Questions on Entanglement and Double-Slit Experiment

[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.

 

[ttn]

tnn
- 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.

Except that isn't what "complete" actually means.

- 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.

First, MWI i s not non-local. Second, how is it valid to ever say something like "BM offers no experiments that exceed the ability of QM to make predictions."? The two theories make the same predictions. So one can just as correctly say "QM offers no experiments that exceed the ability of BM to make predictions... so to hell with QM". Get it? There are two theories. They make the same predictions. So it is completely invalid to dismiss one of them merely on the grounds that it just reproduces the predictions of the other. In fact, people who make that argument are using it as a smokescreen to hide the fact that they have some kind of indefensible bias against one of the theories.

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.

Not to speak for Dr C, but I'm pretty sure he doesn't agree with that. He's argued with me all over the place here over the years that one gets to choose either to reject locality or ... some other thing.

It will take something other than Bell in some experiment to select between QM, MWI, BM, etc.

Of course. Who ever said that Bell's theorem proves one of these right as against the others?

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.

That's one piece of bad news, yes. But there is also the measurement problem, the fact that it is a nonlocal theory, etc...

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.

"Local realist" is not a theory. And as I said before, "realist" (or "realism" or whatever) has no place in any of these discussions anyway. Bell's theorem proves that any empirically viable theory has to be nonlocal. That's it. Anyone who thinks "realism" is also at play better explain what they mean by that term.

 

[DrChinese]

1. Not to speak for Dr C, but I'm pretty sure he doesn't agree with that. He's argued with me all over the place here over the years that one gets to choose either to reject locality or ... some other thing.

2. Anyone who thinks "realism" is also at play better explain what they mean by that term.

1. You are so correct!

2. Realism is simply another word for the completeness doctrine, really as EPR defines it. This can be expressed many different ways as words (and they are just words):

a) Non-realistic = QM is Complete = No greater description of state possible = Observer Dependence.

b) Realistic = QM is Incomplete = Hidden variables = Observer Independent Reality

In the QM formalism, I see this as saying that the state function fundamentally obeys the HUP, so statistical outcomes are dependent on what is observed.

 

[NateTG]

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”.

In some sense, 'Bell Test' is a misnomer since Bell's Theorem does, in fact, involve untestable assumptions such as Bell Locality and realism.

- 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.

From the Stanford Encyclopedia of Philosophy:
http://plato.stanford.edu/entries/qm-bohm/

It is perhaps worth mentioning that despite the empirical equivalence between Bohmian mechanics and orthodox quantum theory, there are a variety of experiments and experimental issues that don't fit comfortably within the standard quantum formalism but are easily handled by Bohmian mechanics. Among these are dwell and tunneling times (Leavens 1996), escape times and escape positions (Daumer et al. 1997a), scattering theory (Dürr et al., 2000), and quantum chaos (Cushing 1994, Dürr et al., 1992a).

 

[exeric]

tnn
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.

You are wrong. I can think of at least another.

Eric

 

[wm]

2. Realism is simply another word for the completeness doctrine, really as EPR defines it. This can be expressed many different ways as words (and they are just words):

a) Non-realistic = QM is Complete = No greater description of state possible = Observer Dependence.

b) Realistic = QM is Incomplete = Hidden variables = Observer Independent Reality

In the QM formalism, I see this as saying that the state function fundamentally obeys the HUP, so statistical outcomes are dependent on what is observed.

Is there a problem with the middle-way?

c) Realistic = QM is Incomplete = Hidden variables = Observer Dependent Reality = the particular hidden variable exposed is dependent on the observer's choice of ''measurement''.

 

[ueit]

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?

Bell wasn't wrong and he did acknowledged the limitations of his theory.

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 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.

Well, it seems you didn't read Bell's work carefully enough or you didn't pay attention to the assumptions he makes. If one assumption falls, the theory falls, regardless of how "detailed" is the "proof of his conclusion".

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.

So, the burden of proof is on you to show that Bell was wrong when he said...

"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."

...otherwise, you're just some..., oh, forget it.

 

[ueit]

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

That's a very strange idea about locality. So, a set of billiard balls, perfectly following Newtons' laws of motion is a non-local system. I can only wonder what do you think it is a local mechanism. An example would be great.

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?

Please read my post to ttn and see how I gave him the exact quote from the book that supports my position. I don't have the time to buy and read three books and read everything on the subject on this forum in order to guess what your argument may be. So, please post Smolin's words where he says that GR is non-local.

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.

What is the speed of gravity in Newton's theory? What happens with planetary orbits if one assumes a finite speed?

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 think I do.

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

I disagree with that. Please, read Bell's own words from my post to ttn.

– The Whole Point Is - the evidence so far is for a Non-Local World.

No, the evidence forces someone to choose between a philosophical assumption, without a shred of scientific evidence (free will) and locality.

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.

So, everything boils down to your opinion that determinism is a "ridiculous hypothesis". Although you are right that determinism implies the conclusion that everything goes back to the Big-Bang (and possibly beyond it) it may be not necessary to go that far. For example it may be that the PDC is influenced (locally, at the speed of light) by the field generated by the detectors. That's enough, I don't need to take Jupiter's position into the account.

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 don't debate peoples' opinions. When I'll see an argument I'll answer to it. And you should remember that classical physics is deterministic and didn't look absurd at all to past physicists.

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

Yeah, this is a good advice for you, because you are the one who needs the free-will assumption and refuses to support that assumption with scientific evidence.

 

[ttn]

2. Realism is simply another word for the completeness doctrine, really as EPR defines it. This can be expressed many different ways as words (and they are just words):

a) Non-realistic = QM is Complete = No greater description of state possible = Observer Dependence.

b) Realistic = QM is Incomplete = Hidden variables = Observer Independent Reality

In the QM formalism, I see this as saying that the state function fundamentally obeys the HUP, so statistical outcomes are dependent on what is observed.

OK, I think that's a dumb way to use the word, but so be it. But the question is: how does this justify the use of the phrase "local realism"? Is your claim that Bell uses some such *assumption* as this "realism" in deriving the inequality? Because that is just wrong. The inequality follows from locality *only*.

Also, it's ludicrous to put "observer dependence" and "observer independent" in your list above, as if these (whatever the heck they are supposed to mean exactly) were somehow equivalent to the other things on the list. If, for example, the wave function alone does provide a complete description of physical states, then this is a fact independent of any "observer". The only sense that this terminology might possibly have is in reference to the fact that, in OQM, a measurement "disturbs" the wave function (the collapse rule). But something like this is true in any theory: if you insert a detector somewhere and let it interact with some system, it's going to affect the state of that system. For example, this is true in Bohm's theory, which you call "realistic".

So, seriously, you need to rethink this terminology. Yes, it's true, virtually everyone around today uses the phrase "local realism" to name the assumptions of Bell and/or the alternatives to OQM. But the mere f act that everybody's doing it, doesn't make it right. In following these unthinking people unthinkingly, you are just buying into their confusions.

 

[ttn]

Well, it seems you didn't read Bell's work carefully enough or you didn't pay attention to the assumptions he makes. If one assumption falls, the theory falls, regardless of how "detailed" is the "proof of his conclusion".

Everybody knows about this possibility of super-determinism. But there is a big difference between noting that this is indeed an assumption that's made (in the empirical tests more than the derivation of the theorem, by the way) and asserting that the "assumption falls." I mean, do you actually believe that this assumption is false? That experimenters don't have the freedom to choose what they measure -- or more precisely given the way the experiments are actually done, that there was some kind of systematic correlation between the deliberately uncorrelated random number generators on the two sides of the experiment? Saying "it's possible there's some kind of conspiracy" is completely empty. If you think there's some kind of conspiracy, explain why you think that. Otherwise, the rational response is the same as if you had said "maybe we're all brains in vats" -- namely, unless you can provide at least some shred of evidence to suggest that this is possible, then it's just made up empty BS.

So, the burden of proof is on you to show that Bell was wrong when he said...

"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."

...otherwise, you're just some..., oh, forget it.

I don't think he was wrong when he said that. I just don't think there is any actual evidentiary basis for believing that there is this kind of conspiracy. And by the way, there is a mountain of positive empirical evidence that this is *not* the case -- namely that we are able to understand a zillion other physical phenomena without any such massive metaphysical conspiracy. Note in particular that one could make this same objection to anything. A "randomized" double-blind drug trial showed that some new drug cures the cancer in all the patients that were given it? So this drug is the cure for cancer! Sweet! Oh, but no, you say that maybe it wasn't double-blind and randomized after all, there was some conspiracy that resulted in all the patients who would have survived *anyway* being just the ones who were "randomly" given the drug, so really the data is based on biased sampling and is invalid. Well, the fact is, in science, unless you can actually provide some kind of empirical basis for this speculation (even if it is minimal) nobody will or should listen to you. And the proof that that's the right response is in the pudding: if people did listen to this kind of arbitrary made up objection, we wouldn't have the drugs we have to cure us of terrible diseases, or any of the other wonderful practical things that science has given us.

Here is another objection you might worry about. Maybe all the people who claim to have done these experiments to test the Bell Inequalities have actually been bought off by the government to lie, in their published papers, about what the results were. It's possible, right? So the burden of proof is on you to prove that this didn't happen if you want to accept Aspect's published paper as really reporting the actual results of his experiments... right?

 

[DrChinese]

OK, I think that's a dumb way to use the word, but so be it. But the question is: how does this justify the use of the phrase "local realism"? Is your claim that Bell uses some such *assumption* as this "realism" in deriving the inequality? Because that is just wrong. The inequality follows from locality *only*.

Well, *you* were the one who asked what realism means. And I think Einstein's later quote "a particle must have a separate reality independent of the measurements" easily justifies the use of those definitions, including the concept of observer independence. As I said, they are just words - so pick the ones that best describe.

As to the idea that the inequality follows from locality only... that doesn't even fit with your own previous logic (which said that this assumption didn't change the net conclusion when paired with the EPR argument). Clearly, Bell included an assumption involving a more complete state of the system than is present in QM, and this assumption is absolutely critical to his conclusion. I have pointed this assumption out any number of times, and I again quote from the original (where a and b are unit vectors present in QM, but c is not):

(14) ... "It follows that c is another unit vector..." (followed by the math that leads quickly to the inequality)

Bell could have put stars by this to make it easier for the reader to see, but he didn't.

 

[ttn]

So, everything boils down to your opinion that determinism is a "ridiculous hypothesis". Although you are right that determinism implies the conclusion that everything goes back to the Big-Bang (and possibly beyond it) it may be not necessary to go that far. For example it may be that the PDC is influenced (locally, at the speed of light) by the field generated by the detectors. That's enough, I don't need to take Jupiter's position into the account.

Um, actually that isn't possible. You can let the detectors affect the particle source all you want and it doesn't matter. The "complete state description" lambda that shows up in Bell's definition of locality is taken after the particles are created and in-flight toward the detectors. So either you have to let the detectors affect the state of the particles *after* they are in-flight (and this means that the detector on one side has to be able to affect the particle on the *other* side, which, the way the experiments are done, requires superluminal / nonlocal causation)... or you have to say that there is some kind of sample-biasing conspiracy whereby the "random" setting of the detector angle *after* the particles have already been emitting, actually isn't random at all, and in particular is correlated with the "random" setting on the far side and also with the state of the particle pair.

So now it's not clear what your objection actually is. Before, in your other post to me, it sounded like you were hung up on the fair sampling issue, and the (arbitrary) possibility that one can't actually test the inequality in an unbiased way, because of some conspiracy of pre-determination in the detector settings. But now it sounds like you think there is a much more serious flaw in Bell's argument -- that there are perfectly local mechanisms whereby the inequality could be violated. If you are worried about this, then you're just wrong and haven't understood the theorem.

 

[ttn]

Clearly, Bell included an assumption involving a more complete state of the system than is present in QM, and this assumption is absolutely critical to his conclusion.

Sometimes he does and sometimes he doesn't. But, for the millionth time, either way you're still wrong. In the version of the derivation of the inequality that does assume local deterministic hidden variables, Bell explicitly references the EPR argument as proving that such HV's must exist under the assumption of locality. The logic is really simple:

Locality --> HV's (EPR)

then

HV's --> Bell Inequality


So I think even you should be able to recognize that the Inequality follows from the Locality assumption *alone*. You don't need some other distinct extra assumption about 'realism' or whatever. And anyway, it's possible to derive some other versions of a Bell-type inequality (the CHSH in particular) without even going through this two step derivation involving the EPR argument from locality to HV's. You can just start with locality and derive the inequality from that, straight away.

So as I said, either way you're wrong. The inequality follows from locality alone.

I have pointed this assumption out any number of times, and I again quote from the original (where a and b are unit vectors present in QM, but c is not):

(14) ... "It follows that c is another unit vector..." (followed by the math that leads quickly to the inequality)

Bell could have put stars by this to make it easier for the reader to see, but he didn't.

Yes, you always mention this passage, but it just proves you don't understand the paper. The unit vectors a, b, and c are possible directions along which a spin measurement might be made -- they aren't hidden variables or anything like that. And anyway, even if you were right about that, you'd be pointing to the wrong place. What about the "hidden variable" a or b? Those are already not contained in the wave function (I guess), so why are you so obsessed with c? But then, there is no answer to this kind of question since it's based on a fundamental confusion about Bell's paper in the first place.

 

[DrChinese]

Everybody knows about this possibility of super-determinism. But there is a big difference between noting that this is indeed an assumption that's made (in the empirical tests more than the derivation of the theorem, by the way) and asserting that the "assumption falls." I mean, do you actually believe that this assumption is false? That experimenters don't have the freedom to choose what they measure -- or more precisely given the way the experiments are actually done, that there was some kind of systematic correlation between the deliberately uncorrelated random number generators on the two sides of the experiment? Saying "it's possible there's some kind of conspiracy" is completely empty.

Egads, I actually agree with this! LOL. Just to add: extending ueit's thinking, you could actually say that ALL scientific results show behavior that is false, because the results were "predetermined" to support an otherwise unsupportable conclusion.

I will point out this setup to demostrate how difficult ueit's position is:

Suppose the detector settings are determined by separate radioactive samples* (i.e. not an electromagnetic force) which are themselves spacelike separated from both the detector and the entanglement source. Thus the deterministic "first cause" is being propagated through space-time affecting even the splitting of atoms in a sample in such a way as to act in concert with both a distant photon source AND a second distant radioactive source to produce results that match the predictions of QM. Further, the example could be extended to involve dozens of separate radioactive sources, which must now operate in concert.

Whew!

* The radioactive sample appears random, and would be calibrated to have a 50-50 chance of "clicking" within the desired time window. A click would mean setting X, no click would mean a different setting Y. Under the "strict determinism" concept, the presence or absence of a click would also be predetermined, a hypothesis which is not falsifiable.

 

[ttn]

I just read your post again and was floored by this statement which I barely noticed before:

(where a and b are unit vectors present in QM, but c is not):

(14) ... "It follows that c is another unit vector..." (followed by the math that leads quickly to the inequality)

Seriously, you're totally confused. a and b are unit vectors present in QM? What the hell are you talking about? Where pray tell are these unit vectors in QM? Do you even know what these unit vectors are? It's as if you either hadn't actually read Bell's paper, or had never taken even an undergrad class in QM. There's really no point talking to you about this stuff.

 

[DrChinese]

a and b are unit vectors present in QM? What the hell are you talking about?

You are the one ignoring unit vector c, as you always do. Why won't you address this point? I am saying c is the assumption of realism, one which is not present in the QM formalism and which defies the HUP. If there is no c, there is no Bell inequality. Period. a and b are the setups which match to the predictions of QM AND local realistic theories alike. So a and b are simply common to any theory which purports to describe the results of 2 particle entanglement tests.

 

[DrChinese]

The unit vectors a, b, and c are possible directions along which a spin measurement might be made -- they aren't hidden variables or anything like that.

Well, funny, this is a perfectly good description of a, b and c. The problem is that a and b are testable, a and c are testable, b and c are testable, but a, b, and c together are only hypothetical. THAT IS WHY c IS ASSUMED. How can you be so stubborn about such a simple point? I repeat: QM denies c.

Now please try to derive Bell's Inequality WITHOUT reference to a, b and c simultaneously and show it to us. Then I will gladly accept all of your assertions about locality being the only explicit assumption in Bell.

 

[Nacho]

DrChinese,

* The radioactive sample appears random, and would be calibrated to have a 50-50 chance of "clicking" within the desired time window. A click would mean setting X, no click would mean a different setting Y. Under the "strict determinism" concept, the presence or absence of a click would also be predetermined, a hypothesis which is not falsifiable.

Question: How do we know these are truly random events VS pseudo random events of very close precision to random?

 

[DrChinese]

DrChinese,

Question: How do we know these are truly random events VS pseudo random events of very close precision to random?

That is what ueit is saying... that perhaps the events are not truly random. OK, maybe that is so. But that hardly explains why these "pseudo random" events are able to conspire to achieve the Bell test correlations! That is my point.

 

[Careful]

Here is another objection you might worry about. Maybe all the people who claim to have done these experiments to test the Bell Inequalities have actually been bought off by the government to lie, in their published papers, about what the results were. It's possible, right? So the burden of proof is on you to prove that this didn't happen if you want to accept Aspect's published paper as really reporting the actual results of his experiments... right?

Likewise, the burden is upon you to show that all reputed journals which published papers by local realists proving that in Aspect's experiments neither a genuine Bell inequality was and could be violated as being in some conspiracy to cover up ``the truth''.

Careful

 

[RandallB]

First, MWI is not non-local.

? Man you can be impossible to follow when in the very same post you say

Bell's theorem proves that any empirically viable theory has to be nonlocal.

I though you had cleared weeks ago that MWI is not Bell Local or have you decided that MWI cannot provide a viable solution to correlations for some reason?
How can I follow your line of reasoning with what looks to me like a massive contradiction.

"Local realist" is not a theory. Anyone who thinks "realism" is also at play better explain what they mean by that term.

Of course it is a theory, held and explained by both Einstein & John Bell. So strongly held they proposed the concepts behind on experiment that could prove them correct (EPR and Bell Theorem) even though at the time the test could not be performed. Both were willing to put their ideas at risk of being shown wrong by their own experimental ideas!
It was years after Bell was proposed before real experiments could be run, with negative results so far. BUT, but if you read your logic books carefully negative results for local only implies non-local as correct, it is not a positive proof of non-local in precise logic.

And what of the new theories you favor? Have any put together anything of an idea or concept that might someday be put to the test in a real experiment to positively prove their idea?
None that I’ve heard of, IMO the concept of the Local Realist is more completely thought though and understood by Bell and Einstein etc than any if the current on paper theories.

That's a very strange idea about locality. So, a set of billiard balls, perfectly following Newtons' laws of motion is a non-local system. I can only wonder what do you think it is a local mechanism. An example would be great.

? Reread post #97, billiard balls following Newton’s laws is Bell Local. Newton’s Laws do not require complete predestined and predetermined events. Newton does not deny the ability of an unknown ball with an unknown history from entering a local system – complete deterministic theories do, that’s why they demand no free will.