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

[DrChinese]

Yes, and if FTL brings cause to Bell test experiments, then either Bell's theorem or FTL goes in the paper bin.

And there seems to be additional dark clouds, gathering up on the "Bell sky"...
(original paper from your site)

Be careful of Bell's comment, which can be EASILY misinterpreted:

"Moreover, the signal involved must propagate instantaneously, so that such a theory could not be Lorentz invariant."

This ONLY applies when coupled with: "In a theory in which parameters are added to quantum mechanics to determine the results of individual measurements..." which is the REALISM requirement.

There is another time in the paper in which a similar dichotomy appears, which also can be read as indicating he is on the non-local side of things. In actuality, he personally went back and forth a bit. But his opinion is not the proper conclusion of the paper, you must stop at the local OR hidden variable point. Does that make sense?

 

[ThomasT]

You can entangle atoms that have not interacted with each other by using interaction-free measurement in an interferometer. Accordingly, these atoms don't interact with the photon in the interferometer either.

This is very interesting (reference, link?) and I'd like to learn the setup, but what does this have to do with what I said wrt the FandC and Aspect experiments?

Please recall my statement that entanglement has to do with RELATIONSHIPS between and among the motional properties of entangled entities that result from these entities' interaction with each other or with a common disturbance, or having a common origin, or being part of an encompassing system. These RELATIONSHIPS, when subjected to physical analysis via global measurement parameters, are revealed in the form of correlations predicted by the QM formalism.

My contention is, of course, that any such entanglement RELATIONSHIPS, and observations of them, are compatible with the assumption of locality.

I don't consider it strange or weird at all that entities that have never interacted with each other can be related in a way or ways such that entanglement stats result when these relationships are observed in certain contexts. The orderliness of our universe suggests that a fundamental wave dynamic(s) underlies all of our universe's emergent complexity, and pervades every epistemic and ontic scale. The essence of entanglement is that everything is related to this fundamental dynamic(s).

I've never considered nonlocality or even ftl locality to be serious contenders in the effort to understand and explain EPR-Bell related conundra. For me it's always been about getting at the physical meaning of 'quantum nonseparability', which has to do with the nonseparability of the relationships between the entangled entities wrt the measurement parameters which reveal those relationships in the form of entanglement stats. So, as long as those relationships can be maintained, or insofar as they can be produced, in entities at great separations, then the revealing of the entanglement correlations via the joint analysis of the relationship(s) between those entities can be understood as evolving via local channels no matter how far apart the joint measurements are done.

 

[ThomasT]

You apparently don't follow Mermin closely. He is as far from a local realist as it gets.

Jaynes is a more complicated affair. His Bell conclusions are far off the mark and are not accepted.

I want to say something else about this reply of yours.

It's in response to a rather long post where I laid out what I've been trying to say a bit more clearly, I think. Yet, instead of replying to the substance of the post, to the actual arguments regarding nonviability of lhv theorems per EPR-Bell, you chose this, peripheral, issue to reply to. Very curious.

I'm led to suppose that you're initimidated by the argument that I'm presenting. I'm supposing this because (1) you have yet to directly address it, and (2) in a post of yours you said that I was 'claiming victory' (though I've done no such thing).

So, what is it about the argument that you find so difficult? It can't be that you think that I'm advocating the possibility of lhv theories, because, as I've repeatedly stated, I'm not. In fact, the argument is telling you exactly why lhv theories are impossible. Of course if the argument is correct, then there's no basis for inferring nonlocality.

On the other hand, if the argument isn't difficult or subtle, and if it's obviously incorrect, then why not just refute it outright and maybe I can learn something (you know, point out the error in my thinking). Isn't that what a science advisor is supposed to do?

But instead you said this:

I am through discussing with you at this time. You haven't done your homework on any of the relevant issues and ignore my suggestions. I will continue to point out your flawed comments whenever I think a reader might actually mistake your commentary for standard physics.

This isn't about standard physics. I'm pretty sure we agree on the standard physics. We're not arguing about qm or even Bell's theorem, per se. This is an interpretational issue. The interpretation of the physical meaning of violations of BIs that's been presented happens to be based on standard physics. It simply points out a reason for the incompatibility between lhv formulations (as restricted by Bell and EPR elements of reality) that's been noticed by relatively few commentators on the subject. It makes nonlocality unnecessary. Nonlocality is, anyway, neither standard nor nonstandard physics. It isn't physics at all. It's just a word for ignorance of precisely why lhv theories are impossible and why BIs are violated. An interpretation and explanation for this has been presented which doesn't involve invoking nonlocality. So far it's gone unaddressed. Is it possible that what it entails (that the assumption of locality is compatible with the impossibility of lhv theories vis EPR, Bell, GHZ, etc.) isn't nonstandard enough?

Is it possible that Bell is right and nonlocality is wrong? Of course it is, and that's all that I'm saying.

In a local hidden variable model, each observer is measuring a separate reality. So there is no JOINT observable (or context).

That's right. (You're almost there.) But entanglement IS a JOINT observational context. (Let that sink in for a moment.)

Now, is what's being measured in the separate measurements at A and B the same as what's being measured jointly?
The answer is no. That's why I said:

.It should become clear that the variables which determine individual detection rates can't be made to (can't be put into a form which would) account for the joint detection rates, because they aren't the determining factors in that situation.

... in a local world, what happens here does not affect what happens there.

That's right. But there are only two values for |a - b| where A and B are perfectly correlated (anticorrelated), and these perfect correlations are compatible with the assumption that the relationship between the entangled photons has a local common cause.

But, you might counter, the full range of entanglement stats can't be reproduced by an lhv description of the joint context. And that's correct, but it's because what's being measured in the separate measurements at A and B is not the same as what's being measured jointly.

If there is a "joint detection parameter" observable, it is global. That does not work in a local world either.

It works in a local world. It just doesn't work in a local hidden variable theory per EPR-Bell. (1) The joint measurement parameter is |a - b|. (2) What |a - b| is measuring is the relationship between the counter-propagating disturbances. Both (1) and (2) are compatible with the assumption of c-limited locality. However, the relationship between the counter-propagating disturbances doesn't determine individual results.

So you may be correct ...

It is correct. But the presentation needs some refining.

... but you are not describing a local realistic model.

Hopefully it will become clear that I'm not trying to do that, but rather explain why such a model is impossible, and why the impossibility of constructing such a model doesn't imply nonlocality (or ftl info transfer).

To revisit the Unnikrishnan paper that you didn't want to look at, the purpose of presenting it was to illustrate the point(s) that I've been presenting, not to advocate it as an lhv theory candidate. If you look at it you'll see that it isn't an lhv model in the sense of EPR-Bell. The author even says as much. So it can be taken as further, indirect, evidence that lhv theories per EPR-Bell are impossible. But it is explicitly local. Hence the conclusion: Bell is correct AND nonlocality is obviated.

So, wrt this statement:

There can be no entanglement - in a local realistic world ...

I think that a better way to put it is that there can be no local realistic (per EPR-Bell) theories of entanglement in a local realistic world.

 

[ThomasT]

Not only is it "scientific" to posit that Nature is fundamentally nonlocal, it is also the only "logical" thing to do.

Regarding your lengthy, interesting, and well written post, I agree that nonlocality is a matter of convenience.

And other than that, I am doing my best to continue the tradition of pushing towards a thoroughly believable ontological theory of physical reality here at physicsforums.

And a fine tradition it is. However, my immediate aim, although it might be compatible with this tradition, is simply to understand why lhv theories per Bell-EPR are impossible in a universe which seems to be evolving in accord with the principle of locality. And it turns out, it seems, that this is rather simply explained.

 

[DrChinese]

1. I want to say something else about this reply of yours.

It's in response to a rather long post where I laid out what I've been trying to say a bit more clearly, I think. Yet, instead of replying to the substance of the post, to the actual arguments regarding nonviability of lhv theorems per EPR-Bell, you chose this, peripheral, issue to reply to. Very curious.

I'm led to suppose that you're initimidated by the argument that I'm presenting.

2. To revisit the Unnikrishnan paper that you didn't want to look at, the purpose of presenting it was to illustrate the point(s) that I've been presenting, not to advocate it as an lhv theory candidate. If you look at it you'll see that it isn't an lhv model in the sense of EPR-Bell. The author even says as much. So it can be taken as further, indirect, evidence that lhv theories per EPR-Bell are impossible. But it is explicitly local. Hence the conclusion: Bell is correct AND nonlocality is obviated.

So, wrt this statement:
I think that a better way to put it is that there can be no local realistic (per EPR-Bell) theories of entanglement in a local realistic world.

1. You really are making me laff...

2. This paper does not offer a local realistic model. And your thoughts on non-locality are simply an opinion, much like any interpretation would be considered.

 

[DevilsAvocado]

Be careful of Bell's comment, which can be EASILY misinterpreted:

"Moreover, the signal involved must propagate instantaneously, so that such a theory could not be Lorentz invariant."

This ONLY applies when coupled with: "In a theory in which parameters are added to quantum mechanics to determine the results of individual measurements..." which is the REALISM requirement.

There is another time in the paper in which a similar dichotomy appears, which also can be read as indicating he is on the non-local side of things. In actuality, he personally went back and forth a bit. But his opinion is not the proper conclusion of the paper, you must stop at the local OR hidden variable point. Does that make sense?

To be honest – I’m wandering around in a "personal intellectual mud", up to my knees right now.

We’ve eliminated LHV, NLHV, FTL, Loopholes, Malus, etc, and stated that QM is correct.

What’s left!? How does QM solve this unsolvable problem?? I’m going crazy over here...

I will not believe in MWI before we get a "Hello world!" from a parallel universe (which could take 'awhile')...

What’s your solution??

 

[ThomasT]

1. You really are making me laff...

You're making my case for me. You still haven't addressed the argument(s).

2. This paper does not offer a local realistic model.

No kidding. Maybe you should read the paper, or what I said about it.

To revisit the Unnikrishnan paper that you didn't want to look at, the purpose of presenting it was to illustrate the point(s) that I've been presenting, not to advocate it as an lhv theory candidate. If you look at it you'll see that it isn't an lhv model in the sense of EPR-Bell. The author even says as much. So it can be taken as further, indirect, evidence that lhv theories per EPR-Bell are impossible. But it is explicitly local. Hence the conclusion: Bell is correct AND nonlocality is obviated.

And your thoughts on non-locality are simply an opinion, much like any interpretation would be considered.

Again, duh. What do you think your thoughts on nonlocality are?

Of course, if you won't even address the reasons behind the opinion ...

 

[DrChinese]

What’s your solution??

Easy, drink wine and listen to the Beatles.

 

[DevilsAvocado]

Easy, drink wine and listen to the Beatles.

HAHAHA! Non-local wine, right? And the Beatles from the surrealistic period, right?

 

[DrChinese]

HAHAHA! Non-local wine, right? And the Beatles from the surrealistic period, right?

I'm talking sitars!

 

[DevilsAvocado]

I'm talking sitars!

Yeah, I hear you!

LMPO

 

[my_wan]

I am glad if I was a help in any small way. The point is often to address a different perspective, and in that regard I benefit too.

The help wasn't so small, it was instrumental.

 

[zonde]

I would like to pick up this part of discussion as you made similar comment in other thread:

Don't you think the authors would be raising flags if the stats deviated from QM predictions by a significant amount?

I actually wrote Xian-Min Jin asking this question:
"The question is about calibration data of entangled photon source. And exactly this sentence: "The visibilities for the polarization correlations are about 98.1% for |H>/|V> basis and 92.6% for |+45°>/|−45°> basis, without the help of narrow bandwidth interference filters."
Two visibilities seem quite different. So could you please tell me what is the possible reason for this difference in two visibilities?"

And the answer he gave was:
"About the entanglement source, we employ type II SPDC phase match
to generate biphoton. The obtained two photons are either H1V2 or V1H2 with equal probability. So normally we can get very high visibility when we measure H/V basis. If we want make the two photons be entangled, we need to make the two possible events overlap very well at both spatial and temporal modes so that we can not distinguish them any more without measuring their polarization basis. Experimentally, we can not get so ideal condition, that means H1V2 and V1H2 are partially distinguishable. As a result, the entanglement visibility is limitted, this induce that we can not observe perfect correlation at +/- basis. In my experiment, actually, the visibility is considerablely high comparing with previous work, and sufficient for observation of photonics de Broglie wave."

So my answer regarding your comment is that QM prediction on more detailed level includes product state and entangled state as two extremes for the setup of entangled source.
QM prediction a la Bell is just that theoretically you can reach this entangled extreme for the case of efficient detection. And if you do not perform dedicated research you can never find out whether detection efficiency is one of the factors that influences quality of entanglement or not.

 

[DrChinese]

1. I actually wrote Xian-Min Jin asking this question:
"The question is about calibration data of entangled photon source. And exactly this sentence: "The visibilities for the polarization correlations are about 98.1% for |H>/|V> basis and 92.6% for |+45°>/|−45°> basis, without the help of narrow bandwidth interference filters."
Two visibilities seem quite different. So could you please tell me what is the possible reason for this difference in two visibilities?"

And the answer he gave was:
"About the entanglement source, we employ type II SPDC phase match
to generate biphoton. The obtained two photons are either H1V2 or V1H2 with equal probability. So normally we can get very high visibility when we measure H/V basis. If we want make the two photons be entangled, we need to make the two possible events overlap very well at both spatial and temporal modes so that we can not distinguish them any more without measuring their polarization basis. Experimentally, we can not get so ideal condition, that means H1V2 and V1H2 are partially distinguishable. As a result, the entanglement visibility is limitted, this induce that we can not observe perfect correlation at +/- basis. In my experiment, actually, the visibility is considerablely high comparing with previous work, and sufficient for observation of photonics de Broglie wave."

2. So my answer regarding your comment is that QM prediction on more detailed level includes product state and entangled state as two extremes for the setup of entangled source.

QM prediction a la Bell is just that theoretically you can reach this entangled extreme for the case of efficient detection. And if you do not perform dedicated research you can never find out whether detection efficiency is one of the factors that influences quality of entanglement or not.

1. Great stuff, thank you for sharing his comments. I love hearing more details about these experiments.

2. The quality of entanglement can be measured by how close you come to perfect correlations when setting up the experiment. So you might expect that there is always a mix of ES> + PS> statistics (Entangled and Product). Ideally, ES is 100%. But clearly, that ideal is not met in this experiment and the result will be a deviation from the QM predicted rates accordingly. But not enough to cross back into the Local Realistic side of the Bell Inequality.

So are you saying that the detectors somehow influence this? I don't follow that point or what you think the implications would be. It is the setup that determines things, of which the detectors are an element. But their efficiency shouldn't matter to that setup.

 

[my_wan]

After reading about and debating this issue I began to question the difference in perspective that makes some so willing to question the interpretation of Bell's violations, while others see it as unavoidable. I'm not talking about those who simply refuse on the grounds it's too non-physical. It seems to me to involve different ways of thinking about what constitutes an element of reality. I think of emitted photons as conserved numbers of things, independent of what measurements seem to imply. The converse is to think in terms of the measurements as what's physically real, and assume properties back from that. I can think of countless measurable quantities which depend on elements of reality, but do not represent countable elements of reality.

Consider temperature, easily measurable. We know it's the average momentum of molecular collisions, but temperature alone tells us nothing about the number of particles involved. With the Mole unit we know it's mass, but the notion of a single basic unit of existential mass is speculative. Temperature doesn't even tell us the state of matter at that temperature. Some liquid, some solid, some gas, and some plasma. The notion of Bell realism notion seems a stretch, especially once QM is brought in the picture. I also understand it was used in EPR, and why. In some abstract sense we can make Planck's constant, quantum events, the fundamental unit. But as we'll see below this is not allowed under Bell's theorem.

I began reading this and it made some curious points:
Nonlocality, Bell's Ansatz and Probability - http://arxiv.org/abs/quant-ph/0602080

In section III it says this:

BELL'S[/PLAIN] intention when conceiving of his "proof" excluded insinuating, at the meta-level where the inequalities are being derived, any hypothesis not found in classical, local and realistic physics as it was understood before the discovery of QM, where the interpretation issues of QM do not exist. His explicit purpose was to examine the question of the existence of a covering theory that has just the structure exploited by classical, pre-quantum theories.

In fact my argument that EPR could be a local phenomena explicitly depends on the empirical reality of distinctly quantum effects. Albeit quantum effects that occurs distinctly LOCALLY at the particle detection points. Yet, according to this, that doesn't pass the muster for "local realism" for purposes of Bell's inequality. The notion that QM, which no reasonable person could empirically deny, is disallowed from consideration as a LOCAL mechanism for explaining violations of Bell's inequalities is empirically beyond the pale. It's tantamount to requiring a 'complete' classical theory of the entirety of QM to refute the non-local+non-realistic proof by Bell. Irrespective of whether the effects can be fully described by purely local 'quantum' effects. Entirely unreasonable, and empirically unjustifiable.

Here's another point that was fundamental to my argument:

Of[/PLAIN] course, what is not known in this case is the precise polarization of the signal comprising the pair as emitted at the source but before they reach the polarizer-filters. The polarizer settings can be known because they are inputs into measuring devices under the control of the experimenter who selects their orientation before the pair is generated at the source. Seen this way, it is absolutely clear that such detector settings have no effect on the source, and, therefore, have no effect on the pair of signals before they enter the polarizers.

Some may argue the effect issue claimed here, but again, the unknown polarization at the time of emission was a core feature of my argument. Though I did take the consequences much farther.

I do not wish to further defend my poorly explored interpretation at this point. Nor use it as an instrument to portray potentially false impressions of myself or others. But there's a few things to be learned from this debate, you can take to the bank. The mathematical legitimacy of Bell's theorem is irrefutable. The fact of this legitimacy does not translate to any fact of legitimacy about any given interpretation of what it means. The issues involved are open research, and nobody has all the answers, nor fully appreciates all nuances of alternative viewpoints and issues. If it was really that easy it wouldn't be an open area of research, and that's part of what makes it exciting and curious. Strong arguments for what may or may not ultimately be right can be made on both sides of the fence.

 

[Gordon Watson]

... there's a few things to be learned from this debate, you can take to the bank. The mathematical legitimacy of Bell's theorem is irrefutable. The fact of this legitimacy does not translate to any fact of legitimacy about any given interpretation of what it means...

The mathematical legitimacy of Bell's theorem is irrefutable?

Does Bell use P(AB|H) = P(A|H).P(B|H)?

Is P(AB|H) = P(A|H).P(B|H) valid when A and B are correlated?

Are A and B correlated in EPR settings?

 

[my_wan]

The mathematical legitimacy of Bell's theorem is irrefutable?

Does Bell use P(AB|H) = P(A|H).P(B|H)?

Is P(AB|H) = P(A|H).P(B|H) valid when A and B are correlated?

Are A and B correlated in EPR settings?

That depends on how you define H, the nature of the hidden variable that is presumed to be involved in determining the correlation effects between A and B. I would certainly say H is overly restrictive, even in a 'realistic' sense, but others disagree.

The physical validity doesn't have to be legitimate for the mathematical validity to hold, and models which are limited to H, as it is defined here, are indeed invalid. But I was satisfied with that on Neumann's argument alone. That's only the simplest unabashed classical approach anyway. There are plenty of issues with pre-quantum classical physics, from many areas not just restricted to QM, to justify modifications. Even if it still manages to remain essentially classical in character from some perspective. Even Newton had his critiques over the 'magical' elements of classical theory, and background dependence almost certainly has to go.

 

[zonde]

2. The quality of entanglement can be measured by how close you come to perfect correlations when setting up the experiment. So you might expect that there is always a mix of ES> + PS> statistics (Entangled and Product). Ideally, ES is 100%. But clearly, that ideal is not met in this experiment and the result will be a deviation from the QM predicted rates accordingly. But not enough to cross back into the Local Realistic side of the Bell Inequality.

It is not exactly deviation from QM. You see QM covers this PS> state too. So you don't need to resort to some other idea (LHV or anything) in any case.

I have posted this formula couple of times but maybe it will make more sense now in conjunction with real experimental setup.
$$P_{VV}(\alpha,\beta) = \underset{product\; terms}{\underline{sin^{2}\alpha\, sin^{2}\beta + cos^{2}\alpha\, cos^{2}\beta}} + \underset{interference\; term}{\underline{\frac{1}{4}sin 2\alpha\, sin 2\beta\, \mathbf{cos\phi}}}$$
This is a bit reduced (without $$\theta_{l}$$ factor) equation (9) from paper - http://arxiv.org/abs/quant-ph/0205171/" that describes type-I PDC source.
The same way can be described type-II PDC. I found this out from Kwiat et al "New High-Intensity Source of Polarization-Entangled Photon Pairs" (I won't post the link to be on the safe side with forum rules about copyrights). There equation (1) is:
$$|\psi\rangle=(|H_{1},V_{2}\rangle+e^{i\alpha}|V_{1},H_{2}\rangle)/\sqrt{2}$$
that is basically the same equation but in more QM format.

As you can see from this first formula $$cos\phi$$ acts as coefficient in range from -1 to 1 and accordingly this interference term can change it's weight between maximally negative, none at all and maximally positive. QM does not place any restrictions on that.
So if interference term becomes zero and photon state reduces to completely local realistic product state it's still covered by this QM description.
Physical interpretation in QM about this $$cos\phi$$ coefficient is that it characterizes transverse and longitudinal (temporal) walkoffs.

As experimenter you have a goal to get this $$cos\phi$$ maximally close to either 1 or -1 and if you do not succeed for some reason then interpretation says you have not compensated those walkoffs to satisfactory level.

So are you saying that the detectors somehow influence this? I don't follow that point or what you think the implications would be. It is the setup that determines things, of which the detectors are an element. But their efficiency shouldn't matter to that setup.

It's hard for me to say something about your comment that efficiency shouldn't be a factor. That's because since some time for me it's not the question of "if" but rather "how". And to be precise it's not only efficiency of detectors but rather coincidence detection efficiency of the setup as whole.

But more to the point, I interpret this interference term as correlation in samples of detected photons meaning that they are uneven. If this unevenness is similar we have positive interference term, if this similarity is inverted we have negative interference term and if we have this unevenness in independent "directions" we don't have interference term. Obviously for efficient detection any "direction" in unevenness of sample is no more detectable.

This loss of information for efficient detection can be illustrated with example like this. Let's say we have a box with different objects in it. We have hole in the box and if we shake the box some objects fall out. Afterward we can look at the objects that are outside the box and objects that are left inside. So we can find out some probabilities whether particular object is more likely to fall out of the box or stay inside. If we always shake the box until all the objects fall out of the box (efficient detection) we loose any information about that falling out probability.

 

[Dmitry67]

What’s left!? How does QM solve this unsolvable problem?? I’m going crazy over here...

May be I missed something. What is a problem? Nature is not local. I am ok with it.

 

[DrChinese]

The mathematical legitimacy of Bell's theorem is irrefutable?

Does Bell use P(AB|H) = P(A|H).P(B|H)?

Is P(AB|H) = P(A|H).P(B|H) valid when A and B are correlated?

You do NOT need the probability formula to get the Bell result. Despite some of the posts you may have seen, you can get it a variety of ways. For example: if you accept that:

0<=P(A|H)<=1
0<=P(B|H)<=1
0<=P(C|H)<=1

Then you can derive the formula too. A, B and C can be correlated in any way you like. Because then you have:

0<=P(AB|H)<=1
0<=P(AC|H)<=1
0<=P(BC|H)<=1

and then:

0<=P(ABC|H)<=1

But as I have shown previously, this value is less than -.1 (i.e. less than -10%) for some ABC combinations if the QM predictions are substituted. Obviously, a negative value for P(ABC|H) contradicts the above.

 

[DevilsAvocado]

May be I missed something. What is a problem? Nature is not local. I am ok with it.

Hi Dmitry67, the 'problem' is that you believe in MWI, which I don’t, unless you show me a "Hello world!" form one of those >centillion¹⁰⁰⁰ parallel universes!

 

[ThomasT]

The mathematical legitimacy of Bell's theorem is irrefutable?

Wrt the inequalities it is.

Does Bell use P(AB|H) = P(A|H).P(B|H)?

Yes.

Is P(AB|H) = P(A|H).P(B|H) valid when A and B are correlated?

No.

Are A and B correlated in EPR settings?

Yes.

 

[my_wan]

I wonder if this will make the counterfactual assumptions clearer?

You have:
0<=P(A|H)<=1
0<=P(B|H)<=1
0<=P(C|H)<=1

From which this is derived:
0<=P(AB|H)<=1
0<=P(AC|H)<=1
0<=P(BC|H)<=1

But the P(BC|H) case was never performed in tandem, rather constructed from actual measures P(AB|H) and P(AC|H), and even P(BC|H) for good measure, because the correlations come in pairs. Suppose P(AB|H) and P(AC|H) was constructed from a dataset of 1500 correlations pairs each, 3000 photon count "elements of reality" per detector, 6000 total. Now when you combine B and C, you are adding 1500 pairs of "elements of reality" (3000 total) that never actually existed simultaneously but presumably could. By counterfactually assuming they simultaneously occurred in the same dataset, if C can detect the same "elements of reality" (photon) in some, but not all, cases, it becomes impossible to get the "elements of reality", as defined by the measurements, to equal the "elements of reality" as defined by the number of photons.

This is only a valid concern, if and only if, C is sometimes selecting photons that would have also been selected by B, and visa versa, such that if emitted photons AND detections are both to labelled "elements of reality", the count between the two cannot possibly match. In the combined counterfactual case, B and C can effectively be viewed as the exact same detector with 2 different detection settings at once.

If Malus' Law is a valid in defining the odds of a single photon being detectable with two different detector settings, such that a photon with a specific polarization has a 50% chance of passing a polarizer set 45 degrees to its 'actual' polarization, then the derivation of the mismatch in these two ways of counting the "element of reality" almost exactly matched the negative probabilities derivation.

The only difference is that you take the counterfactual "element of reality" set BC, which is 2 settings of the same detector counting the same set of photons, and subtract the total of both the AB and AC set, and you have the percentage of the detector event defined "elements of reality" minus the photon count defined "elements of reality". Z - (X + Y). Divide by 2 to get a per detector percentage, B and C.

I'm not trying to argue this atm, but it would be cool to make the case clear enough to get some effective criticism.

 

[Dmitry67]

Hi Dmitry67, the 'problem' is that you believe in MWI, which I don’t, unless you show me a "Hello world!" form one of those >centillion¹⁰⁰⁰ parallel universes!

Whats about BM?
Wavefunction is, in any case, non-local.
So MWI or not, nonlocality is inevitable.

I see causality as emergent property of macroscopic world. In that case a-causality is more fundamental, and we are just lucky that our world has causality in IR (macroscopic) limit.

It is curious that the opposite way of thinking is common: "wow, how nature can be non-local! I can't believe!". For me the deeper mystery is why it is causal.

 

[DrChinese]

If Malus' Law is a valid in defining the odds of a single photon being detectable with two different detector settings, such that a photon with a specific polarization has a 50% chance of passing a polarizer set 45 degrees to its 'actual' polarization, then the derivation of the mismatch in these two ways of counting the "element of reality" almost exactly matched the negative probabilities derivation.

The only difference is that you take the counterfactual "element of reality" set BC, which is 2 settings of the same detector counting the same set of photons, and subtract the total of both the AB and AC set, and you have the percentage of the detector event defined "elements of reality" minus the photon count defined "elements of reality". Z - (X + Y). Divide by 2 to get a per detector percentage, B and C.

You cannot get "close" to the negative probability derivation as long as you cling to the idea that:

0<=P(A|H)<=1
0<=P(B|H)<=1
0<=P(C|H)<=1
and Malus.

 

[DevilsAvocado]

Whats about BM?

The future for de Broglie–Bohm theory doesn’t look overwhelmingly bright:

http://arxiv.org/abs/0704.2529"
Anton Zeilinger et.al
...
Here we show by both theory and experiment that a broad and rather reasonable class of such non-local realistic theories is incompatible with experimentally observable quantum correlations. In the experiment, we measure previously untested correlations between two entangled photons, and show that these correlations violate an inequality proposed by Leggett for non-local realistic theories. Our result suggests that giving up the concept of locality is not sufficient to be consistent with quantum experiments, unless certain intuitive features of realism are abandoned.

Add this to Bell’s own conclusion in 1964 (my emphasis):

http://www.drchinese.com/David/Bell_Compact.pdf"
John S. Bell
...
VI. Conclusion
In a theory in which parameters are added to quantum mechanics to determine the results of individual measurements, without changing the statistical predictions, there must be a mechanism whereby the setting of one measuring device can influence the reading of another instrument, however remote. Moreover, the signal involved must propagate instantaneously, so that such a theory could not be Lorentz invariant.

Then we have to reject Einstein, SR and RoS + the physical experiment by Anton Zeilinger + introducing a global NOW (that we know doesn’t work in e.g. GPS satellites)...

It is curious that the opposite way of thinking is common: "wow, how nature can be non-local! I can't believe!".

It’s not the non-locality in itself that brings 'problem'. It’s the fact that Bell's theorem proves that nature at microscopic QM level must be a-casual/true random/stochastic/non-deterministic, i.e. Local Hidden Variables doesn’t work either in theory or experiment.

Now, if we bring in a "FTL mechanism" as an explanation to what goes on in Bell test experiments – that doesn’t work either! Since a "FTL mechanism" brings cause* to Bell's theorem, where cause is forbidden!

Get it?

(*Alice sends a FLT-message to Bob to tell him what to do, in respect of what she just did.)

 

[my_wan]

But the assumption is that P(C|H) is a partial subset of P(B|H) and P(A|H), and partially a set of distinctly unique events. But given that the argument is not being followed, rather that if I cling to what I rejected in the argument, I must be wrong, I have nowhere to go.

 

[DrChinese]

But the assumption is that P(C|H) is a partial subset of P(B|H) and P(A|H), and partially a set of distinctly unique events. But given that the argument is not being followed, rather that if I cling to what I rejected in the argument, I must be wrong, I have nowhere to go.

If a man is Texan, he can also be a college graduate and a musician. These are not exclusive elements of reality. That is my A, B and C. If I can have these attributes simultaneously, then they are realistic. I would expect that their likelihood would between 0 and 100% inclusively. But if I found out that Texas musicians were less than -10% likely to be college graduates, that would cause me to question things. We like our music here. But we're not so dumb as to appreciate college THAT little.

 

[Gordon Watson]

You do NOT need the probability formula to get the Bell result. Despite some of the posts you may have seen, you can get it a variety of ways. For example: if you accept that:

0<=P(A|H)<=1
0<=P(B|H)<=1
0<=P(C|H)<=1

Then you can derive the formula too. A, B and C can be correlated in any way you like. Because then you have:

0<=P(AB|H)<=1
0<=P(AC|H)<=1
0<=P(BC|H)<=1

and then:

0<=P(ABC|H)<=1

But as I have shown previously, this value is less than -.1 (i.e. less than -10%) for some ABC combinations if the QM predictions are substituted. Obviously, a negative value for P(ABC|H) contradicts the above.

Thank you DrC. I hoped that Bell's mathematics might be clearer to my_wan if we began with fundamental mathematical principles. Is there any good reason why not to begin in that way?

 

[Gordon Watson]

Wrt the inequalities it is.

Yes.

No.

Yes.

Thank you ThomasT, but I am confused. Probably I misunderstand your stand on BT? Are you saying Yes (it is irrefutable, it stands forever), Yes, No, Yes? Is your position logical with your other posts? What about

Q1. Are A and B correlated in EPR settings?

Q2. Does Bell use P(AB|H) = P(A|H).P(B|H)?

Q3. Is P(AB|H) = P(A|H).P(B|H) invalid when A and B are correlated?

Q4. Is the mathematical legitimacy of Bell's theorem debatable?

 

[Dmitry67]

DevilsAvocado,

As I remember Demistifier's arguments, BM is compatible with QM, it is Lorentz-invariant, even in fact there is 'hidden' preferred frame. I don't like it, it is urgly, but it is consistent with all experiments. May be you can ask Demistifier about the interpretation of Bell in BM framework, but I am sure there are no problems.

In any case, SM, BM and MWI is all what is left. SM=giving up updarstanding, BM=ugly, conclusion is...

 

[unusualname]

DevilsAvocado,

As I remember Demistifier's arguments, BM is compatible with QM, it is Lorentz-invariant, even in fact there is 'hidden' preferred frame. I don't like it, it is urgly, but it is consistent with all experiments. May be you can ask Demistifier about the interpretation of Bell in BM framework, but I am sure there are no problems.

In any case, SM, BM and MWI is all what is left. SM=giving up updarstanding, BM=ugly, conclusion is...

BM isn't much different to MWI since both are derived from a wavefunction of the universe, which is a bit unappealing, since it seems clear that quantum effects become a statistical non-effect for large particle systems at anything beyond molecular scales. (Although, by intelligent design we will probably improve on nature and build large quantum computers in the near future)

They should have just stuck to de Broglie's original idea of a real guiding wave or even Shrodinger's naive interpretation of a real wave entity, except these days we can validly propose that its existence is generated from signals in other dimensions (or other non-classical space) since all sorts or weird extra dimensions are now being proposed (even if they are compactified, they're extra dimensions, once you propose that I don't see a philosophical reason for not allowing that a noncompactified extra dimension exists which we haven't detected or modeled yet). So we may have a real local theory, except it's not local in einsteinian (classical) space. QED

 

[DrChinese]

Thank you DrC. I hoped that Bell's mathematics might be clearer to my_wan if we began with fundamental mathematical principles. Is there any good reason why not to begin in that way?

I agree entirely. I think it is convenient to follow some of the different ways to get to the Bell result, because otherwise the lingo itself can stand in the way. Bell was writing for a very specific audience, whom he knew could follow his wording. He probably assumed they knew EPR as well. So he did not feel the need to spell everything as a non-professional might prefer.

We have a pair of entangled particles, Alice (and her default measurement setting A) and Bob (and his default measurement setting B). We also have a counterfactual setting C (could be associated with either Alice or Bob, doesn't really matter).

Bell says that in a hidden variable theory (and we will use the symmetric case for simplicity):

Alice@A = Bob@A
Alice@B = Bob@C
Alice@C = Bob@C

And further Bell says that these must be simultaneously true if realism applies. Which is just to say that there are hidden variables which exist independently of the act of observation. If the above is true, then there are 8 possible permutations for Alice@A,B or C (using Heads/Tails notation):

HHH, HHT, HTH, HTT, TTT, TTH, THT, THH

There is no particular requirements for their relative frequencies (yet), but we want the sum of these 8 to add to 100% and we want each individual to be within the range 0 to 100%. Again, this is just the realism requirement.

Is the above agreeable?

 

[DevilsAvocado]

... I hoped that Bell's mathematics might be clearer to my_wan if we began with fundamental mathematical principles.

JenniT, I’m sure you mean well, but I can guarantee you that mathematics is not a problem for my_wan.

 

[DevilsAvocado]

conclusion is...

Ta-da! Aaaaaand the winner is... MWI !

As I said, show me one 'postcard' from any of those +centillion¹⁰⁰⁰ parallel universes, and I’m on the train!