# Talk:Bell test experiments

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## Proposal to archive talk page

It seems to me that it is time to move the existing discussion into an archive subpage. Especially since Caroline Thompson died of cancer died last year, the ongoing debate between her and others comes to an end. I do not agree with many of her opinions but I very much admire her scientific attitude in not accepting "accepted wisdom" but remaining critical and innovative.

Secondly, I have recently edited the end of the entry on loopholes. I do not mean to say anything controversial there, nor do I intend to blow my own horn. I do just to emphasize that no loophole free experiment has been done yet and there do exist serious and respected scientists who make something of this, without necessarily doubting QM in any way. Gill110951 08:12, 1 December 2006 (UTC)

Agreed. I have begun an edit of the loopholes page as well, and done just that with the talk page of the loopholes page. Jan-Åke Larsson 07:52, 6 December 2006 (UTC)

## From here, start of talk page as it was before

Gill110951 08:12, 1 December 2006 (UTC)

Sorry, Dr Chinese, once again I hit a wrong button and saved my reversion before I could justify it! What I was going to say is that (as you well know) experiments cannot be said to have confirmed QM because no valid Bell test has yet been done. Experiments so far fail to discriminate between QM and local realism. Caroline Thompson 22:37, 28 Jan 2005 (UTC)

Caroline: Don't expect any debate on this, because there won't be any. Reverting AGAIN.
Everyone else: Please refer to the Bell's Theorem talk page as there is no point in repeating the identical arguments on each page.
I went ahead and didn't revert, but I did add enough to make it clear it is the authors of the experiments themselves that are doing the claiming. If CT believes they are lying, well that's another matter. In that case, I wish she would notify the authorities immedialtely.
If DrChinese and goes ahead and reverts back, I'm OK with that. It is just tendentious to state "it is claimed" as though it was some clueless bystander who is making these claims.CSTAR 23:34, 28 Jan 2005 (UTC)
Cstar, I am going to take out the "claimed" part because all knowledge is in fact claims. It has the effect of implying that the position is accepted by a minority of scientists, which is not the case. It is one of the subtle ways Caroline has inserted her POV. I am not on a semantic witchhunt, but so much of some of these articles have strange stuff inserted in them that it would be easy for a casual reader to walk away with an erroneous impression. I do plan to return here and insert some of the latest findings ruling out local reality as recent tests have significantly improved on detection and other elements of the tests. Virtually all come up with similar numbers for experimental violations of Bell's Inequality.
I just wanted to correct the "it is claimed" (implying it was a third party conspiracy) while avoiding a revert war.CSTAR 01:17, 29 Jan 2005 (UTC)

I hope everyone agrees with my modification. It is simply not correct to say that experiments give unqualified support to QM. And if you read the actual experimental reports you will find that the experimenters themselves always add qualifications, such as "modulo the fair sampling assumption".Caroline Thompson 10:01, 29 Jan 2005 (UTC)

As stated and within this context, acceptable to me.--DrChinese 15:12, 29 Jan 2005 (UTC)

Caroline: it would be best that you stay out of this article. I plan to rework it so that it makes sense again, and that almost certainly involves reversing just about anything you do. It is a gross waste of time to be worrying about every little edit you make and whether it reflects your biased POV. Do not consider that my NOT reverting every change you make as some endorsement or tacit agreement. Please note that I will be including the state of the art on Bell tests now that local reality is excluded by perhaps a hundred standard deviations. You may rest assured that your attempts to introduce doubt and bias will again be reversed. I will not be debating the subject as this is more properly done outside WP. You should be ashamed of what you have done here in the name of "the end justifies the means". The rest of us operate here in good faith while you make a mockery of the system. I would instead encourage you to state your POV on your personal website where the opinion of the scientific community is not a factor.--DrChinese 04:25, 11 Feb 2005 (UTC)

Dr Chinese, the number of standard deviations is totally irrelevant. I hope that Caroline has taught you something ... Gill110951 08:16, 1 December 2006 (UTC)

## Introductory paragraph needed

Now that the Loopholes material has been moved here, I have eliminated a gross over-abundance of discussion of the loopholes for a more concise presentation. This includes removing Caroline's self-references which are now no longer appropriate in this context. Before my changes, Thompson was the most cited author in the field (as presented LOL) and loopholes included substantially more text that of the experiments themselves. As Thompson is not the original proponent of most of the loopholes, I do not plan to reference her. The loopholes section should be a footnote to the wonderful experiments which are now in the literature.--DrChinese 23:24, 12 Mar 2005 (UTC)

DrChinese: I'm not sure if your reference to Caroline Thompson in the article is a good idea. Should she have her own article in WP? Writing such an article won't be easy, particularly since anything written about her could be considered as a personal attack. CSTAR 23:45, 12 Mar 2005 (UTC)

## Technical difficulties

Is anyone else experiencing this problem? The displayed page has first section "Conduct of Bell test experiments" whilst the text version I find when I try and edit it starts with the section "The Bell inequalities". The displayed version has a little on the loopholes, the text version almost none!

I trust that the info on the various inequalities is intended to be included eventually, though quite where is still a moot point. Caroline Thompson 20:09, 13 Mar 2005 (UTC)

Something is going wrong! The present edition goes from section 4 (Notable experiments) back to section 1 (Hypothetical loopholes), and is still inconsistent when display is compared to text for editing. Caroline Thompson 23:08, 13 Mar 2005 (UTC)
Problem solved: trouble-shooting page told me it was a problem with Microsoft Internet Explorer and the use of cache pages. Solution is to use Ctrl + F5 to download page direct from internet. Caroline Thompson 10:07, 15 Mar 2005 (UTC)

## Nobody is playing games

Re my reversion: Dr Chinese, my edits were necessary! I don't think you can have noticed that the page you reverted to contained next to no information re the actual inequalities. I think the section had been omitted by mistake. It has to be there, otherwise links from, for example, Bell's theorem, offering info on the inequalities do not make sense.

In case you had not realised, what I am trying to do is improve the quality of information put out by wikipedia. I am trying to ensure that adequate refs are given, demonstrating that wikipedia attempts to check its facts and does not merely regurgitate opinions, especially when it comes to the hard science of physics. Caroline Thompson 16:39, 14 Mar 2005 (UTC)

So you've reverted again, Dr Chinese! This is irresponsible, since the your version does not meet the requirement of telling the reader details of the Bell inequalities.
As you will see, I've done a small edit to suggest where such details should be found. Caroline Thompson 22:29, 14 Mar 2005 (UTC)

Caroline, please cool down. Do something else on Wikipedia. Or put your POV into Wikinfo. Or on your site. If your POV is relevant or will become relevant due to new insights you may offer on your own website, somebody else will come and put it back into the Wikipedia articles. But as long as you are the only editor, wanting to insert it, you should accept that it is unencyclopedic for now. --Pjacobi 22:57, 2005 Mar 14 (UTC)

Pjacobi: My earlier comment was in error, due to the technical problems and various ambiguities. Please recognise that I am merely trying to ensure that wikipedia checks its facts, gets its links right and gives sufficient references.
So you've reverted again, Dr Chinese! Those same "technical difficulties", though, are still preventing me from knowing just what your version entails. The displayed version shows no section on Bell inequalities; the text to be edited still shows no section on Hypothetical loopholes! However, it is clear that this section is in error as regards "fair sampling".
1. It was not only Vaidman who dismissed the Rowe et al experiment as a valid Bell test. The was considerable discussion on the matter in sci.physics.research, and various subsequent articles have agreed that the "locality" loophole was wide open, and all loopholes need to be closed at once for the result to count. See for instance:
Grangier, Philippe, “Count them all”, Nature 409, 774, 15 February 2001
2. I realise that you have now decided that no ref to my own papers (in particular, my original Chaotic Ball paper, http://arXiv.org/abs/quant-ph/9611037) is to be allowed here. What, though, is your objection to a ref to Pearle's 1970 paper on the effect of missing detections?
Re the subtraction of accidentals, would you have any objection to a ref by Wesley that makes the same point as my article at http://arXiv.org/abs/quant-ph/9903066 (though based on less information, since Wesley had not seen Aspect's thesis)?
Caroline Thompson 23:32, 14 Mar 2005 (UTC)

Caroline, again. I'll revert your additions. The VfD result was redirect, no merge. Please don't insert something based on your opinion alone. As long as you are the one single editor, who want's this stuff in, I see no proof of relevance. If you consider it nexecessary, you may want to try Wikipedia:Conflict resolution. --11:48, 2005 Mar 15 (UTC)

My understanding of the VfD result was that essential material from Bell inequalities was to be incorporated into [[Bell test experiments], and existing links imply that this will be so. The reason some kind of exposition of the inequalities is needed is that many popular accounts talk only of Bell's original inequality, or of the Wigner-D'Espagnat inequality, and these are never in practice used. The intelligent reader surely deserves to be told this, as interpretation of the statement that an experiment "violated a Bell inequality" depends on which inequality we're talking about. The text books may not be aware of this, but is that sufficient reason for wikipedia to suppress the facts?
As things stand, at least two pages have been left effectively orphaned: GHZ experiment and Sakurai's Bell inequality (which in fact covers the Wigner-d'Espagnat inequality).
You are probably right, in that I shall need to take the matter to conflict resolution. Even my most reasonable edits are being reverted. I can't even remove a circular link! Caroline Thompson 22:27, 15 Mar 2005 (UTC)
Caroline, you are a terrible listener. Yours changes continue to reflect your biased POV. Changing the referenced author from yourself (which was ridiculous on the face of it) to someone else changes nothing. These issues have already been substantially discussed AD NAUSEUM by us and the VfDs reflect a consensus of opinion. You pretend that your "minor" "harmless" edits are reverted; but your make so many POV edits that it is impossible to separate them. My recommendation follows that of the others: take your POV elsewhere and leave Wikipedia alone. I will continue to revert every edit you make because it is not worth my time to keep 1 edit and roll back the other 5. You are playing games by pretending otherwise when you know perfectly well how the rest of us feel. The debates are OVER.--DrChinese 15:49, 16 Mar 2005 (UTC)

## Link to Bell's original inequality page

Dr Chinese, how can you justify your reversion, eliminating this link? There was no subterfuge!

Allow me to repeat the question I put in the discussion at http://en.wikipedia.org/wiki/Wikipedia:Votes_for_deletion/Log/2005_February_25#Bell_inequalities: What part of Bell inequalities is considered to be original research?. Nobody answered this, and nobody in fact gave any reason at all for eliminating the page by a re-direction.

How can it make sense for wikipedia to tell readers details of only one of the Bell inequalities? If, as is the case, Bell's original one is never in fact used, how can you justify not telling the reader what the inequality is and what different assumptions are involved?

You expressed the opinion in the VfD discussion that the page Bell's inequalities did not "add value", but there are real differences between the various inequalities and they are critical to the interpretation of claims to have violated them. If you doubt this, please read Gisin and Gisin's paper:

Gisin, N and B Gisin, “A local hidden variable model of quantum correlation exploiting the detection loophole”, Physics Letters A 260, 323-327 (1999), http://arxiv.org/abs/quant-ph/9905018

I assume you are already familiar with Clauser and Horne's 1974 paper, explaining the assumptions necessary in a usable inequality?

Clauser, J F and Horne, M A, “Experimental consequences of objective local theories”, Physical Review D, 10, 526-35 (1974)

To return to the case in point, the page Bell's original inequality is surely neutral so far as any controversy re NPV is concerned. It contains no original research. There is no mention of my work, only of Bell's own paper. Unless someone gives a valid reason otherwise, I propose to re-revert. Caroline Thompson 17:28, 21 Mar 2005 (UTC)

## Fair sampling

I've made just very slight changes to the wording and added two refs.. I have done my best to ensure that the result is "neutral". I hope Dr Chinese will refrain this time from his usual reversion.

Incidentally, he might like to bear in mind that it is my time that is being wasted as much as anyone else's! Facts are facts and an enclyclopaedia has no real excuse for suppressing them. [This remark applies more to the various Bell inequalities than to the current edit, which is, I hope, not controversial.] Caroline Thompson 10:42, 22 Mar 2005 (UTC)

Dr Chinese, your reversion here was ridiculous. I know you will revert again but I hope you realise how silly this makes you look! All I did was improve the section, making it more accurate and adding refs. And while I was about it, of course, I removed that circular link near the beginning of the page. Caroline Thompson 18:56, 22 Mar 2005 (UTC)
Caroline, of course I reverted again and I will continue to do so. This is a repeat of previous discussion and you are wasting our time while you play games. You placed text, refs and/or links with no real purpose other than to question QM in favor of your local realitistic POV. This will not stand and I am not going to edit every word you write with the idea that some can stay in and some get eliminated. Correct a spelling error and it stays in. Anything else will likely be reverted and I will always do it in toto. The participants in this area have already spoken on your contributions... and loudly: VfD and reversion.--DrChinese 19:31, 22 Mar 2005 (UTC)
Have it your own way, Dr Chinese! I'd just like to make it clear that what you have succeeded in doing is producing a set of pages that is inferior to those you replaced. If a reader now asks for "Bell inequalities" he is sent to Bell's theorem, which tells him about only the one, and that in a confused and misleading fashion. If he wants to know about the various "Bell test loopholes" he is no longer given any useful refs.. The refs in both Bell's theorem and Bell test experiments no longer exactly match the text. Above all, Bell's theorem is not presented in the manner that Bell himself did, starting from the notion of hidden variables and concentrating on the local realist pov, but is obfuscated by unnecessary mathmatics and emphasis on the QM model. The whole balance of the page has swung in favour of the QM pov, whereas it ought to give equal weight to local realism.
And that notation of CSTAR's in Bell's theorem is just plain bad! Why on earth use X and Y to mean simply two different settings, not orthogonal ones? Caroline Thompson 22:26, 22 Mar 2005 (UTC)
Because names are purely conventional; nothing says X, Y have to refer to orthogonal entities of any kind. CSTAR
See my comment in the Bell's theorem discussion (under heading "Sorry CSTAR, but you are wrong!"). After much thought I've come to the conclusion that this is yet one more place where the page shows extreme bias towards the quantum-mechanical point of view. There can be no excuse for this. There is no reason the page should not follow the same kind of reasoning (and notation!) Bell himself used. There is no need to even mention the use of "operators" in any section other than the one specifically concerned with the QM formula. Caroline Thompson 09:03, 29 Mar 2005 (UTC)
Caroline, giving equal weight to your POV has already been debated and you lost. Why keep it going? The rest of us are just as determined as you are. We are trying to clean up the mess YOU created, and we could do a better job without your constant meddling. As it is, we are trying to hit a moving target. If there are some link, grammar, spelling or even substantive issues, we will address without you. Of course, I know you will not be satisfied without the final word. So please, could you give us your FINAL word and then be done with it? --DrChinese 22:37, 22 Mar 2005 (UTC)
I'll be back when I've rallied my troops! Caroline Thompson 09:33, 23 Mar 2005 (UTC)
Troops? CSTAR
Don't bother, you will find that it will not change a thing. Sock puppets and their equivalents do not matter here.--DrChinese 17:25, 23 Mar 2005 (UTC)

## Removal of pov? No, attempted suppression of relevant facts!

Dr Chinese, your reversions are totally out of order! The most recent edit you've removed did not assert any controversial fact. It merely stated that David Elm was among those who thought that there might well be bias in the sample, and gave as useful link. Not that I find this link quite as useful as one to my own work, but, for what it's worth, let's put both on record here:

David Elm's work (copied to the "cycles" web page and accompanied by remarks by Ray Tomes and Ratko Tomic): http://www.cyclesresearchinstitute.org/physics/elm.html

My own most recent paper on fair sampling: C H Thompson and H Holstein , “The ‘Chaotic Ball’ model, local realism and the Bell test loopholes”, http://arxiv.org/abs/quant-ph/0210150

What possible excuse can wikipedia have for making it difficult for its readers to find out the facts? Caroline Thompson 10:06, 12 Apr 2005 (UTC)

### Facts relating to the Bell test loop-holes

Gentlemen, why are you attempting to sanitise the information summarised by Caroline Thompson to conform to your own POV's concerning this environment of related issues. Separate pages relating to the integrity exceptions in modern science should be encouraged in an encycopaedic work of this nature, not listed as requiring deletion due to non-conformance to contemporary "beliefs".

I will not support further MERGE and DELETION of CT's work, and I believe that in all fairness, there is a place in WIKI to hold scholarly summary representations of known integrity exceptions relating to the fundamental experiments of QM, which is exactly what CT has been doing with the "LOOP-HOLES" page, and others.

I suggest that in all fairness Wiki is able to present a number of separate POV on this range of issues, and that there is a place for the exposition of CT's view. This essentially translates to cutting some slack on additional (non-merged) specific pages, such as one related to LOOP-HOLES in the Bell Test experiments. ---- User:PRF Brown

First, the issue of non-standard POVs is unrelated to this specific area of Wikipedia. It should be discussed and debated elsewhere. Standard Wikipedia policy is followed here. Second, the essential element of Caroline's work is that she bring no new facts to the table. She denies the validity of accepted, published experiments. So her universe of relevant information is smaller than that of the rest of us.--DrChinese 14:15, 19 May 2005 (UTC)
Hmmm ... Are you saying that wikipedia pages cannot contain any "new facts"? What on earth can you mean?
It is not appropriate in this encyclopaedia to put things quite as strongly as you suggest: I don't "deny the validity of accepted ... experiments". I merely want to point out that they are not as thoroughly accepted by the experimenters themselves as the public is led (by authors such as Roger Penrose, Amir Aczel and numerous others) to believe. The experimenters are aware of the loopholes and of the need to continue to search for a loophole-free test.
All I'm trying to do is make sure that wikipedia presents a comprehensible set of pages, with sensible links. At present we find links to "loopholes" that lead to the present page, which tells the reader hardly anything on the subject and does not give any useful references. What is wrong with devoting a page to the subject?
And BTW, Dr Chinese, when are you and CSTAR going to re-write Bell's theorem? It's currently a mess! Caroline Thompson 21:06, 19 May 2005 (UTC)
I have been watching this page for a while, and I am getting tired of all this. Dear Caroline. I don't know anything about quantum mechanics. But it seems to me you are wasting your time and the time of everybody else. You better go and publish papers, give talks at conferences and stuff like that. Once your work gets recognized and appreciated, somebody else will certainly come and make sure this article reflects the current scientific knowledge on the subject. Wikipedia is not the place to push your theories. Do it in the proper place. Oleg Alexandrov 21:41, 19 May 2005 (UTC)
Amazing! That comment above SAYS IT ALL! I'm currently refreshing my knowledge on quantum mechanics (thus I'm not yet ready to discuss the fine details), and I'm also interested in psychology. Now here someone who "doesn't know anything about quantum mechanics" nevertheless thinks that scientists who claim that "loopholes" are an important subject "push their own theories". Possible cause for that miscomprehension: misinformation in Wikipedia... In contrast, see for example the opinion of an expert in this field,
http://www.gap-optique.unige.ch/Members/Nicolas/Resume.htm :
"All experiments to date are in perfect agreement with quantum theory. There is thus strong evidence for the view that Nature is nonlocal. However, [...] There is one logical loophole affecting all the experiments carried out so far that deserves special attention. This is the ”detection loophole” [...] it is annoying that this loophole resists after almost 30 years [3] of research and progress!"
http://arxiv.org/abs/quant-ph/9905018
(current version dated "August 30, 2005)
-> Should such statements not have a central place in the article? Of course, it's possible that the date is misleading and that by now prof.Gisin has changed his opinion. I'll ask him!
-> And who is this "DrChinese"? It was me who reverted to the text of CT that he/she deleted and messed up without valid motivation. I agree with the first comments above, and now also I will support NO MORE of that, as I'm only polite to gentlemen! See also the Wikipedia Rules - Harald, Lausanne, 10 October 2005.
Ugh. This is like a chronic flu.--CSTAR 21:54, 19 May 2005 (UTC)
CSTAR: Even Dr Chinese has now implied that he would favour John Bell's own derivation of his inequality rather than the one you use. Moreover, as I've pointed out, the Bell's theorem page prints out badly. The diagrams are inferior to the ones I had provided, and are also misleading. The layout it poor. The content as regards the derivation of the CHSH inequality is disputed.
Oleg: When I've tried to publish in journals such as Physical Review Letters I have been told that all that I am saying is already "well known"! How can you say it is not "current scientific knowledge"? Anyway, my work has been published but not in mainstream journals. Because of the effectively complete block by PRL and PRA on all papers regarding the loopholes, I have instead written to many of the experimenters individually. Many have responded. Some, for example John Rarity, have commented favourably, saying my exposition of the detection loophole was the best around.
For your information, the PRA's editorial policy statement (quoted at the head of my bibliography page) includes:
"In 1964, John Bell proved that local realistic theories led to an upper bound on correlations between distant events (Bell's inequality) and that quantum mechanics had predictions that violated that inequality. Ten years later, experimenters started to test in the laboratory the violation of Bell's inequality (or similar predictions of local realism). No experiment is perfect, and various authors invented "loopholes" such that the experiments were still compatible with local realism. Of course nobody proposed a local realistic theory that would reproduce quantitative predictions of quantum theory (energy levels, transition rates, etc.).
This loophole hunting has no interest whatsoever in physics. It tells us nothing on the properties of nature. It makes no prediction that can be tested in new experiments. Therefore I recommend not to publish such papers in Physical Review A. Perhaps they could be suitable for a journal on the philosophy of science."
Whoever wrote the above evidently did not understand the loopholes! Should his ignorance be propagated in the pages of wikipedia? The loopholes don't need to be "invented" -- they are there to be found by anyone who looks carefully -- and, though I'd be happy to see the whole field of "quantum entanglement", experiments and all, deleted from the record, I personally have learned quite a lot of the physics of light and its interaction with matter by studying the experimental details. Caroline Thompson 09:19, 20 May 2005 (UTC)
It looks to me that the "ignorant" you are talking about is not a single person, rather the whole editorial board at those two journals (or, at all respectable physics journals in general). And it also looks to me that you found an outlet for your "opinions" over here, where of course nobody can completely stop you, being a wiki page. Again, I think there are better places for a respectable scientist to push his/her theories. Besides, you are wasting your time. Even if you manage to push your POV over here, that will not gain you the "well-deserved recognition". You're just damaging your reputation (assuming that you care about that). Oleg Alexandrov 00:53, 21 May 2005 (UTC)
So, one even thinks that no "loophole" papers were published in respectable journals?! Then evidently, we better put a reference to one of them in the article! - Harald, 10 October 2005.
Quoting ET: "Even Dr Chinese has now implied that he would favour John Bell's own derivation".
Oh really? Let's see, you claim that not only can communicate with the dead, but you also somehow manage to read people's thoughts. --CSTAR 13:07, 20 May 2005 (UTC)
I am capable of speaking for myself in this forum, Caroline. And I have already, see above. As to the quote about PRA above, that would (assuming it is accurate) constitute de facto evidence that the "loopholes" should NOT be presented here. PRA does carry a bit of weight with me and, I would trust, a few others out there :) ...--DrChinese 18:39, 20 May 2005 (UTC)
CSTAR, I was quoting Dr Chinese' remark of May 7 (unsigned, but clearly his): "I am certainly happy to make sure the material follows Bell if that is a question".
Dr Chinese: The PRA quote merely tells us that the editors think everyone already knows all they need to know about the loopholes. In particular, they would assume that everyone is aware of and understands Philip Pearle's paper, the first to explain the detection loophole (P Pearle, “Hidden-Variable Example Based upon Data Rejection”, Physical Review D, 2, 1418-25 (1970). But you would not even allow a ref to this paper when I added one! And, as I've pointed out a few times, my own paper, Thompson, C H. "The Chaotic Ball: An Intuitive Analogy for EPR Experiments", Found. Phys. Lett. 9, 357 (1996), http://arXiv.org/abs/quant-ph/9611037, conveys the same message but more intuitively. Caroline Thompson 21:18, 20 May 2005 (UTC)

## Fair Sampling

The clause on fair sampling only deals with the percentage detection. I have no dispute with that part. It does not deal with the fact that when you have two subsamples (as you do at the two detectors) and then you merge them, you throw away the data where there is no detection at one detector. This process of keeping only data that has detections at both detectors is totally built in to quantum theory entanglement, so it works. However it has been demonstrated that realistic models can do the same thing without any FTL signalling. In fact we know that there is no FTL signalling. The sample reduction is done later on the computer and that is where the "signalling" occurs. See David Elm's material on this at http://www.cyclesresearchinstitute.org/physics/elm.html and try to learn about conditional probabilities and subsamples. Ray Tomes 16:08, 20 May 2005 (UTC)

[Though David Elm comes to the right conclusion re the detection (fair sampling) loophole, I found quite a few errors in the paper and some of his ideas are confusing. I'm afraid Nick Herbert's explanation of Bell inequalities may not be the best starting point. Bell's own approach -- preferably his later, 1971, version, Ch. 4 of J. S. Bell, Speakable and Unspeakable in Quantum Mechanics, (Cambridge University Press 1987), is a more reliable one.] Caroline Thompson 09:09, 21 May 2005 (UTC)

## CT's point of view

I'm not trying to gain recognition for myself, only trying ensure a balanced point of view. The "establishment" journals have, ever since Aspect's experiments of 1982-3, been presenting a strongly biased point of view, but this was based on debatable information. It was not realised (due to failure to publish the relevant data other than in randomised form in a PhD thesis) how important the subtraction of accidentals was, at least in two out of his three experiments. For your information, the only useful ref on this (and one that has been quoted on occasion, though not in PRL or PRA) seems still to be my own,

• Thompson. C H: “Subtraction of accidentals and the validity of Bell tests”, various versions submitted to PRL and PRA and rejected, 1998-9; now published as: Galilean Electrodynamics 14 (3), 43-50 (May 2003), http://arXiv.org/abs/quant-ph/9903066

OK, so maybe my work (in de-randomising the data and finding out the effect on the Bell tests) was "original research", but is that sufficient reason for publicising in wikipedia only the opinions of people who have no knowledge of these facts? In most similar instances all this would not matter, but the issue at stake here is a whole paradigm.

Within the small subset of the physics community concerned with Bell test experiments, it is openly recognised that there is no loophole free evidence that the world cannot be fully explained using local realist models. [This is why they are still trying to devise a loophole-free test.] To read books such as Amir Aczel's "Entanglement" or Roger Penrose's "Road to Reality", nobody would know! Caroline Thompson 09:09, 21 May 2005 (UTC)

## loopholes or not loopholes

As I understand the present discussion it seems that only Caroline Thompson want to speak about loopholes. I would like just to remind that even Bell was aware of loopholes in the experimental test of his theorem. He was however convinced that future experimental works will not contradict his result since in principle the efficiency of a detector can increase without limit (this is only valid when you are a theoretician...hihi). His choice is completely logical if you believe that Quantum mechanics is 100% true and will always be true but we can not unfortunatelly be sure of that a priori. Of course I believe in QM and then I dont believe that the loopholes have a physical meaning but we can not omit this chapter from the discussion when we are honest. One of the fundamental reason for the resistance of C. Thompson is I guess the challenege that represent a non local universe for a normal brain. Non locality is indeed a non sense if you don't believe in instantaneous interaction. I understand the reaction of thompson but I am convinced that nonlocality is a real property of the universe and that we should try now to explain this fact with more powerfull model of reality. Probably in 20 or 10 years (perhaps much less) when the complete Bell test will be done we will laugh about this discussion. --Drezet

Mostly I try not to engage in USENET-like discussions, but let me give my two euro cent here. Both the doubters like CT, who are scared by non-locality, and the believers, who make a religion out of non-locality (some "wholeness" etc thrown in), just didn't check what's local and what's non local here. Buchholz has shown in the framework of Local quantum physics, under rather general assumptions, that the algebras of observables of two spacelike seperated regions are "independent", i.e. the algebra generated by the union of both local algebras is isomorphic to their tensor product (A(O1) ∨ A(O2) ≃ A(O1) ⊗ A(O2)), provided that their regions "don't touch" (there is a finite gap between them) [1]. Only the fixation on states of the standard formulation of QM gives the impression of essential non-locality. [2] --21:54, 2005 Jun 9 (UTC) That was me, Pjacobi 11:17, 2005 Jun 11 (UTC)

Is what you are saying that not all versions of QM agree that two separate particles can be covered by a single non-separable wave function? If so, surely these other versions should come under just as much attack as "local realism", since it seems likely to me that the real issue at stake now is not so much theoretical as practical and sociological: if quantum entanglement does not happen then science writers will lose a lot of good stories and people trying to devise quantum computers etc will find it more difficult to get funding. Personally, I see no hope of quantum computers ever achieving anything to rival ordinary ones, but as regards "quantum encryption", what they actually need to get their "quantum key distribution" is just correlation, not entanglement. A spin-off from all the research into quantum entanglement has been the development of means of controlling tiny pulses of light that are indeed highly correlated in pairs, though varying randomly between pairs. This is something real that can be exploited, so all that is needed is to change the wording of the grant requests. Caroline Thompson 09:03, 11 Jun 2005 (UTC)
No, what I'm saying is that the non-locality goes with states, the "wave functions", which can be considered a technical artefact, the observable algebras being the invariant "facts" of QM. Have a look into the papers mentioned, and the cited literature. --Pjacobi 11:17, 2005 Jun 11 (UTC)

when you say that QM is local I agree in the sense that we can not observe directly the non locality . For example we can not transmit instantaneously information using a EPR pair since the correlation appear only when we compare the data from alice and Bob (this is the thesis of David Deutsch [3]). However there is a problem if we think like Bell or Einstein on an ontological point of view (i.e. if you try to understand what is really going on at a dynamical level not only at the observable level). This was the central point of dispute between Bohr and Einstein and it is still the central issue. Indeed what discovered Einstein is that if you accept a single postulat the real objects A and B can not communicate instantaneously then we deduce that we can for example violate the Heisemberg relation. This is completely true but only if you accept the locality and the realism. In addition you will not be able to prove that you are true since you need several experiments to effectivelly measure p (momentum)and x(position) of the 2 EPR particles A and B. The original example chosen by EPR was then perfect for the Einstein purpose since it is possible (as it was proven by Bell later) to find a local model using the Wigner function formalism . However if you consider the Bohm example of two spins in a singlet state then we can not find any local model (Bell's theorem). This is a result only if you think like a normal realist creature (but Bohr at least was not such a creature).

So my conclusion is that Bell's theorem shows the existence of nonlocality if and only if you accept with Einstein the existence of a reality existing independentely of us (realism). --Drezet (10 june 2005)

No, surely that is not reasonable! What Bell's theorem shows is that something weird is happening if the part of QM covering separated particles is correct. If you accept that there are flaws in QM and that this is one area in which it is likely to be wrong, then the loopholes give you a useful let-out clause. You are free to assume that in the real world nothing weird happens at all. Caroline Thompson 09:03, 11 Jun 2005 (UTC)

but as regards "quantum encryption", what they actually need to get their "quantum key distribution" is just "correlation", not "entanglement"
Wrong. Quantum key distribution is a composite protocol (e.g. built out of several subprotocols) for key agreement which can detect lower bounds for leakage of the exchange to an evesdropper. The main sub-protocol is based conceptually on the no-cloning theorem. There is no way any classical communication without entanglement can have this detectability property.--CSTAR 16:40, 11 Jun 2005 (UTC)
Yes, that's as maybe, but in the actual quantum key distribution systems that have now begun to be used do they make any such claim? If they do, is it really on the grounds that they are dealing with entangled photons or on the more prosaic grounds that they are using sources that, since they are "quantum", are genuinely unpredictable? If I am right it is the latter: ordinary correlation will do the trick. In any event, as I understand it, they cannot completely rule out eavesdropping since they cannot reliably produce "single photons".
I'm sure they would like to have entangled photons, and they doubtless perform Bell tests with this in mind, but you will find that the test they use is the CHSH test or similar and their detectors are not 100% inefficient. The loophole means it is not able to discriminate between entanglement and ordinary correlation. Caroline Thompson 16:48, 12 Jun 2005 (UTC)

Dear Caroline , It can be that QM is wrong when we consider detector with high efficiency (as suggested by Santos) and in this case you are right but I think that this chance is very small and if I will be you I will not expect this too seriously (However I appreciate that you insist on this aspct of the problem because I agree cmletey wth you on that point). But if QM is right As I guess and as every one guess then non locality become clearly a condition of any ontological model. But Ok on the general point I agree with you nevertheless. For me it seems strange that QM can be correct at low efficiency of detection and become wrong later on... and it is much more interesting to suppose that QM is correct and to build a correct ontological model to justify non locality. I think that it is much more scientific because you can never guess on waht can be the result of an experiment (I sam experimentalist... ) but If you build a theoreticla model and that your model is correct then it is the jack pot...

Concerning you critics of the web page on Bell's result I agree on one point: The demonstration of this page is not very general. In my knowledge it is the derivation presented by Asher Peres in 1978 in American journal of physics (vol46, pp745-747). This demonstration consider a vry particular model of hidden variable. Suppose that at each experiment 1,2,....N the two particles possess value a(1),a(2).....a(N) as well as a'(1),a'(2).....a'(N) for the particle A and similarly b(1),b(2).....b(N) as well as b'(1),b'(2).....b'(N) for the particle B located far away from A (a a' b b' are for example spin components). Now you can consider the quantity S(i)= a(b(i)+b'(i)) + a'(b(i)-b'(i)) and observe that if a, a' b, b' can only have the value -1 or+ 1 then s(i) is only equal to 2 or -2 then the average S= lim[S(1)+S(2)+....S(N)]/N for N infinite is alway s betweern -2 and 2 [Bell's theorem ]. The problem with this prooof is that we suppose that the each particle has at each experimemt a value for a, a', b b'. This is not necessarily true for any hidden variable model. In other term here the hidden variable are the four observable a,a' b,b' [non contextual model] and this is very restrictive. It will be good if the author of this page refers more to the original reasonnings of Bell and others which are absolutely general. --Drezet (12 june 2005)

You are certainly right that this is based on the proof given by Asher Peres; nevertheless there is nothing in the proof that assumes that a, a', b b' are the only hidden variables. And there is nothing non-contextual about this proof either. Secondly as I mentioned in the remark after the proof, there is no restriction that the values assumed by the variables are only +1, -1 (even though Pere's proof for simplicity does assume this). Finally, to provide a rigorous proof, you will need a formal model of local realism (not entirely trivial) but which is provided by Shimoney's SEP article. --CSTAR 19:29, 12 Jun 2005 (UTC)
Dear CSTAR Your proof is non-contextual in the sense that it supposes that the system of two particles has value of a , a' (for A) and b, b'(for B) at each test (1,2,...N,...). This is not the most general hypothesis . In a general theory the system is characterized at each test by a parameter lambda. This parameter (initial condition ) can be completely different of the value a,a',b,b' observed later and we have not to suppose that these observables exist prior to the measurment. In the language of probabilities you can in your model define a probability P(a,a',b,b') for the four observables . Then you can define P(a,b) for example by
$P(a,b)=\sum_{a',b'}P(a,b,a',b')$

which is identical to

$P(a,b)=\sum_{\alpha,\beta,a',b'}\delta_{\alpha,a}\delta_{\beta,b}P(\alpha,\beta,a',b')$

the Kronecker symbol are introduced in order to define the probabilities

$P_{A}(a|\alpha,\beta,a',b')=\delta_{\alpha,a}$

for the particle A and similarly for B. These kind of notation do the link between the demonstration proposed by you and Peres in one side and the original derivation of Bell and other. indeed in their notation they have

$P(a,b)=\int P_{A}(a|\lambda)P_{B}(b|\lambda)dP(\lambda)$

In the case of a deterministic model we can put

$P_{A}(a|\lambda)=\delta_{A(\lambda),a}$

You can see that your model corresponds to a deterministic theory with :

$\lambda=[a,a',b,b']$.

This is obviously a kind of non contextual model since you suppose that the particle A is characterized by one value a' even if you only observed the quantity a associated with another orientation of the rotator. The same is true for B and the values b ,b'.

Naturally I don't criticize your demonstration which is very simple and elegant I just criticize the generality of the results.

I Will respond more carefully later; However, note that any formalization of local realism has to deal with a non-classical model of probability (that is for this reason that I mentioned Shimony's SEP article). This formalization can be done in other ways as well using non-commutative C*-algebras (this was the content of Pjacobi's remarks I think). A proof of CSHS using this approach was given by Larry Landau around 1985. Thus the expression P(a,b,a'b') may not be meaningful in a general local realist model and certainly can't be manipulated like classical probabilities.--CSTAR 13:55, 13 Jun 2005 (UTC)
Dear CSTAR my argumentation was heavy and I will clarify it later on too but I just give a good reference on this point: A. Fine PRL 48 ,291 (1982). I dont agree in general with the thesis of fine but he give in his paper a good difinition of the kind of model considered by you. If you have not access to prl I can join you the paper by email .

--Drezet Remarks: you say expression P(a,b,a'b') may not be meaningful in a general local realist model this is exactly what I am saying to you from the beginning: your model is very particular. The fact that you can define P(a,b,a',b') is only a proof that this model is very simple (but I agree with you very pedagogical). I have the feeling that we in fact agree ... PS:concerning Shmony His notation are the same than mine... Or I should say in fact my notations are the same than his. He introduces the concept of hidden parameter since the beginning as in the CHSH paper in 1969 (see too CH in 1974) --Drezet

BTW I have no objection to you or (anyone else) editing the Bell's inequality page. Note however, that that page (along with scores of others, including (EPR, Entanglement) have been very contentious because of persistent POV pushing and self-promoting references (see comments to that effect by User:DrChinese and many others including myself).--CSTAR 16:29, 13 Jun 2005 (UTC)
I dont want to change the present web page concerning Bell's theorem (I have not time for that) and in addition the pages look good. I wanted only to suggest some possible changement(s) in order to be completely fair and in order to give a better overview of the problem (the reader dont know necessarily all the story and the present beginnig is a litle bit hard I think): A short introduction should be usefull and after if you like the proof of Peres it is your right :) .....

--Drezet PS: I have question for C.Thompson: imagine, you are in 2023 and a team of physicist directed by the A. Aspect (very old) in the north of Congo publishes the result of a loophole free experiment perfect on all the domains. What will be your reaction? will you continue to doubt over non locality or will you reconsider your current position? This a good question for me because I dont really understand if you are against QM or if you want to defend locality or.... I dont know ?? My second question is then  : Do you think that non locality is crazy and should be wrong by principle? --Drezet (13 june 2005)

## Report criminal behavior

CT: If you really are serious about your critique of QM and your belief that researchers have faked or misintrepreted scientific evidence supporting QM, then you should immediately notify the research funding agencies in Europe and the U.S. (including Darpa or whatever it's now called). You should tell them you believe there is a massive conspiracy to defraud the taxpayers (particularly the american taxpayer, now overburdened with paying for various wars and transfer payments to the ultrarich). Why waste your time writing rebuttals here on lowly Wikipedia? You really could become the whistleblower of the century. And frankly, I think your chances are pretty good here in America; I think you could find a sympathetic reception within the current american administration which is much more likely to regard QM as a sort of underpinning for other theories such as the big bang and evolution which are in stark contrast to theories they may be more favorably disposed to promote, such as young earth creationism.--CSTAR 17:17, 12 Jun 2005 (UTC)

## Peres reasonning

Dear CSTAR, I would to comment a litle bit the reasonning of Peres used in Wikipedia. The Peres reasonning start with an assumption presented at the beginning of his article in 1978: no mention is made of hidden variable or similar superstitions . When I read that the first time I was very surprised since it in my belief Bell's desire was to analyze such hidden variables. Later Peres added the discussion involves a comparison of the results which were actually performed with those of hypothetical experimentals which could have been performed but were not. This sentence showed for me a srong ambiguity in the language of Peres. This is confirmed in the folowwing passage Let us now try to imagine what could have been the results of measurement by and B along other direction alpha' and beta'. It is of course impossible to know for sure these results because the experiments wre unperformed. However thexy could have been performed . We can therefore constructs a table including bothe the actual and the hypothetical results.... .

The demonstration of peres continue like I explained to you before : you can construcfor each experimental test 1,2,.....N a quantity S(i)= a(i)(b(i)+b'(i))+ a'(i)(b(i)-b'(i)) equal to -2 or 2 and then by averaging obtained the CHSH theorem. This is great but suppose that the system i posses value like a a' b b' even if all these quantities are not observed . This is a clear reference to a specifical modle of hidden variable and we can not omit this .

So now there is the page of wikipedia starting with the formulation of Peres. For a beginner starting with such proof it would seem that Bell speak only about simple hidden varaible model supposing that the thing that we want to observe exist already before. But Bell was aware of Bohm's ontological model in which the spin doesnt exist really before the measurement. for this reason I think that the current page should use more of the historical back ground . I understand that the page of Thompson was not neutral but many elements presented by her should be used (in a more neutral way however) Drezet

Je suppose que c'est dans ce sens ci que vous dites que le modèle de Peres est non-contextuel. Cependent il est bien facile de modifier le modèle presenté pour tenir compte de cette possibilite. c.a.d. que, au lieu d'avoir un nombre reels comme le resultat de chaque experience, on a une variable aleatoire. En outre, comme vous connaissez bien, le "realisme locale" est une propriete differente de l'existence de variables cach'ees. Salut. --CSTAR 20:15, 14 Jun 2005 (UTC)
Merci beaucoup for your answer your french is obviously better that my english but I will nevertheless continue in english since I am pretentious. My answers to your questions are : Yes it is in that sense that Peres model is non-contextual.

The modification proposed by you is as I understand to consider random variables for a(i) ,b(i),... but this is not really a modification and is not in contradiction with my claims concerning the limitation of the Peres argument. In fact Peres didn't proposed a model for the production of the particles pairs and this is not important for the result. The production mechanism can be random (stochastic )or not (deterministic) but in both cases all pairs possess the four numbers a(i),a'(i) [for A] and b(i),b'(i) [for B]. This is the ontological part of the model. Now when i say that it is a deterministic model it is not at the source charactristic that I think but at the measurement process: Each time that one particle says A is characterized by the value a of the spin (for a given orientation of the rotator ) then the measurements return the result a. This is a one to one relation and this is the meaning of the kronecker symbol in my notation (see for example me in this small paper [[4]]) En vous remerciant. --Drezet

Hmmm I suppose I am pretentious using French. Oh well, I was trying to do my share in combatting anglocentrism.
I think we are dealing with different (though related) issues.
The proof currently explicitly refers to counterfactual definiteness, which is the claim that all pairs possess the four numbers a(i),a'(i) [for A] and b(i),b'(i) [for B]. However, I claim that in a minor modification of the Peres model, (possibly not envisioned by Peres himself) we can do away with this restrictive form of counterfactual definiteness; in fact, the argument still goes through even if it is possible for Alice's measuring the variable XA still leave her other variable YA "undetermined", e.g it is a random variable with a non "delta-function" distribution.
This is analogous to classical "conditioning". In one extreme case, given random variables X,Y, an observation of X may leave the distribution of Y completely unaffected; e.g., if X, Y are independent. In fact unless, Y is a function of X the observation of X will not always completely determine Y, e.g., it will not be a "delta-function".--CSTAR 22:09, 14 Jun 2005 (UTC)
Dear CSTAR (is your name connected to the symbol C*?) , Anglocentrism is a clear drama for humanity (Beeing french it is like a tradition since the midle age to be anti anglais but this is just a joke I love english and I speak only to my girl friend in english and even I eat my steak with jam....).

Concerning your model I can say one thing : Youpi!! Congratulation: You just reinvent the Bell theorem like it was considered in Clauser et Horne PR article in 1974 using what they called OLT (Objective Locale theory). I agree with you that if you introduce a conditional probability different from the delta function then you have a different local model more general but this model is now stochastic and different from the one proposed by Peres. The notations of Bell include all the possible models and this is for me a proof of their superiority and generality.--Drezet

Well, of course this isn't a research paper! I was trying to write an expository article. Maybe you should write it! --CSTAR 22:33, 14 Jun 2005 (UTC)
First to eliminate a possible ambiguity I precise that my Youpi was not an agressive or laughing Youpi. Secondly I think that to write an expository article on Bell theorem seems to be a hard job for me. You are certainly better that me at this game (style , grammar, time perhaps ect...) so please continue your article and don't care about me  :))

--Drezet

No I realize that there was (probably) no intention of aggression; however, writing that article has been a thankless task. One thing I tried to avoid was discussing formal models of local realism (see the discussion in the article interpretation of quantum mechanics).

One suggestion for improvement: modulo some changes, (for example the claim "far from settled" is ridiculous or term "quantum correlation") the first three paragraphs of CT's version User:Caroline_Thompson/Bell's_theorem isn't bad. It could be used as an intro. The current intro could be cut down and put into the correlation section or in a new section called overview. The intro now does mention the no-communication theorem which is crucial to dispel any suggestion that failure of Bell's theorem is quackery. I hope I don't piss anybody off by making this suggestion.--CSTAR 16:33, 15 Jun 2005 (UTC)

A) There was no intention of agression, I become rarely agressive (and even in the case of Afshar's experiment that you know I was only completely laughing about Danko's no-thesis).

B) Your suggestions are very good , and when I considered the page of Thompson I was effectively sad that the good part of her work (e.g the part which stays prudent and objective ) was damaged by her personal point of view ( a personal point of view can appear one time in such article but too often transform the objetivity into a thesis). I can understand that in the particular context of the Bell theorem one can have a favorite point of view (non locality or locality) but since the experiment indicate at the present moment that every thing seems to go in the direction of non locality I will be pruden with the discussion concerning loopholes. C) Concerning the idea to avoid any references to a particular hidden variable I have some doubt. Historically Bell observed that the model propsoed by Bohm and de Broglie is nonlocal. Bell was motivated by this fact to see if yes or not the result is not general and if any model able to justify the EPRB experiment is nonlocal. Of course it is not necessary to describe Bohm's model since it is already done. But an introduction presneting the motivation of Bell is crucial. In addition I think that if we say what should be a hidden variable model and what should be a local model evry thing will be consistent.

--Drezet


I've been away otherwise I would have contributed earlier to this discussion. Drezet has made some very good points. I have not time now to go into the in's and out's of Peres' approach (as used by CSTAR), but would only re-iterate that to use this approach will only lead to confusion. Bell's theorem is all about what a hidden variable theory can and cannot do, and the use of a supposed derivation that does not even mention their existence seems odd, to say the least.
Why not look carefully through my original Bell's theorem page (see http://en.wikipedia.org/wiki/User:Caroline_Thompson ) and prune out (if you really have to!) refs to my own work?
Re suggestions that I have been accusing experimenters of fraud, this is not the case. I have merely been pointing out what they already know well: they have yet to do a loophole-free test, so that, as far as the experimental evidence is concerned, my stance of believing in a version of local realism that depends (in much the same kind of way that Einstein et al were thinking in 1935) on hidden variables is perfectly tenable. It is not so much the experimenters themselves as science journalists who make all these claims about quantum entanglement being an established fact. They have built up a myth that has become so strong that it now influences decisions on fund allocation. Experimenters are effectively forced to say that they are working with applications of entanglement, whether they believe it or not. When they come to write up their results, though, they are pretty careful to say only the truth: that they infringed so-and-so inequality, which would be proof of entanglement were it not for the loopholes.
I would gladly say all this to the authorities, but are they going to listen? They may do eventually, but not until after the physics community has accepted that they have underestimated the importance of the loopholes. There is some fascinating history to be unearthed here, incidentally. A series of unfortunate mistakes may have contributed to the initial misinterpretations. [For more on this, see “Clauser and Horne’s 1974 Bell inequality: a neglected escape route from the ‘fair sampling’ loophole” http://freespace.virgin.net/ch.thompson1/Papers/CH74/CH74assumptions.htm and other articles on my site.]
Re Shimony's Stanford Encylopaedia derivation of Bell's inequality, as far as I can see it is equivalent to Clauser and Horne's OLT one, which was supported by Bell once he began to think in terms of real experiments. Shimony's version is more rigorous, couched in set-theoretical terms, but when it comes down to it all he means is that the state of the source determines hidden variables which, in turn, influence (but do not fully determine) the outcomes. Caroline Thompson 12:23, 17 Jun 2005 (UTC)

## A matter of logic

Dr Chinese, for your information it is necessary to conduct a Bell test experiment in which all loopholes are closed simultaneously before you can begin to claim that any particular one has been closed! The fact that the Rowe et al expt had many other loopholes, just one of them being mentioned in Vaidman's article, means that its claim of having blocked the detection loophole is not relevant to any other experiment. The same is true of all experiments that block just one specific loophole. One of Aspect's blocked the locality loophole (to my satisfaction, at least) but it did block at the same time at least one other important one.

Where did you get this funny idea from that blocking each in term was in any way the same thing as doing a full "loophole-free" test?

Why do you think they are still searching for a loophole-free test?

As a matter of fact, I think the experiment suggested by Grangier's team last year would be a valid test, but I confidently predict that, in consequence, it will not be found to violate a Bell test. (See my paper, which is currently being revised for submission to J Opt B.)

Caroline, thanks for giving me a laugh about your PRL submission. And may I remind you that Wikipedia is not the place to debate research ideas anyway. As to your idea that all loopholes must be closed simultaneously: again, this is a separate subject and has absolutely nothing to do with Bell tests. (If you accept that premise: there exist loopholes in all experiments, and we have no scientific knowledge whatsoever; such is an absurd and vacant result.)
I am not planning to revert the last few wording changes as long as it doesn't go any further than it has. My reasoning is that the state of the art on Bell tests has gone well past what is mentioned here anyway. I am planning to use more up-to-date references which make it clearer that Bell Inequalities are violated in virutally every reasonable permutation. I expect to begin this process shortly, so some of the wording arguments will be moot. -DrChinese 20:44, 11 October 2005 (UTC)

## Minority view

I do not say I believe or do not believe in local realism, but I do believe it is very interesting that no-one has done a loophole free Bell test despite so many years improvement and refinement of experimental technique. And people are still trying very hard. In my opinion it is a logical possibility that quantum mechanics is true (or very very close to true) and simultaneously no-one ever will be able to do a loophole free test: quantum mechanics itself could forbid one from ever creating the good "initial conditions" (two parts of an entangled quantum system "to order" in two distinct, distant locations). See for instance quant-ph/0410193, Bell's theorem and the experiments: Increasing empirical support to local realism, by Emilio Santos, and quant-ph/0301059, Time, Finite Statistics, and Bell's Fifth Position, by myself (Richard Gill).

You're right, Richard, in many ways, yet at the end of the day I think local realism will win. It will not, though, be Bell tests that finally discriminate between the rival theories (I agree that a loophole-free one that both sides agrees relies on no unsatisfactory assumptions is never likely to be found). It will simply be found that a continuous wave model for light is always superior to a photon one at the end of the day, and that the mathematical formalism of QM has been holding back our understanding in this area. QM lost the plot when lasers were invented! It really lost is rather further back than this, when it was decided to model only "observables", not realising the extent to which this tied it to the mechanisms of existing measuring instruments. [Sorry: this is perhaps not the place to introduce such a big subject!]
Caroline Thompson 10:01, 8 November 2005 (UTC)

## Not "hypothetical" loopholes

According to some Wikipedia editors, loopholes are "hypothetical". However, the loopholes are real as several have been identified, there is nothing "hypothetical" about it. For example, according to Nicolas Gisin, so far no single experiment managed to close simultaneously the detection and the locality loophole. Harald88 21:46, 27 November 2005 (UTC) Note: I now realise that "Possible loopholes" is almost as misleading, for until now they are neither hypothetical nor possible but actual. Thus, to avoid such smoke screens, the header should be simply "Loopholes". How did the text become so twisted, anyone who knows? Harald88 12:58, 28 November 2005 (UTC)

We have already been through this and the matter is settled. I will continue to revert and I can do this as long as necessary. The main element of this page is always going to be the experimental tests of Bell's Inequality. That there are hypothetical "loopholes" is being acknowledged to a degree but there is no point in making those the focus of the page. The "loopholes" are not considered by the scientific establishment to be particularly significant, any more so than in any scientific experiment. Asher Peres summed up the majority view of the peer-reviewed world nicely and Caroline generously quotes him on her page. Please note that I am not going to repeat what I have already said on this subject: read anything I have said in this talk page or any of the other Bell related pages. -DrChinese 23:16, 2 December 2005 (UTC)

Yes it appears that the matter was settled, I even see a remark of you like that above. For some reason you now unsettled it, maybe as a reaction to the addition of some stuff by someone, I'll have a look at it. Apart of that, Dictionary.com, Hypothetical:

"1.Of, relating to, or based on a hypothesis: a hypothetical situation. See Synonyms at theoretical. 2. a.Suppositional; uncertain. See Synonyms at supposed. b. Conditional; contingent. n. A hypothetical circumstance, condition, scenario, or situation: OK, let's consider this possibility thenjust as a hypothetical. "

And I'm also not going to repeat what I said. Harald88 09:54, 3 December 2005 (UTC)

## recently added loopholes, now parked here

Recently the following loopholes were added, making the article contents largely an article about loopholes (sorry dr.Chinese, I had not noticed that). I will cut them out and parked them temporarily here, for discussion about which ones are worth mentioning, and what to do with them. Most appropriate to me seems to make a subpage to this article with a detailed loopholes discussion, and that is linked to from the main article, as is common practice in other articles. Then we can shorten that paragraph in this article. Please comment on each loophole separately. Harald88 10:39, 3 December 2005 (UTC)

Enhancement

The CH74 inequality, and some others, are derived using the assumption that the presence of the analyzers never increases the probabilities of certain outcomes. If an experiment shows that these inequalities are violated then we do not have a general disproof for all local hidden variable theories, just those for which the analyzers cause no enhancement.

Rotational Invariance

It is assumed in Bell test experiments that it is only the angles between different detector orientations, not the actual angles themselves, that are significant in the data, meaning that rotating all detectors by the same angle will have no effect. If the photons involved in the experiments prefer some polarization direction then the test is not rotationally invariant, as a rotation of both detectors will have an effect. Rotational invariance is not an assumption required to derive Bell's inequalities, so this is not a theoretical problem, but the assumption is often used to analyze data in experiments and so could cause data to suggest violations of the inequalities when really they may not.

Double Detections

If local hidden variable theories are true then it is theoretically possible that in some situations a detector could have cause to measure both +1 and -1 simultaneously. This is not possible in quantum mechanics and is also not possible due to the electronics of the detectors used. This means that the physical constraints of the detectors may bias the data towards quantum physics.

The Memory Loophole

Local hidden variable theories could be constructed that violate the inequalities if the particles involved had memory, that is if the measurement of the nth pair was affected by the n-1 pairs that preceded it. A related loophole, the simultaneous measurement loophole, states that local hidden variable theories could be constructed that would violate the inequalities if all pairs are measured simultaneously. There has been some research in the area of these loopholes (Barrett, 2002; Gill, 2001) that show how the data can be analyzed so as not to be biased towards quantum mechanics. When analyzed in this way, however, the data still suggests that quantum mechanics is correct.

Topology change

Finally, there is a theoretical loophole, which holds that a Bell violation is not a superluminal influence if two entangled particles are viewed as colocated (for instance, if they are opposite ends of a wormhole, as proposed by Einstein and Rosen and more recently by Durand [1]). In other words, a local realistic theory remains possible if "local" is redefined to reflect the predictions of quantum mechanics. However, wormhole creation is a topology change (i.e. addition of a new "handle" to spacetime), which implies causal violations (see for instance the chapter on topology change in Visser's book Lorentzian Wormholes from Einstein to Hawking).'

.

"Enhancement" should be mentioned as it is considered important by Marshall et al, who are prominent members of the local realist camp. It could happen in actual experiments though I don't think personally that it does.
"Rotational invariance" deserves a mention if only because most quantum theorists don't seem to stop to think whether or not it holds. They just take it for granted. Experimenters are more careful, but all the same may find its failure biasing their presentations.
"Double detections" are an interesting real possibility but probably too technical to deserve mention.
As far as I'm concerned, the other two "loopholes" are not real possibilities and I would not mention them. I've always taken the word "loophole" to mean real weakness in the experimental design or analysis, not theoretical fantasy.
Despite this desire to stick to reality, perhaps one more loophole should be added, since it is generally referred to as such: the "light cone" or "locality" loophole -- the one that Aspect's and Weihs' time-switching experiments were designed to close.
Caroline Thompson 09:51, 4 December 2005 (UTC)
Harald88: Thank you for noticing that this page has become about loopholes and not experiments. I appreciate what you have done to address this. I have reverted anyway, because this is exactly the ground we already covered. The current amount of text related to loopholes was struck as a balance. Just as I do not repeat every single Bell test to support one side, we do not repeat every loophole. Loopholes are give their due, no one can walk away from here without getting the idea. As to the word hypothetical - this opens up a debate of no end. Asher Peres spoke on this, and I think the position taken is more than adequate to provide a balanced perspective to Wikipedia reader. By the way, most experiments no longer subtract accidentals so as to parry this objection; or at a minimum they report them and address the issue straight on so there is no question that accidentals are not an issue. See for example Dehlinger & Mitchell (2002) which I will be adding to the page. -DrChinese 02:09, 6 December 2005 (UTC)
DrChinese, you're welcome, but please keep to the Wikipedia rules and *don't just delete* established contributions of others or alter the phrases from NPOV to your own POV. Today I have no time, so I must leave it like this for now, but probably there is a way to solve this matter between you and others in an agreeable way: starting with agreeing on a linked page about the subject of related non-hypothetical loopholes to which all relevant loophole examples are moved, and a short, unbiased paragraph about it on this page. BTW, I also discovered that already a loophole page exists that should be merged(?!) with this page, but I trust that that is not the concensus, at least it's obviously not what you want and I think that most editors will agree not to do so. Regards, Harald88 08:03, 6 December 2005 (UTC)
Dr Chinese: You may have a point re the subtraction of accidentals. My original entry (see my user page) read simply:
===Subtraction of “accidentals”===
Adjustment of the data by subtraction of “accidentals”, though standard practice in many applications, can bias Bell tests in favour of quantum theory. After a period in which this fact has been ignored by some experimenters, it is now once again accepted . The reader should be aware, though, that it invalidates many published results. Notable examples in which there were large numbers of accidentals are Aspect's experiments (Aspect, 1981, 1982a,b) and the early "long-distance" Bell tests conducted in Geneva (Tittel, 1997). These experiments are discussed in (Thompson, 2003).
You might be happier with this. Someone else had expanded it and diverged from the original usage of the term as per Stuart Freedman and Alain Aspect's PhD theses. I'm sorry I had not explained fully in the first place but the issue is all about possible mis-pairings when more than one atom emits a pair of photons at the same time. Aspect had to assume that all atoms emitted independently so that there was nothing special about simultaneous emissions. He justified this decision in a paper in 1985, but his arguments depended on a lot of quantum mechanics and I know of other physicists who dispute them. Under a wave theory of light it is much more likely that the whole bunch of atoms will act in resonance and between them produce only one pulse of light. If this is what happened, then the observations would have been made on two particular frequencies, filtered from a whole spectrum emitted, these two classical waves being designated the two experimental "photons". The important thing is that at any one point of time only one pulse (of finite duration) is emitted so there can be no accidentals due to this cause at or near the zero point of the coincidence time spectrum.
See http://freespace.virgin.net/ch.thompson1/Aspect/ch5.pdf
(Translation of part of Aspect's thesis)
and:
http://arxiv.org/abs/quant-ph/9711044
(Timing, 'accidentals' and other artifacts in EPR experiments)
Caroline Thompson 11:00, 6 December 2005 (UTC)
Caroline, I follow DrChinese in his proposal to remove the detailed examples from this page (he didn't exactly say so, but he demonstrated it!), and he may not care much about the way they will be presented on another page as he dismisses the whole issue as irrelevant, if I read him well. Harald88 19:48, 6 December 2005 (UTC)

I found the existing loophole page back: Loopholes in optical Bell test experiments. Let's simply add to the Bell test article a short comment on typical debated loopholes and if within a week there are no objections to moving the examples, then create a link from this page and move all detailed loophole examples to that page (first to its Talk page). Regards, Harald88 19:48, 6 December 2005 (UTC)

PS I now copy all loophole examples plus Carolines' comments to the Talk page of that article, in preparation of the move. Harald88 19:57, 6 December 2005 (UTC)

Harald88: It is acceptable to me to move the loopholes to a separate page and link that page from the experiments page after a very short mention. That has always been my preferred way of presenting, and I will not do anything to block that. I would ask that the loopholes page not come to the conclusion that the tests are actually invalid, simply state the loopholes and say that some do not accept test results. It would make more sense if the loopholes that have been closed by recent experiments are either excluded or noted as such. But I am personally more flexible on that point. The loopholes pages should not become a rant against the tests; it should reflect current scientific consensus as to the actual "loopholes" still under active consideration.
I should say this as well: If I recall correctly, that presentation method - link to loopholes - was not acceptable to some others. I cannot provide the details at this time. But regardless, I will not object. I personally consider the subject of loopholes itself a legitimate topic. I do object to placing a link to the loopholes on the main Bell page(s) - it belongs off of the test page to make any sense. -DrChinese 02:01, 7 December 2005 (UTC)
DrChinese, thanks for the clarification; at least the two of us have consensus on this and apparently Caroline agrees too. Let's wait a while for comments from others. Harald88 07:59, 7 December 2005 (UTC)

As there were no other comments, I now go ahead with the "clean-up", in an as neutral way as possible. Harald88 21:30, 12 December 2005 (UTC)

I removed the excessively strong statement "No absolute check on its validity is feasible." at the end of discussion on the fair sampling loophole. Dave Kielpinski 03:23, 14 December 2005 (UTC)

## Quantum erasure deserves a separate mention

I think the 1982 quantum erasure experiements deserve a separate mention here.

Bell inequality is very importent, and who can give all original literatures that can be free downloaded? And now these fangio.magnet.fsu.edu/~vlad/pr100/ are dead! Mhims 05:19, 10 July 2007 (UTC)

## wow..

i think i was aware of caroline's frustration with conventional bullheaded-ness, but i'm not sure i was aware of her battle with wp editors.. when i knew caroline, i invited her to join Faraday Group which is supposed to be an open forum for "free thinkers" like her .. but she declined .. she was already a member of a loose association of "physics interested people" .. i think she saw no gain to join FG - she simply wanted venues to "push her ideas" .. but i believe science needs ppl like caroline - they make us question our assumptions. for instance, cannot the Bell-type experiments be explained by a symmetrical decay process? if two photons/particles are emitted with opposite spin/polarization, cannot we suppose that they actually have opposite polarization? is it a sin to suggest they actually have a particular spin? sequentially, physics has rejected local determinism in favor for the random-wave model of e.p.s. so this section will be automatically dismissed by conventional thinkers. but if we accept the possibility that e.p.s and photons actually can have definite characteristics, explanation of Bell-type experiments becomes a moot point. "entanglement" is simply a reflection of a symmetrical decay process. local realism is far from dead. engineers have dealt with local reality for as long as physics has suckled random-wave and reduction. exact atomic control is a fair example of recent evidence that the "supremely important" Heisenberg uncertainty relations are becoming a relic. also, the theoretical side is being developed independently. Markus Lazar, published in arXiv, has developed a theoretical framework for e.p.s as distortions in space-time. in other words, he's on the verge of unifying the forces of nature from a deterministic POV. he's also found a correspondence between vortices (the e-m part of e.p.s) and deformations (the mass part of e.p.s). it's truly ground breaking work formally developed. i have long predicted engineers would do the job of unification "for" physicists .. a much less formal approach to the same was developed by yours truly over a 25 year period culminating in several booklets and papers including the following: N and Omega and Temporal Curvature and Elementary Particles. it's too bad caroline did not live to see these developments.. sam micheal&Delta (talk) 05:04, 24 November 2008 (UTC)

## External link does not work

The external link in reference 2 does not work, probably because access needs a subscription. Is there an alternative?WMdeMuynck (talk) 21:47, 5 February 2009 (UTC)

## Article need major rewrite

I rewrote the lead of ths article. I think the article as a whole needs a lot more work done on it. It is confused and out of date, and also rather biased to the point of view that local realism is a logically necessary fact of life and that all Bell experiments so far have failed to prove otherwise due to the loophole issues, as of course must be the case, according to this point of view. Richard Gill (talk) 18:34, 6 June 2012 (UTC)