Talk:Quantum mechanics

Did you know nomination

The following is an archived discussion of the DYK nomination of the article below. Please do not modify this page. Subsequent comments should be made on the appropriate discussion page (such as this nomination's talk page, the article's talk page or Wikipedia talk:Did you know), unless there is consensus to re-open the discussion at this page. No further edits should be made to this page.

The result was: promoted by SL93 (talk) 02:17, 10 April 2021 (UTC)

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• ... that the principles of quantum mechanics have been demonstrated to hold for complex molecules with thousands of atoms? Source: "... we report interference of a molecular library of functionalized oligoporphyrins with masses beyond 25,000 Da and consisting of up to 2,000 atoms, by far the heaviest objects shown to exhibit matter-wave interference to date. We demonstrate quantum superposition of these massive particles by measuring interference fringes..." ([1])

Improved to Good Article status by XOR'easter (talk) and Tercer (talk). Nominated by Tercer (talk) at 13:30, 23 March 2021 (UTC).

• New GA, promoted 22 March (2 days ago), plenty long enough, and meets policy (except for the last sentence in history - more modern history than 1930 is needed, but in a bit more detail and with references! And there are some other unreferenced bits that could do with improving in the future, e.g., at the end of the mathematical formulation first part, but I don't think that's needed for this). Hook is referenced, and is interesting - although possibly there are more interesting hooks you could pull out of the article. No QPQ needed (1st DYK). The big problem, though, is that the article was on the main page as a Featured Article in 2004, I need to double-check with others that this is allowed. Thanks. Mike Peel (talk) 18:52, 24 March 2021 (UTC)
  • Asked at Wikipedia_talk:Did_you_know#DYK_that_was_formerly_Today's_Featured_Article?. Thanks. Mike Peel (talk) 18:58, 24 March 2021 (UTC)
  • If you have other suggestions for the hook I'd be happy to hear. As for the history, yeah, it should be expanded. One should be careful not to confuse it with quantum field theory, QED, QCD, etc., but there were plenty of interesting developments on the basic non-relativistic quantum mechanics. Tercer (talk) 19:33, 24 March 2021 (UTC)
    • @Tercer: It's up to you to suggest alt hooks if you want. No problems with the history needing to be expanded, but that paragraph (and probably the others) should be referenced - looking again at Wikipedia:Did you know/Reviewing guide it says 'A rule of thumb for DYK is a minimum of one citation per paragraph, possibly excluding the introduction, plot summaries, and paragraphs which summarize information that's cited elsewhere.'. Thanks. Mike Peel (talk) 19:56, 24 March 2021 (UTC)
      • I'm not going to start randomly inlining citations because of some arbitrary rule from DYK. The article is well-sourced. I removed this particular paragraph in any case, as that subject was better covered elsewhere in the article. Tercer (talk) 23:00, 24 March 2021 (UTC)
        • @Tercer: Thanks for removing the paragraph, but I hope it can be added back later with much more info. It's generally a good idea to include inline cites - if it was a paper introduction then they would be expected, it's not an arbitrary rule for DYK. So now, the main issue is whether this is OK given the past FA appearance - I expect it is, but let's wait a little to see what others think. Thanks. Mike Peel (talk) 23:11, 24 March 2021 (UTC)
          • @Tercer: Seems to be OK per the discussion at Wikipedia talk:Did you know. Thanks. Mike Peel (talk) 17:35, 25 March 2021 (UTC)
            • Great, thanks for letting me know. Tercer (talk) 17:39, 25 March 2021 (UTC)

Another citation is needed

@Logic314: Another citation is needed. Cannot use the Bell citation by itself to back the claim of nonlocality. We would need another source. It's possible to cite other sources. -- Ancheta Wis   (talk | contribs) 08:51, 20 May 2023 (UTC)

I don't think we need to say more about Bell's theorem in this article than we already do. XOR'easter (talk) 16:25, 20 May 2023 (UTC)

If you are not aware that Bell's Theorem does indeed prove nonlocality for tiny-scale quantum mechanics, I suggest you do some research on the Web to learn about it for yourself. There are many misconceptions about QM in circulation, and it is not a burden on WP editors to prove facts to other editors. David Spector (talk) 13:44, 9 August 2023 (UTC)

Hilbert's contribution

My problem is with the following:

"By 1930 quantum mechanics had been further unified and formalized by David Hilbert, Paul Dirac and John von Neumann with greater emphasis on measurement, the statistical nature of our knowledge of reality, and philosophical speculation about the 'observer'."

The single citation given for this sentence only emphasises von Neumann's contributions. While this work was based on the mathematics of Hilbert (i.e. Hilbert spaces), I have not found any sources to back up the claim that Hilbert himself was key to developing quantum mechanics during its later stages.

Proposal: remove Hilbert's name from this sentence (unless a reference can be found to support up this claim). Instead add something about the importance of his earlier mathematical innovations. 138.38.94.186 (talk) 11:24, 15 June 2023 (UTC)

Hilbert's contributions were abstract and influenced the physicists. The respect and esteem with which Born (and other close associates like v.Neumann) held Hilbert comes to mind, but Born's formulation of inner product for QM (B. formulated it in the 1920s) wasn't rewarded until 1955. Perhaps Hilbert's influence on Born and von Neumann might be the subject for an appropriate citation (from a historian of science). Or perhaps some parentheses, such as 'By 1930 quantum mechanics had been further unified and formalized by Max Born, Paul Dirac and John von Neumann (who were themselves influenced by David Hilbert)'.

I forgot Schwarz inequality. But this goes outside QM. There are other applications. (Think Signal processing in electrical engineering) --Ancheta Wis   (talk | contribs) 16:20, 15 June 2023 (UTC)

Hilbert contributed the mechanism that makes reasoning about measurements in the tiny scale easier, so I'd rather his name be retained. But it is also true that he was not one of the principal developers of QM. David Spector (talk) 13:48, 9 August 2023 (UTC)

Superdeterminism?

https://en.wikipedia.org/wiki/User:Proshno has been attempting to edit this article to claim that local realism may still obtain in quantum mechanics. However, this unusual claim is not backed up with any reliable references. This edit (https://en.wikipedia.org/w/index.php?title=Quantum_mechanics&diff=next&oldid=1169333352) cannot be allowed, per WP policies. Let's discuss here instead of edit-warring. David Spector (talk) 13:41, 9 August 2023 (UTC)

Superdeterminism, which Proshno was adding, is a theory that would explain quantum mechanics' violation of Bell's inequality without giving up local realism:

• "Another weak link in Bell's argument is associated with the assumption of statistical independence. The strategy is to allow systematic violations of statistical independence in favor of 'super-deterministic' theories..."Knox, Wilson, The Routlege Companion to Philosophy in Physics p.190
• "...Bell nonlocality can be demonstrated as soon as the processes that choose the inputs and those chosen by the players are independent. The strongest way to deny this measurement independence is superdeterminism..." Scarani, Bell Nonlocality, p.20

"The strongest way to deny this measurement independence..." Anyone can spin a conjecture up to speed and deny any scientific knowledge whatsoever. It takes real intelligence and ethics to refrain from doing so. Measurement independence has been validated by every experiment in quantum mechanics throughout its history. It seems to me foolish to give serious concern to this, or to local realism itself, and deny all the experiments performed up to now, or the theories supported by them. I'm not opposed to conjecture, but asking that conjecture be reflected in a basic science article in WP is counter to what I have learned in my ten years as a WP editor. David Spector (talk) 21:12, 9 August 2023 (UTC)

• Bertleman, Zeilinger, Quantum (Un)speakables: Half a century of Bell's theorem, p.135
• "...in order for our discussion to be complete, it is necessary to mention an argument [superdeterminism] some have advanced for the purpose of avoiding the nonlocality condition. However... the proposed idea is not only artificial, but also quite radical and unwarranted" Hemick, Shakur, Bell's theorem and Quantum Realism, p.54
• "By proposing that the theory underlying quantum mechanics be both local and deterministic, superdeterminism removes both fundamental incompatibilities at once..." Adlam, Foundations of Quantum Mechanics, p.17

However I'm not sure it has sufficient support among physicists to merit Proshno's statement. --Chetvorno^TALK 18:52, 9 August 2023 (UTC)

I think it's okay for WP to mention the frontiers of thinking about QM, in the proper context. But in the context of a basic article about QM, I don't think that all conjectures need to be included. Certainly all major theorems and facts need to be included. Nonlocality, along with quantization, linear superposition, and wave/particle duality, is at the basis of QM. It is these basics that need to be in this article. Let's put the conjectures and ontological interpretations in a small section, with a link to an article that focuses just on them.

Our commonsense intuition, which validates local realism, is certainly valid in large scales, all the way up. But it is just as certainly misleading when applied to the very tiniest of scales. Let's maintain balance, and explain what has actually been discovered about QM, both experimentally and theoretically, and leave the interpretations and conjectures for another article. Otherwise, we run a serious risk of misleading those wishing to learn what is really known about QM. David Spector (talk) 19:40, 9 August 2023 (UTC)

Response to certain users' editing out the Superdeterminism loophole from relevant sections

What User:David spector is saying in support of editing out the sentence about the superdeterminism loophole are all known facts in Qauntum Mechanics. I already know that superdeterminism is not well accepted within the physics community, and I respect that. Therefore, I only added one single sentence in the article Quantum Mechanics, under the paragraph for hidden variables, without editing out any previous sentences: "However, Bell tests cannot close the superdeterminism loophole, therefore, local hidden variables cannot be completely ruled out." This is a small addition compared to the entire article, and it's only an addition at the end of a relevant paragraph, which was on hidden variables. Besides, the existence of local hidden variables have been supported by Einstein and Schrodinger, and has been suggested by John Bell himself, and is still supported by a Nobel winner Gerard 't Hooft. So I don't understand David Spector and User:Tercer's strong objection to it.

Anyone who has read anything about quantum mechanics has read statements like "Our commonsense intuition, which validates local realism, is certainly valid in large scales, all the way up. But it is just as certainly misleading when applied to the very tiniest of scales." However, if I follow that reasoning, I could also say that, "Our commonsense intuition, which validates randomness, is certainly valid in large scales, all the way up. But it is just as certainly misleading when applied to the very tiniest of scales." In our everyday observations, a lot of things seem random, but once we think deeply and find patterns, we find a very deterministic mechanism. This can apply for quantum mechanics as well.

Superdeterminism loophole was not simply created to prove Bell's theorem can't be used to disprove the existence of local hidden variables (I discovered this loophole on my own independently the first time I read about Bell's theorem almost a decade ago, and back then, I didn't even know someone else on earth also thought of this loophole and came up with this term "superdeterminism"). It's just a name given to the internal logical fallacy, namely a circular reasoning, itself within Bell's theorem. Bell's theorem attempts to disprove local hidden variables, and local hidden variables would have made the whole quantum mechanics a completely deterministic system. However, Bell's theorem also requires that measurement settings can be chosen randomly. The problem within this theorem is that, if local hidden variables really existed, measurement settings can never be chosen randomly in the first place. So if you already make the assumption that measurement settings can be chosen randomly, I don't see the point of doing all those experiments to prove that the observations of quantum mechanics are really random. Local hidden variables may really not exist, that's a reasonable possibility. However, even if local hidden variables didn't exist, we can't use Bell's theorem to disprove local hidden variables, because it requires the assumption that local hidden variables don't exist (ergo, circular reasoning). But if local hidden variables exist, the inevitable consequence is that Nature is deterministic, therefore the universe must be derdeterministic from the moment of Big Bang. This is now unfortunately called "supderdeterministic", but there is nothing "super" about it.

So basically, when we see randomness in the quantum world, we have two options:

(1) We can refuse to accept the principle that reality is deterministic, even though a vast number of observations in physics (everywhere except the quantum-scale world) support it and this deterministic principle (local reality) has been successful to explain countless phenomena, and accept that observations in the quantum world are really random, which would lead to all these "counterintuitive" observations and paradoxes.

(2) We can refuse to accept the principle that reality is random, even though a vast number of observations in physics (only in the quantum-scale world) support it and this indeterministic principle (absence of local reality) hasn't prevented us from being successful in explaining countless phenomena, and accept that observations in the quantum world are really deterministic, in which case, we have to assume the existence of a local hidden variable.

For a minority group of people including me, Option 2 seems more sensible, because I don't believe that Nature can have paradoxes, and I believe that there is a underlying mechanism for every inexplicable observation and we can eventually know that mechanism. Accepting Option 2 would still leave the room open that perhaps someday someone will develop concrete theories for local hidden variables (just like how the existence of germs was denied by academics for a long time, and just like how the existence of atoms was also denied by academics for a long time until the twentieth century, but they were eventually proved to be correct). But denying the possibility of its existence altogether would discourage a lot of physicists to explore this idea altogether, because they would wrongly assume that local hidden variables have been completely ruled out, which Bell's theorem can't really do.

But if someone accepts Option 1, this is a dead end.There would be no way to resolve paradoxes and inexplicable things in the quantum world, and it would be impossible to reconcile quantum mechanics with general relativity (a theory that has also been immensely successful), let alone predicting motions of individual elementary particles. I don't understand why anyone would have a strong opposition to a completely deterministic reality and why anyone would really think that things are really random rather than considering the possibility that perhaps there is something more to it that we still don't know but can potentially discover eventually. I don't understand why the majority supports randomness even after physics has been able to show again and again that a lot of observations that initially seemed random were later turned out to be deterministic and can be explained with equations. But that's not for me to think about.

David Spector and Tercer, if my arguments sound reasonable to you, I can add back that sentence to the article on Quantum Mechanics. While I think that your editing out a row from the table within the article Interpretations of Quantum Mechanics and your editing out a few sentences that I added in the Superdeterminism article can be debated, I strongly believe that that single sentence ("However, Bell tests cannot close the superdeterminism loophole, therefore, local hidden variables cannot be completely ruled out.") still has a much-deserved place in the article Quantum Mechanics. Please let me know your thoughts. Proshno (talk) 02:35, 11 August 2023 (UTC)

It's Wikipedia policy to not give prominence to minority views. The whole subject of Bell's theorem got a single paragraph here. Using this little space to mention the views of a tiny minority would be a gross violation of policy. See WP:DUE. Superdeterminism is mentioned in the Bell's theorem article.

You have misunderstood the assumptions of the theorem, by the way. One does not need the measurement settings to be chosen randomly. The actual assumption is that the settings are uncorrelated with the hidden variables, it is known as "statistical independence". It's perfectly possible for them to be deterministic and uncorrelated. Tercer (talk) 09:23, 11 August 2023 (UTC)

"the existence of local hidden variables have been supported by Einstein and Schrodinger, and has been suggested by John Bell himself, and is still supported by a Nobel winner Gerard 't Hooft. So I don't understand David Spector and User:Tercer's strong objection to it." - I'm not sure about Erwin Schrödinger, but Einstein held to local realism until shortly before he died, that is true. I believe it was his third major mistake, after the three famous mistakes he admitted to. Our incorrect commonsense intuition is that strong. And Louis de Broglie made the situation worse by his attempt at a local hidden variables theory, which he himself retracted when its flaws were pointed out by others. But John Bell did the opposite of suggesting a local hidden variables theory: he proved mathematically that no local hidden variables theory could be correct. Read about it before you express your incorrect opinions, please. As for Gerard 't Hooft, he and a few other physicists are fond of exploring the frontiers of science, conjectures for which correctness is unimportant. Such conjectures are not part of physics and thus should not be reflected in WP articles. Do you understand our objection to including an incorrect sentence now? I will get to the rest of your lengthy posting when I have time; very busy now. David Spector (talk) 10:04, 11 August 2023 (UTC)