Talk:Schrödinger's cat/Archive 5

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Change in definition

I notice that a sentence in the lead that defines Schrodinger's cat has been changed to "The scenario presents a cat that is randomly put in a state where alive and dead are both possibilities, requiring further observation to determine which." This seems to be a modern view or a resolution of the "paradox," but I don't think it accurately describes the thought experiment as originally put forth by Schrodinger. A previous version of that sentence read, "The scenario presents a cat that may be both alive and dead, this state being tied to an earlier random event." As I understand it, this is the "quite ridiculous case" that Schrodinger envisioned. I understand the reason for the change, but perhaps the description would be more complete if it were something like, "Originally, the scenario presented a cat that may be both alive and dead, this state being tied to an earlier random event. However, today the scenario is generally presented as a cat that is randomly put in a state where alive and dead are both possibilities, requiring further observation to determine which." The difficulty I see with the current wording is that there's no sense at all why this scenario would be considered paradoxical, or a problem (mentioned in the sentence before the definition). Schrodinger wrote of "the living and dead cat mixed or smeared out in equal parts" which is not the same as the currently presented definition. Thoughts? -Jordgette [talk] 01:54, 1 February 2015 (UTC)

The definition should not say that the cat is alive and dead at the same time, as it is not clear that the concept makes any sense. I say that it is better to give a definition that anyone can understand, and then explain later how the quantum superposition of states is puzzling. Roger (talk) 03:43, 1 February 2015 (UTC)
Jordgette is right. The point of the thought experiment is that the inside of the box may be in a superposition for an undetermined amount of time, consisting of a linear combination of eigenstates containing a live cat and eigenstates containing a dead cat. If you look at the archives of this Talk page, you find that an extremely common misconception is that people think the cat is in a definite state at all times, either alive or dead, and the only "paradox" is that an observer outside the box doesn't know what that state is. The article needs to use language (from the beginning) that avoids this misconception and indicates the existence of the superposition. Yes, this is more difficult to understand, Roger, but it is the essence of the experiment. It is why Schro's Cat has been debated by scientists and philosophers for 80 years. --ChetvornoTALK 07:19, 1 February 2015 (UTC)
"...you find that an extremely common misconception is that people think the cat is in a definite state at all times, either alive or dead,..."
Cats are in a definite state at all times, either alive or dead. It is only by the quantum interpretation of the experiment that the cat is both alive and dead. That's the point of the experiment. To illustrate that we need not, and perhaps should not, apply quantum mechanics to the macro-world, however blurry the experiment makes that line. --RacerX11 Talk to meStalk me 07:45, 1 February 2015 (UTC)
No, that is a matter of interpretation. In some interpretations, as you say the wavefunction collapses and the cat is either alive or dead. However, as the article indicates, in others, such as the Many worlds interpretation, there is no wavefunction collapse, the "macro-world" splits, and there are multiple worlds, some with live cats and some with dead cats, all equally real. People usually have their favorite interpretation of the experiment and violently disagree with others, but to be WP:NPOV the article must include the range of scientific opinion. --ChetvornoTALK 08:19, 1 February 2015 (UTC)
I suggest the following: "It illustrates what he saw as the problem of the Copenhagen interpretation of quantum mechanics, which, when applied to everyday objects, can result in absurd conclusions. The scenario presents a cat that may be considered as being simultaneously both alive and dead, this state being tied to an earlier random event. The thought experiment is often featured in theoretical discussions of the interpretations of quantum mechanics, where different interpretations give different accounts of the underlying nature of Schrödinger's scenario." Or something like that. -Jordgette [talk] 22:13, 1 February 2015 (UTC)
That sounds okay to me. --ChetvornoTALK 23:05, 1 February 2015 (UTC)
No, the opening paragraph should not say that the cat is both dead and alive. That is a particular interpretation, and I do not think that either Schroedinger or the early Copenhagen proponents subscribed to it. Maybe you could say that later, as long as it is attributed to whoever believed that. But the opening paragraph should just describe the experiment in terms where everyone would agree. Roger (talk) 00:27, 2 February 2015 (UTC)

Actually, that isn't an interpretation. You'd be hard pressed to find a physicist who believes that the cat is objectively both alive and dead. The thing that is disputed is how the globally superposed system transitions into a definite state of cat. In fact, everyone does agree on what Schrodinger intended with the thought experiment -- that it's a reductio ad absurdum which Schrodinger created to make a point. Trying to change the definition so that it "makes sense" or so that it doesn't sound absurd does the opposite of what Schrodinger intended. -Jordgette [talk] 01:29, 2 February 2015 (UTC)

Were you referring to Many Worlds when you said "that isn't an interpretation"? I always thought the literature regarded it as one. Plenty of WP:RSs seem to say that in the Many Worlds interpretation the cat is both objectively alive and dead: [1], [2], [3], [4], [5], [6], [7]. The live and dead cats can't both be observed by the same observer; due to decoherence they are in separate "worlds", but they both exist simultaneously. I agree that in recent years research has focused on decoherence (how the "globally superposed system transitions into a definite state of cat") and it has been established as the cause of the appearance of wavefunction collapse. But I am not clear that decoherence has replaced the interpretations as a "solution" to Schro's Cat. Until WP:RSs say that, it seems to me the article should treat the major interpretations, including MW, on an even basis, in which case "simultaneously alive and dead" is one valid scientific view of the experiment. --ChetvornoTALK 03:46, 2 February 2015 (UTC)
I meant simultaneously and objectively in the same world, i.e. persisting in a macroscopic state of superposition like a room-temperature SQUID despite what we know about decoherence. Sorry for the confusion. -Jordgette [talk] 04:55, 2 February 2015 (UTC)

I do not see a consensus here. The proposed text has these weasel words: "may be considered as being simultaneously both alive and dead". May be considered by whom? Or by what interpretation? Not by Schrodinger and not by Copenhagen, so how can the reader make sense of this? The next clause is even more confusing: "this state being tied to an earlier random event". Does "this state" refer to being simultaneously alive and dead? If so, how is it tied to an earlier event? Usually event means a determinitive outcome, in which case the cat would be alive or dead, but not both. I think this is very confusing and unnecessary, considering that the situation is explained much better later in the article and in Copenhagen interpretation. Roger (talk) 23:49, 4 February 2015 (UTC)

Actually, the version you just reverted was much closer to the previous version before you came on the scene, which had been arrived at by consensus over several years (see archives and history). And now you've removed sourced content and replaced it with your previously removed original-research definition of Schrodinger's cat. So with one revert, you've (1) removed sourced content, (2) edited against consensus, (3) inserted original research, and (4) edit-warred. Here's a thought: Can you produce a reliable source (or 5) which state that Schrodinger's intent for the thought experiment is as you define it? If not, please do not change the definition again. -Jordgette [talk] 00:31, 5 February 2015 (UTC)
@Roger:I agree with the above. Here are my answers to the questions you posed:
  • "By whom?": Well, for starters, by the 5 WP:RELIABLE SOURCES which I cited, which you reverted without providing a single source to support your wording. I could cite a lot more; "alive and dead" is one of the most common ways of describing the paradox of Schrodinger's Cat.
  • "not by Schrodinger": In case you haven't read anything on SC published in the last 70 years, Schrodinger is not the last word on Schrodinger's Cat. Schro didn't believe the cat could be alive and dead, but many, many other physicists since his time have devised alternate interpretations of the experiment, and by some of them, the cat is regarded as alive and dead.
  • "...by what interpretation?": Many Worlds, as the above discussion, the article, and three of the texts I cited state. There may be others.
  • "The proposed text has these weasel words: "may be considered..."": These are not weasel words, but a description of the multiple possible interpretations which are consistent with the thought experiment. The cat "may be considered" alive and dead in some interpretations and "may be considered" alive or dead in others.
  • "The next clause is even more confusing: "this state being tied to an earlier random event"": I agree, that wording might not be the best. I would be open to discussion of rephrasing that part, but not "alive and dead".
My objection objection to your wording is that it is not going to mean much to nontechnical people who are reading about Schrodinger's Cat for the first time. Their reaction is likely to be: "A cat is . . . put in a state where alive and dead are both possibilities"??? So what? ANY cat, put into ANY box so you can't see him, alive and dead are both possibilities. So the cat is either killed by the poison or it isn't. Big deal. The significant point of SC is the superposition states; the wavefunction in the box starts out in a superposition of "cat alive" and "cat dead" states, and we don't know how long it lasts; it may last until the cat is both killed and not-killed, so there is a superposition of "live cat" and "dead cat" in the box. --ChetvornoTALK 01:15, 5 February 2015 (UTC)
In place of "this state being tied to an earlier random event", how would you feel about: "...as a result of its fate being linked to a random event which may or may not occur"? -Jordgette [talk] 01:49, 5 February 2015 (UTC)
I was wondering if we could get some reference to "superposition" or "quantum event" into the wording? Or do you think that's too confusing for the introduction? It seems to me that one source of confusion is that the wording of the intro doesn't include the point that the cat's survival has to be dependent on a particular type of random event: a "quantum" event, a "quantum superposition". Therefore people are getting the idea that the issue of Schrodinger's Cat is something that applies to any random event occurring in a closed box, so they think all it means is "nobody knows the outcome of a random event in a closed box until it's opened". Other than that, I don't really have much objection to the existing wording. Your alternate wording above doesn't seem all that different, but I'd be okay with it too, if you prefer it. --ChetvornoTALK 02:49, 5 February 2015 (UTC)
Perhaps: "...as a result of its fate being linked to the occurrence or non-occurrence of a random subatomic event"? This also addresses Roger's valid objection below. It would be nice to get the basic idea across without having to introduce terms that haven't been explained yet, of course without oversimplifying. -Jordgette [talk] 19:24, 5 February 2015 (UTC)
I think "subatomic event" is a little better and I wouldn't mind that wording, but I'd prefer "quantum event" or "superposition". Maybe introducing the latter term in the intro, even without explanation, is worth it? I don't see that Roger's objection is valid; I think once again he has the wrong view when he writes: "The event is not what makes the cat alive and dead at the same time. Arguably it is the "may or may not"..." Every WP:RS description of the Schrodinger's cat thought experiment makes clear that the cat must be entangled with a quantum superposition, and specifically explains how the non-classical quantum aspects of the superposition result in the possibility of alive-and-dead cat. As I say, I think the initial sections of our article soft-peddle this point, and general readers are not understanding the crucial concept that all the strange aspects of the SC thought experiment come from this very special quantum state. --ChetvornoTALK 22:15, 5 February 2015 (UTC)
You don't really have 5 sources. The only one that says the cat is alive and dead is "The Complete Idiot's Guide to Theories of the Universe". It is not the best source as it oversimplifies.
Yes, some people believe the cat is alive and dead, and some believe in Many Worlds, but Schrodinger was critiquing Copenhagen, not Many Worlds.
You say that my sentence does not seem mysterious enough. Yes, but the physical setup is not mysterious at all. It only becomes mysterious when you add some confusing quantum interpretation.
I think "fate being linked to a random event which may or may not occur" is confusing. The event is not what makes the cat alive and dead at the same time. Arguably it is the "may or may not", but it takes some explanation.
If you don't like my sentence, and want "both dead and alive", then I suggest the paragraph on the subject at Copenhagen interpretation. It seems more correct to me. Roger (talk) 03:28, 5 February 2015 (UTC)
The fact that virtually every author on Schrodinger's cat, whether or not he agrees with the interpretation, uses the words "alive and dead" to describe the cat, shows that the possibility of the cat being both alive and dead is the essence of the experiment. This Wikipedia article would be grossly biased if it did not include the possibility of the cat being "alive and dead". --ChetvornoTALK 11:58, 5 February 2015 (UTC)
Schrodinger himself used the phrase "living and dead cat", as quoted later in the article. If you define the S Cat the way he does, then I can have no objection. But he does not say that the cat is really alive and dead. He says that this is a ridiculous case, that the psi-function expresses a mixture of a live and dead cat, that direct observation resolves the indeterminacy, and that we do not accept the blurred model as reality. Say those things, and I am fine with the "living and dead cat".
I concede that there are quantum popularists who express this in a sloppy way, and that Many Worlds believers say that the cat really is alive and dead at the same time. But Schrodinger was not a believer in Many Worlds, and the paradox was aimed at Copenhagen, not Many Worlds. The opening paragraph should describe Schrodinger's cat, not the Many Worlds cat. Roger (talk) 19:00, 5 February 2015 (UTC)

Here are a couple more possibilities for the wording of the definition: (1) "The scenario presents a cat that may be considered as being simultaneously both alive and dead, a state known as quantum superposition, where the cat's life or death is linked to a random subatomic event that may or may not occur." Or perhaps more rigorously but less readable: (2) "The scenario presents a cat that may be considered as being simultaneously both alive and dead, as a result of being part of a system that exists in a state known as quantum superposition, where the cat is causally linked to a random subatomic event that may or may not occur." I am avoiding using the term "determines" or "is determined by" which existed in a previous form of the definition and may lead to confusion. -Jordgette [talk] 02:41, 7 February 2015 (UTC)

No, this is still wrong for all the reasons I have listed before. I don't even know what you mean by it. When you say the weasel "may be considered", do you mean by Schrodinger, by Copenhagen, or by the Many Worlds interpretation? If Schrodinger, it is contradicted by his own description later in the article. If Copenhagen, it is debatable and hence confusing. If Many Worlds, then yes the cat is alive and dead, but then "event that may or may not occur" is inaccurate because the event both occurs and does not occur. So I do not see how to make sense out of it. And a non-expert reader is going to be thrown by the word "superposition". I would leave that word out of the first paragraph. Roger (talk) 05:57, 7 February 2015 (UTC)
@Jordgette: Either (1) or (2) would be fine, a big improvement. I don't mean to be picky, but my feeling is it would be even better to indicate that the original random event must be a quantum superposition; something along the lines of a previous version you had: "The scenario presents a cat that may be considered as being simultaneously both alive and dead, due to its survival being linked to a random subatomic event which may or may not occur, a state known as a quantum superposition." --ChetvornoTALK 06:28, 7 February 2015 (UTC)
I think I prefer #2 -- I like that it mentions that the system is causally linked and the system would be in a global state of superposition, according to Schro's original vision (which then leads to the entanglement concept that follows). I'm not crazy about the construction "...its survival being linked to a random subatomic event which may or may not occur, a state known as quantum superposition" because that sounds like its survival is a state of superposition. I'd really like to get one more opinion. Roger, "may be considered" is fine even when referring to Schrodinger; Schrodinger did consider that according to Copenhagen, the cat would be both alive and dead, and so he rejected this conclusion. -Jordgette [talk] 22:41, 8 February 2015 (UTC)
No, neither of you are addressing anything I said. Schrodinger does not say that the cat is alive and dead under Copenhagen. He says "The psi-function of the entire system would express this by having in it the living and dead cat (pardon the expression) mixed or smeared out in equal parts." He is talking about what psi expresses, not what the cat is. You persist in an interepretation that is contrary to what Schrodinger said. Roger (talk) 23:53, 8 February 2015 (UTC)
@Roger: You seem to want the introduction to the article to reflect only Schrodinger's view and the Copenhagen Interpretation of the experiment. This contradicts the sourced Interpretations of the experiment section. In order to take this view, the article would require WP:RSs that the Copenhagen Interpretation is the only valid interpretation of the experiment. And not just some, but enough to refute the many, many authors that present other interpretations. I don't see that there is any such unanimity of opinion. --ChetvornoTALK 01:36, 9 February 2015 (UTC)
Not at all. I favor describing the facts common to all interpretations. If there is room for opinions and interpretations in the opening paragraph, then go ahead, as long as they are carefully labeled. I agree that there is no unanimity of opinion about interpretation. As it stands, the paragraph uses passive voice and weasel words to avoid saying whose interpretation it is, while letting the reader infer that it is Schrodinger's, as he is the only one mentioned. But it is not the opinion of Schrodinger, it is the opinion of the Idiot's Guide. Roger (talk) 03:42, 9 February 2015 (UTC)

@Jordgette: I'd say go ahead with either (1) or (2); they're both compatible with the citations. --ChetvornoTALK 13:15, 9 February 2015 (UTC)

You should be remove the "by whom" from "may be considered" unless you are willing to say who considers it that way. It is nearly always very bad form to say "may be considered" without saying by whom. Roger (talk) 04:24, 14 February 2015 (UTC)

@Roger: That question is answered in the Interpretations of the experiment section, as well as in the 7 supporting citations. The introduction is just a summary of the article. It's way too confusing, and not important to go into multiple interpretations there. --ChetvornoTALK 05:29, 14 February 2015 (UTC)
So what is the answer? If it is so important to say that someone considers the cat to be dead and alive, then why not say who it is?
You are edit warring instead of addressing the issues on the Talk page. Yes, Schro's Cat is explained elsewhere reasonably. But you insist on a wrong explanation in the lead paragraph. Roger (talk) 05:52, 14 February 2015 (UTC)
@Roger: If not "dead and alive", what wording would you like to see in the intro? --ChetvornoTALK 09:10, 14 February 2015 (UTC)
My suggestion is here. [8] I would also be fine with how Schrodinger explained it. [Schr%C3%B6dinger%27s_cat#The_thought_experiment] Or how it is explained in [Copenhagen interpretation]. Or as it is in the simplified WP. [9] Or anything that is consistent with textbook treatments of quantum mechanics. Don't just say "may be considered" unless you are willing to say who considers it that way. Roger (talk) 15:44, 14 February 2015 (UTC)

Jordgette, you just made another dubious edit. You changed it to "According to the thought experiment, a cat must be simultaneously both alive and dead". On this talk page, you said "You'd be hard pressed to find a physicist who believes that the cat is objectively both alive and dead." So why do you persist in saying something that no physicist believes? Roger (talk) 07:01, 15 February 2015 (UTC)

Schrodinger's cat is a reductio ad absurdum. The idea of a reductio ad absurdum is to come up with a scenario that is intentionally absurd-sounding, in order to argue against a proposition. "It illustrates what he saw as the problem of the Copenhagen interpretation of quantum mechanics applied to everyday objects...Schrodinger considered the scenario 'quite ridiculous,'" etc. I answered this question previously, in fact two sentences after the one you quoted. Surely by now you must grasp that the whole point of the thought experiment was to present a scenario designed so that no one should believe it is actually true (even though, today, some do apply it literally to multiple worlds). -Jordgette [talk] 20:00, 15 February 2015 (UTC)
Exactly. Roger, you're missing the point about Schrodinger. Schrodinger invented the thought experiment to create an "alive and dead cat" state, to show what he felt was the absurdity of the Copenhagen Interpretation. Right? Even though he didn't believe it was possible, the "alive and dead cat" was the whole point. The same applies to modern views of the experiment. Some scientists regard the "alive and dead cat" state as possible, some regard the experiment as a "reductio ad absurdam". For both, the possibility of creating an "alive and dead cat" state is what the experiment is all about. If we don't say "alive and dead cat", we're leaving out the whole point of Schrodinger's absurdity demonstration. --ChetvornoTALK 20:36, 15 February 2015 (UTC)
Maybe you guys think that quantum mechanics is absurd, or the Copenhagen interpration is absurd. I don't know. But your current wording is contradicted by your own sources. It says "a cat must be simultaneously both alive and dead". But no source says "must". A couple of them only say that the many-worlds interpretation makes the cat dead and alive. One says that "some physicists would argue" for alive and dead, but then says that "a more plausible view" is otherwise.
Jordgette, you say "Surely by now you must grasp that the whole point of the thought experiment was to present a scenario designed so that no one should believe it is actually true". No, I do not get this point out of anything you have written on this subject, nor do I think that the typical WP reader would either. You seem to be saying the opposite. And why are you edit warring for text that no one should believe? Roger (talk) 21:37, 15 February 2015 (UTC)

Edit conflict over wording of introduction

There is an edit war developing over the wording in the introduction

"The scenario presents a cat that may be simultaneously both alive and dead, a state known as a quantum superposition, due to a random subatomic event that may or may not occur."
  • One editor, Roger, favors
"The scenario presents a cat that is randomly put in a state where alive and dead are both possibilities, requiring further observation to determine which."

Which wording should the article use? --ChetvornoTALK 18:43, 17 February 2015 (UTC)

The argument is over the phrase "alive and dead" cat, which we favor. It is supported by 7 citations in the introduction. No supporting citations have been given for the 2nd wording. Schrodinger designed the thought experiment to produce a superposition of states containing both alive and dead cat. Although he didn't believe that such a state was possible and intended the experiment to show the absurdity of this interpretation of quantum mechanics, the "alive AND dead" cat was the point of the experiment. Almost every author on Schrodinger's cat, whether or not he agrees with that view, describes the experiment in those words. Note the wording does not say the cat must be alive and dead. However, some interpretations of quantum mechanics (Many Worlds) do regard the alive and dead cat superposition as actually occurring. The 2nd wording, which says that "alive and dead are both possibilities", simply describes a classical view in which the cat is either alive OR dead. This wording completely misses the point of the experiment, and Schrodinger's intent, and leads to common misunderstandings by general readers which constantly show up on this Talk page. --ChetvornoTALK 19:53, 17 February 2015 (UTC)
Support #1 - not much more to say, you've summed up the reason why the first sentence is better. Primefac (talk) 21:23, 17 February 2015 (UTC)
Support #1 - this is a no-brainer. #1 is agnostic and widely accepted, #2 is a minority interpretation. — Cheers, Steelpillow (Talk) 21:47, 17 February 2015 (UTC)
No, #1 is not agnostic. It mainly follows the many-worlds interpretation. #2 just describes the physical setup, without invoking any quantum mechanics or interpretation. Roger (talk) 00:01, 19 February 2015 (UTC)
Can you explain why it's preferred not to invoke quantum mechanics when describing a thought experiment about quantum mechanics? This is like describing the Michelson–Morley experiment without mentioning the aether, and instead just saying that two light beams were found to behave the same despite being perpendicular. It's not a helpful introduction; the experiment seems irrelevant and uninteresting. -Jordgette [talk] 02:26, 19 February 2015 (UTC)
Invode QM all you want, but do it correctly. Some interpretations say that the cat is both alive and dead. Some do not. To just make a blanket statement that the cat is alive and dead is wrong. Roger (talk) 03:18, 19 February 2015 (UTC)
According to the thought experiment, the cat is alive and dead. This can either be absurd or literal, depending on one's interpretation, but SC is about the cat being alive and dead. I'm sorry but you'll never win that particular argument. -Jordgette [talk] 04:28, 19 February 2015 (UTC)
No, that is not right. Just read Schrodinger. He said: "The psi-function of the entire system would express this by having in it the living and dead cat (pardon the expression) mixed or smeared out in equal parts." He did not say that the scenario presents a cat which may be simultaneously both alive and dead. Roger (talk) 23:01, 19 February 2015 (UTC)
So why then does he describe that scenario as being "quite ridiculous"? What do you suppose he actually meant when he said the system's wave function would be smeared out into equal parts containing "the living and dead cat"? -Jordgette [talk] 00:53, 20 February 2015 (UTC)
I assume that he meant what he said. The scenario is ridiculous because it ties atomic decay to the life of a cat. He might have said "amusing" or "silly". His comment about the wave function means that quantum mechanics gives a superposition, and the probabilities of various cat observations can be calculated by the appropriate inner products on that wave function. Schrodinger explains himself quite clearly, and more clearly than the WP opening paragraph. Roger (talk) 05:37, 20 February 2015 (UTC)
As for Michelson-Morley, I would say in the first paragraph that it was an attempt to detect a difference between the speed of light in perpendicular directions on Earth. Looking at the article, you have to wade thru a lot of aether stuff and buy into a particular aether interpretation before finding out what the experiment did. I would say that article should describe the experiment before babbling about interpretations that Michelson and Morley probably did not even subscribe to. Roger (talk) 03:18, 19 February 2015 (UTC)
The idea that #1 is effectively the many-words interpretation is absurd and needs no further rebuttal. More significantly, Wikipedia does not document what editors believe to be true, it documents what reliable sources tell us is true - see WP:VERIFIABILITY and WP:RS. — Cheers, Steelpillow (Talk) 08:29, 19 February 2015 (UTC)

Oppose #1 - It is incorrect and not supported by any of the references. The preceding sentences are about Schrodinger and Copenhagen, but as explained later in the article, neither Schrodinger nor Bohr believed the cat to be both alive and dead. The promoters of many-worlds say that, as some of the references say. However this is an article about Schrodinger's cat, not the many-worlds cat. I am fine with how Schrodinger describes it, or how it is described elsewhere on WP or in quantum textbooks. See above discussion for more details. Roger (talk) 00:01, 19 February 2015 (UTC)

The key point about the thought experiment was that Schrödinger did not believe the Copenhagen interpretation. The lead needs to explain the thought experiment and its absurd proposition that Schrödinger did not believe. His personal interpretation may then be covered later in the lead and/or later in the main text. — Cheers, Steelpillow (Talk) 08:29, 19 February 2015 (UTC)
I agree, I think the 2nd sentence of the intro makes (or attempts to make) that point. --ChetvornoTALK 17:04, 19 February 2015 (UTC)

Roger, you need to stop WP:PUSHing your unsourced WP:FRINGE viewpoint. You are the only editor who supports this view against 7 sources and the consensus of 4 editors. --ChetvornoTALK 01:51, 22 February 2015 (UTC)

No. My edit is not against any of the sources. Nor is it against any consensus here. If it is wrong, then please explain it here or point to some source that says it is wrong. I follow what Schrodinger said, and what the textbooks say. Roger (talk) 02:47, 22 February 2015 (UTC)

Regardless of one's personal opinion, the consensus on this talk page is rather clear. I should point out to other interested editors that the caption on the illustration remains worded against that same consensus, having been changed to the "possibilities" wording along with the original introduction edit [10], which has since been changed. -Jordgette [talk] 03:51, 22 February 2015 (UTC)

Additional entry in the Section titled "Interpretations of the experiment."

Resolution based on standard quantum theory and experiments

Schrodinger died before the investigations of the nonlocal properties of entangled systems initiated by John Bell's work in 1964. [1] [2] The Schrodinger's cat issue needs to be revisited in light of current knowledge about nonlocality. Bell's work led to experiments with entangled photon pairs that demonstrate the nonlocal nature of entanglement. [3] [4] Experimenters were able to vary the quantum "phases" of both entangled subsystems (i.e. both photons), making it possible for the first time to understand precisely what is superposed when quantum systems are entangled. [5] [6] The interference effects observed upon varying the photons' phases revealed that the entangled state is not a superposition of different states of the individual photons, but rather a superposition of the possible correlations between the states of the photons. The entangled state arising from a measurement is simply a special case of this nonlocal entangled state, namely the case in which both subsystems' phases are set to zero so that outcomes are 100% positively correlated. Thus the state of Schrodinger's cat is simply a superposition of two correlations: A live cat is perfectly correlated with an undecayed nucleus, and a dead cat is perfectly correlated with a decayed nucleus. [7] That is, in every experimental trial of the cat experiment, we will find either a live cat and an undecayed nucleus or a dead cat and a decayed nucleus. This is what we want, and is not paradoxical. Quantum physics does not predict a superposed dead-and-alive cat, and the supposed paradox vanishes. Art Hobson (talk) 18:19, 12 February 2018 (UTC)Art Hobson, Emeritus Professor of Physics, University of Arkansas, Fayetteville

The entry as written has, at best, undue weight. At present, with no secondary sources having commented on the paper, one sentence mentioning the suggested resolution would be generous. -Jordgette [talk] 06:21, 14 February 2018 (UTC)

References

  1. ^ Bell, J.S., (1964), "On the Einstein-Podolsky-Rosen paradox," Physics 1, 195-200.
  2. ^ Gilder, L., (2008): The Age of Entanglement: When Quantum Physics Was Reborn (Alfred A. Knopf).
  3. ^ Clauser, J. F., and Freedman, S. J. (1972): "Experimental test of local hidden-variables theories," Physical Review Letters 26, 938-941.
  4. ^ Aspect, A., Dalibard, J. and Roger, G., (1982): "Experimental test of Bell's inequalities using time-varying analyzers," Physical Review Letters 49, 1804-1807.
  5. ^ Rarity, J.G., and Tapster, P.R., (1990), "Experimental violation of Bell's inequality based on phase and momentum," Physical Review Letters 64, 2495-2498.
  6. ^ Ou, Z.Y., Zou, X.Y., Wang, L.J., and Mandel, L. (1990), "Observation of nonlocal interference in separated photon channels," Physical Review Letters 66, 321-324.
  7. ^ Hobson, A. (2017): "Review and suggested resolution of the problem of Schrodinger's cat," Contemporary Physics 59, 16-30.

I refuse to accept it

I don't care how many pretty diagrams you use, how many big-name scientists talked about it, or your expirements on atoms. A cat can NOT be alive and dead at the same time. If this article does convince someone that such a thing is possible, then we have a Lenin was a mushroom-type case on our hands. 217.100.32.162 (talk) 08:58, 21 June 2019 (UTC)

The point of the thought experiment was to present an absurd scenario. So, I'm glad you got that part. Now maybe you can learn why Schrodinger wanted to present an absurd scenario. -Jordgette [talk] 21:17, 21 June 2019 (UTC)
This article really does not make that point clear. There seem to be quite many people who believe that it has been seriously suggested that a cat might be both alive and dead at the same time. And it really doesn't help that many physicists reinforce this belief in their attempts to popularize quantum mechanics. Yuhani (talk) 16:05, 17 July 2019 (UTC)
I think the second sentence of the intro makes it clear, as do several other passages in the article. Can you think of any ways that such misunderstandings can be further reduced, without oversimplifying the concept or stripping it of its nuance? -Jordgette [talk] 17:05, 17 July 2019 (UTC)

Maybe I'm missing something ...

I feel like I'm not understanding something, or maybe I'm just accustomed to thinking in terms of statistical processes, and so I'm possibly an "ensemblist". I don't see the paradox in Schrödinger's cat experiment. It seems like it is a paradox *only* if one insists on trying to interpret quantum mechanics in a purely deterministic way. Otherwise, if one accepts the statistical nature of quantum mechanics, there is no problem that I can see. If this is the dichotomy, then perhaps the article can make this point more clearly. Attic Salt (talk) 15:15, 23 December 2019 (UTC)

It's not really a paradox. It's a paradox, of sorts, if you believe that superpositions can become wildly macroscopic — but the discovery of decoherence has put that to rest. And even without decoherence, the cat is an observer. For that reason I rather prefer "Einstein's powder keg" myself. -Jordgette [talk] 18:51, 23 December 2019 (UTC)
Yeah, as you say "paradox" is not totally accurate. @Attic Salt: The article doesn't go into detail much. It could probably be improved. The point of the experiment is: exactly when and where does wavefunction collapse occur? On an atomic scale, the wavefunction representing a particle can be in a superposition of states, it can have components representing the particle at different positions or states at the same time. In the Schrodinger experiment it is a radioactive nucleus; before they are observed, radioactive nuclei are in a superposition of an undecayed nucleus and a nucleus which has emitted gamma rays. In the experiment this particle in a superposition interacts with more and more other particles (the "outside world") in such a way that the two different possible states of the particle result in very different macroscopic states, a dead cat vs a live cat. The problem is, the Schrodinger equation is linear, so when a particle in a superposition interacts with (is entangled with) other particles, the result is to put them in a superposition too. But at the end of the process, when we open the box, we don't find a "superposition", but only one of the two states, live cat or dead cat. So the question is, at what point in the process does the superposition collapse into one or the other final state?
In the experiment, if the radioactive nucleus decays, the gamma ray released will enter the geiger counter tube and ionize the gas. Since the nucleus is in a superposition of decayed and undecayed states, the gas in the geiger counter should be in a superposition of ionized and unionized states. If the gas is ionized, it allows a pulse of electric current to pass into the geiger counter electronics, so the geiger counter electronics should be in a superposition of pulse/no pulse states. The geiger counter amplifies the pulse to a current which is applied to an actuator which releases a hammer which smashes the poison bottle, releasing the poison. Since the geiger counter is in a superposition, the poison bottle should be in a superposition of smashed/unsmashed states, resulting in a cat in a superposition of alive and dead states. Where in this process does wavefunction collapse occur, and how, and why? --ChetvornoTALK 16:00, 24 December 2019 (UTC)
As Jordgette said, the process of decoherence provides a generally accepted explanation for apparent collapse; it says that when a superposition expands to the point where it entangles a large number of particles, the different component states stop interacting, become mutually unobservable, so we only experience the state we're in, dead cat or live cat. I don't really understand whether this means the other state doesn't exist, or whether it exists in another "state space" undetectible from ours (which I guess is the Many-worlds interpretation). --ChetvornoTALK 20:17, 23 December 2019 (UTC)


@Jordgette: I didn't quite get your statement about the cat as an observer. From what I understand, the importance of the cat as an "observer" is not an issue. The idea that a living brain, cat or human, has some special ability in QM that is required to collapse a wavefunction ("consciousness causes collapse") is obsolete. "Observers" are made of atoms, and have the same ability as everything else to be in superpositions and experience wavefunction collapse. Whether a cat, a person, or a video camera, is in the box, it will record the same thing; only one of the two possible histories: "radioactive decay/released poison/dead cat" or "no decay/no poison/live cat" will be left afterwards. --ChetvornoTALK 16:00, 24 December 2019 (UTC)
The idea of a cat being an observer comes from the relational interpretation, which is discussed in the article. See also Wigner's friend. -Jordgette [talk] 05:22, 25 December 2019 (UTC)
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