Talk:Schrödinger's cat

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Edit conflict over wording of introduction[edit]

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 [1], which has since been changed. -Jordgette [talk] 03:51, 22 February 2015 (UTC)

Additional entry in the Section titled "Interpretations of the experiment."[edit]

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)

Copied to Quantum Mind page[edit]

The following section was copied to the Quantum Mind page on 4 Feb 2018 by user: wcrea6:

Erwin Schrödinger described how one could, in principle, create entanglement of a large-scale system by making it dependent on an elementary particle in a superposition. He proposed a scenario with a cat in a locked steel chamber, wherein the cat's life or death depended on the state of a radioactive atom, whether it had decayed and emitted radiation or not. According to Schrödinger, the Copenhagen interpretation implies that the cat remains both alive and dead until the state has been observed. Schrödinger did not wish to promote the idea of dead-and-alive cats as a serious possibility; on the contrary, he intended the example to illustrate the absurdity of the existing view of quantum mechanics.[8] However, since Schrödinger's time, other interpretations of the mathematics of quantum mechanics have been advanced by physicists, some of which regard the "alive and dead" cat superposition as quite real.[9][10]

  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.
  8. ^ Schrödinger, Erwin (November 1935). "Die gegenwärtige Situation in der Quantenmechanik (The present situation in quantum mechanics)". Naturwissenschaften. 23 (48): 807–812. Bibcode:1935NW.....23..807S. doi:10.1007/BF01491891. 
  9. ^ Polkinghorne, J. C. (1985). The Quantum World. Princeton University Press. p. 67. ISBN 0691023883. Archived from the original on 2015-05-19. 
  10. ^ Tetlow, Philip (2012). Understanding Information and Computation: From Einstein to Web Science. Gower Publishing, Ltd. p. 321. ISBN 1409440400. Archived from the original on 2015-05-19.