Is action at a distance possible as envisaged by the EPR Paradox.

[Deepak Kapur]

ThomasT has indicated previously that there are definitional issues with entanglement. I don't see those particular ones and neither do most folks. So it gets hard to have a discussion because his vewpoint hinders that. There is a generally accepted common ground to discuss these issues, and that usually goes all the way back to EPR.

I think that the real issue is with the definition of 'Local Realism'.

'Local Realism' assumes (as I feel about it):

1. Certainity is inherent in all the objects of nature (big or small). They always tend to 'possess' properties if someone tries/does not try to measure them.

2. Things/objects that are great distances apart (say light years apart in case of our Earth or say 100 feet apart in case of sub atomic particles, no proportion intended) don't get affected by other entities (especially when it come to the measurement of their properties).

In other words if we conduct any kind of measurement related to Earth, the effect of a star (say that is in the farthest corner of Andromeda galaxy) will not have any effect on this measurement.


I have a faint inclination that 'this star' will certainly have an influence on our measurement related to Earth (however small this effect may be). If an instrument could be formed that is (hyper)ⁿ sensitive, we may be able to gauge the effect. And it would depend on the (refinement)ⁿ/nature of our measurement wheter we take this effect to be of any consequence or not.

 

[Frame Dragger]

I think that the real issue is with the definition of 'Local Realism'.

'Local Realism' assumes (as I feel about it):

1. Certainity is inherent in all the objects of nature (big or small). They always tend to 'possess' properties if someone tries/does not try to measure them.

2. Things/objects that are great distances apart (say light years apart in case of our Earth or say 100 feet apart in case of sub atomic particles, no proportion intended) don't get affected by other entities (especially when it come to the measurement of their properties).

In other words if we conduct any kind of measurement related to Earth, the effect of a star (say that is in the farthest corner of Andromeda galaxy) will not have any effect on this measurement.


I have a faint inclination that 'this star' will certainly have an influence on our measurement related to Earth (however small this effect may be). If an instrument could be formed that is (hyper)ⁿ sensitive, we may be able to gauge the effect. And it would depend on the (refinement)ⁿ/nature of our measurement wheter we take this effect to be of any consequence or not.

That is a very long way of saying that you believe in Hidden Variables, but with the addition that you're speculating in a manner that has nothing to do with physics.

@hmm.max: I would respond, but DrChinese has done so quite nicely, as has DevilsAvocado.

 

[DevilsAvocado]

Just adding to what was said already: you had some great posts above... good stuff.

Thanks a lot DrChinese! I’m fairly new here, but I do understand you are the 'grandmaster' of EPR here on PF; therefore I’m now feeling something like this... + + + +

Thanks! ;)

 

[DevilsAvocado]

ThomasT has indicated previously that there are definitional issues with entanglement. I don't see those particular ones and neither do most folks. So it gets hard to have a discussion because his vewpoint hinders that. There is a generally accepted common ground to discuss these issues, and that usually goes all the way back to EPR.

Right, I cannot see how his 'local constant' can ever help him (even if entangled)... Maybe I misinterpreted ThomasT, or he has maybe misinterpreted some of EPR...

 

[DrChinese]

'Local Realism' assumes (as I feel about it):

1. Certainity is inherent in all the objects of nature (big or small). They always tend to 'possess' properties if someone tries/does not try to measure them.
...

There are 4 closely related terms, sometimes used interchangeably, sometimes used in the specific:

a. Realism - a la EPR's "elements of reality".
b. Hidden Variables - Essentially a deduction from realism.
c. Non-contextuality - the context of an experiment does not matter to the realism of an observable.
d. Counterfactual Definiteness - you can speak meaningfully about unmeasured observables.

I don't like to discuss the implications of the differences in these terms when discussing Bell or Aspect, because I think it leads to semantic arguments. For MOST purposes, I consider these terms interchangeable. So do most writers based on my readings, although there are a few who attempt to distinguish among them. Funny thing, the math is pretty much the same regardless. So too the predictions of QM.

 

[DrChinese]

Thanks a lot DrChinese! I’m fairly new here, but I do understand you are the 'grandmaster' of EPR here on PF; therefore I’m now feeling something like this... + + + +

Thanks! ;)

Between you, RUTA, FrameDragger, SpectraCat and a number of others (sorry if I left out your name too), I think we have seen some great additions around here. I consider the quality of the discussions to be inversely proportional to the number of ZapperZ posts! That meaning, in my book, that he does not need to pop in as much with his wise and informed comments.

 

[DevilsAvocado]

This is unfair in respect to Many-worlds interpretation, right?

Well... no, that’s actually not my point. To me it’s almost clear that EPR must be some kind of "gun smoke" of the next 'paradigm' in physics ('smoke' without 'fire'!? ). It’s a clear sign that we do not know everything there is to know, yet.

And I’m almost stunned by the numerous attempts to run "business as usual" – stating "well, this doesn’t mean anything... it’s a matter of QM interpretation", or "it’s hard to measure photons, therefore EPR is most probably misleading".

I don’t think that’s fair to all the intelligent persons that spent a lot of time working on this problem.

And if we look with some 'perspective' on the criticism of Bell test experiments – What are they saying? Well, most agree that Bell's theorem is correct and sound, but there is some "magical entangled loophole" that exposes itself in different ways, in different experiments!?

Yet we know that the 'overlapping effect' of all performed Bell test experiments, together with Bell's theorem is very convincing. And over time it will be definite.

I’m not an explicit supporter of MWI, it could be the correct solution, but I can’t get the 'pragmatic workings' of MWI into my head. Therefore I’m (for now) anticipating some hardnosed evidence from another 'branch'...

To consider this experiment as an EPR paradox test is a bit of stretch. EPR paradox considers separate measurements of two systems that are not interacting at the moment of measurement. But in this experiment there is only one joined measurement of both systems.

This is exactly what I’m talking about – the "magical entangled loophole"!

Yes, in most cases fair sampling assumption is considered reasonable. But in this case fair sampling assumption necessarily comes packaged with one of the not-so-reasonable speculations like MWI, superdeterminism or nonlocality of Pilot-wave.
And in that light fair sampling is as reasonable as most reasonable one of those alternatives.

Agree. It’s maybe not wise to deduce the problem of explaining EPR as an immediate proof of even weirder 'things'...

As you say

Welcome to the club!

When Bell said that? Definitely it was quite some time ago. And still there is uncomfortable lack of experiments that explicitly test what happens when counter efficiency is changed above usual ~10% level even when there is constant improvement in photon detection technologies.

Again, we have a very solid theory in Bell's theorem, and the experiments are improved day by day.
Where are the theories proving that it’s impossible to ever prove Bell's theorem? Any equations? Anything? Except opposition, and the "magical entangled loophole"...??

How would science look if we apply this 'approach' to everything else? Did the Big Bang really happen? Well, apparently not! No one was there to make the 'proper experiments', and the CMB is just a bunch of photons that we don’t know how to measure with 100% efficiency! Conclusion: Big Bang is not true, and we can explain everything we see with the "Turtle Interpretation"!

(to be drastic )

 

[DevilsAvocado]

... I consider the quality of the discussions to be inversely proportional to the number of ZapperZ posts!

 

[DevilsAvocado]

I think that the real issue is with the definition of 'Local Realism'.
...
I have a faint inclination that 'this star' will certainly have an influence on our measurement related to Earth (however small this effect may be). If an instrument could be formed that is (hyper)ⁿ sensitive, we may be able to gauge the effect. And it would depend on the (refinement)ⁿ/nature of our measurement wheter we take this effect to be of any consequence or not.

Deepak Kapur, I think the possibility for EPR to ever prove Local realism is almost zero, since it requires local hidden variables (as Frame Dragger & DrChinese already pointed out), and Bell has shown that quantum mechanics is not 'compatible' with LHV, and QM predictions are the most precise in all of physics.

Still, we can be pretty sure that the Moon is "out there" even when no one is observing it...

Or put it this way – if observations are required for distant stars and galaxies to be 'real' objects – we could today only observe galaxies as they appeared < 4.5 billion years ago, which of course is not true.

The farthest galaxies in this picture (the very faint red specks) are seen as they appeared more than 13 billion years ago.

It’s more than 'tough' to put macroscopic objects in superposition or entanglement, and this probably has something to do with the observed facts above... (= my speculation)

 

[zonde]

Well... no, that’s actually not my point. To me it’s almost clear that EPR must be some kind of "gun smoke" of the next 'paradigm' in physics ('smoke' without 'fire'!? ). It’s a clear sign that we do not know everything there is to know, yet.

And I’m almost stunned by the numerous attempts to run "business as usual" – stating "well, this doesn’t mean anything... it’s a matter of QM interpretation", or "it’s hard to measure photons, therefore EPR is most probably misleading".

To me it seems like you are contradicting yourself.
From one side you say that we do not know everything there is to know, yet.
From the other side you do not accept neither indirect modifications of QM - interpretations nor direct modifications of QM - position that QM is incomplete.

Or do you imply that we should modify anything but QM?

I don’t think that’s fair to all the intelligent persons that spent a lot of time working on this problem.

And I do not understand this completely.
Are you saying that if all those intelligent persons spent a lot of time working on this problem we shouldn't work on this problem any more and abandon it?

And if we look with some 'perspective' on the criticism of Bell test experiments – What are they saying? Well, most agree that Bell's theorem is correct and sound, but there is some "magical entangled loophole" that exposes itself in different ways, in different experiments!?

Yet we know that the 'overlapping effect' of all performed Bell test experiments, together with Bell's theorem is very convincing. And over time it will be definite.

I’m not an explicit supporter of MWI, it could be the correct solution, but I can’t get the 'pragmatic workings' of MWI into my head. Therefore I’m (for now) anticipating some hardnosed evidence from another 'branch'...

This is exactly what I’m talking about – the "magical entangled loophole"!

Interpretation of Rowe's experiment rests on assumption that photons scattered from two ions can not possibly interact (locally) as to change the count of photons that ends in detector. This assumption contradicts with results of double slit experiment not speaking about anything else.
There is no "magical entangled loophole" in Rowe's experiment just plain wrong assumption (even from perspective of QM).

Again, we have a very solid theory in Bell's theorem, and the experiments are improved day by day.
Where are the theories proving that it’s impossible to ever prove Bell's theorem? Any equations? Anything? Except opposition, and the "magical entangled loophole"...??

How would science look if we apply this 'approach' to everything else? Did the Big Bang really happen? Well, apparently not! No one was there to make the 'proper experiments', and the CMB is just a bunch of photons that we don’t know how to measure with 100% efficiency! Conclusion: Big Bang is not true, and we can explain everything we see with the "Turtle Interpretation"!

Science in general does not depend so much from "no go theorems" as Bell's theorem. There are quite different rules for theories that state "what can be" contrary to "what can't be".
If a theory states "what can be" given this and that it can be quite usable. And actually every theory has limited domain of applicability and still the science provides usable results.

 

[DrChinese]

Interpretation of Rowe's experiment rests on assumption that photons scattered from two ions can not possibly interact (locally) as to change the count of photons that ends in detector. This assumption contradicts with results of double slit experiment not speaking about anything else.
There is no "magical entangled loophole" in Rowe's experiment just plain wrong assumption (even from perspective of QM).

I just don't get this at all. You speak as if Rowe is the ONLY Bell test. We already knew that spacelike separation - what you are complaining about - makes no difference from Weihs et al (as well as Aspect). What Rowe shows is that the fair sampling assumption does not make any difference either.

As it stands, we have the following:

a) No individual Bell test "loopholes" exist.
b) No existing/remaining local realistic theory purports to replicate the predictions of QM and explain entanglement test results.

Some scientists hope to eventually close all loopholes simultaneously, although there are others who do not see this as anything other than desirable - so as to end further discussion of the matter by the few remaining local realists. (Like that would make any difference!)

 

[RUTA]

You are diverting my point, by raising another. Tit for Tat RUTA... "A cat for a hat, or a hat for a cat, but nothing for nothing."

Sorry, I was distracted and my latest post, plus some other quotes, were actually supposed to be in the first post. That's why the first post doesn't look like we had a disagreement. We do disagree on the value of time spent on interpretations. I believe it's valuable, while you don't find it particularly so. That's my understanding.

As for the rest, why do you feel I have a metaphysical interpretation?

You need to make ontological assumptions in order to map theory to experiment/experience, otherwise you're doing math, not physics. You can explore the mathematical consequences of equation X of theory Y, but to do physics, you would have to map those consequences to experiment/experience, which tacitly, if not explicitly, entails ontology (metaphysics). So, when you use the term "Planck scale" you've some ontological baggage if you're talking physics, not math.

I don't see that as a logical conclusion from the standpoint of wanting to see the two major theories of physics AGREE (i.e. GR/QM). As for believing that interpeting QM will lead to breakthroughs... I'm yet to see that. It DOES provide people with something to say other than, "we don't know"... a notoriously bad phrase to place in a grant request. Please don't assume what I "must" or must not believe.

You might read Gilder's "The Age of Entanglement" or Beller's "Quantum Dialogue" in order to appreciate the extent to which the development of quantum physics was tied to its interpretation. In reference to Beller's work, Smolin notes "there was not a single calculation in [Bohr's] notebooks, which were all verbal argument and pictures." [p 309 of Smolin's "The Trouble with Physics"]. Here is a quote fm Einstein writing to a young physics student (p. 310-11 in Smolin):

"I fully agree with you about the significance and educational value of methodology as well as history and philosophy of science, So many people today -- and even professional scientists -- seem to me like someone who has seen thousands of trees but has never seen a forest. A knowledge of the historical and philosophical background gives that kind of independence from prejudices of his generation from which most scientists are suffering. This independence created by philosophical insight is -- in my opinion -- the mark of distinction between a mere artisan or specialist and a real seeker after truth."

Smolin goes on to argue for the importance of relating our formal approaches "to the older writings by physicists and philosophers on the big issues in the foundations of space, time, or quantum theory."

No one knows why QM and GR don't marry up. Those of us in foundations are compelled to search for the key to unification in, among other places, our ontological biases. Those who search in this area are of course very interested in "interpretations."

 

[ThomasT]

As a reader of this thread, I would personally rather that ThomasT wasn't discouraged from participating in the conversation.

Thanks, but I'm not discouraged.

As you've read, there's some disagreement regarding the title question of this thread. The fact of the matter is that what's called nonlocality or action at a distance (wrt EPR or Bell tests) comes from:

(1) deductions based on the data and associated instrument settings and/or,

(2) interpretations (the semantics) of the associated QM and/or Bell's theorem formalisms (Bell inequalities, GHZ, etc).

But none of it contradicts locality. Bell's theorem (via Bell inequalities, GHZ, etc.) is about formal constraints, not what does or doesn't exist in Nature.

 

[Frame Dragger]

Sorry, I was distracted and my latest post, plus some other quotes, were actually supposed to be in the first post. That's why the first post doesn't look like we had a disagreement. We do disagree on the value of time spent on interpretations. I believe it's valuable, while you don't find it particularly so. That's my understanding.




You need to make ontological assumptions in order to map theory to experiment/experience, otherwise you're doing math, not physics. You can explore the mathematical consequences of equation X of theory Y, but to do physics, you would have to map those consequences to experiment/experience, which tacitly, if not explicitly, entails ontology (metaphysics). So, when you use the term "Planck scale" you've some ontological baggage if you're talking physics, not math.



You might read Gilder's "The Age of Entanglement" or Beller's "Quantum Dialogue" in order to appreciate the extent to which the development of quantum physics was tied to its interpretation. In reference to Beller's work, Smolin notes "there was not a single calculation in [Bohr's] notebooks, which were all verbal argument and pictures." [p 309 of Smolin's "The Trouble with Physics"]. Here is a quote fm Einstein writing to a young physics student (p. 310-11 in Smolin):

"I fully agree with you about the significance and educational value of methodology as well as history and philosophy of science, So many people today -- and even professional scientists -- seem to me like someone who has seen thousands of trees but has never seen a forest. A knowledge of the historical and philosophical background gives that kind of independence from prejudices of his generation from which most scientists are suffering. This independence created by philosophical insight is -- in my opinion -- the mark of distinction between a mere artisan or specialist and a real seeker after truth."

Smolin goes on to argue for the importance of relating our formal approaches "to the older writings by physicists and philosophers on the big issues in the foundations of space, time, or quantum theory."

No one knows why QM and GR don't marry up. Those of us in foundations are compelled to search for the key to unification in, among other places, our ontological biases. Those who search in this area are of course very interested in "interpretations."

Well, it seems we come from deeply different views on the matter, but then, I have the benefit of not being a physicist... a luxury really. I'm just trying to learn for the sake of learning, and I don't need to produce new theories. If I did, I WOULD probably stick to the math, but I wouldn't conclude that because X maps to y that it really has a physical reality.

I respect your approach, but I don't share it. I do see what you mean by bias however, so I think mine is: GR is wonderfully predictive, as in QM. I believe that modificationa and unification of both will reveal new physics. I have no CLUE as to what, except a hope that it explains a bit more.

@ThomasT: None of it contradicts Locality, but then you need a theory to compete with QM's predictions. So far, QM leads, with dBB being able to match the predictions. It's not enough to simply say that Bell doesn't rule out Locality, becuase it DOES if you accept the predictions of QM.

So, yes, bell is about constraints, but it is an EFFECTIVE constraint which has strangled all LHV theories that have been put forward.

 

[RUTA]

Well, it seems we come from deeply different views on the matter, but then, I have the benefit of not being a physicist... a luxury really. I'm just trying to learn for the sake of learning, and I don't need to produce new theories. If I did, I WOULD probably stick to the math, but I wouldn't conclude that because X maps to y that it really has a physical reality.

You hold the mainstream view. If you're interested in why that came to be the mainstream view, you can read either Gilder or Beller. But, rest assured, I'm the "quack" in this conversation, not you :-)

I respect your approach, but I don't share it. I do see what you mean by bias however, so I think mine is: GR is wonderfully predictive, as in QM. I believe that modificationa and unification of both will reveal new physics. I have no CLUE as to what, except a hope that it explains a bit more.

As an example of how one might use a QM interpretation to inspire an approach to unification, look up Hiley's recent work. In a summer 2009 preprint he writes,

"Since the advent of general relativity in which matter and geometry codetermine each other, there is a growing realisation that starting from an a priori given manifold in which we allow material processes to unfold is, at best, limited. Can we start from something more primitive from which both geometry and material process unfold together? The challenge is to find a formalism that would allow this to happen. In the early sixties David Bohm introduced the notion of a discrete structural process, [1], [2], in which he takes as basic, not matter or fields in space-time, but a notion of `structure process' from which the geometry of space-time and its relationship to matter emerge together providing a way that could underpin general relativity and quantum theory. Bohm provides a detailed discussion of the general notions implicit in this approach, but the problem of how to develop these ideas into a well defined mathematical structure remained unanswered."

In this paper he introduces what he hopes will serve as Bohm's missing mathematical structure. Just an example.

 

[DevilsAvocado]

To me it seems like you are contradicting yourself.
From one side you say that we do not know everything there is to know, yet.
From the other side you do not accept neither indirect modifications of QM - interpretations nor direct modifications of QM - position that QM is incomplete.

Or do you imply that we should modify anything but QM?

And the short answer is – I have absolutely no idea!

Seriously, let’s be honest, I’m only a layman with this as a hobby, and if I’d proclaim – "Hey guys! This is the way to do it! I got the final solution!" Then my claim in https://www.physicsforums.com/showpost.php?p=2675332&postcount=18" that "I’m not stupid", would most certainly be 'somewhat' questioned.

I do understand why you think I’m contradicting myself. My last post will not gain a 'rhetorical medal'... (under stress by 'reality', sorry)


Let’s do it right, let’s take one step back. In https://www.physicsforums.com/showpost.php?p=2679632&postcount=40" I pointed out Rowe as an example where the detection methods were almost 100% efficient, as a way of ending the discussion around the "Detection efficiency loophole" and "The fair sampling assumption". Your reaction was:

To consider this experiment as an EPR paradox test is a bit of stretch. EPR paradox considers separate measurements of two systems that are not interacting at the moment of measurement. But in this experiment there is only one joined measurement of both systems.

Then DrChinese hits the nail on the head (thanks DC!):

You speak as if Rowe is the ONLY Bell test.

If we also add this statement of yours:

Yes, in most cases fair sampling assumption is considered reasonable. But in this case fair sampling assumption necessarily comes packaged with one of the not-so-reasonable speculations like MWI, superdeterminism or nonlocality of Pilot-wave.

(emphasis by me)

Now, I hope I can explain, by the means of above, clearly what I’m arguing about:

To me, it seems as if there are two 'camps', struggling to 'get rid of' the EPR paradox (no offense!). One is the "Denial Camp" who tries with all means available to 'diminish' Bell's theorem and Bell test experiments, not to have to face the facts of even 'uglier beasts' like the MWI.

And the other is the "Interpretation Camp" who just loves freaky things – Is there a problem!? What problem?? We just sent it to a parallel universe! Let’s have dinner now... yawn.

(And then the public, who likes some 'excitement', but in the end always prefers to live in a 'logical world'.)

Get it?


Now back to DrChinese and Rowe. Do you really think it’s fair to avoid 'the sum' of all performed Bell test experiments? If we can rule out one loophole in one experiment, why do you insist on bringing it back in another? Is that really what 'the rules of science' tells you??

Is it healthy science to deny, in absurdity, the facts DrChinese points out??

As it stands, we have the following:

a) No individual Bell test "loopholes" exist.
b) No existing/remaining local realistic theory purports to replicate the predictions of QM and explain entanglement test results.

So what do I want!?

Well, to start with: Let’s throw the 'blinders' away. Let’s not have preconceptions. Let’s not explain 'weird things' with even 'weirder things', that can’t be physically proved in less than +1000 years. Let’s accept what nature shows us, even if it turns out 'crazy'. Let’s accept that the science of nature is not going to be completed in 2010. Let’s find the truth, if there is one.

We know that both QM & GR are very effective in respective domain, thus completely throw one or both out seems farfetched... even if String theory turns out to play the most beautiful music ever heard...


Footnote:
Doesn’t the Double-slit experiment 'crushes' the Ensemble Interpretation, by the footprint of the wave function in the interference pattern??

 

[DevilsAvocado]

We talk about moon becuase we see it the way our eyes/brains have been tuned to do so. Our instruments are also made/operated/analysed by our brains/eyes (that are tuned in a particular way).

It may be possible that moon/matter is not at all visible/detectable to someone from other stranger universe. (just foolish speculation with a small tinge of logic).

What would then become of our 'surity' about things.

Well, all this about 'personal interpretation' of the world is very true. Colors e.g. are only in our heads. In nature, there are only electromagnetic waves of different lengths.

But, you cannot avoid the fact that stars and galaxies evolves under a very long time, under gravity. And to make this argument even stronger: When the very first stars formed there where absolutely no life in the universe (to perform any observations)!

How do you explain that?

 

[Frame Dragger]

You hold the mainstream view. If you're interested in why that came to be the mainstream view, you can read either Gilder or Beller. But, rest assured, I'm the "quack" in this conversation, not you :-)

We don't agree, but if you're a quack then I'm the pope. As I'm not an old german man coming to grips with scandal, I suspect you're not a quack. I've read Gilder, not Beller (but I will now!), and I don't see how curiosity = quackery. You're not pushing a view, you're discussing it. I respect that.

As an example of how one might use a QM interpretation to inspire an approach to unification, look up Hiley's recent work. In a summer 2009 preprint he writes,

"Since the advent of general relativity in which matter and geometry codetermine each other, there is a growing realisation that starting from an a priori given manifold in which we allow material processes to unfold is, at best, limited. Can we start from something more primitive from which both geometry and material process unfold together? The challenge is to find a formalism that would allow this to happen. In the early sixties David Bohm introduced the notion of a discrete structural process, [1], [2], in which he takes as basic, not matter or fields in space-time, but a notion of `structure process' from which the geometry of space-time and its relationship to matter emerge together providing a way that could underpin general relativity and quantum theory. Bohm provides a detailed discussion of the general notions implicit in this approach, but the problem of how to develop these ideas into a well defined mathematical structure remained unanswered."

In this paper he introduces what he hopes will serve as Bohm's missing mathematical structure. Just an example.

I've read that (thanks to Demystifier and Zenith8, two very bright and interesting Bohmians here on PF), and I respect the goal. I think that a field with people taking different, but complementary approaches is a PLUS. This isn't fringe, anymore than EPR itself is "fringe". It's a well formulated objection to a formalism that is EFFECTIVE (mostly), but not satisfying or fully explanatory.

What can I say RUTA, you make a good case for your view, and I will continue to explore it. That said, I still maintain my formalism. I look forward to more of your posts.

 

[Frame Dragger]

And the short answer is – I have absolutely no idea!

Seriously, let’s be honest, I’m only a layman with this as a hobby, and if I’d proclaim – "Hey guys! This is the way to do it! I got the final solution!" Then my claim in https://www.physicsforums.com/showpost.php?p=2675332&postcount=18" that "I’m not stupid", would most certainly be 'somewhat' questioned.

I do understand why you think I’m contradicting myself. My last post will not gain a 'rhetorical medal'... (under stress by 'reality', sorry)


Let’s do it right, let’s take one step back. In https://www.physicsforums.com/showpost.php?p=2679632&postcount=40" I pointed out Rowe as an example where the detection methods were almost 100% efficient, as a way of ending the discussion around the "Detection efficiency loophole" and "The fair sampling assumption". Your reaction was:



Then DrChinese hits the nail on the head (thanks DC!):



If we also add this statement of yours:

(emphasis by me)

Now, I hope I can explain, by the means of above, clearly what I’m arguing about:

To me, it seems as if there are two 'camps', struggling to 'get rid of' the EPR paradox (no offense!). One is the "Denial Camp" who tries with all means available to 'diminish' Bell's theorem and Bell test experiments, not to have to face the facts of even 'uglier beasts' like the MWI.

And the other is the "Interpretation Camp" who just loves freaky things – Is there a problem!? What problem?? We just sent it to a parallel universe! Let’s have dinner now... yawn.

(And then the public, who likes some 'excitement', but in the end always prefers to live in a 'logical world'.)

Get it?


Now back to DrChinese and Rowe. Do you really think it’s fair to avoid 'the sum' of all performed Bell test experiments? If we can rule out one loophole in one experiment, why do you insist on bringing it back in another? Is that really what 'the rules of science' tells you??

Is it healthy science to deny, in absurdity, the facts DrChinese points out??




So what do I want!?

Well, to start with: Let’s throw the 'blinders' away. Let’s not have preconceptions. Let’s not explain 'weird things' with even 'weirder things', that can’t be physically proved in less than +1000 years. Let’s accept what nature shows us, even if it turns out 'crazy'. Let’s accept that the science of nature is not going to be completed in 2010. Let’s find the truth, if there is one.

We know that both QM & GR are very effective in respective domain, thus completely throw one or both out seems farfetched... even if String theory turns out to play the most beautiful music ever heard...


Footnote:
Doesn’t the Double-slit experiment 'crushes' the Ensemble Interpretation, by the footprint of the wave function in the interference pattern??

Awesome post, and very clear. As to the footnote, I had this very argument (and "lost) with Zenith and Demystifier. The claim of dBB is that the interference is a function of the PILOT wave, which "guides" the particles. The particles themselves follow Classic Schrodinger trajectories. I don't believe this, but it matches the predictions of QM, so my belief is pretty irrelevant.

When it comes to dBB, you can't go wrong chatting with Zenith and/or Demystifier.

 

[Deepak Kapur]

Well, all this about 'personal interpretation' of the world is very true. Colors e.g. are only in our heads. In nature, there are only electromagnetic waves of different lengths.

But, you cannot avoid the fact that stars and galaxies evolves under a very long time, under gravity. And to make this argument even stronger: When the very first stars formed there where absolutely no life in the universe (to perform any observations)!

How do you explain that?

Actually, I was talking of a universe that is older/different/stranger than our own (I think this thing is not supported by the present super-structure of science).

 

[Frame Dragger]

Actually, I was talking of a universe that is older/different/stranger than our own (I think this thing is not supported by the present super-structure of science).

Ok, I'm genuinely confused... If there are other universes, we'd be completely cut-off from them. Another universe would also lack (us as) observers, so... I'm not sure what you're getting at, supported or not. I get the sense that in many of your posts you're expressing a similar idea about cosmology, but I'm never quite sure what it is. Sometimes you make VERY odd statements (from my perspective), and the other times you ask perfectly reasonable questions.

If you present your beliefs for critique, it may be that you can really learn quite a bit here. Remember, learning about a view that differs from your own doesn't preclude holding personal beliefs. That said, it's difficult to know if you're trying to offer a personal theory, or if you're truly confused... or both! Hell, I'm not sure from one post to the next which it might be. This isn't the thread for it, but maybe you could post your full view in the lounge (which is much more liberal), and start from there. If you present it as your current understanding, and not an attempt to "convert" so to speak, and are open to discussion... well... you might find the rest of the site more useful.

For example... an "older/different/stranger universe"... Different in what ways? Strange how? Our universe seems pretty weird as it is to be fair. Do you mean a previous "incarnation" of this universe is a cyclical model, or something out of Brane Cosmology? I'm just not sure if you're swinging for the fences, are deeply misinformed (not uncommon), or if this is an attempt to reconcile spiritual/religious beliefs with science?

 

[inflector]

No one knows why QM and GR don't marry up. Those of us in foundations are compelled to search for the key to unification in, among other places, our ontological biases. Those who search in this area are of course very interested in "interpretations."

To me, this is a key observation. Something about science's collective understanding is incomplete or incorrect, something very significant.

The biases of scientists over the last century have cut off certain paths of inquiry as "unfruitful," "impossible," "foolish," etc. It may be that the key to progress lies at least partway down one of these discarded paths.

Nowhere do these ontological biases show up more strongly than in the interpretations of QM itself. This is one of the reasons that I find dBB to be so interesting. Here we have a perfectly valid way of looking at QM that allows for a broad range of new possibilities. It represents largely unmapped territory. It may be that thinking about QM from a different perspective, would provide fertile soil for the germ of an idea that develops into a unification of QM and GR.

Besides, there has been 70 years or more when physics has been dominated by other interpretations, perhaps these other interpretations have been limiting our capacity to imagine the truth in some way. Perhaps the ontological biases implicit with these interpretations are the blocks that have been keeping us from seeing the obvious.

As an example of how one might use a QM interpretation to inspire an approach to unification, look up Hiley's recent work. In a summer 2009 preprint he writes,

"[snip]...Can we start from something more primitive from which both geometry and material process unfold together? The challenge is to find a formalism that would allow this to happen. In the early sixties David Bohm introduced the notion of a discrete structural process, [1], [2], in which he takes as basic, not matter or fields in space-time, but a notion of `structure process' from which the geometry of space-time and its relationship to matter emerge together providing a way that could underpin general relativity and quantum theory. ...[snip]"

In this paper he introduces what he hopes will serve as Bohm's missing mathematical structure. Just an example.

This is a great example of a different way of looking at things. This idea may or may not bear fruit but at least it is new ground, interesting, and offers some potential for advancement.

Do you have a link to this Hiley paper? I'd love to read it. I couldn't find it using google. Is it on arXiv?

 

[zonde]

I just don't get this at all. You speak as if Rowe is the ONLY Bell test. We already knew that spacelike separation - what you are complaining about - makes no difference from Weihs et al (as well as Aspect). What Rowe shows is that the fair sampling assumption does not make any difference either.

I am not complaining about spacelike separation of ions. The problem is that this experiment fails to demonstrate entanglement between two ions.

Non-local correlation does not have to appear at the moment when ions scatter light.
This correlation can appear later quite locally when light from two ions overlap. And then there is no spooky action at a distance but quite local interference of light.

You can try to extend result of Weihs et al experiment to two ions in a way that if they are entangled it can not be explained by some mysterious communication at light or sub-light speed. The problem is that they don't have to be entangled at all to explain results of this experiment.

 

[Frame Dragger]

I am not complaining about spacelike separation of ions. The problem is that this experiment fails to demonstrate entanglement between two ions.

How so?! This seems like it would require some serious citation.

Non-local correlation does not have to appear at the moment when ions scatter light. This correlation can appear later quite locally when light from two ions overlap. And then there is no spooky action at a distance but quite local interference of light.

Again, this is a spectacular claim which requires commensurate support.

You can try to extend result of Weihs et al experiment to two ions in a way that if they are entangled it can not be explained by some mysterious communication at light or sub-light speed. The problem is that they don't have to be entangled at all to explain results of this experiment.

See previous objections. This seems like an opinion which is largely discarded. I'll ask again, as has Dr.C: What LHV theory survived Bell? It's not enough to object, you need to provide an alternative to QM which is at least as predictive. Otherwise, you're just explaining a personal bias.

 

[DrChinese]

I am not complaining about spacelike separation of ions. The problem is that this experiment fails to demonstrate entanglement between two ions.

Non-local correlation does not have to appear at the moment when ions scatter light.
This correlation can appear later quite locally when light from two ions overlap. And then there is no spooky action at a distance but quite local interference of light.

You can try to extend result of Weihs et al experiment to two ions in a way that if they are entangled it can not be explained by some mysterious communication at light or sub-light speed. The problem is that they don't have to be entangled at all to explain results of this experiment.

Huh? You ARE complaining that they are not spacelike separated! You say that a sub-c effect could account for that. Of course, it would be new and previously undiscovered - probably worth a Nobel. Oh, and it would not account for the results of Weihs et al.

So as I say, don't treat Rowe as if it is a lone experiment. It isn't.

 

[RUTA]

To me, this is a key observation. Something about science's collective understanding is incomplete or incorrect, something very significant.

When I first entered the foundations community (1994), there were still a few conference presentations arguing that the statistical and/or experimental analyses of EPR-Bell experiments were flawed. Such talks have gone the way of the dinosaurs. Virtually everyone agrees that the EPR-Bell experiments and QM are legit, so we need a significant change in our worldview. There is a proper subset who believe this change will be related to the unification of QM and GR :-)

Do you have a link to this Hiley paper? I'd love to read it. I couldn't find it using google. Is it on arXiv?

He only wrote it last summer (2009) and sent it to us last fall (2009) in preparation for an upcoming conference. At that time it was still a work in progress and he asked that we not disseminate it. I was hoping he had it posted on the arXiv by now (there are actually two of them -- one for the Dirac equation and one for the Schrodinger equation). If that's not the case, there should be something out there because I remember seeing mention on PF of Lorentz invariant Bohmian mechanics and that's what his Dirac version shows. I'm sorry I don't have more info for you, I'm not a dBB guy :-)

 

[ThomasT]

None of it contradicts Locality, but then you need a theory to compete with QM's predictions.

Any representation of entanglement conforming to Bell's ansatz will satisfy a Bell inequality and be incompatible with QM. There's no disagreement about this, and it has nothing to do with nonlocality in Nature.

The salient features of Bell's general lhv formulation (ie., that the joint probability be expressed as a product of the individual probabilities involving the hidden variable) place certain limits on the range of the predictions that are possible using that form.

These limits are embodied in the various Bell inequalities. Experimental violation of the Bell inequalities tells us that a viable lhv theory can't have the form specified by Bell. It doesn't imply that nonlocality or ftl propagations exist.

It's not enough to simply say that Bell doesn't rule out Locality, becuase it DOES if you accept the predictions of QM.

? See above.

So, yes, bell is about constraints, but it is an EFFECTIVE constraint which has strangled all LHV theories that have been put forward.

If it wasn't effective then it wouldn't be a constraint.

Anyway, regarding the topic, we can't infer the existence of actions at a distance or ftl propagations from this.

 

[RUTA]

Experimental violation of the Bell inequalities tells us that a viable lhv theory can't have the form specified by Bell. It doesn't imply that nonlocality or ftl propagations exist. ... Anyway, regarding the topic, we can't infer the existence of actions at a distance or ftl propagations from this.

Correct. There are different ways to parse it, but the way I prefer is this:

Violations of Bell inequalities imply nonlocality and/or nonseparability.

So, nonseparability alone would do the trick, thereby saving locality (no FTL causal connections).

It's rare to hear anyone considering a nonseparable ontology, though. We presented a nonseparable interpretation of QM at New Directions in the Foundations of Physics (2005). We had a full 2 hours of discussion after which Jeff Bub told us, "Congratulations on your new interpretation. Don't be discouraged that they didn't seem to understand it. It took me 3 epiphanies to understand your nonseparable ontology and each epiphany would require a week of lectures in a graduate-level course." Nonseparability violates our dynamical bias at a fundamental level. That's probably why you rarely hear it mentioned as an explanation for violations of Bell inequalities.

 

[DrChinese]

So, nonseparability alone would do the trick, thereby saving locality (no FTL causal connections).

It's rare to hear anyone considering a nonseparable ontology, though. We presented a nonseparable interpretation of QM at New Directions in the Foundations of Physics (2005). We had a full 2 hours of discussion after which Jeff Bub told us, "Congratulations on your new interpretation. Don't be discouraged that they didn't seem to understand it. It took me 3 epiphanies to understand your nonseparable ontology and each epiphany would require a week of lectures in a graduate-level course." Nonseparability violates our dynamical bias at a fundamental level. That's probably why you rarely hear it mentioned as an explanation for violations of Bell inequalities.

I liked it after 1 epiphany (I haven't had the other 2 yet).

 

[RUTA]

I liked it after 1 epiphany (I haven't had the other 2 yet).

Didn't you also admit that you're committed to, or rather live on, Shutter Island?

 

[DrChinese]

Didn't you also admit that you're committed to, or rather live on, Shutter Island?

Yes, I live there... in fact I am the detective in charge. Just ask the warden.

 

[Frame Dragger]

Any representation of entanglement conforming to Bell's ansatz will satisfy a Bell inequality and be incompatible with QM. There's no disagreement about this, and it has nothing to do with nonlocality in Nature.

Riiight.. which is why I specified that there ARE no theories describing the kind of Locality that you seem to favour. That is why I said,

None of it contradicts Locality, but then you need a theory to compete with QM's predictions.

Which you have NOT responded to. Responding to part of a single sentence, is another form of the good old fashioned Straw Man. You're making a case for something... what is it?

 

[DevilsAvocado]

So, nonseparability alone would do the trick, thereby saving locality (no FTL causal connections).

It's rare to hear anyone considering a nonseparable ontology, though. We presented a nonseparable interpretation of QM at New Directions in the Foundations of Physics (2005).

...Houston, we've had a problem...

English is not my mother tongue; my mother’s tongue is somewhere else... don’t ask...

So, I got very interested and googled in a hurry nonsenseparability. Even misspelled () I got two (2!) hits (1 epiphany), and the first was clearly accurate:

http://plato.stanford.edu/entries/physics-holism/#Spatial"

Nonseparability: Some physical process occupying a region R of spacetime is not supervenient upon an assignment of qualitative intrinsic physical properties at spacetime points in R.

It is important to note that nonseparability entails neither physical property holism nor spatial nonseparability: a process may be nonseparable even though it involves objects without proper parts. But this section has explained that either of the latter principles entails nonseparability under quite weak assumptions.

My very first impression was that this phraseology penetrated alco-holism, but that turned out to some extent off beam... (2 epiphany)

Now I knew I was close, and asked my dear grandfather if he could do the interpretation... but his tongue was occupied explaining the nature of the "Hole-o-graphic Torus Topology of the Universe":

https://www.youtube.com/watch?v=<object width="480" height="385"><param name="movie" value="http://www.youtube.com/v/mbs64GvGgPU&hl=en_US&fs=1&rel=0&color1=0x006699&color2=0x54abd6"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/mbs64GvGgPU&hl=en_US&fs=1&rel=0&color1=0x006699&color2=0x54abd6" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="480" height="385"></embed></object>

Please, maybe some of the more 'subtitle contributors' in this thread could elaborate on this matter. I know I can get there... 3 epiphany is around the corner... I’ve seen the light from the lighthouse...


Footnote:
Do they serve a fruitcake on Shutter Island??

 

[DevilsAvocado]

Awesome post, and very clear. As to the footnote, I had this very argument (and "lost) with Zenith and Demystifier. The claim of dBB is that the interference is a function of the PILOT wave, which "guides" the particles. The particles themselves follow Classic Schrodinger trajectories. I don't believe this, but it matches the predictions of QM, so my belief is pretty irrelevant.

Thanks a lot FD! Ahhhouch you’ve lost! Did you 'torture' them with the Quantum eraser experiment? Or the Delayed choice quantum eraser?? What kind of PILOT could handle that...!?
()

 

[DevilsAvocado]

Actually, I was talking of a universe that is older/different/stranger than our own (I think this thing is not supported by the present super-structure of science).

Err... have you ever heard the 'turtle story'...?

Turtles all the way down

A well-known scientist once gave a public lecture on astronomy. He described how the Earth orbits around the sun and how the sun, in turn, orbits around the center of a vast collection of stars called our galaxy. At the end of the lecture, a little old lady at the back of the room got up and said:

"What you have told us is rubbish. The world is really a flat plate supported on the back of a giant tortoise."

The scientist gave a superior smile before replying, "What is the tortoise standing on?"

"You're very clever, young man, very clever", said the old lady. "But it's turtles all the way down!"

We can run this 'quarrelling' on every 'turtle', and still the outcome will be the same...

 

[DevilsAvocado]

Responding to part of a single sentence, is another form of the good old fashioned Straw Man.

This is somewhat familiar... but in my case... they just dump the whole post!

 

[Frame Dragger]

This is somewhat familiar... by in my case... they just dump the whole post!

Yeah, I hear you.

 

[inflector]

Err... have you ever heard the 'turtle story'...?

Of course, I'm very familiar with the https://www.amazon.com/gp/product/007148664X/?tag=pfamazon01-20 (since I wrote that book). Oh, but I suppose you mean another sort of turtle.

This is one of the philosophical problems that trips up both creationists and atheists alike. What came first? An all-powerful deity? Or perhaps a universe spontaneously erupting from nothingness?

 

[RUTA]

Please, maybe some of the more 'subtitle contributors' in this thread could elaborate on this matter.

That was a great post! I'm stealing your "nonsenseparability" and "alco-holism" for use in my QM PowerPoint lecture. I'll cite you, but most people will assume "DevilsAvocado" is just part of the joke :-)

As I warned, nonseparability is much more difficult to understand than nonlocality. I suspect this is because what (most) people need to "understand" nonseparability is a nonseparable ontology. The definition you provided from SEP doesn't give an ontology, it pretty much just says, "The reason for entangled outcomes in QM is not causal nonlocality." This is a gross oversimplification, but let me continue along these lines in an effort to give you SOMETHING you can wrap your head around.

Suppose you have two, entangled, space-like related measurements, A and B. That A and B are "space-like related" means that, per special relativity, in some frames of reference A occurs before B, in some frame of ref A and B are simultaneous, and in other frames of ref B occurs before A. Another way of saying this is a line between A and B would represent a FTL connection. [The combination of these two facts about space-like related events entails, for example, that A cannot be the cause of B unless you believe a cause need not precede its effect or you believe there is a "preferred frame," i.e., one in which A occurs before B.] That A and B are "entangled" means, given repeated trials, correlations in the outcomes of A and B violate a Bell inequality. We have conducted experiments which satisfy this situation and QM accurately predicts the observed correlations, so what's the "problem?"

Quantum physics as a whole has many technical issues (see the SEP entry on QFT, for example), and of course there is the problem of reconciling formally QM and GR, but the "problem" I want to focus on here is simply that of ontology. What is the nature of reality such that we find space-like separated experimental results that violate Bell's inequality?

The SEP entry on nonseparability is (overly) simplistically put just saying no "spooky action at a distance," i.e., no FTL causal connection between A and B. So, here's what you have: You're the guy doing measurement A. You get a result at A, call it "red." If there is no FTL causal connection between A and B, then the reason you got red as a result of your measurement A is not attributable to you, your device, the quantum entity (whatever it is or isn't), or anything else in the immediate vicinity of that measurement. EPR argued that it was possible to know (probability 1) something about the outcome at A due to a measurement at B (the entangled property). So, if you don't have "spooky action at a distance" between A and B, there must be a fact of the matter at A, due entirely to the situation in the immediate spacetime vicinity of A to account for your red outcome. QM doesn't give us any way to obtain those "hidden" facts, so it's clearly incomplete. But, violation of the Bell inequality means EPR are wrong, QM is right, so without "spooky action at a distance" the red outcome at A cannot be due to the situation in the immediate spacetime vicinity of A. That's all SEP tells you, really.

Since the SEP characterization of nonseparability isn't giving you an ontology to "explain" the red outcome, you're probably saying "WTF?" SEP distilled the mystery of nonseparability from the violations of Bell inequalities by telling us what ISN'T true ontologically, but didn't RESOLVE anything mysterious USING nonseparability! To do that they need to tell us what IS true ontologically! Of course, the good philosophers at SEP will simply reply, "We did tell you what IS the case per the second principle of logic, i.e., excluded middle. Your desired ontology is that which we did not exclude in our statement." But, our brains work according to what they say is NOT true, so we just don't have anything left to "see."

At least that's my theory as to why you're confused by what you found on nonseparability :-) If not, well you have my best Roseann Rosanadana, "Nevermind."

 

[zonde]

How so?! This seems like it would require some serious citation.

Again, this is a spectacular claim which requires commensurate support.

I am afraid I can not give you citations but let's look at this experiment from QM perspective (no LHV or anything).
We can compare it with double slit experiment:

In interpretation of experiment wave nature of light is completely ignored, insted photons are treated as particles. But if there are two indistinguishable paths for photons treating photons like particles gives wrong result.

Of course it would be nicer if I could give calculations proving that photon interference alone can account for observed result but even without them it's clear that interpretation of experiment is incomplete and can not be considered conclusive.

 

[zonde]

I am not complaining about spacelike separation of ions.

Huh? You ARE complaining that they are not spacelike separated!

It seems we have communication problem.

You say that a sub-c effect could account for that. Of course, it would be new and previously undiscovered - probably worth a Nobel. Oh, and it would not account for the results of Weihs et al.

Again you are seeing in my post something I do not see.

 

[zonde]

To me, it seems as if there are two 'camps', struggling to 'get rid of' the EPR paradox (no offense!). One is the "Denial Camp" who tries with all means available to 'diminish' Bell's theorem and Bell test experiments, not to have to face the facts of even 'uglier beasts' like the MWI.

And the other is the "Interpretation Camp" who just loves freaky things – Is there a problem!? What problem?? We just sent it to a parallel universe! Let’s have dinner now... yawn.

(And then the public, who likes some 'excitement', but in the end always prefers to live in a 'logical world'.)

Get it?

Got it.
I am in "Denial Camp" definitely.

Now back to DrChinese and Rowe. Do you really think it’s fair to avoid 'the sum' of all performed Bell test experiments? If we can rule out one loophole in one experiment, why do you insist on bringing it back in another? Is that really what 'the rules of science' tells you??

Yes, I really think it’s fair to avoid 'the sum' of all performed Bell test experiments.
Let me give you an example.
Lets say we set out to find what influence two polarizers have on each other and measurements of polarization by them if they are put side by side. Suppose (naturally) we find out that they do not have any detectable effect.
Now encouraged by our result we make another setup where we put two Stern-Gerlach apparatuses side by side and claim that they will not influence each other and respective spin measurements.
Now do I have to explain why this claim will be invalid? I hope not.

So what do I want!?

Well, to start with: Let’s throw the 'blinders' away. Let’s not have preconceptions. Let’s not explain 'weird things' with even 'weirder things', that can’t be physically proved in less than +1000 years. Let’s accept what nature shows us, even if it turns out 'crazy'. Let’s accept that the science of nature is not going to be completed in 2010. Let’s find the truth, if there is one.

We know that both QM & GR are very effective in respective domain, thus completely throw one or both out seems farfetched... even if String theory turns out to play the most beautiful music ever heard...

Who talks about throwing away something really useful? Not me.
Well ok as far as it concerns me you can replace GR with something else because it's so complex and it seems that it is not used so much as it could be if it would be more simple. But definitely not SR, no way.
And of course not QM. Well, less no-go theorems would be preferable and of course with entanglement replaced by something else.

 

[SpectraCat]

I am afraid I can not give you citations but let's look at this experiment from QM perspective (no LHV or anything).
We can compare it with double slit experiment:

In interpretation of experiment wave nature of light is completely ignored, insted photons are treated as particles. But if there are two indistinguishable paths for photons treating photons like particles gives wrong result.

Of course it would be nicer if I could give calculations proving that photon interference alone can account for observed result but even without them it's clear that interpretation of experiment is incomplete and can not be considered conclusive.

Well, I don't think this is much of a problem for the Rowe experiment, because the ions were well-separated in two distinct traps more than 1 mm apart. That is more than 1000 times the wavelength of light used, and thus rather far for any of the double-slit effects you are talking about to play a significant role. So, I don't think your objection holds any water in this case.

I am pretty sure that Rowe et al. anticipated just this sort of criticism when designing their trap ... here is an earlier paper detailing the painstaking testing that they did to ensure their design was suitable for this sort of experiment: http://arxiv.org/abs/quant-ph/0205094.

 

[DrChinese]

Yes, I really think it’s fair to avoid 'the sum' of all performed Bell test experiments.
Let me give you an example.
Lets say we set out to find what influence two polarizers have on each other and measurements of polarization by them if they are put side by side. Suppose (naturally) we find out that they do not have any detectable effect.
Now encouraged by our result we make another setup where we put two Stern-Gerlach apparatuses side by side and claim that they will not influence each other and respective spin measurements.
Now do I have to explain why this claim will be invalid? I hope not.

Yes, I really have no idea what you are talking about. This makes no sense at all relative to our discussion.

 

[ThomasT]

You're making a case for something... what is it?

That there's a simpler explanation for why BIs are violated than positing the existence of nonlocality or ftl causality.

It has to do with the constraints on lhv formulatio0ns imposed by Bell (which are the basis for BIs) and the relevance of these constraints to the experimental situations to which they're applied.

Consider, for example, that Bell's locality condition reduces to the definition of statistical independence. But we know that the statistical dependence observed in Bell tests can be produced via local interactions/transmissions.

Do you see the problem? If BIs are derived from the predictive limits of an lhv formulation that doesn't discern nonlocality, then how can we infer the presence of nonlocality due to the violation of those BIs.

The answer is that we can't.

Wrt the topic of this thread, note also that nonlocality (spooky action at a distance) isn't a physical explanation anyway, as it refers to the absence of any intervening physical mechanism between two (apparently invariantly) related events, A and B.

That is, nonlocality is ultimately a word that refers to our ignorance -- or else there isn't any physics underlying the relationship between A and B to be discovered.

 

[zonde]

Well, I don't think this is much of a problem for the Rowe experiment, because the ions were well-separated in two distinct traps more than 1 mm apart. That is more than 1000 times the wavelength of light used, and thus rather far for any of the double-slit effects you are talking about to play a significant role. So, I don't think your objection holds any water in this case.

Thanks for constructive comment.

But I think spatial distance doesn't really matter. What matters is if two optical paths are distinguishable, isn't it so? For example if optical path length difference is around 1000 wavelength then my argument is quite questionable because then we can not speak about interference of the "same" photon any more.

 

[DrChinese]

Consider, for example, that Bell's locality condition reduces to the definition of statistical independence. But we know that the statistical dependence observed in Bell tests can be produced via local interactions/transmissions.

No, they can't. You know that because of experiments like Weihs et al.

 

[ThomasT]

No, they can't. You know that because of experiments like Weihs et al.

Which experiment -- is the link on your website, or can you provide one here? Thanks.

 

[ThomasT]

Violations of Bell inequalities imply nonlocality and/or nonseparability.

So, nonseparability alone would do the trick, thereby saving locality (no FTL causal connections).

I don't think that that's needed. At least I hope not because I'm pretty sure I don't understand what you mean by nonseparability.

Anyway, regarding BI violations, my (current) understanding is that they're sufficiently explained by the disparity between (1) the limitations imposed (and expressed in BIs) by Bell's formal constraints on lhv representations of entanglement, and (2) Bell test preparations -- independent of considerations of nonlocality or ftl causality.

That is, the incompatibility between (1) and (2) is evident enough that appealing to nonlocality and or nonseparability isn't required.

 

[DrChinese]

Which experiment -- is the link on your website, or can you provide one here? Thanks.

It is on my website, and here as well:

http://arxiv.org/abs/quant-ph/9810080

Violation of Bell's inequality under strict Einstein locality conditions

Authors: Gregor Weihs, Thomas Jennewein, Christoph Simon, Harald Weinfurter, Anton Zeilinger

Abstract: We observe strong violation of Bell's inequality in an Einstein, Podolsky and Rosen type experiment with independent observers. Our experiment definitely implements the ideas behind the well known work by Aspect et al. We for the first time fully enforce the condition of locality, a central assumption in the derivation of Bell's theorem. The necessary space-like separation of the observations is achieved by sufficient physical distance between the measurement stations, by ultra-fast and random setting of the analyzers, and by completely independent data registration.

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

Let's review what this is saying. Suppose there were a LHV that you proposed. According to Bell, it would need to meet these requirements: a) It makes predictions consistent with experiment; b) It does not violate a Bell Inequality. Clearly,per experiments such as Aspect and many others, a BI is violated. So a) is not possible. Unless...

Now, there is still a possibility that sub-c signalling of detector settings are being communicated between Alice and Bob - which would allow an alternative explanation for the BI violation? With this experiment, however, you can rule that alternative explanation out. They strictly control this so that such signalling is not viable. The essential result was already in the literature, but with this version it rules out any reasonable possibility of another avenue.