Talk:Quantum mechanics/GA1

GA Review

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Reviewer: Ján Kepler (talk · contribs) 06:53, 5 March 2021 (UTC)

Hi, thanks for nominating the article. As a quantum mechanics "fan", I'll try to review it. I plan to read the article this weekend, but at first glance, it looks good. --Ján Kepler (talk) 06:53, 5 March 2021 (UTC)

Thanks for volunteering to review the article. I'll address your comments. Tercer (talk) 09:09, 13 March 2021 (UTC)

GA review (see here for what the criteria are, and here for what they are not)

1. It is reasonably well written.

   a (prose, spelling, and grammar): b (MoS for lead, layout, word choice, fiction, and lists):

2. It is factually accurate and verifiable.

   a (reference section): b (citations to reliable sources): c (OR): d (copyvio and plagiarism):

3. It is broad in its coverage.

   a (major aspects): b (focused):

4. It follows the neutral point of view policy.

   Fair representation without bias:

5. It is stable.

   No edit wars, etc.:

   This version is stable for several months already, so yes.

6. It is illustrated by images and other media, where possible and appropriate.

   a (images are tagged and non-free content have fair use rationales): b (appropriate use with suitable captions):

   User:Tercer I would replace the very first image for some more instructive one, but maybe there aren't any? --Ján Kepler (talk) 08:07, 14 March 2021 (UTC)

   I like that image; it represents one of the earliest successes of quantum theory, and is something that makes perfect sense to draw in real space. In general illustrating quantum mechanics is rather difficult. If you have a specific idea I'd be happy to hear. Tercer (talk) 09:07, 14 March 2021 (UTC)

7. Overall:

   Pass/Fail:

Comments

Overview Let's dive into it. I already made some edits to the article, but feel free to revert them. The comments below are just idea how to improve the article.

• It is typically applied to microscopic systems: molecules, atoms and sub-atomic particles. – The word typically looks confusing to me in this sentence. Or does it mean that some people apply it to macroscopic systems?

  Yes, it does mean that it is also applied to macroscopic systems. I rewrote it to make this point more explicit. Tercer (talk) 09:49, 13 March 2021 (UTC)

• Applying the Born rule to these amplitudes gives a probability density function for the position that the electron will be found to have when an experiment is performed to measure it. – maybe add that it DOESN'T say WHERE the electron is (it could be confusing like this for some people?)

  Indeed, we should emphasize that the properties are probabilistic. Done. Tercer (talk) 09:49, 13 March 2021 (UTC)

• their properties become so intertwined that a description of the whole solely in terms of the individual parts is no longer possible. – maybe this is described too complicatedly? For example the definition here I find much more straightforward (that the quantum state of each particle of the pair or group cannot be described independently of the state of the others, including when the particles are separated by a large distance.).

  The definition in quantum entanglement is misleading. One can attribute an independent quantum state to the individual parts, a reduced density matrix. The problem is that these independent states are not enough to describe the whole entangled state, one necessarily loses information. This is explained more precisely in the section Quantum_mechanics#Composite_systems_and_entanglement, I wanted to leave the Overview section as nontechnical as possible. Tercer (talk) 09:49, 13 March 2021 (UTC)

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Mathematical formulation

• In the mathematically rigorous formulation of quantum mechanics developed by Paul Dirac,[15] David Hilbert,[16] John von Neumann,[17] and Hermann Weyl,[18]] – was it really only these four? — Preceding unsigned comment added by Ján Kepler (talk • contribs) 08:07, 13 March 2021 (UTC)

  No, quantum mechanics was developed by dozens of people. It culminated with the work of von Neumann, from them on it stayed essentially unchanged. But it's silly to try to do a proper attribution in this section, its goal is to present the mathematical formulation, attribution belongs in the History section. I removed this sentence. Tercer (talk) 09:57, 13 March 2021 (UTC)

• I like how is this section written: I think it's the most straightforward way it can be written, but I would advise you to contact someone from WikiProject Physics to review this part. Overall, as this is a very important article, I will ask for a second opinion after I complete the review.

  I am the person from WikiProject Physics that would review that. I have a PhD in physics and my area of research is quantum mechanics. Of course, I don't object to a second opinion, it is a very important article and it is perfectly possible that I missed something. Tercer (talk) 09:07, 14 March 2021 (UTC)

• The uncertainty principle states that {\displaystyle \sigma _{X}\sigma _{P}\geq {\frac {\hbar }{2}}.}{\displaystyle \sigma _{X}\sigma _{P}\geq {\frac {\hbar }{2}}.} – maybe write somewhere what does the "h" mean as it wasn't mentioned anywhere in the article before? --Ján Kepler (talk) 08:03, 14 March 2021 (UTC)

  Good catch, I introduced the missing definition. Tercer (talk) 09:19, 14 March 2021 (UTC)

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Examples

• and the "upper" path {\displaystyle \psi _{u}={\begin{pmatrix}0\\1\end{pmatrix}}}{\displaystyle \psi _{u}={\begin{pmatrix}0\\1\end{pmatrix}}}, that is, {\displaystyle \psi =\alpha \psi _{l}+\beta \psi _{u}}{\displaystyle \psi =\alpha \psi _{l}+\beta \psi _{u}} for complex {\displaystyle \alpha ,\beta }\alpha ,\beta such that {\displaystyle |\alpha |^{2}+|\beta |^{2}=1}{\displaystyle |\alpha |^{2}+|\beta |^{2}=1}. – the last statement (abs alpha squared... + beta ... = 1) was also never mentioned in the article before, so maybe put a link to somewhere in parenthesis?

  That's just the normalisation requirement, I added an explanation. Tercer (talk) 13:13, 14 March 2021 (UTC)

• will then end up in the state {\displaystyle BPB\psi _{l}=ie^{i\Delta \Phi /2}{\begin{pmatrix}-\sin(\Delta \Phi /2)\\\cos(\Delta \Phi /2)\end{pmatrix}},}{\displaystyle BPB\psi _{l}=ie^{i\Delta \Phi /2}{\begin{pmatrix}-\sin(\Delta \Phi /2)\\\cos(\Delta \Phi /2)\end{pmatrix}},} what does BPB mean?

  The multiplication of the B, P, and B matrices. I clarified the text. Tercer (talk) 13:13, 14 March 2021 (UTC)

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Applications

• Solid-state physics and materials science are dependent upon quantum mechanics. – I know this is very obvious, but maybe still add a reference?

  Sure, I added a reference. Tercer (talk) 13:24, 14 March 2021 (UTC)

• In many aspects modern technology operates at a scale where quantum effects are significant. Important applications of quantum theory include quantum chemistry, quantum optics, quantum computing, superconducting magnets, light-emitting diodes, the optical amplifier and the laser, the transistor and semiconductors such as the microprocessor, medical and research imaging such as magnetic resonance imaging and electron microscopy.' – perhaps add quantum teleportation? --Ján Kepler (talk) 10:58, 14 March 2021 (UTC)

  I don't think quantum teleportation is an application; it is a fundamental effect, but until now it wasn't used for anything. Tercer (talk) 13:13, 14 March 2021 (UTC)

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Relation

• large quantum numbers. – how much is large?

  It's not well-defined, this is just a heuristic, not a mathematical theorem. It is described in the source. Tercer (talk) 15:38, 17 March 2021 (UTC)

• Quantum electrodynamics is, along with general relativity, one of the most accurate physical theories ever devised – maybe add even more references?

  Why? Anything wrong with them? Tercer (talk) 15:38, 17 March 2021 (UTC)

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Philosophy

• This is not accomplished by introducing a "new axiom" to quantum mechanics, but by removing the axiom of the collapse of the wave packet. All possible states of the measured system and the measuring apparatus, together with the observer, are present in a real physical quantum superposition. While the multiverse is deterministic, we perceive non-deterministic behavior governed by probabilities, because we don't observe the multiverse as a whole, but only one parallel universe at a time. Exactly how this is supposed to work has been the subject of much debate. Why we should assign probabilities at all to outcomes that are certain to occur in some worlds, and why should the probabilities be given by the Born rule? – shouldn't this be in quote marks?

  Why? It is not a quotation. Tercer (talk) 15:38, 17 March 2021 (UTC)

  Well then it's OR, no? Wikipedia articles shouldn't ask questions. — Preceding unsigned comment added by Ján Kepler (talk • contribs) 16:36, 17 March 2021 (UTC)

  It's phrased as questions, but they're questions that have been asked in the literature, as the cited sources indicate. Nothing original on our part. Maybe the phrasing could be tweaked to clarify this? (It seems clear enough to me at present, but somebody might have a good idea for an improvement.) XOR'easter (talk) 17:50, 17 March 2021 (UTC)

  I would definitely edit it, because it doesn't make sense to have question marks in Wikipedia articles when it's not a quotation. --Ján Kepler (talk) 11:29, 18 March 2021 (UTC)

  I don't see the problem with having a question mark per se. We are reporting on questions that have been asked in the literature. It paraphrases this quotation by Wallace [1]: It is useful to identify two aspects of the problem. The first might be called the incoherence problem: how, when every outcome actually occurs, can it even make sense to view the result of a measurement as uncertain? Even were this solved, there would then remain a quantitative problem: why is that uncertainty quantified according to the quantum probability rule (i. e. , the Born rule), and not (for instance) some other assignment of probabilities to branches?. Tercer (talk) 12:00, 18 March 2021 (UTC)

  I don't know how to do it, but in this version, is unacceptable for me. Who is we? And should Wikipedia articles really have words like should? Also having one source on This is not accomplished by introducing a "new axiom" isn't very good in my opinion. I get what that the paragraph is just a summary of some quantum mechanics interpretation, but I think it's now done in a bad way. Why not just say something like "MWI thinks X and Y, because of Z"? After fixing this, the article would definitely pass GAC.--Ján Kepler (talk) 07:24, 20 March 2021 (UTC)

  Ok, I see your point, the paragraph is written in an argumentative style, which is not very encyclopedic. I've rewritten it to make it more straightforward and remove excessive detail. Tercer (talk) 10:36, 20 March 2021 (UTC)

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History

• No mentions about de Broglie?

  He should be mentioned, I added a couple of sentences. We have to be careful not to put too much detail, in order to keep with summary style. Tercer (talk) 15:38, 17 March 2021 (UTC)

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GA

I think the article now passes the GAC, do you agree XOR'easter so I can close this? --Ján Kepler (talk) 16:32, 22 March 2021 (UTC)

I was actively involved in editing the article prior to its nomination, so nothing I say here should count as a reviewer's opinion. But I do think the article is in pretty good shape, and the GA review process did improve it, for which I am thankful. XOR'easter (talk) 16:38, 22 March 2021 (UTC)

OK, the article passed GA criteria. Thanks to both of you (and others who've written the article)! --Ján Kepler (talk) 19:25, 22 March 2021 (UTC)

I'm glad to hear that! Thanks again for volunteering. Tercer (talk) 21:35, 22 March 2021 (UTC)