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Why the De Raedt Local Realistic Computer Simulations are wrong

by DrChinese
Tags: local, raedt, realistic, simulations
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Varon
#55
May1-11, 05:11 PM
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DrChinese, I'm also interested in the same paper (mentioned in the message just before this) that alleged that Bell's Theorem was wrong and really supported Local Realism. Were you able to find a flaw after 4 months of analyzing it? If you can't find a flaw, then Bell's Theorem is refuted and local realism holds? This is important as proof of the paper claims can refute even Aspect experiment, etc. and entertain the possibility of local hidden variables and let us return back to the days of Einstein EPR.
DrChinese
#56
May2-11, 08:52 AM
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Quote Quote by Varon View Post
If you can't find a flaw, then Bell's Theorem is refuted and local realism holds? This is important as proof of the paper claims can refute even Aspect experiment, etc. and entertain the possibility of local hidden variables and let us return back to the days of Einstein EPR.
I have not read it to the depth I want yet. It is not going to overturn Bell anyway. If you are imagining a return to the days of EPR (1935), I would recommend you buy some Louis Armstrong records.
harrylin
#57
Jun16-11, 06:29 AM
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Quote Quote by daezy View Post
Since this thread is about de Raedt.. what do you guys think of his paper "Extended Boole-Bell inequalities applicable to quantum theory" in which he stated that:

"Our proofs of the EBBI do not require metaphysical assumptions
but include the inequalities of Bell and apply to
quantum theory as well. Should the EBBI be violated, the
logical implication is that one or more of the necessary conditions
to prove these inequalities are not satisfied. As these
conditions do not refer to concepts such as locality or macroscopic
realism, no revision of these concepts is necessitated
by Bell’s work. Furthermore, it follows from our work that,
given Bell’s premises, the Bell inequalities cannot be violated,
not even by influences at a distance.".

Does it mean Bell's Theorem is wrong? Hope DrChinese who is familiar with de Raedt work can comment esp if he has read the paper with links at
http://arxiv.org/PS_cache/arxiv/pdf/...901.2546v2.pdf

This link has been posted before here months ago and it is a valid argument and not crackpottry so hope it won't be removed by the moderators. Many Thanks.
The topic of that paper is quite different from the topic of computer simulations; please don't mix different topics. As it's now officially been published, a thread on that paper's discussion of Boole-Bell inequalities was started here:
http://physicsforums.com/showthread.php?t=499002
DevilsAvocado
#58
Jun16-11, 06:41 PM
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Quote Quote by DrChinese View Post
If you are imagining a return to the days of EPR (1935), I would recommend you buy some Louis Armstrong records.
Yup, that’s the way to do it.

May I just add that there’s one variable missing to get this kind of realism working; Varon also need to update his gear and get an authentic phonograph. I guess any local dealer could help him out, they often keep this stuff in the basement, hidden under 9″ of dust.




... or one could just make it easy and watch The Return of the Living Dead – it will have the same effect ...
DrChinese
#59
Jun17-11, 08:51 AM
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Love it!
DevilsAvocado
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Jun17-11, 09:02 AM
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harrylin
#61
Apr26-12, 01:58 PM
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Thanks for the link!
Again it is a completely artificial mechanism, so what you call it is completely irrelevant. When talking about a suppression mechanism, I may call mention Detector Efficiency while they call it Coincidence Time Window.
If I hear you correctly, what you call "detector efficiency" (which refers to a physical characteristic of the detector) is in fact the data picking by means of the time window - that is, a human choice.
But nothing changes. There is no more one effect than the other. As you look at more of the universe, you get farther and farther away from the QM predictions and that never really happens in actual experiments.
To the contrary, their simulation matches Weihs' experiment rather well on exactly that issue. That topic is discussed here: http://physicsforums.com/showthread.php?t=597171
So the Suppression Mechanism must grow if you DO want it to match experiment! And THAT is the Unfair Sampling Assumption.
Now THAT is a less well defined term. Perhaps most people mean with the Unfair Sampling Assumption a detector characteristic, but I agree with you that their model is based on an unfair data picking explanation. That could equally well be called an Unfair Sampling, or more precisely, Sub-sampling Assumption.
DrChinese
#62
Apr26-12, 02:17 PM
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Quote Quote by harrylin View Post
If I hear you correctly, what you call "detector efficiency" (which refers to a physical characteristic of the detector) is in fact the data picking by means of the time window - that is, a human choice.
It was an incorrect use of language on my part. Mentally, I group all models in which there is some bias which causes the accepted sample to differ sufficiently from the universe as a whole. But there are definite legitimate differences between the models.

So my apologies. I will use the term "coincidence time window" instead of detector efficiency, with the understanding that in a computer simulation, some of this is arbitrary. If it were to be considered a candidate model, you would want to challenge whether such an effect really existed. Specifically, how does the photon get delayed without losing its entangled characteristic (i.e. perfect correlations)? Because if it lost that, it should NOT be considered at all.

If you vary the k= setting (in the spreadsheet, tab B. Entangled) from 1 to 30 to 100 you will see how things change in a very unphysical manner.
harrylin
#63
Apr27-12, 12:41 PM
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Quote Quote by DrChinese View Post
[..] Mentally, I group all models in which there is some bias which causes the accepted sample to differ sufficiently from the universe as a whole. But there are definite legitimate differences between the models. [..]
Good to see that we now agree on this, and apology appreciated.
I will use the term "coincidence time window" instead of detector efficiency, with the understanding that in a computer simulation, some of this is arbitrary. If it were to be considered a candidate model, you would want to challenge whether such an effect really existed. Specifically, how does the photon get delayed without losing its entangled characteristic (i.e. perfect correlations)? Because if it lost that, it should NOT be considered at all.
That is exactly the kind of things that I try to discuss in the thread on "ad hoc" explanations. However, if I'm not mistaken it was you who pointed out that certain interactions do not or hardly affect entanglement.
If you vary the k= setting (in the spreadsheet, tab B. Entangled) from 1 to 30 to 100 you will see how things change in a very unphysical manner.
I'll try that.
DrChinese
#64
Apr27-12, 02:14 PM
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Quote Quote by harrylin View Post
That is exactly the kind of things that I try to discuss in the thread on "ad hoc" explanations. However, if I'm not mistaken it was you who pointed out that certain interactions do not or hardly affect entanglement.
That is true, generally I would not expect that the transport mechanism would be much of a factor. However, I guess it is *possible* that one photon could have an interaction that would reveal its spin (of course not to us) AND delay it both. If that case occurred, for example, it correctly should not be considered as the pair is no longer entangled on the polarization basis.
DrChinese
#65
Apr27-12, 03:28 PM
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By the way, this thread is dredged up from some time ago. I would like to say that the de Raedt team was kind enough to work with me to refine my spreadsheet model. After they supplied me with some modifications to their original Fortran code, my primary objection* to their model disappeared. I have not come to understand why it was able to accomplish that feat - simply because I have not devoted the time to the matter.

So while I disagree with Hans and Kristel on the conclusions that should be drawn from the model, I agree with its operation.

Here is the link to the Excel spreadsheet model:

http://drchinese.com/David/DeRaedtCo...hPhotons.C.xls




* Which had to do with a specific case of PDC simulation, not the general case.
billschnieder
#66
Apr27-12, 04:22 PM
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Quote Quote by DrChinese View Post
I have not come to understand why it was able to accomplish that feat - simply because I have not devoted the time to the matter.
...
[b]So while I disagree with Hans and Kristel on the conclusions that should be drawn from the model, I agree with its operation.
So you agree with the way it works although you do not understand why it works but you disagree with their conclusion nonetheless?

If you could be kind as to explain why you disagree with their conclusion, despite agreeing that their model is local and realistic, then we can discuss that.
DrChinese
#67
Apr27-12, 05:10 PM
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Quote Quote by billschnieder View Post
If you could be kind as to explain why you disagree with their conclusion, despite agreeing that their model is local and realistic, then we can discuss that.
There are a lot of problems with the model when you talk about it as more than a computer simulation. I.e. if you want to consider it as somehow corresponding to something physical. Hard to know where to begin really, so here are my opinions for what they are worth:

The good:
- It is 100% local and realistic, so no issue there.
- It does violate a Bell Inequality, so it succeeds there.
- It did model product state statistics correctly when it needed to, which was my original objection to the simulation itself.

The bad:
- It posits physical effects that are new, and subject to experimental rejection or confirmation (don't hold your breath on that one).
- It only matches experiment when the window size is very small, otherwise it deviates quite quickly towards the Bell boundary.
- It beats the Bell Inequality when the window size is made to be medium, but only barely.
- And most telling, it does not match QM for the full universe. Now, you don't seem to think this is a problem but it really is quite serious for a model of this type. Because there would be tests that could be constructed to exploit this difference. This is part of the reason that the team has attempted to construct further simulations to take things a few steps farther.
- It does not match the dynamics of actual data when the time window is varied. I.e. it is obviously ad hoc.

-DrC
billschnieder
#68
Apr27-12, 08:56 PM
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Quote Quote by DrChinese View Post
- It only matches experiment when the window size is very small, otherwise it deviates quite quickly towards the Bell boundary.
Just like the experiments it is modelling.

- It beats the Bell Inequality when the window size is made to be medium, but only barely.
Just like the experiments it is modelling

- And most telling, it does not match QM for the full universe. Now, you don't seem to think this is a problem but it really is quite serious for a model of this type. Because there would be tests that could be constructed to exploit this difference.
There is no such thing as QM prediction for "full universe". QM only makes predictions about actual measurement outcomes.

- It does not match the dynamics of actual data when the time window is varied.
Just like the experiments it is modelling. QM doesn't match the experiments either when the time window is varied.
DrChinese
#69
Apr30-12, 09:05 AM
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Quote Quote by billschnieder View Post
1. There is no such thing as QM prediction for "full universe". QM only makes predictions about actual measurement outcomes.

2. Just like the experiments it is modelling. QM doesn't match the experiments either when the time window is varied.
1. Of course it does. The expectation is cos^2(theta) always. But that is not the case with the De Raedt et al model.

2.Not so! Otherwise it wouldn't be an issue.
billschnieder
#70
Apr30-12, 10:53 AM
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Quote Quote by DrChinese View Post
1. Of course it does. The expectation is cos^2(theta) always. But that is not the case with the De Raedt et al model.

2.Not so! Otherwise it wouldn't be an issue.
1) cos^2(theta) is the expectation value for OUTCOMES. QM does not predict anything other than what is observed!!!!! You change the time window you get a DIFFERENT observation!!! Looking at stuff that is not observed and calling ing "full universe" is simply wrong-headed.
2) This is false. Look at figure 2 in their article in which they analyze the actual experimental data, varying the window: http://arxiv.org/pdf/1112.2629v1.pdf. QM is violated by 5 standard deviations!
harrylin
#71
May2-12, 09:31 AM
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Quote Quote by billschnieder View Post
1) cos^2(theta) is the expectation value for OUTCOMES. QM does not predict anything other than what is observed!!!!! You change the time window you get a DIFFERENT observation!!! Looking at stuff that is not observed and calling ing "full universe" is simply wrong-headed. [..]
While De Raedt et al's simulation did succeed in its intended purpose, it does appear that in principle (and likely also in practice) their model makes slightly different predictions from QM. That may allow for a comparison of both with existing data, as is intended in the thread on "Weih's data" (should have been Weihs' data).
DrChinese
#72
May2-12, 10:44 AM
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Quote Quote by billschnieder View Post
1) cos^2(theta) is the expectation value for OUTCOMES. QM does not predict anything other than what is observed!!!!! You change the time window you get a DIFFERENT observation!!! Looking at stuff that is not observed and calling ing "full universe" is simply wrong-headed.
"Full universe" is what they usually call the portion that is not included in a sample (along with the sample itself of course). What do you call that? Because QM makes the same prediction for everything, while the de Raedt et al model does not. In that model, there is always a difference between the sample and the full universe.


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