Gordon Watson
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vanesch said:Ok, noted and done.
Thank you vanesch.
Can you also fix each page header?
It would give PF a better look if its page-headers were error-free.
vanesch said:Ok, noted and done.
No, but both involve a statistical correlation between a collection local facts. Clearly the assumption of local realism does not rule out the existence of such correlations between local facts, and whether you call them "relationships between local facts" or "relationships between relationships", we could find the same kind of relationships in classical electromagnetism which is a local realist theory, do you disagree?ThomasT said:The relationship between the polarizers isn't a local fact, and the relationship between the photons isn't a local fact.
And couldn't we find relationships between two electromagnetic waves generated by the same source in classical electromagnetism?ThomasT said:Wrt the polarizers this relationship just refers to their angular difference ( θ). Wrt the photons, things aren't so simple. What the polarizers are jointly physically measuring during any coincidence interval is the relationship between two optical disturbances emitted by the same atom -- a relationship that's expressed vis the applicable conservation law.
But E(A,B) for any joint detection attributes we could come up with in a classical EM experiment would be determined solely by local variables in the region of each measurement, do you disagree?ThomasT said:What the experiment is correlating to θ is the rate of generation of identical detection attributes. The joint detection attribute, (A,B), is also not a local fact. E(A,B) isn't, effectively, determined by local hidden variables.
No it isn't, this is an idea I've seen you refer to before, but if you think this is the way physicists conceive of it then that's a misconception. The hidden variable is sometimes imagined to be, not any sort of "vector", but simply a function that assigns a + or - to every possible detection angle in advance...but one of the points of Bell's proof is that it requires no understanding of what the local hidden variables would actually be or exactly how they would determine the measurement results.ThomasT said:Wrt the two photon scenarios, the hidden variable, λ, is typically taken to refer to the optical vector of the polarizer-incident photons.
JesseM said:It's just an empirical observation that photons emitted by the same atom are correlated in this way, but it doesn't tell you, for example, whether they are correlated because they were each assigned identical hidden variables at the moment they were created and they just carried the variables with them as they traveled, or whether the fact that they were created together gives them an FTL connection which allows a measurement on one to instantly affect the behavior of the other, or some other picture of what's going on "behind the scenes".
But "relationship between their motional properties is due to their being emitted in opposite directions from the same atom during the same transition" is still very vague, it doesn't tell me what this "due to" consists of--for example, whether you are imagining that "due to their being emitted in opposite directions" they were assigned the same properties at birth and just carried these unchanging properties with them to the location of the measurements (which of course would mean the properties were local hidden variables, so that's ruled out by Bell), or if "due to their being emitted in opposite directions" they were given an FTL connection that causes any measurement on one to instantly affect the other, or some other picture of exactly how their common emission explains later correlations.ThomasT said:The assumption that the relationship between their motional properties is due to their being emitted in opposite directions from the same atom during the same transition seems to me to be the most reasonable assumption. Isn't this what qm's application of the law of conservation of angular momentum in Aspect 1982 is based on?
JesseM said:I don't understand what you mean by "aren't applicable".
Doesn't help me either--and here you snipped out the questions about classical EM which were meant to specifically probe my confusion about what you mean by terms like "aren't applicable" and "irrelevant", which is why I repeat them again in this post, please actually address these questions this time. Again, I'm confused about whether you think that the nature of the experiment and what sort of correlations are being measured (ignoring the detailed statistics of the results) invalidates Bell's local realist assumptions, or whether you agree that with slightly different results Bell's assumptions might indeed by applicable.ThomasT said:As in irrelevant. See above.
It doesn't "require" the inclusion of the hidden variable. If I say that in general z can be a function of w,x,y and write this as z=f(w,x,y), this doesn't rule out the possibility that y is irrelevant and the correct function is z=w^2 + 2x, since you could always rewrite this as z=w^2 + 2x + 0y. Bell's proof is general, it totally rules out the possibility that the QM measurement statistics could be explained by any local realist theory, including one where the only local variables that influenced the measurement results were non-hidden ones.ThomasT said:BIs are violated because they're based on a formulation of joint detection (entanglement) preparations which requires the inclusion of a variable which is irrelevant wrt those contexts.
No, it's definitely not possible to understand the experiments in local realist terms, if you think it is you're fundamentally misunderstanding Bell's proof. If you assume there are no hidden variables and simply redefine λ to refer to the state of all non-hidden local variables in the immediate region of the each measurement (including variables whose state may represent properties of the electron that it was assigned at birth and that it just "carried with it", unchanging, to the region of the measurement, so that the states of these variables could be correlated for the two particles in the region of each measurement) then the proof would still work fine and would show that you can't explain the violation of BI in a local realist theory where the measurement results are determined by local non-hidden variables in the region of the measurement.ThomasT said:It's possible to understand these experiments in local realist terms without requiring that the mathematical model include any local hidden variables.
I don't know what you mean by "relate those relationships" as separate from "define the relevant relationships". QM just gives mathematical functions which tell you the probability of some measurement result(s) given knowledge of some other measurement result(s).ThomasT said:Edit: Isn't what qm does is define the relevant relationships and then relate those relationships accordingly?
JesseM said:... <SNIP> ...
QM just gives mathematical functions which tell you the probability of some measurement result(s) given knowledge of some other measurement result(s).
Those probabilities are for the various hidden-variable states, not for measurable outcomes (you can't measure more than one angle a, b, or c for a given particle). Since QM doesn't say anything about hidden-variable states which may or may not exist, only about measurable outcomes, QM does not assign probabilities to P1-P8. But what Bell shows is that we can imagine any possible combination of probabilities for P1-P8 in a hidden-variable theory (with the probabilities being in the range 0 ≤ Pn ≤ 1 and adding up to 1, of course), and the theory will always predict that the inequality P(a+, b+) ≤ P(a+, c+) + P(c+, b+) will be respected, but QM predicts this inequality is violated.JenniT said:Dear JesseM and vanesch, I agree with Jesse's point above.
Earlier in this thread, vanesch cited Sakurai and http://en.wikipedia.org/wiki/Sakurai%27s_Bell_inequality
I'd be pleased to see the QM probabilities for the eight (8) probabilities (P1-P8) in the cited text.
Can you provide them, please?
Thank you, JenniT
JesseM said:Those probabilities are for the various hidden-variable states, not for measurable outcomes (you can't measure more than one angle a, b, or c for a given particle). Since QM doesn't say anything about hidden-variable states which may or may not exist, only about measurable outcomes, QM does not assign probabilities to P1-P8. But what Bell shows is that we can imagine any possible combination of probabilities for P1-P8 in a hidden-variable theory (with the probabilities being in the range 0 ≤ Pn ≤ 1 and adding up to 1, of course), and the theory will always predict that the inequality P(a+, b+) ≤ P(a+, c+) + P(c+, b+) will be respected, but QM predicts this inequality is violated.
I think as long as you are willing to listen to arguments as to why your argument might be flawed, it should be OK to post. Keep in mind though, the idea is that on each trial the experimenters choose randomly which of the 3 angles a, b, c to use, in a way that's uncorrelated with which of the 8 hidden states occur on that trial, and that it must be true that whenever they pick the same angle, they get the same result (which is guaranteed as long as you assume the possible hidden states of the particle pair must be one of the 8 listed in the wikipedia article, rather than other possibilities where not all the hidden states are opposite for Alice and Bob, like if Alice's state was +++ while Bob's was +--) And do you understand that if Alice chooses angle a and Bob chooses angle b, it must be true that P(a+, b+) is equal to P3 + P4 since those are the only probabilities corresponding to hidden states which have + in the a-column of Alice's particle and + in the b-column of Bob's particle? Likewise if Alice chooses a and Bob chooses c, then P(a+, c+) = P2 + P4, and if Alice chooses c and Bob chooses b, then P(c+, b+) = P3 + P7. If all the probabilities have non-negative values, it should be obvious that you can't come up with any values for the probabilities that don't satisfy P3 + P4 ≤ (P2 + P4) + (P3 + P7), since this can be rearranged as (P3 + P4) ≤ (P3 + P4) + P2 + P7 and neither P2 nor P7 can be negative.JenniT said:Thanks Jesse,
So: Would it be OK if I post, for discussion, a local realistic hidden-variable theory under this heading: What's wrong with this local realistic counter-example to Bell's theorem?
The OP will:
A: Deliver P1-P8.
B: Have them summing to unity.
C: Have them fully compatible with QM-style experiments.
D: Have them recognizing topology associated with the spherical symmetry of the singlet state.
E: Have them breaching Bell's inequality.
F: Have them based on nothing more than high-school maths and logic.
PS: I'm an engineer, I'm here to learn, and I could be mistaken -- which is not the same as being crackpot.
Thanks again,
JenniT
JenniT said:Thanks Jesse,
So: Would it be OK if I post, for discussion, a local realistic hidden-variable theory under this heading: What's wrong with this local realistic counter-example to Bell's theorem?
The OP will:
A: Deliver P1-P8.
B: Have them summing to unity.
C: Have them fully compatible with QM-style experiments.
D: Have them recognizing topology associated with the spherical symmetry of the singlet state.
E: Have them breaching Bell's inequality.
F: Have them based on nothing more than high-school maths and logic.
PS: I'm an engineer, I'm here to learn, and I could be mistaken -- which is not the same as being crackpot.
Thanks again,
JenniT
ThomasT said:In the last paragraph, after equation 30.[/QUOTE
There he writes that "one can exchange signals" as the proper-time τ elapsed for each of the particles is unequal to zero...
To me that sounds as if it can have to do with the entangled particles exchanging signals at speeds less than light.
(About "none of which contradicts [..] the assumption that nature is locally causal": - see also my PS below!)
"LR" stands for local realism I suppose... Thus you hold that the class of LR theories that the Bell Inequality disproves is incompatible with the experimental preparation??That's the view of many, and maybe it was Bell's intention, but that isn't what BI violations, definitively and unarguably, indicate -- which is that the LR formulation on which the formally and experimentally violated BI is based is incompatible with standard qm and the experimental preparation. No more, no less. This is what I meant by the minimalist interpretation and unarguable applicability of Bell's theorem. [..] BI violations don't contradict the assumption that nature is exclusively local.
As I mentioned in a previous post, BIs are based on the requirement that entanglement be modeled by (local hidden) variables which are irrelevant (even in an exclusively locally causal world) wrt entanglement (which depends exclusively on global properties and measurement parameters), and that if lhv's are required in the model of entanglement, then the predictions of such a model will necessarily be skewed.
Then according to you, Bell's theorem (BI => "no local deterministic hidden-variable theory can reproduce all the experimental predictions of quantum mechanics") is basically wrong or misunderstood?
For it does not make sense to require a theory to model an effect by means of irrelevant variables - that is a false requirement!
PS: I now see that my questions here above about "none of which contradicts the assumption that nature is locally causal" have already largely been answered - apparently both with "yes".
...I should have said "which of course would mean the properties were local variables, so that's ruled out by Bell", as the properties that each particle carries with them may not necessarily be hidden ones, and as I explained Bell's proof rules out all local realist explanations regardless of whether they involve hidden or non-hidden variables.JesseM said:But "relationship between their motional properties is due to their being emitted in opposite directions from the same atom during the same transition" is still very vague, it doesn't tell me what this "due to" consists of--for example, whether you are imagining that "due to their being emitted in opposite directions" they were assigned the same properties at birth and just carried these unchanging properties with them to the location of the measurements (which of course would mean the properties were local hidden variables, so that's ruled out by Bell), or if "due to their being emitted in opposite directions" they were given an FTL connection that causes any measurement on one to instantly affect the other, or some other picture of exactly how their common emission explains later correlations.
That is not the case, see my comment in post #34.JesseM said:[..]In any case, based on Avodyne's comment in post #30 it sounds like Joy Christian's model just ignores the real-world observation that the experimenter always sees one of two discrete results (pointer going to +1 or -1), and instead posits a sort of hypothetical universe where the results are elements of Clifford algebra.[..]
OK, if the communication was by email, do you still have the emails? I'd be interested to see his exact words...harrylin said:That is not the case, see my comment in post #34.
JenniT said:Thank you vanesch.
Can you also fix each page header?
It would give PF a better look if its page-headers were error-free.
vanesch said:I could, but it is too much work. I'd have to edit each individual post.
vanesch said:We're walking on a thin line here, I'm not entirely sure that all my co-mentors will agree.
But for sake of pedagogy, be my guest. It is clear to me (and to Jesse I think) that you have a misunderstanding of what is claimed, what is going on and what all this is about, so as it is always pedagogically interesting to see a wrong argument developed in order to pinpoint the misunderstanding, go ahead.
However, I have to warn you: you are attempting to find numbers which have to satisfy mutually incompatible inequalities.
You are trying the equivalent of something like the following: find 2 numbers x and y such that x > 0, y > 0 and x + y < x - 1 and x + y < y - 1 or something.
[Emphasis added by JenniT.]
So "good luck"![]()
Yes, but this has to do with what "amounts to a null-like condition on the spin bi-vector", and that "despite that the addition of two momenta in ordinary spacetime remains timelike and the difference of the momenta is spacelike, consistent with the spacelike separation of the two particles 1, 2 moving along the z-axis in opposite directions, the addition laws of the poly-momentum in C-space is null-like". So, "since the interval in C-space (X1 − X2)2 is null one can exchange signals from the locations 1, 2 in C-space".harrylin said:There he writes that "one can exchange signals" as the proper-time τ elapsed for each of the particles is unequal to zero...
To me that sounds as if it can have to do with the entangled particles exchanging signals at speeds less than light.
Yes LR stands for Local Realism or Local Realistic.harrylin said:"LR" stands for local realism I suppose...
Yes. At least that much follows from the fact of experimental violations of BIs.harrylin said:Thus you hold that the class of LR theories that the Bell Inequality disproves is incompatible with the experimental preparation??
ThomasT said:As I mentioned in a previous post, BIs are based on the requirement that entanglement be modeled by (local hidden) variables which are irrelevant (even in an exclusively locally causal world) wrt entanglement (which depends exclusively on global properties and measurement parameters), and that if lhv's are required in the model of entanglement, then the predictions of such a model will necessarily be skewed.
I think that it's been thoroughly demonstrated, that "no local deterministic hidden-variable theory can reproduce all the experimental predictions of quantum mechanics" wrt entanglement preparations. But many (most?) people take violations of BIs to be indicating that either nature is nonlocal or that local hidden variables don't exist. I just currently think that there's a more parsimonious explanation for why BIs are violated.harrylin said:Then according to you, Bell's theorem (BI => "no local deterministic hidden-variable theory can reproduce all the experimental predictions of quantum mechanics") is basically wrong or misunderstood?
The lhv's aren't irrelevant physically wrt the individual data streams, but they're irrelevant or superfluous wrt an accurate statistical accounting of the correlation between θ and rate of coincidental detection. My current line of thinking about it might be wrong, but I just have this nagging feeling that the effective reason why BIs are violated, and the correct interpretation of Bell's work, has to do with something much more mundane than that nature is nonlocal or that lhv's don't exist.harrylin said:... it does not make sense to require a theory to model an effect by means of irrelevant variables - that is a false requirement!
Ok, thanks for your comments, JesseM. Not wanting to derail this thread any more, I'm going to go over our discussion in this thread and will probably start a new thread on it, but this will take longer than I originally thought it would.JesseM said:ThomasT, I can't edit the post any more, but when I wrote this:
JesseM said:But "relationship between their motional properties is due to their being emitted in opposite directions from the same atom during the same transition" is still very vague, it doesn't tell me what this "due to" consists of--for example, whether you are imagining that "due to their being emitted in opposite directions" they were assigned the same properties at birth and just carried these unchanging properties with them to the location of the measurements (which of course would mean the properties were local hidden variables, so that's ruled out by Bell), or if "due to their being emitted in opposite directions" they were given an FTL connection that causes any measurement on one to instantly affect the other, or some other picture of exactly how their common emission explains later correlations.
...I should have said "which of course would mean the properties were local variables, so that's ruled out by Bell", as the properties that each particle carries with them may not necessarily be hidden ones, and as I explained Bell's proof rules out all local realist explanations regardless of whether they involve hidden or non-hidden variables.
JesseM said:I think as long as you are willing to listen to arguments as to why your argument might be flawed, it should be OK to post. Keep in mind though, the idea is that on each trial the experimenters choose randomly which of the 3 angles a, b, c to use, in a way that's uncorrelated with which of the 8 hidden states occur on that trial, and that it must be true that whenever they pick the same angle, they get the same result (which is guaranteed as long as you assume the possible hidden states of the particle pair must be one of the 8 listed in the wikipedia article, rather than other possibilities where not all the hidden states are opposite for Alice and Bob, like if Alice's state was +++ while Bob's was +--) And do you understand that if Alice chooses angle a and Bob chooses angle b, it must be true that P(a+, b+) is equal to P3 + P4 since those are the only probabilities corresponding to hidden states which have + in the a-column of Alice's particle and + in the b-column of Bob's particle? Likewise if Alice chooses a and Bob chooses c, then P(a+, c+) = P2 + P4, and if Alice chooses c and Bob chooses b, then P(c+, b+) = P3 + P7. If all the probabilities have non-negative values, it should be obvious that you can't come up with any values for the probabilities that don't satisfy P3 + P4 ≤ (P2 + P4) + (P3 + P7), since this can be rearranged as
(A) (P3 + P4) ≤ (P3 + P4) + P2 + P7 and neither P2 nor P7 can be negative. [Emphasis and identifier added by JenniT.]
edit: another option would be to just say what part of this argument isn't making sense to you...presumably you are not claiming you can find non-negative values for P2, P3, P4, P7 which fail to satisfy (P3 + P4) ≤ (P3 + P4) + P2 + P7 so there must be some earlier point in this argument, like maybe the step that says P(a+, b+) = P3 + P4 and P(a+, c+) = P2 + P4 and P(c+, b+) = P3 + P7, that's different from what you had when you were analyzing the problem.
OK, but do you agree that in a LHV theory, in order to explain how the two experimenters always get the opposite results when they pick the same angle (and they are picking angles at random), it must be true that each time the source sends out a particle pair, it must create them with LHV that predetermine what their results will be for any possible angle, in such a way that they each are guaranteed to have opposite predetermined results for every angle?JenniT said:Thanks Jesse, your attention to explanatory detail is to be applauded. It is much appreciated. (A) is the very point that I planned to address -- a very clear impossibility.
My idea is to show that (A), an impossibility, is not mandated by all local realistic hidden-variable theories.
JesseM said:OK, but do you agree that in a LHV theory, in order to explain how the two experimenters always get the opposite results when they pick the same angle (and they are picking angles at random), it must be true that each time the source sends out a particle pair, it must create them with LHV that predetermine what their results will be for any possible angle, in such a way that they each are guaranteed to have opposite predetermined results for every angle?
If that's the case, then whatever the hidden variables may be, if we are only interested in the predetermined results for three possible angles a, b, and c, every combination of hidden variables should fall into one of the following 8 categories:
1. Particle 1: a+ b+ c+ / Particle 2: a- b- c-
2. Particle 1: a+ b+ c- / Particle 2: a- b- c+
3. Particle 1: a+ b- c+ / Particle 2: a- b+ c-
4. Particle 1: a+ b- c- / Particle 2: a- b+ c+
5. Particle 1: a- b+ c+ / Particle 2: a+ b- c-
6. Particle 1: a- b+ c- / Particle 2: a+ b- c+
7. Particle 1: a- b- c+ / Particle 2: a+ b+ c-
8. Particle 1: a- b- c- / Particle 2: a+ b+ c+
...where, for example, if the hidden variables fall into category #4 that means they predetermine that particle 1 will give + if angle a is chosen, - if angle b is chosen, and - if angle c is chosen, while particle 2 is predetermined to give the opposite result for each angle. Of course the hidden variables can be much more complicated than this, so just knowing that they fall into category #4 doesn't tell you the full value of all hidden variables (for example it doesn't tell you what the predetermined result would be for some different angle d), but even if there are an infinite number of distinct possible hidden-variable states, each one must fall into one of the eight categories above depending on its predetermined results for angles a, b, and c.
If you don't see why this would necessarily be true in a LHV theory, please explain the specific point you would dispute--for example, do you disagree that the hidden variables must give a predetermined result for each possible angle in order to explain how the experimenters always get opposite results whenever they pick the same angle?
JenniT said:I'm about to lose power for 6+ hours; will get back to you.
ajw1 said:For several years Joy Christiaan has been publishing about the disproof of Bell in a typical EPR setup, his latest (?) publication being http://arxiv.org/PS_cache/arxiv/pdf/0904/0904.4259v3.pdf" .
In a nutshell his argument is that Bell uses an invalid topology for the EPR elements of reality (1D instead of 3D). When using Clifford algebra the author says he can reproduce the Bell inequalities.
Does he have a valid argument here?
This http://www.physics.utoronto.ca/~aephraim/2206/Sprague-ChristianDisproofBell.pdf" further summarizes his arguments
ps. I haven't seen his articles being published somewhere else then Arxiv, but Carlos Castro references him claiming about the same http://www.m-hikari.com/astp/astp2007/astp9-12-2007/castroASTP9-12-2007.pdf" .