Talk:Elitzur–Vaidman bomb tester

message: "... even though only one path is actually taken"
That is a classical point of view and has no real meaning in quantum mechanics.  The usual interpretation is that the photon does go through all possible paths, not that it somehow remotely "senses" them. Moo 02:00, 12 February 2007 (UTC)
replies: text: Not when an observer is introduced.  An observer, at the moment of observation, collapses the wave function, so the photon cannot be at two places at once.  The bomb detector acts as the observer. —The preceding unsigned comment was added by Thoreaulylazy (talk • contribs) 21:44, 3 March 2007 (UTC)
replies: text: There is always the old-fashioned point of view where the wave function "collapses" each time there is an observation. I have never liked this perspective, or even understood it, because there was never a formal criterion for when an observation is occurring. But nevertheless, this interpretation persists until today, at least for the Schroedinger equation, and it seems to be self-consistent. Therefore I took this point of view and even reinforced it in the edit I just did. 
178.38.122.45 (talk) 21:26, 10 April 2015 (UTC)
thread_title:  superposition 

message: In 1996, Kwiat et al. have devised a method, using a sequence of polarising devices, that efficiently increases the yield rate to a level arbitrarily close to one.
First of all, polarizing is spelled incorrectly.  Secondly, can anyone come up with a reference to this method?  I'd love to read more about it.  --216.152.208.1 03:40, 16 July 2007 (UTC)
replies: text: Note that a reference for this has now been added, and that "polarizing" is perfectly acceptable for US-English spellers (though I'd prefer the original "polarising") :-) 203.110.13.5 (talk) 05:58, 16 July 2008 (UTC)
thread_title:  Kwiat Reference? 

message: I heard this as a physics folk story, and the teller used plugers. It's an illuminating picture. If you look at the secondary literature on this, I am sure you will find a use of plungers somewhere. It's not wrong, so why delete it?Likebox (talk) 19:23, 4 December 2008 (UTC)
thread_title:  Plungers 

message: "A bomb sorter could accumulate". Hmm.... is it a sorter or a classifier? Cogiati (talk) 11:49, 27 July 2011 (UTC)
thread_title:  sorter? 

message: In linear optics, including the experiment described here, photons do not interact with each other (they can interact with material systems, the 'bomb' being the one relevant to this paper). The proper term for the process that occurs on the second half-silvered mirror is 'Interference'. I noticed that throuout the paper, except from one instance, 'Interaction' was used instead of 'Interference'. I think this should be corrected. 
Just for the record, I note that photon-photon interaction is possible in some circumstances involving highly non-linear materials or an atom strongly coupled to a photonic cavity. But, as stated above, these circumstances do not apply to the particular experiment discussed here.  — Preceding unsigned comment added by 132.77.4.129 (talk) 09:57, 16 January 2012 (UTC)
thread_title:  Interference vs. Interaction 

message: I think it should be stressed out that the presence of a working bomb is equavalent to taking a measurement of the location of the photon, even if the photon didn't hit the bomb, and went in the other direction. The cricial point is that the information about the presence of the bomb is extracted in any case, and not only when the photon hits the bomb. In the present paper this is only implicitly stated (in 'Step by step..').  — Preceding unsigned comment added by 132.77.4.129 (talk) 10:13, 16 January 2012 (UTC)
replies: text: Other noticed this too, see discussion several sections further on. 178.38.122.45 (talk) 21:15, 10 April 2015 (UTC)
thread_title:  Not hitting a working bomb is also a measurement 

message: Thoroughly excised.  — Preceding unsigned comment added by Rulatir (talk • contribs) 14:30, 22 October 2012 (UTC)
thread_title:  Newsweek link requires paid subscription 

message: I removed the following, which was labelled   (so more than two years):
: One conceptual way to understand this phenomenon is through the Everett many-worlds interpretation. This interpretation of quantum physics posits that whenever multiple outcomes are possible, every possible outcome in fact occurs, because the entire universe splits into multiple copies at that point, in each of which one of the possible outcomes has occurred. The parallel universes are completely independent except for the multiple copies (one in each universe) of the particle which caused the split, which can interact with each other giving rise to quantum effects.
: In the many-world interpretation, the superposition behaviour of the photons in the Elitzur–Vaidman bomb tester is interpreted as the result of interactions between the parallel copies of the photon in the multiple parallel worlds corresponding to the possible states of the photon. Therefore, when a photon encounters a half-silvered mirror, two worlds are created. In one world it passes through, and in another world it reflects off the mirror. These two worlds are completely separate except for the just-split photon in superposition. The photon that passes through the mirror in one world may still interact with the photon that reflected off the mirror in the other world; specifically, their waves interfere, giving rise to the effects observed in the experiment.
: 
It's not just that there's no citation yet; I don't think that there's likely to be anything interesting to say.  In a situation with no sentient observer, the different interpretations are generally indistinguishable (with a few exceptions).  Now put Wigner's friend in there with the bomb, and you've got something interesting: not just what the MWI says, but also how other interpretations differ.  (Of course, we would still need to cite a paper or something that that discusses this first.)
That said, there is an implicit claim at the very end that this is a form of weak coupling between worlds, so I left in one sentence to say that.  Of course, that still needs a citation; but I reset the clock to give it a fair chance.
—Toby Bartels (talk) 01:26, 25 August 2013 (UTC)
thread_title:  MWI 

message: I can't make head nor tail of this phrase: "with photons if a usable bomb good (at least some) without detonating it." Typo?  — Preceding unsigned comment added by 84.92.142.51 (talk) 16:14, 8 April 2014 (UTC)
thread_title:  Typo? 

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thread_title:  External links modified 

message: Hi and thanks for your contributions.  Here is a proposed illustration of how the experiment works.  It is a rough draft.  Please give me feedback.  Also, I am concerned about OR, so please consider that as well as the content.  Informata ob Iniquitatum (talk) 20:22, 15 August 2017 (UTC)
thread_title:  Proposed Illustration 

message: Hi all, thanks for contributing!  
This topic is near and dear to me and I have never been terribly happy with the existing article.  I have done a rewrite and propose it for replacing the current article.  Please see it here.
I look forward to people's sundry input, feedback and revisions.  Informata ob Iniquitatum (talk) 08:16, 9 September 2017 (UTC)
replies: text: Hi, I just read your rewrite and like it. Only one small thing I am not so happy with: The old and your new version both say something like "the bomb both explodes and doesn't explode". I would phrase it more cautious: It is not defined if the bomb explodes or not. -Charlie- (talk) 15:10, 19 September 2017 (UTC)
thread_title:  Proposed rewrite  

message: They're switched in the "Results" section. Note that the diagram at the top (near the lede) has C and D in opposite positions from the series of diagrams below. Holy (talk) 00:55, 11 October 2017 (UTC)
replies: text: I agree.  On 24 September informationvsinjustice's addition of Figure 1 interchanged detectors C and D from their positioning relative to the main diagram at the top (near the lede).  The text in the results section is consistent with Figure 1, but not with the diagram near the lede.  One of the two diagrams should be fixed.  (However, it would be possible to make the text consistent with both, but that would be a pity IMHO).  LondonYoung (talk) 14:25, 27 October 2017 (UTC)
replies: text:  The question is is it worth the trouble to fix / make them consistent?Informata ob Iniquitatum (talk) 02:04, 28 October 2017 (UTC)
replies: text:  In my opinion, it is certainly worth modifying the text in the "results" section to be consistent with either diagram.  A slightly better alternative would be to replace the diagram in the lede with Figure 1.  Both of these options are pretty easy.  Ideal would be to swap C and D in the top diagram, but I don't know how to edit a figure like that - so this option might not be worth it.  LondonYoung (talk) 14:38, 28 October 2017 (UTC)
replies: text:  On the lattermost suggestion here, I have edited the top diagram to swap C and D. This alternative has the superficial advantage of consistently assigning the Constructive interference detector with C and the Destructive interference detector with D.  Gizm0steve (talk) 16:09, 18 September 2019 (UTC)

text: Maybe we dare snip from this site for the lede illustration?   https://www.st-andrews.ac.uk/physics/quvis/simulations_html5/sims/QuantumBombGame/Quantum_bomb.html LondonYoung (talk) 20:00, 28 October 2017 (UTC)
thread_title:  C and D are switched! 

message: The many notes that cite "Elitzur Vaidman 1993" simply link back to the Wikipedia article itself. Can someone please link them to the actual paper, if it's available, or remove the links if it's not? I will do so if I find the paper. Thank you. Holy (talk) 22:13, 14 October 2017 (UTC)
replies: text: Fixed, thanks.  I'm only just getting familiar with sfn.  They now properly link to the sources.  Informata ob Iniquitatum (talk) 17:10, 17 October 2017 (UTC)
thread_title:  Links in notes are incorrect 

message: Can someone please explain how the second half-silvered mirror would be made such that constructive interference would force the photon to go to sensor C, but behaving like a particle it would go to either C or D? The article seems to just say that the mirror is aligned "such that" it would behave like this, but without clearly explaining how that works, the whole thing is pretty hard to understand.
The crux of the setup seems to be "if superposition, then C, if particle, then C or D", but it's difficult to understand how that if statement could be arranged in the first place, or how that would work.50.194.115.156 (talk) 14:49, 17 September 2019 (UTC)
thread_title:  How would it be made? 

message: There is a web comic about this (thought) experiment, and since then, this article has seen a lot of attention and changes.  While the additional explanations are mostly very good, it might need a general cleanup now.
--Quazgar (talk) 06:54, 20 September 2019 (UTC)
thread_title:  SMBC comic & cleanup 

message: Sorry if I am wrong, but in the Results section and the paragraph where it says 2.The photon was detected at C: the last sentence states that the photon was reflected off the last mirror, but according to the diagram to take the upper path to get to detector C the photon must have passed through the second silvered mirror. Should reflected off be changed to passed through?
Also in the next paragraph 3.The photon was detected at D: it states that the photon must have passed through the silvered mirror to reach detector D, but to get to detector D from the upper path according to the diagram, the photon must have reflected off the second silvered mirror. Should passed through be changed to reflected off?
:Yes, it's incorrect, please change it. Note the text just below it: . Apparently somebody fixed the figure in the meantime but forgot to fix the text. Tercer (talk) 10:23, 27 September 2021 (UTC)
replies: text: Thanks, all done.49.184.88.41 (talk) 06:32, 29 September 2021 (UTC)
thread_title:  Reflected or Passed Through in Results Section? 

message: It is stated that if the Photon is detected at D then the bomb is live but unexploded. This is because the photon took the upper path. But a photon can also take the upper path when the bomb is a dude.  — Preceding unsigned comment added by 213.225.35.4 (talk) 18:37, 28 October 2022 (UTC)
replies: text: That is correct, but when the bomb is a dud then the photon, even if it "really" takes the upper path, also appears to take the lower path and interferes with itself.  It doesn't actually take the lower path--and therefore doesn't set off the bomb--but in the case of a dud bomb it interferes with itself exactly as if it had taken both paths... and by interfering with itself, it prevents itself from ever hitting D.   The double slit experiment is the most famous practical example of this phenomenon in action.  Yes, this is all really weird. This is why quantum mechanics has the reputation that it has.  -- 184.89.44.198 (talk) 09:16, 6 November 2022 (UTC)
thread_title:  Upper Path not Understood 

message: I don't understand this experiment. If the bomb is obstructing the lower path, won't it obstruct the photon regardless of whether it is dud or working? How can the photon keep going through the bomb if it is dud? 95.172.233.137 (talk) 21:06, 25 May 2023 (UTC)
replies: text: see the section "How it works": the assumption is that the duds do not have light-sensitive sensors that absorb the photon; instead the photon passes undisturbed. ("the triggers on the dud bombs have no sensor, so any light incident on the bomb will not be absorbed and will instead pass straight through"). --Qcomp (talk) 14:55, 27 May 2023 (UTC)
replies: text: Thank you, Qcomp, very much for your reply. It therefore seems to me that for the purposes of this experiment, a "dud" bomb is equivalent to a non-existent bomb. Am I correct? 95.172.233.137 (talk) 14:46, 29 May 2023 (UTC)
thread_title:  Bomb always in the way, dud or working?