About violation of Bell's inequalities

  • #1

Main Question or Discussion Point

About violation of Bell ineqalities (and the Loch Ness monster)
Assuming no loophole experiments can be done... even then I am not sure of what this would mean beyond the fact that QM's prediction on correlation work fine (and where is the surprise there?).

I know that assuming some statistical properties of yet to be proven valid Hidden Variables (HVs) theories, one could replace what cannot be measured by what is measured (no measure of hidden variable can be done, and not much is gained when replacing HVs by realism as Wigner did). But let's be serious: HVs are probably as likely to be relevant as the Loch Ness monster (same thing for naive realism, i.e. realism that does not tae account of the Uncertainty Principle).
Assume that a theory shows that if you put a goat and a goat that has seen the Loch Ness monster on some small boat, that boat will immediately sink. Prosper Youyou shows experimentally that a goat weights less than half the weight that can be carried by the small boat. Then Prosper claims that he has experimentally disproved the Loch Nees and goat theory. Is Prosper entitled to that claim, or has Propser only proved a well-established fact about goats?
Bell's historical paper starts with a strong opinion on the EPR paper that contradicts Einstein's own expressed views: that QM is non-local. This paper of Bell paper then shows that any (naive) HV theory where HVs have the same statistics that QM would also need to be non-local. The strong claim is the one about QM since no one has ever validated HVs.
The proofs about HVs can ONLY be theoretical as long as no one has experimentally shown HV theories to make sense (of course, that experimental proof could be simultaneous with the proof that Bell's Inequalities are violated). But till otherwise proved, Bell's Inequalities are about very hypothetical entities and no experimental proof of their range of validity makes sense.
 

Answers and Replies

  • #2
DrChinese
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I think I see your point. For a local HV theory to be tenable (i.e. taken seriously), one of the following is necessary:

a) There should be some evidence that a Hidden Variable is present, such as a violation of the Uncertainty Principle.
b) The theory should make a claim that the QM correlation statistics (cos^2 relationship) are wrong; this would be very surprising indeed.

So either way, some fundamental element of QM - which has already been experimentally verified - would need to be contradicted first.
 
  • #3
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DrChinese said:
For a local HV theory to be tenable (i.e. taken seriously), one of the following is necessary:

a) There should be some evidence that a Hidden Variable is present, such as a violation of the Uncertainty Principle.
b) The theory should make a claim that the QM correlation statistics (cos^2 relationship) are wrong; this would be very surprising indeed.

So either way, some fundamental element of QM - which has already been experimentally verified - would need to be contradicted first.
A LHV theory is required because QM only gives statistical answers. Such a theory doesn't need to contradict QM in any way, on the contrary, it should give the same statistical results (for example, it should be able to predict, or at least postdict, the timing of a radioactive decay but it doesn't need to predict a different decay probability).

charlylebeaugosse said:
The proofs about HVs can ONLY be theoretical as long as no one has experimentally shown HV theories to make sense (of course, that experimental proof could be simultaneous with the proof that Bell's Inequalities are violated). But till otherwise proved, Bell's Inequalities are about very hypothetical entities and no experimental proof of their range of validity makes sense.
Bell's Inequalities are about a null set of LHV theories, the set of logically impossible ones. The assumption of free will, required for Bell's proof to work, is incompatible with the assumption that the universe is deterministic. It is a circular argument that can be rejected on logical grounds, without any appeal to QM or Aspect's experiments.
 
  • #4
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**
Bell's Inequalities are about a null set of LHV theories, the set of logically impossible ones. The assumption of free will, required for Bell's proof to work, is incompatible with the assumption that the universe is deterministic. It is a circular argument that can be rejected on logical grounds, without any appeal to QM or Aspect's experiments. ***

True, but on the other hand this zero measure class is about the most intuitive ones. But if one looks at the crazy ideas going around in modern theoretical physics, I indeed agree that some liberty SHOULD be granted; actually such extra degrees of freedom are already suggested by what we know to be correct. :smile: Local realism is correct, a simple notion of reality might be misguided (or QM is incorrect which is still a logical possibility).

Careful
 
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How does this work with the Aspect Experiment of 1982? Smoke, and mirrors? Was non-local causality not verified?
 
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drdave616 said:
How does this work with the Aspect Experiment of 1982? Smoke, and mirrors? Was non-local causality not verified?
Aspect's Experiment just like any other of this type assumes that the detector settings are random. Such an assumption cannot be granted when randomness itself is to be tested, therefore no relevant conclusion can come up from these experiments. A correct test of a LHV theory must include the time evolution of the detector itself (including human experimenters or randomizers).
In a fully deterministic system it is trivial to reproduce QM's predictions. Here there is such an example:

http://digitalphysics.org/Publications/Petrov/Pet02m/Pet02m.pdf"

from the above article said:
In the present work we shall construct a classical (i.e. non-quantum) cellular automaton that will be able to produce (we suppose, for a great surprise of many) truly quantum (!) mechanical (namely, EPR) effects. Thus, we shall demonstrate clearly (by giving a concrete example) that the theorem proven by J. S. Bell in 1964 [Bel64] has nothing to do with otherwise purely local and deterministic mathematical models like CAs.
 
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  • #7
DrChinese
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ueit said:
Aspect's Experiment just like any other of this type assumes that the detector settings are random. Such an assumption cannot be granted when randomness itself is to be tested, therefore no relevant conclusion can come up from these experiments. A correct test of a LHV theory must include the time evolution of the detector itself (including human experimenters or randomizers).

In a fully deterministic system it is trivial to reproduce QM's predictions. ...
This is not accurate at a number of levels.

First, strict Bell tests have been performed in which the detector settings are altered at a point in time too late for an effect travelling at c to have any bearing on the outcome. While there are a few who do not accept any Bell tests as valid (mainly on philosophical grounds), it is a generally accepted result within the physics community.

Second, the strange reference to cellular automata is not peer reviewed. Quite honestly, I was not impressed with the line of thinking. It completely ignores the basics of the EPR discussion and does not map to the actual problem in any way. But the author is pretty proud of himself - he claims to have an entirely new physics which should replace all existing physics. You be the judge. :rofl:
 
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DrChinese said:
Second, the strange reference to cellular automata is not peer reviewed. Quite honestly, I was not impressed with the line of thinking. It completely ignores the basics of the EPR discussion and does not map to the actual problem in any way. But the author is pretty proud of himself - he claims to have an entirely new physics which should replace all existing physics. You be the judge. :rofl:
Euh, your webpage isn't peer reviewed either, right ?! Second, what are the basics of the EPR discussions ?? There is no consensus about that at all. I did not finish reading the paper (and will save comments for later, I am a bit worried myself) but the authors clearly state that they go for predeterminism and that is sufficient. Perhaps you could demonstrate that you actually read the paper since somehow I think you did not touch the Selleri book either yet.
 
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I'm still not sold. I would buy verifiable replication, by another source, i.e. a peer review. Others must be able to reproduce it repeatedly.
 
  • #10
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One worry which immediately came to my mind after a very brief look is the issue of apparatus complexity. I mean, usually one expects the internal dynamics of the apparati to be so complex that it would be virtually impossible to read its mind. Anyway, more details regarding such issues would be welcome.

Careful
 
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Bottom line folks, I work with a top-of-the-line spectrophotometer every day, and while it ain't a supercollider, it does give me real empirical data (in nm) from which I can do research. Deviation in the equipment? .0005% okay, it might be wrong that much of the time, but repeatability reduces the error to a satisfactory deviation. It's not numbers on a page representing suppositions. NO measurement, NO verification.Only an example, not a sample relevant to this discussion.
 
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  • #12
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DrChinese said:
This is not accurate at a number of levels.

First, strict Bell tests have been performed in which the detector settings are altered at a point in time too late for an effect travelling at c to have any bearing on the outcome. While there are a few who do not accept any Bell tests as valid (mainly on philosophical grounds), it is a generally accepted result within the physics community.
How the detector settings are changed are simply irrelevant. In a deterministic setup they are correlated with everething else since the big-bang. No signal has to travel between them and the particles. The correlations are a consequence of their common past.

To be more clear I'll quote several writings.

In “Speakable and Unspeakable in Quantum Mechanics”, chapter 12, J.S. Bell writes:

It has been argued that quantum mechanics is not locally causal and cannot be embedded in a local causal theory. That conclusion depends on treating certain experimental parameters, typically the orientations of polarization filters, as free variables. Roughly speaking it is supposed that an experimenter is quite free to choose among the various possibilities offered by his equipment. But it might be that this apparent freedom is illusory. Perhaps experimental parameters and experimental results are both consequences, or partially so, of some common hidden mechanism. Then the apparent non-locality could be simulated.
He then tries to argue that this assumptions should be granted and ends with:

Of course it might be that these reasonable ideas about physical randomizers are just wrong – for the purpose at hand. A theory may appear in which such conspiracies inevitably occur, and these conspiracies may then seem more digestible than the non-localities of other theories. When that theory is announced I will not refuse to listen, either on methodological or other grounds. But I will not myself try to make such a theory.
I say that in a deterministic setup free choice does not exist. Assuming it, makes the argument circular, therefore useless.

Richard Gill, in the article:

http://www.math.uu.nl/people/gill/Preprints/vaxjo.pdf" [Broken]

...in which predeterminism is considered among the possible interpretations of Bell’s experiments, acknowledges this circularity:

I find it fascinating that in order to prove that quantum mechanics is intrinsically probabilistic (the outcomes cannot be traced back to variation in initial conditions) we must assume that we can ourselves generate randomness. And in order to demonstrate the kind of non-separatbility implied by entanglement, we have to assume control and separation of the physical systems which we use in our experiments.
Here there is a pretty recent, peer reviewed article ( American Journal of Physics -- June 2001 -- Volume 69, Issue 6, pp. 655-701):

http://arxiv.org/PS_cache/quant-ph/pdf/0209/0209123.pdf" [Broken]

Along a similar line is what is sometimes called the “fatalistic loophole” (or also “superdeterminism”). The idea is to put into question an implicit assumption of the reasoning that leads to the Bell theorem: the completely arbitrary choice of the settings a and b by the experimenters. Usually, a and b are indeed considered as free variables: their values that are not the consequence of any preliminary event that took place in the past, but those of a free human choice. On the other hand, it is true that there is always some an overlap between the past cones of two events, in this case the choice of the settings. It is therefore always possible in theory to assume that they have a common cause; a and b are then no longer free parameters, but variables that can fluctuate (in particular, if this cause itself fluctuates) with all kinds of correlations. In this case, it is easy to see that the proof of the Bell theorem is no longer possible 33, so that any contradiction with locality is avoided. What is then denied is the notion of free will of the experimenters, whose decisions are actually predetermined, without them being aware of this fact; expressed more technically, one excludes from the theory the notion of arbitrary external parameters, which usually define the experimental conditions. This price being paid, one could in theory build an interpretation of quantum mechanics that would remain at the same time realistic, local and (super)deterministic, and would include a sort of physical theory of human decision. This is, of course, a very unusual point of view, and the notion of arbitrary external parameters is generally accepted; in the words of Bell [93]: “A respectable class of theories, including quantum theory as it is practised, have free external variables in addition to those internal to and conditioned by the theory....They are invoked to represent the experimental conditions. They also provide a point of leverage for free willed experimenters, ...”. Needless to say, the fatalist attitude in science is even more subject to the difficulties of orthodox quantum mechanics concerning the impossibility to develop a theory without observers, etc..
Second, the strange reference to cellular automata is not peer reviewed. Quite honestly, I was not impressed with the line of thinking. It completely ignores the basics of the EPR discussion and does not map to the actual problem in any way. But the author is pretty proud of himself - he claims to have an entirely new physics which should replace all existing physics. You be the judge.
As I've explained above there is no controversy that Bell's proof does not work when a logically consistent determinism is assumed. Petrov's article simply exploits this. It remains to be seen if CA is a fertile idea, I think it is
 
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  • #13
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Repetition builds the concept of constants. Working with variables won't solve anything. We can only rely on that which is constantly available for analytical reference. Repeatable. SHOW ME! again and again, now we're gettting somewhere!
 
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drdave616 said:
Repetition builds the concept of constants. Working with variables won't solve anything. We can only rely on that which is constantly available for analytical reference. Repeatable. SHOW ME! again and again, now we're gettting somewhere!
We are not debating the raw data but its interpretation. What exactly do you want me to show you?
 
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Sorry, You have already shown me a lot. I rely on empirical data proven to me by our current equipment, but theory is provided by you. My facility is one of analysis, but the input by people like you allows me some measure of diagnosis of these results. Everyone doesn't have the analytical mind that you have, thus we must rely on you. It is a mutually beneficial relationship, in that you provide, what I cannot. I have the lab.
 
  • #16
DrChinese
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Careful said:
Euh, your webpage isn't peer reviewed either, right ?! Second, what are the basics of the EPR discussions ?? There is no consensus about that at all. I did not finish reading the paper (and will save comments for later, I am a bit worried myself) but the authors clearly state that they go for predeterminism and that is sufficient. Perhaps you could demonstrate that you actually read the paper since somehow I think you did not touch the Selleri book either yet.
Ya, my isn't peer reviewed... but I simply present a digest of mainstream items that are. Not exactly an apples to apples comparison, is it?

As to Selleri's book... I already told you I have never even seen it for sale. If you can send me yours, I promise I will look at it. :smile:
 
  • #17
DrChinese
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ueit said:
In a deterministic setup they are correlated with everething else since the big-bang. No signal has to travel between them and the particles. The correlations are a consequence of their common past.
From a theoretical (philosophy of science) viewpoint, this is a useless statement. You may as well say that Bell test results are due to the active hand of God personally manipulating the results to make it appear that QM is correct. And why do I say from a theoretical viewpoint? Because these statements explain exactly nothing and are totally superfluous. As well as being completely untestable. According to predeterminism, there is a previous "cause" of the outcome of Bell tests. OK, where is it? Oh, I forgot. It is the entire state of the universe. So that explains how local realism works. That's what I call circular logic.
 
  • #18
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DrChinese said:
Ya, my isn't peer reviewed... but I simply present a digest of mainstream items that are. Not exactly an apples to apples comparison, is it?
You are wrong here, 85 percent of scientists have no particular attitude towards this subject whatsoever and basically have made piece with the fact that they will never have a deep understanding of their calculations, but hey it works. :rolleyes: Then you have the 15 percent fanatics, which admittedly mainly speak in esoteric terms such as nonlocality, consciousness and all that. My point of view is ``less talking, coming up with better alternatives and doing finally a conclusive experiment'' and especially to keep an open mind.


DrChinese said:
As to Selleri's book... I already told you I have never even seen it for sale. If you can send me yours, I promise I will look at it. :smile:
Hehe, you can buy it from amazon.com; it is a good investment I promise you :wink: (on my atheist soul :rofl: )

Careful
 
  • #19
DrChinese
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Careful said:
My point of view is ``less talking, coming up with better alternatives and doing finally a conclusive experiment'' and especially to keep an open mind.
Always good advice... :smile:
 
  • #20
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drdave616 said:
......... provide, what I cannot.
I have the lab.
Are you saying you have, or have direct access to the equipment and facilities to support ".....coming up with better alternatives and doing finally a conclusive experiment’’?
Where if someone where to provide a reasonable and rational alternative to the current explanations -- And more importantly translate that into a performable experiment to test that alternative – You would actually be in a position to have such a test run or considered for testing in your Lab?

I’m assuming this would be an optical lab with detectors suitable for testing correlations of EPR photon polarity entanglement. (Stern–Gerlach measurements of spin seem so much harder to deal with in every way – testing, test design, explaining, and understanding).

What an amazing offer on a forum!!
– of course it’s understood your not just taking in any suggestions
– you’d need some detail as to how any suggested test could produce something new in its results.
A very brief description of your lab capabilities would be nice!
 
  • #21
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ueit said:
In a deterministic setup they are correlated with everething else since the big-bang. No signal has to travel between them and the particles. The correlations are a consequence of their common past.
DrChinese said:
From a theoretical (philosophy of science) viewpoint, this is a useless statement.
Useless or not, this follows as a logical necessity from the assumption of determinism employed in Bell's reasoning. If, for whatever reason, you don't like determinism you may say so and move forward, without the need of useless, circular arguments (I equate here determinism with local realism. It is true that stochastic, local-realistic theories have been proposed but I do not maintain such a position)

You may as well say that Bell test results are due to the active hand of God personally manipulating the results to make it appear that QM is correct.
I may, but I'm not. This is very unparsimonious.

And why do I say from a theoretical viewpoint? Because these statements explain exactly nothing and are totally superfluous.
They are not superfluous, they show that deterministic local-realism is compatible with QM. That's all I'm saying. Bell's theorem is simply irrelevant . This conclusion is not suppose to explain anything but to open the possibility of deterministic theories which could give an explanation.

As well as being completely untestable.
Why do you say that a deterministic theory cannot be testable? The cellular automata model, for example, is testable in principle. I'm not saying CA is the answer, the theory must be developed first, but it is a good example.

According to predeterminism, there is a previous "cause" of the outcome of Bell tests. OK, where is it? Oh, I forgot. It is the entire state of the universe. So that explains how local realism works. That's what I call circular logic.
You are attacking a straw-man here. See above.

Now, can I ask you in turn, what better explanation do you propose? And no, I'll not take "shut up and calculate" or "it's random" or something of this sort as an explanation.
 
  • #22
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ueit said:
That's all I'm saying. Bell's theorem is simply irrelevant . This conclusion is not suppose to explain anything but to open the possibility of deterministic theories which could give an explanation.
I see a significant problem with taking this as adequate ‘proof’ that “Bell's theorem is simply irrelevant”. Presuming you define a deterministic theory that explains correlations; by what test exactly do you propose to verify and prove the claim if not Bell.
Did you have a new kind of test to offer to DrDave (I hope he will comment) to check such future theories against?

Bell designed his theorem to give a HVT to opportunity to do just that. Like it or not I’ve seen no other proposed test that might detect the difference between a Non-local theory (QM, BM MWI etc) and a local deterministic theory.
In fact IMO when a deterministic theory does come along; It will want, It will need, and It must use, BELL to prove its point.
 
  • #23
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RandallB said:
I see a significant problem with taking this as adequate ‘proof’ that “Bell's theorem is simply irrelevant”. Presuming you define a deterministic theory that explains correlations; by what test exactly do you propose to verify and prove the claim if not Bell.
Did you have a new kind of test to offer to DrDave (I hope he will comment) to check such future theories against?
The paper cited clearly intends to violate a particular form of the Bell inequalities. Perhaps let us concentrate on the paper so that we can figure out how the program works and how the data could violate the Bell inequalities. I just looked through the program instructions and did not quite get some things straight away (I guess ueit knows this since he praises the paper) :
(a) there is a left/right assymetry in rule 30, why ??? It does not seem natural to me to break this symmetry.
(b) the source emits left and right travelling virtual particles first which are *determining* the detector settings ?
(c) the colour of the detection does *not* depend upon the detector switch state line but only upon the particle spin !
(d) it is not obvious at first sight that given equal detector settings left and right, the spin measurements are the same, is that proven somewhere?
(e) In the simulation, I had almost 50 percent of the time single hits (and that is extremely bad)! How are these processed in the statistics (substraction I guess, but then it is well known you can violate the Bell inequalities by ``Bell local'' realist theories)??

Anyway, some comments would be welcome before I would put some more time into this.

Careful
 
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  • #24
DrChinese
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ueit said:
Useless or not, this follows as a logical necessity from the assumption of determinism employed in Bell's reasoning.
First: I don't see where determinism - or indeterminism - is a function of Bell's Theorem. Perhaps you can point that particular piece out to us specifically (as in a reference).

Second: you will not find it so easy to develop a local realistic theory - even one which is deterministic in the manner you have cited - which can reproduce the predictions of QM. Anything less than a full example will satisfy only those who don't know any better. The requirements are many.

Third: The premise you are starting from makes little sense: you will have to completely tear down the Uncertainty Principle to achieve your goals (since it is the source of the EPR Paradox). And then we would be left wondering why the Uncertainty Principle even appears to exist! Ah, determinism! What an answer! As said previously, this explains absolutely nothing. I'll stick with Bell's Theorem at this time.
 
  • #25
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RandallB said:
I see a significant problem with taking this as adequate ‘proof’ that “Bell's theorem is simply irrelevant”. Presuming you define a deterministic theory that explains correlations; by what test exactly do you propose to verify and prove the claim if not Bell.
Did you have a new kind of test to offer to DrDave (I hope he will comment) to check such future theories against?

Bell designed his theorem to give a HVT to opportunity to do just that. Like it or not I’ve seen no other proposed test that might detect the difference between a Non-local theory (QM, BM MWI etc) and a local deterministic theory.
In fact IMO when a deterministic theory does come along; It will want, It will need, and It must use, BELL to prove its point.
If I understand correctly, your position is that we should accept a fallacious argument as sound because we don't have a better one. Needless to say, I disagree. If we cannot distinguish between determinism and non-determinism then that's it.
It is sad to see great physicists claiming that it is foolish to investigate LHV theories because they have been proven wrong by Bell and see all kinds of SF-like ideas proposed as serious explanations.
And MWI is said to be both local and deterministic although I disagree.
 

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