social control but it should be at least recognized that it also happens in science just as in non-scientific areas.

Eric

Since when is the advancement of science done on an open internet physics forum?

Again, you AGREED to abide by OUR rules when you signed on. You are more than welcome to 'advance science' elsewhere if you don't care for the guidelines.

Zz.

 

[ttn]

As to the title of the great EPR paper: perhaps you should refresh yourself with EPR's primary conclusion, which was proven and is generally accepted: If Quantum Mechanics is complete (i.e. there is no better description of the state of the system - my words), then there cannot be simultaneous reality to non-commuting operators. The contranegative is also true: if there is simultaneous reality to non-commuting operators, then Quantum Mechanics is incomplete.

I've been over this with you a million times before, but... for the benefit of any intelligent lurkers... the above represents a failure to grasp what is at issue in the EPR argument, and what they were trying to argue for. Dr C suggests that the thrust of the EPR paper was to argue for the following statement: if QM is complete, then there cannot be simultaneous reality to non-commuting operators/observables.

But that's not even the kind of thing one needs to argue for. It's simply a *definition* of completeness -- or more specifically, it's a clear litmus test for completeness in the context of a theory which simply doesn't *allow* the assignment of simultaneous definite values to non-commuting operators. It's just a given that, in orthodox QM, you can't do this. And so, to whatever extent, out there in physical reality, such observables *do* possesses simultaneous definite values, then orthodox QM is not complete.

So not only is that not the main thing EPR are arguing for, it's not the kind of thing one needs to argue for at all. To understand what the statement means is to see it as obviously true. The hard part is to construct some kind of argument that, in fact, out there in physical reality, such observables (i.e., those corresponding respectively to non-commuting operators) do possesses simultaneous definite values. And Dr C seems to completely miss that there is something like this argument in EPR, though, admittedly, it is hard to understand because of the way Podolsky wrote the manuscript. (Einstein didn't see the final draft and got mad that Podolsky had "buried" the main argument.) But now we know what Einstein had in mind. The argument was fundamentally based on *locality*. See "Einstein's Boxes" for further details.

EPR then speculates as follows: a) that there is simultaneous reality to non-commuting operators MUST be true; therefore QM is incomplete;

This is a ridiculous piece of trash. As a fan of Einstein I'm personally insulted that someone would publicly suggest that this was the EPR argument. I mean, come on. Einstein "speculates" (i.e., just makes up arbitrarily because he feels like it, not based on any argument) that observables corresponding to non-commuting operators "MUST" have simultaneous definite values? He just makes it up? I mean, please. It's a disgusting insult to the greatest physicist ever. Anyone who has a shred of respect for the great man should realize, if they think this was the argument, that maybe they just haven't *understood* the argument yet... and so they should go back and do some homework to find out what Einstein actually thought, rather than spread vicious lies and confusions that make Einstein sound like a moron.

or b) there exists non-local forces (spooky action at a distance).

Look, the argument is that *unless* one accepts spooky nonlocal forces, one must posit certain elements of reality. There's an actual *argument* there. If you haven't understood the argument, go back and study the issue some more. But don't keep spouting this nonsense that Einstein just arbitrarily "speculated" that it was a or b... Sheesh.

Since Einstein did not believe b) was true, this shows that he believed in a) and ultimately that the predictions of QM could not hold in this case.

Where did Einstein ever say that "the predictions of QM could not hold"? Actually the whole EPR argument (or his Boxes version) is premised on the predictions of QM being true. The whole argument is that the only way to explain certain correlations (namely, those *predicted by QM*) LOCALLY is to posit certain "hidden variables".

This speculation is what ultimately led to Bell's paper, which showed that: if QM is incomplete but otherwise correct in its predictions, then there must exist non-local forces.

You misunderstand this as well. One needn't assume that "QM is incomplete" in order to derive a Bell type inequality. The inequality follows from locality (a certain mathematically precise definition thereof which Bell first articulated) alone. That's it. Of course, it is possible to get a Bell inequality by first assuming certain hidden variables (and locality). But this doesn't change what I just said, since the existence of those hidden variables is itself a logical consequence of the locality assumption. That, as Bell points out repeatedly in his papers, is the EPR argument. Locality *requires* those hidden variables. So if Bell assumes them (and sometimes he does, but not always and it isn't logically necessary) it doesn't matter one way or the other. Either way, the inequality follows from Locality alone. The only question is whether one gets there in one step or two.

I don't expect to change your mind on any of this since I've tried so many times before and failed completely. But I can't in good conscience sit here and watch you disgustingly pervert these beautiful arguments. Not in front of what might (for all I know) be innocent children.

 

[RandallB]

EPR then speculates as follows: a) that there is simultaneous reality to non-commuting operators MUST be true; therefore QM is incomplete; or b) there exists non-local forces (spooky action at a distance). Since Einstein did not believe b) was true, this shows that he believed in a) and ultimately that the predictions of QM could not hold in this case.

I’m sorry tnn I just don’t see where this is an insult to Einstein any more than calling HV theories a belief in "naive locality / realism". It true and there is nothing wrong with that – it’s just not likely a correct view of actual reality based on testing so far.

Maybe using the word asserts instead speculates would help. I’ll sleep on it and reread your point in the AM.

 

[exeric]

Since when is the advancement of science done on an open internet physics forum?

Again, you AGREED to abide by OUR rules when you signed on. You are more than welcome to 'advance science' elsewhere if you don't care for the guidelines.

Zz.

I thought I said you could delete the post involving quantum entanglement in protons. Do you want to argue with me now by projecting on to me that I didn't accept that? I did.

Are you annoyed because I accepted it with protest? Well, then be annoyed. I'm annoyed too. But I'm not threatening to kick you off like you are threatening me. I can live with annoyance. I guess you can't.

Hazzard the thought that we would EVER want to think deeply about science and not just accept the status quo.

Eric

 

[lalbatros]

Doc Al,
ZapperZ,
Dear All,

I don't understand this part. How do you separate out, for example

|\Psi> = |up>_1|down>_2 + |down>_1|up>_2

There are no unitary transformation to a different basis that you can do that separate them out, are there?

Would it not be possible to take

|\Psi>

as a basis vector and build the space by orthogonality around it?

I know that doing this would not only mix the spin part of the state but also the particle part. But why would that be a problem? Maybe because the particle state IS the preferred "frame of reference" ? If I consider photons as an exemple, should such a photon-mix state be less preferred?

Michel

 

[ZapperZ]

Doc Al,
ZapperZ,
Dear All,



Would it not be possible to take

|\Psi>

as a basis vector and build the space by orthogonality around it?

Then show me how you would do that. How do you separate out each of the ket vectors.

Zz.

 

[DrChinese]

I've been over this with you a million times before, but... for the benefit of any intelligent lurkers...

1. But that's not even the kind of thing one needs to argue for. It's simply a *definition* of completeness -- or more specifically, it's a clear litmus test for completeness in the context of a theory which simply doesn't *allow* the assignment of simultaneous definite values to non-commuting operators. It's just a given that, in orthodox QM, you can't do this. And so, to whatever extent, out there in physical reality, such observables *do* possesses simultaneous definite values, then orthodox QM is not complete.

2. This is a ridiculous piece of trash. As a fan of Einstein I'm personally insulted that someone would publicly suggest that this was the EPR argument. I mean, come on. Einstein "speculates" (i.e., just makes up arbitrarily because he feels like it, not based on any argument) that observables corresponding to non-commuting operators "MUST" have simultaneous definite values? He just makes it up?

3. Look, the argument is that *unless* one accepts spooky nonlocal forces, one must posit certain elements of reality. There's an actual *argument* there.

4. Where did Einstein ever say that "the predictions of QM could not hold"?

The paper says exactly what I say, it is you that brings in discussion from after EPR.

1. Wrong! It may be the definition today, but hardly at the time. In effect, EPR is attacking the HUP and is connecting the HUP to the completeness argument. It's a great piece of work, and I think it stands the test of time.

2. I didn't insult Einstein, would never do that. But I did accurately relate the EPR arguments. There is speculation in the last sentence of the paper, which sums it up: "We believe, however, that such a theory [local realistic] is possible." And clearly, the statement 2 sentences previously: "No reasonable definition of reality could be expected to permit this" is completely speculative. QED.

3. They are trying to make the argument that it is an either/or, I have no disagreement with that. There is non-locality on one side (expressed by the statement "there is no longer any interaction between the two parts"), and something else on the other - whatever you want to call it. I specifically pointed this out to you in my post, see my a) and b) !

4. Wigner said in the 30's that Einstein believed "...that quantum mechanics has a limited validity, just as the basic ideas of Newton were..." I can't find a more suitable quote at this time, but I certainly don't believe for one moment that Einstein ever believe that any apparently non-local effect would be discovered from space-like particles which had interacted in the past. Of course he also did not have the benefit of Bell to make this dilemma more clear.

 

[ueit]

First off, in the context you used "it" for was not for the person Bell you were referring to the "Bell Theorem" or its application.

OK, my mistake.

And just declaring the "assumption that we live in a local deterministic universe" does show anything beyond establishing a point of faith maybe.

It's not about faith, it's a hypothesis, and this hypothesis cannot be proven wrong by Bell's theorem. This is all I'm saying. I do not claim that it is true. It may be, we don't know yet.

And GR has not be shown to be "local" - plenty to read by Smolin on the requirement for indeterminate background for GR (Non-local IMO) that has not been disproved to any reasonable satisfaction.

I've never seriously studied GR so you may be right, but can you be more specific about this? Gravity travels at c, so at least GR is not non-local in the way Newtonian gravity was. What exactly is that travels at infinite velocities in GR?

And the idea that when setting of two space like separated wheels (detector switches) we a powerless to use free will or judgment to set them differently that what the Big Bang preset deterministic universe has already decided what we will do, is just pointless. Talk about an un-testable theory - it demands that we can only know a proof for it IF it has been predetermined for us to learn it.

Free will is a very weak hypothesis, in fact is almost certainly wrong even if QM is fundamentally random, because the neural activity is in the classical regime.

The absence of free will is a logical consequence of determinism unless you believe that humans are somehow above nature (immaterial souls?).

I don't think that a deterministic theory is untestable. May be "it has been predetermined for us" to test it.

If you understand what LOCAL means, you would recognize this as a Non-Local Local theory. It is only local within itself as it reaches out to its preset deterministic values to explain correlations. Just like non-local BM and MWI are local within those theories, using invisible guide-waves and multi-dimensional extended realities to explain correlations within their theory.

A deterministic universe (classical or non) is not a Local (Bell Local) theory, and if you want to apply Occum's to the Non-locals this one IMO falls to the bottom of that list.

I don't propose any "extended realities". Think at those wheels as the known particles. For example, it may be that BM could find a local explanation just like Newtonian gravity found one in GR (I know, you object to that but you should at least agree that gravity does not propagate at an infinite velocity in GR).

Personally I think realty is local and real does not need some kind of strange extended reality; but that is just an opinion, I don't go around declaring it as a fact.

This is my opinion too. And I don't claim it is a fact either. The only claim I make is that Bell's theory doesn't disqualify local realistic theories from the start. That is, it is logically possible that a local-realistic theory underlies QM. And I think we agree on that.

But unlike yours I know exactly the tool that is required to turn my opinion to fact, and that is the Bell Theorem itself. And it only need do so once, and all the non-locals will fall including yours. But no individual Non-local theory even has a tool that has an expectation of excluding other theories.

I don't propose any non-local theory, in fact I'm not capable of proposing any theory to revolutionize physics. I only try to point some logical mistakes frequently done even by experienced physicists when interpreting Bell's theorem.

So if you cannot even produce a tool that might provide a proof of your theory at least state it as an opinion or personal preference and do not demand it be accepted as a simple fact.

I didn't intended for my analogies to be taken as "theories". They are only examples of how non-local correlations could be simulated in a local theory.

 

[ttn]

The only claim I make is that Bell's theory doesn't disqualify local realistic theories from the start. That is, it is logically possible that a local-realistic theory underlies QM. And I think we agree on that.

Bell's theorem has nothing to do with 'realism', but it does prove that no local theory can agree with experiment. You have a "hunch" that says otherwise... but is this actually based on anything? For example, can you tell us exactly where Bell went wrong in his reasoning? He quite unambiguously states -- and I have studied his work in detail and believe he is right -- that the theorem proves that no local theory can be viable. The argument -- the detailed proof of this conclusion -- is right there in his papers. So the burden is clearly on you to justify your speculation that he was wrong. Otherwise, you're just some schmuck spouting BS on an internet forum.

I only try to point some logical mistakes frequently done even by experienced physicists when interpreting Bell's theorem.

So point to them.

 

[RandallB]

"assumption that we live in a local deterministic universe"
It's not about faith, it's a hypothesis, and this hypothesis cannot be proven wrong by Bell's theorem. This is all I'm saying. I do not claim that it is true. It may be, we don't know yet.

Of course Bell doesn’t address deterministic it only address Local vs. Non-local. And deterministic theories are non-local

I've never seriously studied GR so you may be right, but can you be more specific about this? Gravity travels at c, so at least GR is not non-local in the way Newtonian gravity was. What exactly is that travels at infinite velocities in GR?

I already gave you Smolin – 3 books and lots of papers; plus READ though the forum below this one (SR & GR) that more than enough to keep you out of trouble till to start to understand enough to talk about GR – take your time and think as you go – remember it took Einstein 10 years – you think you should get it in ten minuets?

Plus, what do infinite velocities have to do with anything? Newton was very clear about gravity and he never called for infinite velocity, if someone says he did ask them in which Newton Book, Issue, Chapter, Page and Line he did.

….. it is logically possible that a local-realistic theory underlies QM. And I think we agree on that.

NO we don’t agree because you’re saying that locality could be a correct underlying part of a correct and complete QM – you do not understand Bell-local here. I agree or I should say QM agrees with me, including DrC IMO, that IF (read it again IF) locality is shown to be true, at that instant anyone that understands QM will admit QM is wrong – The Whole Point Is - the evidence so far is for a Non-Local World.

I don't propose any non-local theory …….

But you DO! A classical deterministic is NOT BELL LOCAL.
Bell Local means that as each of the series of individual photons the meet up with the PDC to interact with it there are only the local inputs of the PDC and the one Photon that creates two Photons, only local variables can exist in each of them based on all the conservation of etc. etc. There is nothing to keep the two connected they depart that local area to how ever far away taking only Local Variables with them.
The results found at the later distant test say we don’t know all those variables. Plus even no unknown hidden one we can come up with will explain is the results seen there so far. Thus – if this conclusion is correct then our common sense realistic ideas of reality are wrong; that is the correct reality is non-local and our comfy local realist inclinations are just wrong. Bell can say no more than this – period!

Sure the PDC and each of those photons have a history – BUT to “extend ancient reality” of them to the past reality of any possible measuring devise they may encounter. Even if the have to go all the way back to the big bang, AND expect that “extended reality” to be informative enough as to cause the correlations we see. And sure full and complete determinism would do that but it sure is not BELL LOCAL! And IMO it is a ridiculous hypothesis. The Non-local BM and MWI theories (and others) with realities that add guide waves and extra dimensions to the “realistic” are far more sensible than any deterministic theory no matter how many dimensions it may or may not have.

SO PLEASE take this, no free will, deterministic “science” to the Philosophical forums, just use the menu to get there.

 

[NateTG]

And sure full and complete determinism would do that but it sure is not BELL LOCAL! And IMO it is a ridiculous hypothesis. The Non-local BM and MWI theories (and others) with realities that add guide waves and extra dimensions to the “realistic” are far more sensible than any deterministic theory no matter how many dimensions it may or may not have.

I almost don't have the heart to point out that MWI is, in fact, an example of 'full and complete determinism' which just uses a slighly different form of bookkeeping. After all, from the point of view of the interpreation, any time a measurement takes place, all possible results occur even if the observer (after measurement observers) must individually go with each of these results. Really, the difference between this, and a 'braindead' all measurements are determined in advance according to rules x, y and z approach is that one is more frequentist while the other is more baesian.

 

[RandallB]

I almost don't have the heart to point out that MWI is, in fact, an example of 'full and complete determinism' which just uses a slighly different form of bookkeeping.

I disagree; it seems easy to me that a MWI view can maintain free will as it will only serve to limit the MW’s to those uncertainties within the bounds of free will choices. Be those choices made by an amoeba or some other free will form.
Sure a more restrictive interpretation may be defined, especially if one desires to describe MWI as brain-dead.
But, as I’m not a fan of MWI, I have not right to demand that it be interpreted as using 'full and complete determinism' just so I can discard the theory; without my offering some proof that it must be thought of that way and I cannot.

As long as it is used to create extended HV’s in a definition of “local” that simply extends beyond our 3D world into some extra-dimensional MW view of reality I cannot refute MWI’s ability to resolve entanglement its own non-local manor.

BUT, I don’t accept that view or any non-local view until it can create an experiment that can produce convincing results that only that view can explain. No non-local has and if QM is correct none ever will, including QM.

 

[RandallB]

Bell's theorem has nothing to do with 'realism',

tnn
I disagree as since the ‘realism’ or reality expected by a “local realist” (like me) is not just local but “Bell Local”. To the extent that Bell Tests have demonstrated that expectation (mine) is wrong; it means that the correct reality is something other than 'realism' expected by a “local realist”.

I’ve tried to understand the conflict between you and DrC, but at the end of each of your respective points to me you both seem to end up at the same place.

- EPR and Bell as the modern distillation of it can looks for LHV’s in an effort to decide between Local vs. Non-Local. It can not confirm anyone version of a Theory, Bell tests can only comment on the local vs. non-local issue.

- QM claims to be complete; Complete in that no physical explanation of reality can provide greater predictive ability than the statistical “shut-up and calculate” style of QM.

- Other Non-Locals (BM, WMI, M, Strings etc.) claim to have a ‘good’ explanation, BUT offer no experiments that exceed the ability of QM to make predictions.

The only place I see conflict might be in an expectation that Bell could prove a theory, and that is clearly wrong for either side as I think we all agree EPR-BELL can only address Local vs. Non-Local. It will take something other than Bell in some experiment to select between QM, MWI, BM, etc.

For QM the bad news is there can be no experiment ever that can affirmatively prove the claim of completeness. For such a positive proof to be found and made it could only do so by revealing something new QM had not already accounted for, thus showing itself to have been incomplete! That is the claim of QM is even if something like MWI or BM is correct – it will be impossible to every find a way to prove it.

For the other Non-Locals (MWI, BM, etc) they can hold out hope that something someday may prove their case, by showing us something that QM cannot. But no one has yet proposed any experiment or prediction of an event that can only be explained by their theory.

In fact there has been only one theories that has been able to even propose an idea or experiment capable of proving itself correct. That would be the Local Realist and the experiment, EPR-Bell; as both Einstein and J. Bell hoped it would make known the unknown hidden variable that must exist for the Local Realist”. BUT, Part of the risk of putting forward such an experiment is that it may just falsify you own ideas; which seems to be the case so far.