Talk:Complementarity (physics)

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Dubious article[edit]

I'm not sure this article should exist. It throws together various only vaguely related ideas of two things being "complementary" into a conglomeration / mingle-mangle of an article. It doesn't seem very rigorous and seems very outdated in several places. It wasn't written by someone with a physics background, that's clear. There's a clear "popscience" handwriting over it. The only way I see it should exist is if it covers the historical approach Bohr took in his research, but only that. Otherwise I think the article needs to be deleted. It provides no insights and if it claims to still be relevant it's misleading. 95.116.25.75 (talk) 11:06, 12 March 2019 (UTC)[reply]

https://en.wikipedia.org/wiki/Conjugate_variables seems like a superior article covering a similar topic but more rigorously and less.. superficially. 95.116.25.75 (talk) 12:24, 12 March 2019 (UTC)[reply]

Well, complementarity comes from the Copenhagen interpretation, and unlike conjugate variables, it relates to the wave vs. particle question. I suppose it could merge with, and then redirect to, the Copenhagen interpretation article. Otherwise, I don't think it is so bad to need deletion, but like most, could still be improved. Gah4 (talk) 13:37, 12 March 2019 (UTC)[reply]

photons[edit]

The addition of photons to complementarity reminds me of discussion about photons and quantization going back to the beginning of QM. For a long time, pretty much only Einstein believed that light was actually quantized. Planck who introduced his constant, and many others, believed that the energy level changes were quantized, but not the field itself. It seems that one of the reasons was the Maxwell's equations worked so well, that it was hard to believe that they were wrong. That is, that is was hard to believe in a quantized photons and continuous Maxwell's equations at the same time. And that is complementarity. Gah4 (talk) 19:42, 1 January 2020 (UTC)[reply]

Mathematical formalism section is off topic.[edit]

The section "Mathematical formalism" is about the uncertainty principle, not about Complementarity. Wave-particle duality is part of Complementarity and yet the formalism section does not apply. Johnjbarton (talk) 22:34, 8 August 2023 (UTC)[reply]

How is a section sourced to papers that explicitly discuss what "complementarity" means in finite-dimensional Hilbert spaces off-topic? XOR'easter (talk) 22:13, 11 August 2023 (UTC)[reply]

The paper on "Complementarity Polytope" appears to be a mathematical paper. It is on-topic on if there was a context to discuss it and if the results were somehow related back to the topic. But the math formalism seemed just stuck on and the reference stuck on to that.

I suppose it could fit in, but I think it would take a lot of work. Johnjbarton (talk) 00:02, 12 August 2023 (UTC)[reply]

Sorry, I don't understand the concern here. The point of the paper is to construct a finite dimensional analogy to the complementarity of position and momentum in the continuous case. It's all about how the qudit version of complementary observables is mutually unbiased bases. XOR'easter (talk) 00:52, 12 August 2023 (UTC)[reply]

Great, but not in any place in this article is mutually unbiased bases discussed or even hinted at. This may be a great paper for some article, or for a version of this article that articulated what a mutually unbiased bases was, but otherwise it is just a random article. The article belongs in [mutually unbiased bases]] or some similar mathematically oriented article.

If the article did explain, as a review or accessible discussion, how mutually unbiased bases related to complementarity and if thos article included discussion of that connection it would make sense to me. But otherwise its just a math article. Famous wikipedia editors commonly point out how many wonderful articles exist, but we need not include them for that reason alone. Johnjbarton (talk) 01:05, 12 August 2023 (UTC)[reply]

I'm still confused. What more does this article need to say than what it says at the moment? This has been generalized to discrete observables with more than two possible outcomes using mutually unbiased bases, which provide complementary observables defined on finite-dimensional Hilbert spaces. The mutually unbiased bases article is there for all the gory details, while this page says what the conceptual relation is. XOR'easter (talk) 01:10, 12 August 2023 (UTC)[reply]

Ok I read up on this subject a bit. I still think the section lame but I think it can be built in to something useful based on Englert's work.

Johnjbarton (talk) 23:25, 12 August 2023 (UTC)[reply]

Made some progress, but not satisfied. Please review. Johnjbarton (talk) 19:12, 15 August 2023 (UTC)[reply]

Is the article about the right thing?[edit]

Bohr principle of complementarity is a rather philosophical position on how to understand quantum mechanics. There are lengthy papers on how to discuss this without any math. However the mathematical description of this article seems to be about the incompatibility of observables. Something is off here. ReyHahn (talk) 19:14, 22 October 2023 (UTC)[reply]

I assume you are referring to the section "Mathematical formalism". I made essentially the same comment 2 months ago. Johnjbarton (talk) 20:06, 22 October 2023 (UTC)[reply]

Yes I just noticed it. Maybe that section is not necessary.--ReyHahn (talk) 20:40, 22 October 2023 (UTC)[reply]

The literature treats it as part of the subject of complementarity, so it belongs here. The article shouldn't be mathless if the literature is mathful. XOR'easter (talk) 15:47, 23 October 2023 (UTC)[reply]

The math and mathless section are completely disconnected here: they act like separate articles and that confuses the topic. Johnjbarton (talk) 16:02, 23 October 2023 (UTC)[reply]

I should also say that there is quite a bit of modern that claim to test complementarity and the mutually unbiased bases work is part of that. I think the real issue is that the article lead does not hint at this and the transition is unclear. (And the subject is unclear to me, as it seems to overlap uncertainty and which-way experiments). Johnjbarton (talk) 20:42, 22 October 2023 (UTC)[reply]

I agree, did Bohr ever use it in the sense of uncommutable operators?--ReyHahn (talk) 06:59, 23 October 2023 (UTC)[reply]

In "The Causality Problem in Atomic Physics" (1938), he treats complementarity as the "ultimate reason" that an uncertainty relation holds for canonically conjugate observables. XOR'easter (talk) 16:17, 23 October 2023 (UTC)[reply]

It seems that complementarity is used in (at least) two ways. One the way mostly used in the article, and the other as Classical and Quantum Complementarity, on the connection between classical and quantum measurement. Gah4 (talk) 05:24, 23 October 2023 (UTC)[reply]

By the "way most used in the article" do you mean wave-particle duality or incompatibility of observables?--ReyHahn (talk) 06:59, 23 October 2023 (UTC)[reply]

Wave-particle duality is one expression of incompatible observables; uncertainty is another; complementarity in Bohr's sense is another. Bohr said an experiment set for waves will never show particle behavior. Others called this "duality". If you see 100% waves you will see 0% particle behavior. Uncertainty is just the closer to 50/50 mix: more local means less clear waves. Johnjbarton (talk) 16:01, 23 October 2023 (UTC)[reply]

It seems to me that the Classical and Quantum Complementarity you link to uses complementarity the same way at this page does. The paper shows that the concept applies to classical diffraction optics. To me that is no surprising since light diffraction is actually a quantum effect identical to electron diffraction. Labeling it "classical" is a matter of history not physics. Johnjbarton (talk) 17:08, 16 November 2023 (UTC)[reply]

The first paragraph of the lead still makes this looks like "complementary principle"="incompatible observables" but I have never seen anybody use the former in that way in practice. If that were the case it would be used much more but it is usually left out to old quantum mechanics discussions. I think there is a more vague philosophical principle to be highlighted here.--ReyHahn (talk) 14:00, 16 November 2023 (UTC)[reply]

"If that were the case it would be used much more"? References 28 to 30 are modern works. I'm sure we can find more.

The "vague philosophical" bit is, as far as I know, caused by Bohr's non-mathematical style and the reluctance of other physicists to admit that he was correct. But the mutually unbiased basis work is not philosophy, nor Ziegler's experimental work.

I'm unclear if you think the article is incorrect or that you just want more about Bohr here?

An idea that is closely related to Bohr's point of view on complementarity is ontology vs epistemic models. Lots of philosophy folks have weighed in on that; an interesting related topic that I don't see covered on Wikipedia. The closest I've stumbled upon is Relational quantum mechanics. Johnjbarton (talk) 16:14, 16 November 2023 (UTC)[reply]