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)

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)

Regarding your statement: "It's Wikipedia policy to not give prominence to minority views." I don't think I was giving it "prominence". It's a single sentence put at the end of a very misleading statement. Without that sentence, readers will be misled severely into thinking that there's a consensus that all the loopholes in Bell's theorem can be fully closed and therefore, local hidden variables can be disproved with a certainty. (To be more exact, within scientific methodology, we can't really prove non-existence of something. That's not the job of science in the first place. But I won't get into philosophy of science here.)

Regarding your statement: "I think you misunderstood the Bell's theorem". I don't personally like saying things like this. I'd have ideally used something like: "My understanding of Bell's theorem is different than yours", rather than telling someone I'm disagreeing with that they do not have a proper understanding and I'm the one who understands it correctly, just to remain respectful in the conversation and not to assume I have the authority of understanding of the topic. But, since you used that statement, I'll also use your language: I think you misunderstood the loophole in Bell's theorem.

"The actual assumption is that the settings are uncorrelated with the hidden variables". Yes, but that's the loophole, because it's an inconsistent reasoning if you're trying to disprove local hidden variables (i.e., if you hypothesize that, if local hidden variables exist, X, Y, Z will happen, you cannot also say that the settings are uncorrelated with hidden variables.) It's inconsistent, because the measurement device is itself made of particles, and if a object to be measured has local hidden variables, so does every particle in the measurement device (as well as in everything else in the universe). As long as the measurement device and the object to be measured have local hidden variables, it's impossible to have statistical independence between the local hidden variables of the measurement device and the local hidden variables of the object being measured, because, if local hidden variables exist, everything originated from the initial state after Big Bang would be bound to be statistically correlated. The only way you can have measurement settings uncorrelated with the hidden variables of the object to be measured (i.e., the only way you can achieve statistical independence) is if your measurement settings were truly random.

You said, "It's perfectly possible for them to be deterministic and uncorrelated." That's incorrect. If you think the universe had a beginning (that is, if it began with a Big Bang) and if you also hypothesize that local hidden variables exist, then the only conclusion could be: nothing in the universe can be both deterministic and uncorrelated at the same time.

Let me know if you didn't understand this. I'm happy to explain again in a different way. Proshno (talk) 20:18, 11 August 2023 (UTC)

On the contrary, there is consensus that all relevant loopholes have been closed and local hidden variables can be excluded with as much certainty as anything can in science. Including your sentence would mislead the reader into thinking there's still a debate. That's the point of WP:DUE.

And frankly, it's not my job to teach you basic physics, and Wikipedia is not the place to do it. If you want to argue about superdeterminism there are several other websites for that, like the physics stack exchange or the AskScience subreddit. Tercer (talk) 06:48, 12 August 2023 (UTC)

I disagree that my sentence would have mislead readers into believing there is still a debate. I never mentioned anything about a debate. What I mentioned is the existence of a loophole, which does exist, according to Bell himself. I forgot to quote Bell in my last message. There you go: "There is a way to escape the inference of superluminal speeds and spooky action at a distance. But it involves absolute determinism in the universe, the complete absence of free will. Suppose the world is super-deterministic, with not just inanimate nature running on behind-the-scenes clockwork, but with our behavior, including our belief that we are free to choose to do one experiment rather than another, absolutely predetermined, including the "decision" by the experimenter to carry out one set of measurements rather than another, the difficulty disappears. There is no need for a faster than light signal to tell particle A what measurement has been carried out on particle B, because the universe, including particle A, already "knows" what that measurement, and its outcome, will be." And I don't think you understand local hidden variables or superdeterminism better than him.

And frankly, it's not my job to teach you consistencies in logical reasoning, and Wikipedia is not the place to do it. I don't know of any platform that can help you with that. Proshno (talk) 07:14, 12 August 2023 (UTC)

Actually I found one platform that could potentially help you with logical reasoning: ChatGPT. Please view this thread. Best of luck! Proshno (talk) 02:15, 13 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)

You said, "I'm not sure about Erwin Schrödinger, but Einstein held to local realism until shortly before he died, that is true."

What's your source? I don't know of any source where it's mentioned that Einstein gave up on local hidden variables at some point in time.

Regarding Schrodinger, he was on Einstein's side in the Einstein-Bohr debate. This is well-documented.

You said, "Our incorrect commonsense intuition is that strong." Once again, "our commonsense intuition" does not mean anything. There is nothing called "our commonsense intuition". To you, the weirdness in quantum mechanics seem real and you can only say that's your sense. If anything, the "common sense" is that things can happen randomly and there are some things that can't be explained with an underlying mechanistic principle. Most people's "common sense" tells them that the universe is not deterministic and there are mysterious things that can't be explained with science. Most people's common sense tells them there is mystery and randomness instead of considering that perhaps it's just our ignorance. Even before Newton came up with a universal law, people used to think that many natural observations cannot be explained with logic and then attributed them to God. Even today, if you talk to people about their lives, their first bias is towards the idea that not everything can be explained with logic (even people who don't know about quantum mechanics.)

You said, "which he himself retracted when its flaws were pointed out by others". Yes, but that doesn't necessarily mean "others" were correct either.

You said, "John Bell did the opposite of suggesting a local hidden variables theory: he proved mathematically that no local hidden variables theory could be correct." That's the common misunderstanding of his theorem. He didn't "mathematically prove" that, because nobody can mathematically prove the nonexistence of something when you don't even know what that is. What his theorem says is essentially this: "If local hidden variables existed, there would be a constraint on the correlations between two measurements." The problem with this argument is, he has no way to know how local hidden variables would really affect measurements, because he doesn't know what those local hidden variables are in the first place.

You said, "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." No, he isn't just "fond of" exploring the frontiers of science. He calls this quantum weirdness a "disease" and we need to cure it.

Do you understand my objection to abruptly ending a paragraph that could potentially mislead readers now? I will reply to your replies when I have time; very busy now. Proshno (talk) 20:45, 11 August 2023 (UTC)

From his wall-o-text above, it’s clear Proshno doesn’t understand Bell’s Theorem. --Chetvorno^TALK 15:56, 11 August 2023 (UTC)

From their brief comment, it's clear User:Chetvorno doesn't understand the loophole in Bell's theorem. Proshno (talk) 21:43, 11 August 2023 (UTC)

For future readers' judgement regarding who understands Bell's theorem, I had a conversation on this with ChatGPT. Here is the thread. Proshno (talk) 02:17, 13 August 2023 (UTC)

We need a section shortly after the lead

We need a section shortly after the lead titled something like "Quantum Systems" that defines what a quantum system is and goes into detail about the different types of quantum systems. I'm an IP editor so I can't edit the article.

The impetus for this is: There are many articles in Wikipedia which mention the term "quantum system" or "quantum mechanical system"; Like for example: https://en.wikipedia.org/wiki/Spontaneous_emission . I was reading that article and I wanted to know what a quantum mechanical system is. It is even linked in the article. So I followed the link and I get to the page for quantum mechanics, which explains the field of physics but does not readily define what a quantum system or quantum mechanical system is.

So in short, this article needs a section that goes over what a quantum mechanical system is, including the different types of common systems like molecule, atom, subatomic particle, and potentially many particle systems.

Something like the following:

== Quantum Systems == A quantum system is a physical system that can be analyzed using quantum mechanics. Quantum systems are fundamentally irreducible, in that to analyze the system one needs to know the total state of the system to make any useful observation on it. In contrast, an [[open quantum system]] is one where not all the information about the system need to be known to be able to make a useful analysis. Examples of quantum systems include: * [[atom]]s * molecules * subatomic particles * other many particle systems Mathematically, a quantum system is the [[tensor product]] of its component systems.<ref>https://www.sciencedirect.com/topics/engineering/quantum-system</ref> — Preceding unsigned comment added by 96.227.223.203 (talk • contribs)

Bound states are not discussed.

The intro has a paragraph featuring bound states but the text has no corresponding section. Johnjbarton (talk) 16:03, 16 December 2023 (UTC)

It has a subsection on the particle-in-a-box and another on the harmonic oscillator, both of which explicitly mention constraints leading to discretization of energy levels. XOR'easter (talk) 16:46, 16 December 2023 (UTC)

Quantization is much more important for than two examples deep in the article would imply. Johnjbarton (talk) 19:32, 16 December 2023 (UTC)

Quantization in Bound states

Hello. This is regarding a minor edit that was recently reverted.

'Quantum mechanics differs from classical physics in that energy,..., bound states are restricted to discrete values(of energy,...)' which had a change of 'are' to 'can be' since Bound states may not necessarily have discrete energy, for example.

@Johnjbarton Let's put our arguments and wait to see what others think. I think the article can remain as 'can be' to avoid inaccuracy in the meanwhile. EditingPencil (talk) 16:38, 16 December 2023 (UTC)

"Bound state" is probably a sufficiently esoteric term that the intro should avoid it, if possible. XOR'easter (talk) 16:48, 16 December 2023 (UTC)

First: the entire subject of "bound states in the continuum" is too advanced for this article. As you say these things don't have discrete energy. (IMO these things have been given unimaginative names).

But the reason I reverted your change has to do with the "differs from classical physics". These exotica are also classical. The point of the paragraph is to point out differences and the bound states of QM systems have discrete energy values whereas the bound states (orbits) of classical systems do not.

The discrete energy levels of QM systems is a distinction essential to the character of the theory. Johnjbarton (talk) 16:56, 16 December 2023 (UTC)

imho, it still conveys that point. I guess we can worry about re-wording it if more people share this issue.

Since I don't disagree with you, I don't mind if it were edited to include both facts. I guess, the introduction section should be simple to read though. EditingPencil (talk) 17:08, 16 December 2023 (UTC)

I rewrote the sentence entirely to focus on quantization. Johnjbarton (talk) 17:26, 16 December 2023 (UTC)

I think the wording is fine, but I still think it's better to use the weaker form of the sentence. If this thread finds more support for the later, we should change it. EditingPencil (talk) 18:23, 16 December 2023 (UTC)

Weaker? What would you propose? Johnjbarton (talk) 19:31, 16 December 2023 (UTC)

Maybe something like 'can have' instead of 'have'? I guess it's too pedantic so, I think I will leave this. EditingPencil (talk) 19:55, 16 December 2023 (UTC)

"Quantum realm" listed at Redirects for discussion

The redirect Quantum realm has been listed at redirects for discussion to determine whether its use and function meets the redirect guidelines. Readers of this page are welcome to comment on this redirect at Wikipedia:Redirects for discussion/Log/2024 April 25 § Quantum realm until a consensus is reached. Utopes _{(talk / cont)} 00:25, 25 April 2024 (UTC)