Local realism ruled out? (was: Photon entanglement and )

[yoda jedi]

Again, the WORD "Realism" does not matter. The term Realism in this context is the realism as defined by EPR. Call it butternut squash if that helps... the name doesn't matter, the understanding of the principle does.

oh sorry, then EPR is the owner of reality
consecuently,

http://physicsworld.com/cws/article/news/27640
"Quantum physics says goodbye to reality"

...giving the uneasy consequence that reality does not exist when we are not observing it...


then nothing exist, of course ! who care about names, words, concepts ! if nothing exist !

or if i or you wish name CAT to BUILDINGS or BUILDINGS to CATS who cares ?
and cats does not exist, is just semantics, all depend of the context, you live in some context (wait, you not exist if nobody measure you) and myself live in other context (if somebody measure observe me ! or EPR save me)

REALITY goes beyond contextuality or non-contextuality, counterfactual definiteness or indefiniteness, determinism or indeterminism, with unitary evolution or not.

the misundertanding goes back to:


http://arxiv.org/ftp/quant-ph/papers/0402/0402001.pdf

...Quantum Mechanics is not complete. And this is why such additional properties are referred to as « supplementary parameters », or « hiddenvariables.-----Einstein actually did not speak of « hidden variables » or « supplementary parameters », but rather of
« elements of the physical reality ». Accordingly, many authors refer to « realistic theories » rather than to « hidden variable theories », or to « supplementary variable theories »...

 

[Frame Dragger]

No, but to have a discussion about something we have to first agree on what it is we're talking about. It happens to be that in the case of BELL the standard for reality that was "agreed" on WAS EPR, so yes... EPR owns reality as far as Bell's Theorems are concerned. That's the whole damned point. If you don't get that, you're missing everything that follows.

 

[DrChinese]

1. What I'm asking is:

How is, eg., (1-P(|a-b|)) + (1-P(|a-b|)) => 1-P(2|a-b|) , the simplest and archetypal Bell inequality, derived?

2. The assumption of a local common cause wrt the relationship between entangled photons isn't enough to warrant the assumption that the above inequality literally represents. So, I'm guessing that the derivation of this inequality depends on the assumption of realism wherein the term realism means attributing definite values to the relevant property (or properties) of polarizer-incident optical disturbances in optical Bell tests.

As I see it, the assumption of local common cause, without realism, justifies the application of Malus Law in Bell tests. Would you agree with this?

3. Considering this, and from Tresser's and others' formulations of inequalities without an explicit locality condition, it appears that not only can nonlocality in Nature not be inferred but also that the applicability of Malus Law supports the continued assumption that Nature is exclusively locally causal in line with the requirements of SR.

So, it seems to me at this time (and of course I'm still somewhat confused by it all ) that LR models ARE ruled out -- but due to the realism part (not the localism part).

1. This is essentially a restatement of the realism requirement for ANY 2 pairs of "somethings" that take binary values. It could be sock colors, coin sides, or pretty much anything. This is not the "proper" form but I follow what you mean. This requirement has nothing at all to do with quantum mechanics. It follows some the probability ideas of Kolgomorov.


2. What you call a common cause is expressed a little differently usually. This comes from EPR originally, and I would say it is the idea that there are elements of reality. Those elements of reality would be what you would get from this idea:

A experiments measuring any observable attribute of Alice would allow you to predict the same attribute on Bob.

Keep in mind: these particles do NOT need to be entangled to demonstrate this effect. So it is not an assumption. It will be a demonstrated fact.


3. I happen to agree with this, although as I say it is not from a rigorous perspective. If you take a single photon - not part of an entangled pair but just one lone photon - you will eventually realize that Malus does not provide a self-consistent description of its spin either. So whatever the issue is, it does not seem to me to relate to separability/locality.


And I completely agree that if we are going to discuss/debate suprerdeterminism, we should start a new thread. Frame Dragger? Although it would probably make sense to skip it for a while if you want to follow some references first.

 

[DrChinese]

No, but to have a discussion about something we have to first agree on what it is we're talking about. It happens to be that in the case of BELL the standard for reality that was "agreed" on WAS EPR, so yes... EPR owns reality as far as Bell's Theorems are concerned. That's the whole damned point. If you don't get that, you're missing everything that follows.

You are SOOOOOO right about this. It makes it hard to discuss local realism when you change definitions away from the EPR/Bell concepts. Bell knew that his idea of realism would be immediately obvious to those who knew the EPR paper (his audience). He didn't really bother with explanations and definitions, thinking that the result he had would speak for itself.

Bell/Einstein realism = EPR elements of reality, including counterfactuals, since Einstein insisted on this.

Bell/Einstein locality = No spooky action at a distance, for similar reasons.

At the time of Bell's paper, there was a standoff: it was generally believed that QM was correct in all particulars, but might be a subset of a greater theory yet to be discovered. Much like Special Relativity was a subset of General Relativity. So the importance of Bell was to show that Einstein's realism was incompatible with Einstein's locality.

Now, the question many ask is: Does Bell locality = Einstein locality? In other words, is Bell's separability the same thing as Einsteinian locality? I am not really into debating that, because I think you just go around in circles.

As to realism, I think there is no doubt that Bell intended a definition as close to EPR as possible. He specifically talks at length about the idea that the perfect correlations are consistent between some local realistic theories and QM. Which was where the standoff was at that time. Again, the standoff being between those who followed Einstein's tenets versus those that saw QM as complete already. ANd by complete, I mean in the sense of EPR.

 

[Frame Dragger]

@DrChinese: I found some good references and am reading through them, I won't derail the subject! Pinky swear.

Edit: I see your second post... hmmm... First thank you. Second... I really don't know. Circles, as you say. It makes me wonder if we're really capable of formulating this "theory of everything" in terms that will make sense to us as humans. It may provide guidance as to the future of technology, but so many of these issues still come down to the fact that we're brains in a box so to speak.

I agree that Bell and EPR Realism are the same; as you say it was CLEARLY Bell's intent.

I hope we all live long enough to see something like answers to these questions... they're so captivating.

 

[yoda jedi]

No, but to have a discussion about something we have to first agree on what it is we're talking about. It happens to be that in the case of BELL the standard for reality that was "agreed" on WAS EPR, so yes... EPR owns reality as far as Bell's Theorems are concerned. That's the whole damned point. If you don't get that, you're missing everything that follows.

agreement on ? on misunderstandings ? (from whoever)

and agreement ? ...where ?
here, there are only claims, opinions, if you (or whoever) wish name cat to reality or reality to cats that is your (their) misinterpretation (oh sorry !, you do not exist !, you are not real ! ).

 

[Frame Dragger]

agreement on ? on misunderstandings ? (from whoever)

and agreement ? where ?
here, there are only claims, opinions, if you (or whoever) wish name cat to reality or reality to cats that is your (their) misinterpretation (oh sorry, you do not exist, you are not real ).

*sigh* Just because your nickname is Yoda, doesn't mean you have to start rambling like him...

 

[ThomasT]

1. This is essentially a restatement of the realism requirement for ANY 2 pairs of "somethings" that take binary values. It could be sock colors, coin sides, or pretty much anything. This is not the "proper" form but I follow what you mean. This requirement has nothing at all to do with quantum mechanics. It follows some the probability ideas of Kolgomorov.


2. What you call a common cause is expressed a little differently usually. This comes from EPR originally, and I would say it is the idea that there are elements of reality. Those elements of reality would be what you would get from this idea:

A experiments measuring any observable attribute of Alice would allow you to predict the same attribute on Bob.

Keep in mind: these particles do NOT need to be entangled to demonstrate this effect. So it is not an assumption. It will be a demonstrated fact.


3. I happen to agree with this, although as I say it is not from a rigorous perspective. If you take a single photon - not part of an entangled pair but just one lone photon - you will eventually realize that Malus does not provide a self-consistent description of its spin either. So whatever the issue is, it does not seem to me to relate to separability/locality.


4. And I completely agree that if we are going to discuss/debate suprerdeterminism, we should start a new thread. Frame Dragger? Although it would probably make sense to skip it for a while if you want to follow some references first.

1. Ok, and its connection to Nature is via the faulty assumption that we can attribute definite values to the property or properties being jointly analyzed in Bell tests.

2. Ok, what I meant by common cause doesn't imply that we can attribute definite values (vis EPR elements of reality) to the locally imparted common property or properties. The only assumption necessary to justify the application of Malus Law in optical Bell tests is that whatever property or properties are being jointly analyzed, and whatever values they might have wrt some specific value of the global measurement parameter, they are the same for each of the counter-propagating disturbances incident on a and b during any given emission-coincidence interval.

It also follows from this assumption that if the angular difference of the joint polarizer settings |a-b| = 0, then the results at A and B for this setting should be identical -- and we can deduce A given B, and vice versa.

3. I think that many useful explanatory schemes don't start out very rigorously. The application of Malus Law in Bell tests follows from its application in previous (to Bell tests) similar setups (or setups with similar features). The considerations and assumptions leading to its application are all grounded in the assumption that Nature is exclusively locally causal in line with SR.

The assumption of nonlocality wrt entangled photons is just a bit too convenient, imho -- and, it creates other problems while still not really explaining entanglement.

4. As far as I'm concerned there's nothing to discuss/debate wrt superdeterminism. I agree with you that it's a completely superfluous consideration.

 

[yoda jedi]

.....differed with Einstein about the (allegedly) fundamental nature of the Born probabilities and hence on the issue of -> determinism. Indeed, whereas Born and the others just listed after him believed the outcome of any individual quantum measurement to be unpredictable in principle, Einstein felt this unpredictability was just caused by the incompleteness of quantum mechanics (as he saw it)......


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


...Bell himself has stressed this aspect and has remarked that it is extremely difficult to eradicate this prejudice:

"My own first paper (Physics 1, 195 (1965.) on this subject starts with a summary of the EPR argument from locality to deterministic hidden variables. But the commentators have almost universally reported that it begins with deterministic hidden variables." ...

...It has to be remarked that deterministic hidden variable theories assume that the complete specification of the state of the system implies that all physical properties are actually possessed by the systems prior to any measurement process. This is equivalent to the request of realism discussed by the above mentioned authors...

 

[DrChinese]

...Bell himself has stressed this aspect and has remarked that it is extremely difficult to eradicate this prejudice...

"My own first paper (Physics 1, 195 (1965.) on this subject starts with a summary of the EPR argument from locality to deterministic hidden variables. But the commentators have almost universally reported that it begins with deterministic hidden variables."

...It has to be remarked that deterministic hidden variable theories assume that the complete specification of the state of the system implies that all physical properties are actually possessed by the systems prior to any measurement process. This is equivalent to the request of realism discussed by the above mentioned authors...

Yes, this is a bit of a tricky area. First, Bell did write about his paper after the fact... and in some cases those words can be different than the original paper. So which is the proper reference? What do you make of an author's subsequent comments to an important paper like this?

Second, what difference does it make whether he goes from locality to realism (or determinism or hidden variables or whatever) or vice versa? I think you end up at the same point either way.

Lastly, I think Bell should be looked at like a road map. Once you can see where Bell journeyed, the path becomes so much clearer for those who follow. Once you see the internal inconsistency of a local realistic approach, you realize that something has to give.

 

[yoda jedi]

Second, what difference does it make whether he goes from locality to realism (or determinism or hidden variables or whatever) or vice versa? I think you end up at the same point either way.

absolute irrelevant, directionality it doesn't matter, the emphasis is on DETERMINISM look the word FROM not bold, but persist the word TO (my mistake).

i have to post in this way:

.....differed with Einstein about the (allegedly) fundamental nature of the Born probabilities and hence on the issue of -> determinism. Indeed, whereas Born and the others just listed after him believed the outcome of any individual quantum measurement to be unpredictable in principle, Einstein felt this unpredictability was just caused by the incompleteness of quantum mechanics (as he saw it)......


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


...Bell himself has stressed this aspect and has remarked that it is extremely difficult to eradicate this prejudice:

"My own first paper (Physics 1, 195 (1965.) on this subject starts with a summary of the EPR argument from locality to deterministic hidden variables. But the commentators have almost universally reported that it begins with deterministic hidden variables." ...

...It has to be remarked that deterministic hidden variable theories assume that the complete specification of the state of the system implies that all physical properties are actually possessed by the systems prior to any measurement process. This is equivalent to the request of realism discussed by the above mentioned authors...

Realism is not Determinism (and Determinism is not Realism)
Reality can be deterministic or not, be real is exist, determined or undertermined (defined or undefined, counterfactual definiteness or indefiniteness) contextual or non contextual, predictable or unpredictable.
be real is : "being qua being", just being.

 

[Eye_in_the_Sky]

"counterfactuality"

Back in post #477, I wrote the following:

"Counterfactual definiteness" is a weaker premise than "instruction sets".

"Counterfactual definiteness" is the assumption that there would have been definite outcomes in the counterfactual cases (without necessarily assigning specific values to those outcomes).

"Instruction sets" is the assumption in which the definite outcomes in (at least some of) the counterfactual cases are assigned specific values.

3. Sorry, to me CD = realism and yes I know that it doesn't to some people. If you can give me a specific example of a relevant difference, that would be wonderful.

Below, I give an example in which counterfactual reasoning is used to reach a certain conclusion. If the argument is valid, then one of the following must be relinquished:

(i) 'free-choice' ,

(ii) QM is "local" ,

(iii) QM is "complete" ,

(iv) some other (implicit, currently unidentified) assumption .

The validity of the argument itself requires the acceptability of a certain type of 'counterfactual reasoning'. What I have in mind is a principle which asserts merely that

there would have been definite outcomes in the counterfactual cases.

Taken on its own, the principle would not permit an a priori assignment of specific values to any of the outcomes in the counterfactual cases. [... And, as far as I can tell, nowhere in the argument is such an assignment required to be made.]

Perhaps such a principle is not the same as "CFD", i.e. "counterfactual definiteness", and so I am incorrect in my post #477 characterization of "CFD" (repeated at the top of this post) [... at later time, I would like to look into this question of 'definition' in more detail]. Therefore, I will return to my earlier nomenclature of using the expression "CF" ("counterfactuality") to denote the notion of 'counterfactual reasoning' in general.

Finally, the question I wish to raise (at least, preliminarily) is the following:

What, if anything, is wrong with the type of CF employed in the argument of the example below?
_______________________________________

Example

Let us formulate an argument from the perspective of the mutual rest frame of Alice and Bob.

Suppose that at time t₁ Alice makes a 'free-choice' to measure the spin component of her incoming particle along some axis and that at a later time t₂ the outcome has been registered. Let Bob's laboratory be situated farther from the source than Alice's laboratory such that he can invoke a 'free-choice' of his own at a time t₃ after t₂, with subsequent registration occurring at a time t₄.

So, we have

t₁ [Alice chooses] < t₂ [Alice gets result] < t₃ [Bob chooses] < t₄ [Bob gets result] .

Next, consider the spacetime region A temporally bounded by t₁ and t₂, and spatially bounded by the walls of Alice's laboratory. Similarly, consider the spacetime region B temporally bounded by t₃ and t₄, and spatially bounded by the walls of Bob's laboratory. Finally, assume that Bob's laboratory (although farther from the source than Alice's) is still close enough to the source so as to ensure a spacelike separation of the two spacetime regions A and B.

Consider now the following counterfactuals (where a and a' are nonparallel unit vectors):

(1) Alice chooses to measure the spin component along the a-axis;

(2) Alice chooses to measure the spin component along the a'-axis.

Let us fix our attention to a time t, where t₂ < t < t₃. In case (1), Quantum Mechanics would inform Alice that she is justified in ascribing an eigenstate of S_a as a characterization of the 'information' relevant to region B for any measurement Bob may happen to choose, whereas, in case (2), Quantum Mechanics would inform Alice that she is justified in ascribing an eigenstate of S_a'.

Since Alice's measurement choice as well as the registration of the associated outcome are each comprised of events which are "local" to the spacetime region A, it follows from "local causality" that the 'real factual situation' in spacetime region B must be independent of the cases (1) and (2). Yet, in case (1) an eigenstate of S_a would apply, whereas in case (2) an eigenstate of S_a' would apply.

Thus, two (actually ... infinitely many) distinct quantum states can apply to the same 'real factual situation' in region B. Since these distinct states have distinct physical implications in connection with the various possible measurements Bob has at his disposal to perform, it follows that at most one of these states (if any, at all) can provide a "complete" characterization of the relevant 'information'.

From this, we see that – in relation to the various measurements from which Bob can choose – the "quantum-mechanical state" which Alice ascribes to region B cannot in general provide a "complete" characterization of relevant 'information'.

Therefore, Quantum Mechanics is "incomplete".

 

[DrChinese]

...it follows from "local causality" that the 'real factual situation' in spacetime region B must be independent of the cases (1) and (2). Yet, in case (1) an eigenstate of S_a would apply, whereas in case (2) an eigenstate of S_a' would apply...Therefore, Quantum Mechanics is "incomplete".

This was the EPR argument. Local causality + HUP -> (QM is incomplete) or (Reality is observer dependent - in this case Alice).

The above statement is a shortcut way of saying this argument is no longer accepted. It was not universally accepted even when first presented in 1935. But certainly it went out of fashion after that.

Note your assumption: local causality. Hmmm. Is that valid? No, that is suspect. Also, the usual deduction is that Bob's reality is dependent on a choice made by Alice if QM is complete. I would say this is a generally accepted conclusion: that either locality does not hold, or reality is dependent on observeration.

 

[RUTA]

Below, I give an example in which counterfactual reasoning is used to reach a certain conclusion. If the argument is valid, then one of the following must be relinquished:

(i) 'free-choice' ,

(ii) QM is "local" ,

(iii) QM is "complete" ,

(iv) some other (implicit, currently unidentified) assumption .

Finally, the question I wish to raise (at least, preliminarily) is the following:

What, if anything, is wrong with the type of CF employed in the argument of the example below?
_______________________________________

Example

Let us formulate an argument from the perspective of the mutual rest frame of Alice and Bob.

Suppose that at time t₁ Alice makes a 'free-choice' to measure the spin component of her incoming particle along some axis and that at a later time t₂ the outcome has been registered. Let Bob's laboratory be situated farther from the source than Alice's laboratory such that he can invoke a 'free-choice' of his own at a time t₃ after t₂, with subsequent registration occurring at a time t₄.

So, we have

t₁ [Alice chooses] < t₂ [Alice gets result] < t₃ [Bob chooses] < t₄ [Bob gets result] .

Next, consider the spacetime region A temporally bounded by t₁ and t₂, and spatially bounded by the walls of Alice's laboratory. Similarly, consider the spacetime region B temporally bounded by t₃ and t₄, and spatially bounded by the walls of Bob's laboratory. Finally, assume that Bob's laboratory (although farther from the source than Alice's) is still close enough to the source so as to ensure a spacelike separation of the two spacetime regions A and B.

Consider now the following counterfactuals (where a and a' are nonparallel unit vectors):

(1) Alice chooses to measure the spin component along the a-axis;

(2) Alice chooses to measure the spin component along the a'-axis.

Let us fix our attention to a time t, where t₂ < t < t₃. In case (1), Quantum Mechanics would inform Alice that she is justified in ascribing an eigenstate of S_a as a characterization of the 'information' relevant to region B for any measurement Bob may happen to choose, whereas, in case (2), Quantum Mechanics would inform Alice that she is justified in ascribing an eigenstate of S_a'.

Since Alice's measurement choice as well as the registration of the associated outcome are each comprised of events which are "local" to the spacetime region A, it follows from "local causality" that the 'real factual situation' in spacetime region B must be independent of the cases (1) and (2). Yet, in case (1) an eigenstate of S_a would apply, whereas in case (2) an eigenstate of S_a' would apply.

Thus, two (actually ... infinitely many) distinct quantum states can apply to the same 'real factual situation' in region B. Since these distinct states have distinct physical implications in connection with the various possible measurements Bob has at his disposal to perform, it follows that at most one of these states (if any, at all) can provide a "complete" characterization of the relevant 'information'.

From this, we see that – in relation to the various measurements from which Bob can choose – the "quantum-mechanical state" which Alice ascribes to region B cannot in general provide a "complete" characterization of relevant 'information'.

Therefore, Quantum Mechanics is "incomplete".

Your use of the term "locality" encompasses both causal locality and separability, but otherwise it looks like the EPR argument with the same conclusion. To finish the story you've only to add QM's predicted violation of the Bell inequality with its subsequent experimental confirmation whence people believe QM is complete. Get rid of superdeterminism (keep free will) and that leaves you having to discard causal locality and/or separability, which is where the debate is centered.

 

[yoda jedi]

Back in post #477,

(iii) QM is "complete" ,


Therefore, Quantum Mechanics is "incomplete".

the quantum state is not just incomplete, but epistemic, i.e. a representation of an
observer’s knowledge of reality rather than reality itself.

 

[Frame Dragger]

...the quantum state is not just incomplete, but epistemic.....

...And yet his was still not a particularly good way of demonstrating that.

 

[yoda jedi]

being incomplete can not propose or derive any ontological premise.

 

[Frame Dragger]

being incomplete can not propose or derive any ontological premise.

I truly look forward to RUTA's reply to this, as I suspect s/he will have something interesting on the subject.

 

[Demystifier]

If the argument is valid, then one of the following must be relinquished:

(i) 'free-choice' ,

(ii) QM is "local" ,

(iii) QM is "complete" ,

(iv) some other (implicit, currently unidentified) assumption .

I think that we can safely say that (i) is not compatible with (iii).
Namely, if QM (where by QM I mean QM in its standard form) is complete then everything about nature can be derived from QM. However, from QM one cannot derive that some macroscopic objects (e.g., humans) have ability to make a free choice. Therefore, if QM is complete, then free choice does not exist.
Similarly, if free choice exists, then it is something that is not explained by QM. Therefore, if free choice exists, then QM is not complete.

It follows that QM cannot be consistently interpreted such that only (ii) or only (iv) or even only (ii) and (iv) are relinquished. Instead, one must relinquish (i) or (iii) or both. (Which does not exclude the possibility that something else should be relinquished as well.)

 

[SpectraCat]

Let us formulate an argument from the perspective of the mutual rest frame of Alice and Bob.

Suppose that at time t₁ Alice makes a 'free-choice' to measure the spin component of her incoming particle along some axis and that at a later time t₂ the outcome has been registered. Let Bob's laboratory be situated farther from the source than Alice's laboratory such that he can invoke a 'free-choice' of his own at a time t₃ after t₂, with subsequent registration occurring at a time t₄.

So, we have

t₁ [Alice chooses] < t₂ [Alice gets result] < t₃ [Bob chooses] < t₄ [Bob gets result] .

Next, consider the spacetime region A temporally bounded by t₁ and t₂, and spatially bounded by the walls of Alice's laboratory. Similarly, consider the spacetime region B temporally bounded by t₃ and t₄, and spatially bounded by the walls of Bob's laboratory. Finally, assume that Bob's laboratory (although farther from the source than Alice's) is still close enough to the source so as to ensure a spacelike separation of the two spacetime regions A and B.

Consider now the following counterfactuals (where a and a' are nonparallel unit vectors):

(1) Alice chooses to measure the spin component along the a-axis;

(2) Alice chooses to measure the spin component along the a'-axis.

Everything up to here looks fine

Let us fix our attention to a time t, where t₂ < t < t₃. In case (1), Quantum Mechanics would inform Alice that she is justified in ascribing an eigenstate of S_a as a characterization of the 'information' relevant to region B for any measurement Bob may happen to choose, whereas, in case (2), Quantum Mechanics would inform Alice that she is justified in ascribing an eigenstate of S_a'.

Here is where you run into problems IMO ... Alice in fact cannot say anything about the "information" relevant to region B at any point. She cannot know for sure if her measurement was the one that destroyed the entanglement, and thus established the eigenstates of which operator (Sa or Sa') should be measured in region B, until she hears from Bob on a normal channel. Until then, she must allow for the possibility that Bob previously made a measurement that destroyed the entanglement, and she is measuring the projection of a well-defined eigenstate at her end.

Since Alice's measurement choice as well as the registration of the associated outcome are each comprised of events which are "local" to the spacetime region A, it follows from "local causality" that the 'real factual situation' in spacetime region B must be independent of the cases (1) and (2). Yet, in case (1) an eigenstate of S_a would apply, whereas in case (2) an eigenstate of S_a' would apply.

Thus, two (actually ... infinitely many) distinct quantum states can apply to the same 'real factual situation' in region B. Since these distinct states have distinct physical implications in connection with the various possible measurements Bob has at his disposal to perform, it follows that at most one of these states (if any, at all) can provide a "complete" characterization of the relevant 'information'.

From this, we see that – in relation to the various measurements from which Bob can choose – the "quantum-mechanical state" which Alice ascribes to region B cannot in general provide a "complete" characterization of relevant 'information'.

Hopefully my comment above helps to illustrate why (I think) the above analysis is flawed. The space-like separation between Alice and Bob means that they cannot know anything about measurements performed in the each other's regions until those results are communicated somehow. Alice is of course free to *assume* whatever she likes about what is going on in region B, but she can't *know* for sure until she hears from Bob. The apparent contradiction you have raised therefore does not seem to hold for Alice, or for Bob ... it would only hold for a hypothetical omniscient observer who could "see" what was going on in both space-time regions simultaneously. Since we know from SR that such an observer cannot exist, I don't see any contradiction here. Am I missing something?

 

[Gordon Watson]

What am I missing?

If I prepare photon-pairs correlated via identical linear polarization (say, some pairs V-correlated and some pairs H-correlated) then Bell-tests show Bell's inequality to be satisfied ... with no suggestion of nonlocal influences. Right? [Let's call these photon-pairs classically correlated.]

BUT if I prepare more highly correlated photon-pairs (say, correlated via identical angular momentum) then Bell-tests show Bell's inequality to be false. [Let's call these photon-pairs quantum-mechanically correlated.]

Why should more highly correlated results (from more highly correlated photon-pairs) be attributed to nonlocal influences?

 

[DrChinese]

What am I missing?

1. If I prepare photon-pairs correlated via identical linear polarization (say, some pairs V-correlated and some pairs H-correlated) then Bell-tests show Bell's inequality to be satisfied ... with no suggestion of nonlocal influences. Right? [Let's call these photon-pairs classically correlated.]

2. BUT if I prepare more highly correlated photon-pairs (say, correlated via identical angular momentum) then Bell-tests show Bell's inequality to be false. [Let's call these photon-pairs quantum-mechanically correlated.]

3. Why should more highly correlated results (from more highly correlated photon-pairs) be attributed to nonlocal influences?

1. These are not polarization entangled. The Bell Inequality does not really apply.

2. These are polarization entangled. The Bell Inequality should apply if you assert local realism, but experiments show the inequality is violated.

3. Because the inequality is violated, you must reject local realism. Essentially, the correlation level crosses a boundary. You shouldn't be able to have this level of correlation if locality and realism apply. So many people reject locality, and assert non-locality.

 

[Gordon Watson]

1. These are not polarization entangled. The Bell Inequality does not really apply.

2. These are polarization entangled. The Bell Inequality should apply if you assert local realism, but experiments show the inequality is violated.

3. Because the inequality is violated, you must reject local realism. Essentially, the correlation level crosses a boundary. You shouldn't be able to have this level of correlation if locality and realism apply. So many people reject locality, and assert non-locality.

Thank you DrC.

1, was given to show that entangled photons are not just of identical linear polarization.

2, was given to question why locality would be abandoned, in that the correlations in #1 do not require such abandonment.

3, in view of the HUP, appears to require the abandonment of EPR elements of reality. That seems to be easy, because EPR-realism neglects the quantum-of-action in any measurement.

4. So why is it not the case that EPR-realism is universally abandoned while locality (and hence relativity) is retained?

5. Does the double-slit experiment favor nonlocality?

6. There must be some strong reason for nonlocality being widely supported? As against the easy job of dropping EPR-realism: Yes?

 

[DrChinese]

Thank you DrC.

1, was given to show that entangled photons are not just of identical linear polarization.

2, was given to question why locality would be abandoned, in that the correlations in #1 do not require such abandonment.

3, in view of the HUP, appears to require the abandonment of EPR elements of reality. That seems to be easy, because EPR-realism neglects the quantum-of-action in any measurement.

4. So why is it not the case that EPR-realism is universally abandoned while locality (and hence relativity) is retained?

5. Does the double-slit experiment favor nonlocality?

6. There must be some strong reason for nonlocality being widely supported? As against the easy job of dropping EPR-realism: Yes?

1, 2: Sorry, not sure I follow what you are saying. If Bell's Inequality is respected, the photons are not polarization entangled. Entangled photons can be entangled on one or more pairs of observables.

3. Yes and no. There is no quantum of action to figure in for the realistic argument.

4. Some in fact do abandon realism. I personally lean in that direction a bit. But I am also slippery and sometimes change my mind.

5. Double slit is not a factor either way.

6. There are reasons, although they are subjective: a) It is easier to picture a non-local influence than the non-realistic alternative. I.e. thinking of a physical mechanism. b) Bohm worked out a non-local model to a sufficient level as to show it is conceptually viable.

 

[RUTA]

1, was given to show that entangled photons are not just of identical linear polarization.

2, was given to question why locality would be abandoned, in that the correlations in #1 do not require such abandonment.

3, in view of the HUP, appears to require the abandonment of EPR elements of reality. That seems to be easy, because EPR-realism neglects the quantum-of-action in any measurement.

4. So why is it not the case that EPR-realism is universally abandoned while locality (and hence relativity) is retained?

5. Does the double-slit experiment favor nonlocality?

6. There must be some strong reason for nonlocality being widely supported? As against the easy job of dropping EPR-realism: Yes?

I took the non-separable approach (aka non-EPR-realism) in my interpretation (“Reconciling Spacetime and the Quantum: Relational Blockworld and the Quantum Liar Paradox,” W.M. Stuckey, Michael Silberstein & Michael Cifone, Foundations of Physics 38, No. 4, 348 – 383 (2008), quant-ph/0510090 & “Why Quantum Mechanics Favors Adynamical and Acausal Interpretations such as Relational Blockworld over Backwardly Causal and Time-Symmetric Rivals,” Michael Silberstein, Michael Cifone & W.M. Stuckey, Studies in History & Philosophy of Modern Physics 39, No. 4, 736 – 751 (2008). http://dx.doi.org/10.1016/j.shpsb.2008.07.005 ).

I've given many presentations to experts in the foundations community and even though the formalism is textbook (irreps of spacetime symmetry group (FoP supra) or path integrals over graphs (arXiv 0908.4348)), people have a very difficult time with our brand of nonseparability, i.e., ontic structural realism. It runs contrary to the fundamental manner by which our brains construct perceptions -- things moving in space as a function of time, i.e., dynamism. In all honesty, my colleagues and I sometimes find ourselves asking questions in the wrong (dynamical) fashion and we've been working with RBW for 5 yrs.

So, I suspect we hear more about non-local solutions to EPR than non-separable ones because at least people can imagine a non-local dynamism.

 

[Gordon Watson]

I took the non-separable approach (aka non-EPR-realism) in my interpretation (“Reconciling Spacetime and the Quantum: Relational Blockworld and the Quantum Liar Paradox,” W.M. Stuckey, Michael Silberstein & Michael Cifone, Foundations of Physics 38, No. 4, 348 – 383 (2008), quant-ph/0510090 & “Why Quantum Mechanics Favors Adynamical and Acausal Interpretations such as Relational Blockworld over Backwardly Causal and Time-Symmetric Rivals,” Michael Silberstein, Michael Cifone & W.M. Stuckey, Studies in History & Philosophy of Modern Physics 39, No. 4, 736 – 751 (2008). http://dx.doi.org/10.1016/j.shpsb.2008.07.005 ).

I've given many presentations to experts in the foundations community and even though the formalism is textbook (irreps of spacetime symmetry group (FoP supra) or path integrals over graphs (arXiv 0908.4348)), people have a very difficult time with our brand of nonseparability, i.e., ontic structural realism. It runs contrary to the fundamental manner by which our brains construct perceptions -- things moving in space as a function of time, i.e., dynamism. In all honesty, my colleagues and I sometimes find ourselves asking questions in the wrong (dynamical) fashion and we've been working with RBW for 5 yrs.

So, I suspect we hear more about non-local solutions to EPR than non-separable ones because at least people can imagine a non-local dynamism.

Dear RUTA: Your alternative approach sounds interesting, and worthy of extra study, and in line with my own thoughts, so I'd encourage you to put ALL your papers on arViv (with hot-links on PF, if that is permitted). Or open a PF IR page with hot links?

"Studies in History & Philosophy of Modern Physics" is not available at my library.

I would introduce RBW as an explicit non-EPR-realism [nEPRr] approach <full stop> on the grounds that you see clearly that EPR "elements of physical reality" are false and that (as a consequence), locality does not need to be abandoned until we have explored more realistic [i.e., nEPRr] approaches. [EPR-realism being totally unrealistic, IMO.]

In this way you can introduce strangers such as me to your "non-separable" approach without the suspicion that "non-separable" is sneaky shorthand for "non-locality". As to the difficulty of imagining your approach? Can it be more difficult than imagining that the speed of light is constant?

I'm off to study your RBW.

Is RBW the correct and universal designation of your approach?

 

[Gordon Watson]

1, 2: Sorry, not sure I follow what you are saying. If Bell's Inequality is respected, the photons are not polarization entangled. Entangled photons can be entangled on one or more pairs of observables.

3. Yes and no. There is no quantum of action to figure in for the realistic argument.

4. Some in fact do abandon realism. I personally lean in that direction a bit. But I am also slippery and sometimes change my mind.

5. Double slit is not a factor either way.

6. There are reasons, although they are subjective: a) It is easier to picture a non-local influence than the non-realistic alternative. I.e. thinking of a physical mechanism. b) Bohm worked out a non-local model to a sufficient level as to show it is conceptually viable.

Dear DrC, what I was saying in my 1 and 2 is not that important. It was not (in your words)

"If Bell's Inequality is respected, the photons are not polarization entangled"

but rather:

"Classically-correlated photons satisfy BI, quantum-correlated photons do not."

This view leads me to reject EPR-realism (which I view as so amateurish as to be not worthy of a second thought). IMO, EPR-realism neglects the measurement interaction (for I understand EPR-realism to mean that measurement outcomes reflect "one-to-one" input properties) and yet we see that (in a Bell-test) even classically-correlated photons are modified by measurement.

So my 1 and 2 were to explain why I reject EPR-realism ... and seek a new REALISM ... before I reject locality.

That is why I am interested in (and don't understand) those who take the opposite approach. And why I'm interested especially in what leads you to occasionally flip-flop?

Also, how do you view RUTA's RBW approach?

 

[RUTA]

Dear RUTA: Your alternative approach sounds interesting, and worthy of extra study, and in line with my own thoughts, so I'd encourage you to put ALL your papers on arViv (with hot-links on PF, if that is permitted). Or open a PF IR page with hot links?

"Studies in History & Philosophy of Modern Physics" is not available at my library.

You can get the RBW papers from my homepage: http://users.etown.edu/s/stuckeym/

I would introduce RBW as an explicit non-EPR-realism [nEPRr] approach <full stop> on the grounds that you see clearly that EPR "elements of physical reality" are false and that (as a consequence), locality does not need to be abandoned until we have explored more realistic [i.e., nEPRr] approaches. [EPR-realism being totally unrealistic, IMO.]

In this way you can introduce strangers such as me to your "non-separable" approach without the suspicion that "non-separable" is sneaky shorthand for "non-locality". As to the difficulty of imagining your approach? Can it be more difficult than imagining that the speed of light is constant?

I'm off to study your RBW.

Is RBW the correct and universal designation of your approach?

Thanks for the hints as to how to explain RBW :-) Yes, Relational Blockworld or RBW is the "universal designation."

 

[DrChinese]

Dear DrC, what I was saying in my 1 and 2 is not that important. It was not (in your words)

"If Bell's Inequality is respected, the photons are not polarization entangled"

but rather:

"Classically-correlated photons satisfy BI, quantum-correlated photons do not."

This view leads me to reject EPR-realism (which I view as so amateurish as to be not worthy of a second thought). IMO, EPR-realism neglects the measurement interaction (for I understand EPR-realism to mean that measurement outcomes reflect "one-to-one" input properties) and yet we see that (in a Bell-test) even classically-correlated photons are modified by measurement.

So my 1 and 2 were to explain why I reject EPR-realism ... and seek a new REALISM ... before I reject locality.

That is why I am interested in (and don't understand) those who take the opposite approach. And why I'm interested especially in what leads you to occasionally flip-flop?

Also, how do you view RUTA's RBW approach?

Flip flop! Me?

I flip flop a bit on interpretations, mainly because I am always trying to determine if any interpretation might make a subtle assumption which could lead to a test.

I really like the RBW approach. It considers future context as relevant to fundamental quantum interactions, which seems to make sense (to me).

On the other hand: I would not be so quick to reject the EPR definition of realism. It is a powerful definition, a good line in the sand.

 

[IcedEcliptic]

how do we talk about local realism without invoking EPR? "real" has too many definitions otherwise, we need somewhere to begin, yes?

 

[yoda jedi]

how do we talk about local realism without invoking EPR? "real" has too many definitions otherwise, we need somewhere to begin, yes?

be real is independent of any conceptual consideration.

 

[IcedEcliptic]

be real is independent of any conceptual consideration.

We need to discuss something yoda jedi, and reality is a standard we believe we experience. Contrasting with that seems sensible.

 

[RUTA]

I had just posted this reference in another thread, but maybe you should read it to if you're not aware of it.

M.D. Reid et al. Rev. Mod. Phys. v.81, p.1727 (2009).

If you think that none of the violation of EPR/Bell, GHZ, CHSH, Leggett, etc. inequalities constitutes a violation of local realism, then you ARE proposing something that is not already established. This means that you need to back this up with a published work to support that you are not proposing your own personal theory.

Zz.

Do you have a title for that reference? The title is required for my interlibrary loan request.

 

[yoda jedi]

We need to discuss something yoda jedi, and reality is a standard we believe we experience. Contrasting with that seems sensible.

Reality does not need you, to exist.

 

[IcedEcliptic]

Reality does not need you, to exist.

Cute, but metaphysics and philosophy, and not helpful when discussing non-locality.