# Template talk:Quantum mechanics

WikiProject Physics (Rated Template-class)
This template is within the scope of WikiProject Physics, a collaborative effort to improve the coverage of Physics on Wikipedia. If you would like to participate, please visit the project page, where you can join the discussion and see a list of open tasks.
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## the organization of the talk page

Many talk pages on wikipedia are a mess and difficult to follow. Let's keep this one clean and organized in a logical way, by putting a meaningful title to each talk section, and by keeping the discussion of each topic within its proper section. Put new threads at the bottom, and don't forget to date/sign your post. Thanks. (btw, are there guidelines at all, for talk pages?) AugustinMa 05:21, 30 December 2006 (UTC)

Yeah, here. Sean Heron (talk) 10:33, 7 March 2008 (UTC)

## Missing elements / Which elements to include?

...what about the neutron? quarks? Crappitrash 16:05, 15 December 2006 (UTC)

I added them. The template is a stub: please complete it as you find missing elements, and add the template to the relevant pages. Thanks. AugustinMa 09:07, 16 December 2006 (UTC)

I suggest Listing all particles including theorised ones - gluinos, gauginos, etc. Listings can be condensed logically. -Ste|vertigo 00:31, 26 December 2006 (UTC)

What is it about particles that merits a mention here? Okay, they obey quantum laws -- but so does the rest of the universe; should we therefore list everything here, from electrons to elephants, gluons to galaxies? I suggest listing no particles. The atomic hypothesis predates 1900. --Michael C. Price talk 12:51, 1 January 2007 (UTC)
Unless anyone objects I'll remove the particles from here and create a/update the particle template. OK? --Michael C. Price talk 09:19, 6 February 2007 (UTC)
Created Template:Particles --Michael C. Price talk 10:16, 6 February 2007 (UTC)

## Popper's experiment and other trivial stuff/ Which elements to include? part II

Is Popper's experiment really as important as the other 5? They were all devised in the early 20th century, early in the history of quantum mechanics, whereas from what I can tell from the article Popper's experiment comes from the 80s. If it is included why are the other experiments in http://en.wikipedia.org/wiki/Category:Quantum_measurement not? — Preceding unsigned comment added by 83.244.146.66 (talkcontribs)

Please sign your posts, even if you're not logged in or haven't an account, otherwise things get really confusing for later readers. Yes, Popper's experiment should be deleted IMO -- it seems it is probably theoretically unsound. Certainly it doesn't have widespread acceptance as a meaningful test of any validity. --Michael C. Price talk 10:23, 9 August 2007 (UTC)

I also nominate for removal from the interpretations section Relational quantum mechanics and Orch-OR. The former seemed to be the hobby horse of someone who has now left Wikipedia and is mostly sourced from one academic, the latter is not taken seriously except by a very small Penrosian group -- neither are sufficiently mainstream to merit mention here. What do people think?--Michael C. Price talk 10:34, 9 August 2007 (UTC)

Done. --Michael C. Price talk 03:27, 12 August 2007 (UTC)
Papers are still being published on the relational interpretation. I am going to add it to the box. Quantum logic, on the other hand, is not an interpretation in its own right, and shouldn't be included here. If there are no objections, I'll remove it. --Auspex1729 (talk) 20:51, 23 August 2008 (UTC)
I don't know how you arrive at the conclusion that quantum logic isn't an interpretation. Any sources for the claim? --Michael C. Price talk 07:49, 24 August 2008 (UTC)
Re-added quantum logic since it appears on the interpretation page. --Michael C. Price talk 08:37, 24 August 2008 (UTC)
I arrive at the conclusion that quantum logic isn't an interpretation in the same way I arrive at the conclusion that the Dirac formalism isn't an interpretation -- they are both used and universally accepted, independent of interpretation. What's more, this is the only place I have ever seen the claim that quantum logic is an interpretation. I do not need a citation that it isn't one, the onus is on you to give a citation that it is, in fact, an interpretation of quantum mechanics.--Auspex1729 (talk) 14:51, 24 August 2008 (UTC)
No, the onus is on you to argue your case over at the interpretation of quantum mechanics page, where quantum logic is listed as an interpretation. Wikipedia must be internally consistent. BTW quantum logic is not universally accepted. Quantum logic as an interpretaton --Michael C. Price talk 14:57, 24 August 2008 (UTC)
10 of the 11 pages of that preprint are dedicated to summarizing the quantum mechanical formalism, using the behavior of quantum mechanics as a justification for the use of quantum logic. The paper's title, which is "An Interpretation of Quantum Logic", not "Quantum Logic as an Interpretation" (as you have suggested), reflects this. The paper is an insufficient and irrelevant citation. I have, in any case, taken this to the talk page of the interpretation list page.--Auspex1729 (talk) 16:12, 24 August 2008 (UTC)
The problem is that "quantum logic" has a number of meanings. One is as an interpretation. Anyway, it's good that the discussion should be at the interpretation talk page. --Michael C. Price talk 17:02, 24 August 2008 (UTC)

## Presentation / style

Some of the headings would have many links, e.g. the sub-atomic particles are numerous. Maybe it is not convenient to list them one per line. We should consider having them in a simple comma separated list. Please improve the template as you see fit. AugustinMa 09:09, 16 December 2006 (UTC)

I suggest removing the particles altogether. The electron was dscovered before quantum theory. Particles obey quantum theory, but are not "quantum" any more than the rest of fundamental physics is -- we have to cut off somewhere. I suggest we only include things that relate directly to quantum theory. --Michael C. Price talk 07:29, 17 December 2006 (UTC)
I suggest
1. Changing the format to one with less syntax/code. There are better template formats out there that handle lots of material. example.
2. Removing the list of scientists, or else placing it at the bottom, and listing only last names.
3. List all particles including theorised ones - gluinos, gauginos, etc. Listings can be condensed logically. -Ste|vertigo 00:31, 26 December 2006 (UTC)
1) ok.
2) A list of last names at the bottom is fine, but keep the names somewhere.
3) ok. You can comment on this in the section above (missing elements).
AugustinMa 05:15, 30 December 2006 (UTC)

## Redone

Ive done most of the changes Ive suggested. I take back the suggestion of having a list of particles, though that might be better for a template:particle physics. There are some other areas which might need some area-specific templates, (below).-Ste|vertigo 01:46, 7 February 2007 (UTC)

You might like to look at template:particles. --Michael C. Price talk 02:08, 7 February 2007 (UTC)

## Quantum communications

I am not having an easy time finding quantum communications; a new article at Physorg.com[1] states: "In an important step for the infant field of quantum communications, researchers from the University of Geneva in Switzerland have, for the first time, realized an “entanglement swapping” experiment with photon pairs emitted continuously by two different sources." I hope to be able to read about this infant field soon on the Wikipedia. User:Mr Accountable --71.124.183.105 16:27, 14 October 2007 (UTC)

## Penrose

What has Penrose contributed to the foundations of QM? Not as much as the others. --Michael C. Price talk 18:59, 21 October 2007 (UTC)

I disagree. Penrose made an valuable contribution: he wrote an 1100 page textbook. I have already added it to Template:Theory of everything so that they English-majors can see the dues that they are supposed to pay in terms of homework before they come here and ask us to dumb down article for them.--Truthnlove (talk) 18:59, 4 March 2008 (UTC)

## Quantum state

I think quantum state belongs on the template as a "fundamental concept"...moreso than, say, the Ehrenfest theorem. Can I add it in? Swap it in for Ehrenfest? (The template's already getting quite long.) Thoughts? --Steve (talk) 17:47, 21 November 2007 (UTC)

Transformation theory seems, to me, even less warrented of a spot in the "fundamental concepts" section; it's not even a full article, and as far as I can tell, it's of primarily historical interest. I would suggest taking it out. It need not be replaced (again, the template is oversized), but if it were, I think a better replacement would be Wave-particle duality, which is also primarily of historical interest, but at least it's more often discussed in and out of the physics community. Thoughts? --Steve (talk) 22:43, 21 November 2007 (UTC)

## Compact template

It has been observed that this template is getting overly large. This is probably mostly to do with the breadth of the field as the content generally seems relevant. There are certainly additional topics that could be added.

I have created a compact version of the template (see below), using collapsible tables, with conditional statements that ensure that the section including the current article is expanded by default, although any and all sections can be expanded on any page (see for example Template:Electromagnetism3).

Comments, criticisms, suggestions for improvement welcome. Most of all, opinions on whether this (or a version of it) should replace the current template. --DJIndica (talk) 06:26, 28 November 2007 (UTC)

Quantum physics
$\Delta x \, \Delta p \ge \frac{\hbar}{2}$
Quantum mechanics
I think it's a great improvement, especially since there are many articles where the template would be useful but isn't there because it doesn't fit. --Steve (talk) 16:37, 28 November 2007 (UTC)
It looks good to me. Well done. Please Be Bold in changing the templace and adding it to relevant pages. Blessings. AugustinMa (talk) 10:56, 29 November 2007 (UTC)
I updated PhysicsNaviagtion to use collapsible frames, though it still uses the old NavFrames. If someone knows a fix plz tell me. I hacked around for quite a while, but gave up frustrated. I still didn't get the problem with NavFrames, maybe someone could post a e.g. a picture where it fails.
I had a discussion with Djindica, if the look & feel should be the same in all Naviagtion Templates in Physics or not, any ideas or complains ? Or more ideas how to improve the template ? {Sheliak (talk) 16:03, 29 November 2007 (UTC)}
OK, now I get the point with NavFrames. I will work on that problem, just give me some time. Till then either reformulate the captions or use
so it's readable for resonable text sizes. {{{Sehliak}}}
For the moment i'm going to change pages over to Template:Quantum mechanics2. --DJIndica (talk) 16:54, 29 November 2007 (UTC)
If your're in such a hurry, do what you like {{{Sheliak (talk) 17:07, 29 November 2007 (UTC)}}}

I think that the new template is much nicer, however, instead of having the "logo" of QM be the uncertainty principle, which is really just a property of waves, why not use $\hat{H}|\psi\rangle = E|\psi\rangle$ ? ॐ नमःशिवाय Śaiva Sujīt सुजीत ॐ 22:49, 30 November 2007 (UTC)

I have received no opposition here in the past week; I am going to go ahead and implement the change that I've suggested. Please do discuss this change here, if any of you find it displeasing. ॐ नमःशिवाय Śaiva Sujīt सुजीत ॐ 04:57, 8 December 2007 (UTC)
I think that was a bad move. The uncertainty principle is both much better known and is more fundamental to QM. Also easier to portray as a meaningful equation. If we go with the SEQ, why not the Dirac equation or the Proca equation or .... but there is only one uncertainly principle. --Michael C. Price talk 11:56, 7 March 2008 (UTC)

This template is not currently being used because Template:PhysicsNavigation on which it is based is still being worked on. Template:Quantum mechanics2 is the one currently being used; I find your change reasonable, so I have replicated it there. Ideally I think there should be some kind of picture, however quantum mechanics doesn't lend itself to pictorial description. Early versions of this template included images of Schrödinger's cat and the Bloch sphere, neither of which really worked. If anyone has any bright ideas then let's hear them.--DJIndica (talk) 15:51, 8 December 2007 (UTC)
I agree with the Schrodinger equation over the uncertainty principle, and also that diagrams (whether Bloch spheres or cats) aren't particularly helpful. However, I think the time-dependent equation
$i \hbar \frac{\partial}{\partial t} | \psi \rangle = \hat{H} | \psi \rangle$
is more suitable. This describes the fundamental dynamics of a system. The time-independent equation is, to my eyes, merely an eigenvalue equation, albeit a special one.
We could possibly have |ψ(t)> instead of |ψ>, but I think that could add clutter. If no one disagrees, I will replace the equation. --Masud (talk) 10:59, 12 December 2007 (UTC)
I liked the formula the way it is, time dependency must not be mentioned explicitly. To be real correct you should write psi(x,t) and that will certainly add some clutter. {Sheliak (talk) 16:49, 12 December 2007 (UTC)}
ψ(x,t) is incorrect as it only works for single particles. In the context of general systems of particles (or indeed fields), the only proper parameter is time. Also, you write it with x dependence if you project the H operator and the |ψ> kets onto x-space using the position operator. The most general statement you can make is that relating H|ψ(t)> and its time-derivative.
Furthermore, Hψ = Eψ only holds for time-independent Hamiltonians. The fact is that the Hamiltonian generates infinitesimal time translations (i.e. kets obey the time-dependent Schr. equation) and the conserved quantity arising from time invariance is energy and so we can write Hψ = Eψ. Viewed this way, Hψ = Eψ is a secondary fact to the time-dependent Schr. equation.
Edit: I corrected the above, where I wrote time-independent where I meant time-dependent.
--Masud (talk) 05:18, 13 December 2007 (UTC)
It is wrong to have psi(x,t) in the dirac notation, because it is basis-independent. psi(t) would of course be the more correct way to do it, but I think you're right in saying that it would be too messy. This is actually the same reason why I chose the TISE. It seems much elegant as being the iconic QM equation. ॐ नमःशिवाय Śaiva Sujīt सुजीत ॐ 22:55, 31 December 2007 (UTC)
My last edit has the "Advanced theories" permanantly expanded (at least on my browser). I can't see where I've gone wrong though :(. Help, please! Sean Heron (talk) 11:24, 7 March 2008 (UTC)
Very odd. I can't see what's wrong either. --Michael C. Price talk 12:12, 7 March 2008 (UTC)
The error was due to discontinous numeration (jump from 6 to 8). I will fix the template soon to avoid this in the future. (Sheliak (talk) 12:26, 7 March 2008 (UTC))
Fixed okay, I see, but I don't understand -- the problem existed when the numbering was continuous as well. --Michael C. Price talk 12:31, 7 March 2008 (UTC)

## Consciousness causes collapse

ScienceApologist just removed consciousness causes collapse ("CCC") from "Interpretations of Quantum Mechanics", with the comment, "not a proper interpretation..." I'd disagree--maybe it's not a good or correct interpretation of quantum mechanics, but it's an interpretation of quantum mechanics (albeit one with many variants, but every interpretation on the list comes in many different versions). Perhaps you have some technical definition of "interpretation" in mind that rules out everything in the article CCC. In that case, perhaps you should rethink your definition: As the term is commonly used, including in other wikipedia articles (Interpretations of quantum mechanics, and CCC itself), CCC is an interpretation.

The topic is not very important in modern-day physics, to be sure, but practicing physicists aren't the only ones interested in quantum mechanics. I think it would be inappropriate not to include a link, in the QM template, to one of the most widely-discussed aspects of QM in popular culture. I'm putting it back for now, but of course we can continue this discussion here :-) --Steve (talk) 23:36, 10 February 2008 (UTC)

Let's approach this from a reader's perspective. Imagine coming to this template not knowing anything about quantum mechanics. The problem is that listing this as an interpretation will falsely influence the amateur researcher into believing in parity between this particular idea (which has no supporters outside of Fritjof Capra's cadres) and actual notable interpretations such as Many Worlds and Copenhagen. I think this might be better included in a new section about quantum pseudoscience. There, we could include things like quantum mysticism, quantum mind, Quantum Archeology and the like without confusing the reader in messy demarcation. ScienceApologist (talk) 16:06, 11 February 2008 (UTC)
I like your idea of a new section. "Quantum pseudoscience" might not be the best title, though, since it's so obviously and over-broadly pejoritive (for example, not everything in quantum mind is garbage, and quantum mysticism isn't pseudoscience when it only claims to be metaphorical). However, I can't think of a perfect title myself either. The best I can think of right at the moment is "Philosophy, Pseudoscience, and Religion Inspired by Quantum Physics".... --Steve (talk) 18:25, 11 February 2008 (UTC)
The one thing that all these things have in common is "consciousness": which is also the thing that physicists hate the most when people try to attach it to quantum mechanics. Hmm, let's see. The idea is that people use quantum mechanics to support their ideas of consciousness, spirituality, identity, mysticism, etc. This is because, as the authors of Quantum Engima put it, qm juts up against our very definition of what it means to take an observation (though it doesn't directly address this question). Certainly, we can all blame the Copenhagen Interpretation for "sweeping" this junk under the rug, but the fact is that there are a lot of people outside of science trying to lift up that rug and dig some of that stuff out again.
Okay, so how about a section called "Extra-scientific sepculations about quantum physics". Does that do the trick?
ScienceApologist (talk) 18:37, 11 February 2008 (UTC)
OMG! I know *exactly* what you are talking about. My favorite target on this issue is not the biggest player, its Lynne McTaggart, who hawks new-age derivative drivel and speculation based on zero-point field. She tarnished the reputation of a Pulitzer Prize winner and now gets involved in hijacking zero point. Ugh!--Truthnlove (talk) 18:15, 4 March 2008 (UTC)
Good to see that others agree with the feeling I had when I ended up on the consciousness collapse page of "how the hell did I land here?" (I have the habit of browsing multiple windows at once). Anyway the article of that name has now been deleted, so I've changed the link to correspond with the redirect. I also put it into its own section, though I must admit I have about zero knowledge of the matter.I had thought of renaming "Interpretations" into "Scientific interpretations", but I have no idea if that would be correct, so I went with the less controversial "Interpretations by quantum physisists" (not that I know that is true either...). Please, please change if appropriate (or if you think appropriate), including just removing the "quantum mystism" link. Sean Heron (talk) 11:08, 7 March 2008 (UTC)
Erm, I pressed Enter while writing my edit summary... I changed it back to "Conciousness..." and now pointed the link to a section of the "interpretations" page (seeing that the "Conciousness..." page has been deleted. Sean Heron (talk) 16:25, 7 March 2008 (UTC)

Isn't "Consciousness causes collapse" just a variant of the Copenhagen interpretation and, as such, does not require its own entry? --Michael C. Price talk 21:21, 7 March 2008 (UTC)

### Merge with Template:Quantum mechanics

If no one disagrees, I will merge this template with Template:Quantum mechanics as its finally also supports collapsing.(Sheliak (talk) 13:36, 13 February 2008 (UTC))

Fine with me! If you're changing links from one to the other, here's the list to make sure you get all of them: [2] Have fun :-) --Steve (talk) 18:53, 13 February 2008 (UTC)
I support this too. ScienceApologist (talk) 18:56, 13 February 2008 (UTC)

## Use of Schrodinger equation: no caption?

This template prominently displays a Schrodinger equation. At first glance, this is probably pleasing to those editors familiar with the subject but to the average reader who then wants to know something about that equation, they might have some difficulty. The natural thing the reader will do is to click on the "Quantum mechanics" link, but the equation is not presented again on that page. I think that we should either:

1. Provide a caption and link to the Schrodinger equation article as part of this template
2. Replace with an image of the equation and link that image to the equation article
3. Update the "Quantum mechanics" to show the equation exactly as it is in this navigation template
4. Remove/replace with something more easily identified to the average reader.

I prefer the first option, but concern has already been raised about "clutter". This navigation template is supposed to provide clarity, ease-of-use and, ideally, no new usability mysteries for the user. I realize that this is a tough choice because those who do have a sense of mastery in understanding the equation are appropriately pleased with themsevles and find it to be pretty.--Truthnlove (talk) 14:46, 29 February 2008 (UTC)

Hi, yes I agree with your objection. I removed the caption and placed a link above the formula. I hope your pleased with this solution, but feel free to choose another symbol. ° Is not very intuitive, but I found no other yet. I think we should also update the QM article, the SEQ should really be mentioned there. Once we found a good solution I will update the PhysicsNaviagtion template. (Sheliak (talk) 18:02, 29 February 2008 (UTC))
A point of style, any sort of subscript/superscript might start to look like a part of the equation. Let's a a small caption. For the sake uniformity, I have also taken the liberty of copying the equation from Schrödinger equation#Mathematical formulation. We should strive for uniformity in our notation and presentation. I would like you guys to look at this Theory of Everything (TOE) diagram in the "Quantum Gravity" section of [3] which presents the "Theory of Everything" as a spatial cube with axes of (G,h-bar,c). It occurs to me that even greater uniformity might be achieved if we just used h-bar.--Truthnlove (talk) 05:30, 1 March 2008 (UTC)
I will removed the t dependence of your H operator, as you can also have a static potential. See above discussion of compact template. For the caption, we will see. I look for the symbol which is used for external links, then user certainly would not think this is part of the equation —Preceding unsigned comment added by Sheliak (talkcontribs) 09:34, 1 March 2008 (UTC)
That makes things more aesthetically pleasing for you but more difficult for the average reader. I have implemented Template:Theory of everything and the shorthand I use are the three physical constants. I did not bother with h-bar.--Truthnlove (talk)
Well I don't think the average reader would know about the Hamiltonoperator, i and so on either. That's why the Introduction to QM is on the top of the template. For the average physics, that shouldn't be a problem to recognize the SEQ. Also, we should split between the popular article for everyone and that for physics. I prefer the popular articles with no formula on the top of the box and the advanced in collapsible boxes.(Sheliak (talk) 13:57, 1 March 2008 (UTC)). (P.S. nice SM template !)

Looking forward, I would like to strengthen this emphasis on G,c,h as the coordinate system the reader should use to keep track of what is encompassed by TOE. I do not think a 3-D cube representation is necessary, but I would like to think that interested readers will get a feeling of the "big picture" from Template:Theory of everything even if they only took, say, three semesters of physics in college. I like this idea of using equations that use the appropriate number of the constants G,c,h. It helps to distinguish between quantum mechanics and quantum field theory, because important QFT equations include both h-bar and c. I was thinking about what simple equations might be appropriate for quantum gravity and TOE. Do you think that the reader would be mislead if we presented the formula for Hawking radiation on a TOE template? It does, after all, contain G,c and h. Also: is there any notable equation that includes exactly G and h?--Truthnlove (talk) 03:45, 2 March 2008 (UTC)

I finally realized that the Planck scale and Hawking radiation are merely "related" to TOE. Back to this template: Can we remove the "advanced" subjects that are strictly QFT things? I would like to emphasize to the reader that QFT is a distinct field.--Truthnlove (talk) 21:35, 2 March 2008 (UTC)
Bear in mind that QFT is simply quantum mechanics applied to a classical field. It is still quantum mechanics, when all is said and done. --Masud (talk) 05:15, 3 March 2008 (UTC)
I stand corrected. Penrose unleashed in 2004 the 1100-page monster on the world. There is now a single textbook that provides the prerequisites required for TOE. He has done his homework (and dares the reader to do the same) and then exercises a well-earned privilege of suggesting his own pet theory rather than string theory. I love it!--Truthnlove (talk) 19:03, 4 March 2008 (UTC)

## Topics in Template

Let's bring the Dirac equation & KG-Eq back to life in this template, so we have a smooth transition from QM to QFT where the user may click on KG-eq in the QM template and in the KG article sees the QFT template with other links which covers the broad spectrum of KG etc. (Sheliak (talk) 07:50, 3 March 2008 (UTC))

Done.--Truthnlove (talk) 11:32, 3 March 2008 (UTC)

## History of quantum mechanics

I think this article deserves a place on the template - originally I was thinking of replacing the currently redlinked "other scientists", but perhaps it could also go at the top as well. Akriasas (talk) 03:41, 6 March 2008 (UTC)

I strongly prefer that the link will be at the top, under the Introduction to qm..,too. Unfortunately the historic introduction is a little bit short, maybe someone could extend it in the future ? (Sheliak (talk) 07:21, 6 March 2008 (UTC))

## Scientists

Please don't add to much scientists to the template, instead move them to others (see Contributors to general relativity for example). Jordan & Hawking are not very famous for QM. Restrict number to max. 10 guys. (Sheliak (talk) 14:30, 8 March 2008 (UTC))

They are hidden, so I see no need for an arbitrary restriction to 10. --Michael C. Price talk 14:37, 8 March 2008 (UTC)
Yeah, but when I click on show I and see a bunch of names I'll get confused. So please use others, where you can also written in which way they contribute (esp. Hawking, he's contributions are related to QFT and definitely not for QM) —Preceding unsigned comment added by Sheliak (talkcontribs) 14:39, 8 March 2008 (UTC)
Please, be serious; eleven names is hardly information overload. As for Hawking, I added him and Bekenstein to QFT, but only Hawking to QM for his exploding black holes work (which I do regard as important enough to qualify as QM as well as QFT). And Jordan's input was foundational, as was Everett's. --Michael C. Price talk 14:45, 8 March 2008 (UTC)
Well, well, well. Do what you want. I don't regard Everett's contributions as importand as Schrödingers, Heisenbergs or Dirac's. Please, just keep in mind that you want present this information to a freshman in a clear & polished way.(Sheliak (talk) 14:50, 8 March 2008 (UTC))
First point is a matter of opinion, the last is entirely valid -- but even freshmen have heard of the Pauli exclusion principle (I hope). Adding 2nd rank physicists to "others", as you suggest, is a good idea. --Michael C. Price talk 14:53, 8 March 2008 (UTC)
You're right, Pauli is indeed an important person for qm, I don't want him to be removed from the list either. Bohm, von Neumann and others, I'm quite familiar with qm now, but never heard of them in this topic and as I know, all of them didn't receive a noble prize for their contributions. Hawking, though I'm an Astrophyisics, most normal guys on earth aren't intereseted in black hole evaporation. But more important he was the first guy who connectes gravity with quantum field theory.

Seeing again the QFT template with so much names, well "don't know where to start, too much to read for a brief overview". But let's stay so for the first (Sheliak (talk) 21:14, 8 March 2008 (UTC))

## Whoops!

I didn't realize there was a discussion page for these templates! I realize now that I was being completely rude, sorry. Here's why I did the changes:

1. While Hawking's contribution to Black hole decay is enormous, his main contribution to QM proper is the suggestion that it's wrong, because black holes destroy information. This is also a very important paradox that led to much progress, but it's not really a very constructive addition, so it's hard to lump in with these guys. I think Hawking belongs on the "Quantum Gravity" template best, although he is a classical gravity guy too. Along with Hawking, there's 'tHooft and Penrose who suggest that QM needs modifying, carrying the Einstein torch.
2. I think the list should end with Everett, because he sort of closed the subject. After him, it's all decoherence and quantum information theory, and not so much measurement that is the basic issue. Personally, I consider him the founder of quantum information theory, but others put it later with Zurek or Deutsch. I think that the modern work should have its own "quantum information theory" box, with Zurek and Deutch and Shor etc etc.
3. Sommerfeld was shafted for the Nobel prize, we don't have to shaft him too. He single handedly created the multi-periodic generalization of old quantum theory. Bohr could not believe that classical mechanics needed so little modification.
4. Kramers is a huge figure in the development of Matrix mechanics, but his greatest contributions came just before matrix mechanics was formulated. He showed that there was a correspondence (in the sense of the correspondence principle) between fourier coefficients and emission and absorption rates, and formulated the matrices with Heisenberg. Heisenberg then completed the program that he started with Kramers. Kramers also did WKB, which reinterpreted the old quantum theory in the new quantum formalism.
5. I also reorganized all the people, so that their names come in approximate historical order of first important contribution. That way, a reader would sort of get the history right.

Anyway, I didn't mean to be rude, and I think that this list is a little long, but these people are all giants, I think they are all equals in the development of QM, and I don't see how to omit any of them.Likebox (talk) 04:13, 13 May 2008 (UTC)

## Bell

Bell, like Feynman, made contributions to QM proper and to Quantum field theory, which makes it difficult to know where to put his handle--- but his name is more often linked to the QM stuff, while the anomaly is more easily associated with Adler/Jackiw. He does come after Everett, but he is clearing up a foundational QM issue.Likebox (talk) 18:29, 13 May 2008 (UTC)

## Why have an equation/logo in the template?

I was reading the Pauli Exclusion Principle page and was confused to find the uncertainty principle equation on the page for no apparent reason. Clicking on it doesn't do anything and so doesn't bring any enlightenment. It took me a while to figure out it was part of this Quantum mechanics template, and I guessed it was supposed to be somehow symbolic of QM in general, and I see here that I was right, but to me it was just confusing and caused a fair amount of wasted effort with guessing and poking around to figure out why it was there

I recommend removing it. It's not enhancing anything and is counter-productive.Atomota (talk) 15:41, 9 July 2008 (UTC)

There is a link to the uncertainly principle directly under the equation.
BTW The general relativity template has an iconic equation, and the quantum field theory template an iconic diagram.
--Michael C. Price talk 16:01, 9 July 2008 (UTC)
The wrong equation in my opinion, but people seem more ready to click revert rather than provide satisfying explanations as to why. And I don't blame them, for the former is a far simpler option than the latter.
--Masud (talk) 18:09, 9 July 2008 (UTC)
There was a discussion as to the merits of the UP or the SEQ. As I said, the UP is more iconic and less arbitrary. (If the SEQ, why not the Dirac equation, or Proca's ...?) The only non-arbitrary equation would be the Klein Gordon equation (since it is universally obeyed) -- but it starts to shade into QFT and is less iconic.--Michael C. Price talk 19:28, 9 July 2008 (UTC)
I have 3 issues with the HUP:
1. The way the HUP is currently written is very easily misunderstood by the layman. The HUP applies to an ensemble of identically prepared systems (how else could you measure the variance of an observable?), whereas the common interpretation is the "uncertainty" in the value of the position/momentum of a particle. The subtlety in the HUP is easy to miss, but is crucial. You can indeed measure the position and the momentum of a system. But don't expect there to be any correlations between the measurements of momentum after the measurement of position of several identically prepared systems.
2. The HUP arises from the commutation relation [x, p] = i (in natural units), so if we are to put down the HUP, we should put down this commutation relation. This relation applies generally, and not arbitrarily to single-particles.
3. The choice of the HUP is arbitrary since there are several other commutation relations in quantum mechanics, and so several other uncertainty principles which arise.
In striving for generality, you have missed it. The HUP is not general - it applies only to single particles and not complicated systems. Also theYour reasons for the HUP are therefore invalid even by your own metric of suitability.
As for the SE, you misunderstood the case I made for it earlier. By the Schrödinger equation I was not talking about (in natural units)
$\left(-\frac{1}{2m}\nabla ^2 + V(\vec{x})\right)\psi(\vec{x}) = E(\vec{x})\psi(\vec{x})$
for indeed, that is not general and it is arbitrary.
Your case for the Klein-Gordon equation is weak too - the Klein-Gordon equation is not universally obeyed, in fact it is only obeyed by scalar fields and single particle momentum eigenstate excitations of scalar fields.
$H|\psi\rangle = i\frac{d}{dt}|\psi\rangle$
This is the most general expression; it is satisfied by every single quantum system ever considered (indeed, in some respects, it is the definition of a quantum state: if a state satisfies this equation, then it is allowed as a quantum state), from your humble simple particle, to your system of electromagnetic and Dirac fields, to your supercooled Bose gas. The Dirac, Proca etc. equations are all specific versions of this equation - they specify the form of H. I would not intend to do that, and thus leave the equation as general as possible.
In summary, by your own requirements for suitability, the above SE should be used, and not the HUP. Ultimately, we should not propagate misinformation in the hope of being iconic - if someone doesn't recognise the equation they can learn about it.
--Masud (talk) 02:32, 11 July 2008 (UTC)
For what it's worth, you might be interested to read through this article. You're limiting yourself to what they call "The Minimal Interpretation", which is the most important one in the practice of modern quantum mechanics, but not the whole story. I made the same mistake in trying to edit that article, and learned through the process. :-)
Anyway, I'm fine with any of the equations that have been brought up, but I think Atomota brings up a legitimate point, that people who aren't familiar with how templates look and function would be confused to see the equation. I would suggest that, whatever equation is to be used, we change the font, and/or the font color, and/or the background color, and/or the orientation of the symbols, or something...so that it looks like an icon, not just a normal, boring equation. I picture something like:
• The letters $\Delta x \, \Delta p \ge \frac{\hbar}{2}$ form an semicircular arc atop a picture of the 2s or 3s atomic state (the latter as in this picture).
...but I'm sure there are better ideas. Eh? What do y'all think? --Sbyrnes321 (talk) 07:19, 11 July 2008 (UTC)
Masud, you should stop calling it the SE, since $H|\psi\rangle = i\frac{d}{dt}|\psi\rangle$ is just one component of the covariant form of the de Broglie hypothesis, $p_{\mu}=-i \hbar \partial_{\mu}$ (sign according to metric convention). Oh, and BTW, the KG equation is universally obeyed by all free particles; any fermion that satisfies the Dirac equation also satisfies KG equation. Same for spin 1 particles etc.
It is called the SE, regardless of what your issue with the equation is; see for instance this or any decent quantum mechanics textbook. It is incorrect to demote the SE to be a "component" of the de Broglie hypothesis - the latter only applies to particles and the former is a more general rule. You can derive the other components of the de Broglie hypothesis from the commutation relations, which again are more general. If you look at any textbook, the HUP, nor the de Broglie hypothesis will be listed as a postulate of quantum mechanics, but the time-dep SE will. Finally, the KG equation is not universal - it does not indicate anything about statistics, which the Dirac equation does for instance, with the anticommuting operators. Just because the square of the Dirac equation leads to the KG equation is irrelevant; the Dirac equation contains new information that wasn't available from the KG equation. And even if you were correct, you say it applies to any free particle; the time-dep SE applies to anything, including the whole system of complicated atoms that makes up your brain. Furthermore, de Broglie's hypothesis only applies to energy-momentum eigenstates; the SE I've listed works for any system, I've said this a few times now. There really is no contention in that statement. I admire the way you missed all the points and arguments against the choice of HUP. --Masud (talk) 00:59, 12 July 2008 (UTC)
Masud, re universality of K-G: I said every particle that obeys the Dirac equation also obeys the Klein Gordon equation. I don't know what part of that you choose not to understand -- you're the one selectively missing points that you find inconvenient; raising the issue of spin is a complete red herring. The only valid point you made was that of momentum eigenstate dependency, and that can easily be removed from $p_{\mu}=-i \hbar \partial_{\mu}$ by explicit conversion into an operator equation: $\hat{p}_{\mu}=-i \hbar \partial_{\mu}$. And please note that $\hat{p}_{\mu}=-i \hbar \partial_{\mu}$ is relativistically valid, unlike the SE (or are you going to redefine your terminology again?). --Michael C. Price talk 03:25, 12 July 2008 (UTC)
No, no, initially you said 'The only non-arbitrary equation would be the Klein Gordon equation (since it is universally obeyed)' (scroll up); then you decided to narrow it down to 'particles that obey the Dirac equation'. You decided to backtrack on that clearly incorrect statement, and that is fair enough, indeed it is admirable to admit when one is wrong.
The SE is relativistically valid. Look back to your QFT course, and remember when you derived the rules for the unitary time evolution operator U(t_0, t) which evolves a Heisenberg state from t_0 to t. That evolution operator arises from considering time evolution of states exactly as given by the time-dep. SE given above.
And finally, could you explain where I redfined my terminology? Thanks, Masud (talk) 05:51, 12 July 2008 (UTC)
I'm not playing the game of calling $H=i\hbar\partial_t$ the SE: it isn't, no matter how often you try to redefine it. It is the definition of the zero component of the energy-momentum operator.
So you disagree with the Wikipedia page I have linked? I could cite some textbooks too, if you wish. Are you telling me you disagree with mainstream teaching of quantum mechanics? The time-dep. Schr. eqn. is listed as a postulate in almost every treatment of QM since von Neumann and Dirac, yet you claim to know better? The HUP is not listed as a postulate, although the commutation relation is. --Masud (talk) 14:11, 12 July 2008 (UTC)
I disagree that $H=i\hbar\partial_t$ is the SE, without specifying the non-relativistic expression for H that Schroedinger gave. --Michael C. Price talk 21:57, 12 July 2008 (UTC)
Your earlier statement that the Klein-Gordon equation is not universally obeyed, in fact it is only obeyed by scalar fields and single particle momentum eigenstate excitations of scalar fields. is false. I cited the Dirac equation as a non-scalar counter-example.
Are you saying that the Dirac equation has the same information content as the Klein-Gordon equation? --Masud (talk) 14:11, 12 July 2008 (UTC)
No. You like asking asinine leading questions, don't you? (a=>b)=/=>(a=b) Look, you clearly understand the technical issues here, so stop pretending that you are as thick as shit. Read and digest Comparison_of_Dirac eqn with Klein-Gordon equation--Michael C. Price talk 21:57, 12 July 2008 (UTC)
I did not limit myself the the Dirac equation; perhaps you missed the (highlighted) clause "any fermion that satisfies the Dirac equation also satisfies KG equation. Same for spin 1 particles etc.". Ok?
Are you still claiming that the Klein-Gordon equation is universal? Could you cite a reference for that? Why do we bother with quantum field theory? Why do we have different representations of the Poincaré group? --Masud (talk) 14:11, 12 July 2008 (UTC)
To your first question: yes. All free particle obey it. As for the last question, don't you understand the irrelevance of it? Any solution to the Dirac equation, for example, is also a solution to the Klein-Gordon equation (as the Dirac equation article says). --Michael C. Price talk 21:57, 12 July 2008 (UTC)
Finally, you previously claimed "The HUP is not general - it applies only to single particles and not complicated systems. " Each particle in any system is subject to the HUP, which also applies to the composite system as a whole. OK? --Michael C. Price talk 07:44, 12 July 2008 (UTC)
What is the momentum of a charged particle? p, or p - qA? --Masud (talk) 14:11, 12 July 2008 (UTC)
p. --Michael C. Price talk 21:57, 12 July 2008 (UTC)
I have no more to say on the matter. --Masud (talk) 00:13, 13 July 2008 (UTC)
The substitution p -> p - qA is a way of moving from the free to the interacting equation for a charged particle. But both before and after p is still the momentum. --Michael C. Price talk 10:06, 13 July 2008 (UTC)
As for Steve's idea to add graphics to make the iconic status clearer, yup that sounds okay. --Michael C. Price talk 07:29, 11 July 2008 (UTC)
• LOOOL*, I don't think that colorizing the equation makes something better. My first impression was that someones vandalised the template. If you want an Icon replace it with a nice picture but keep in mind that the content AND presentation should be pleasent to the eye not just funtional.. (Sheliak (talk) 20:56, 11 July 2008 (UTC))
I thought the colours might be pleasant to the eye, but if not then please revert it. --Michael C. Price talk 03:35, 12 July 2008 (UTC)
Sbyrnes321, please sign off with your own username, not mine. I've edited to correct. --Masud (talk) 00:48, 12 July 2008 (UTC)
Masud, see here. MichaelCPrice changed my sig. Sheliak, I agree that the rainbow HUP is a bit silly (though I like the idea), and that perhaps we should continue to brainstorm. Shadow-lettering? Background picture? I'm no graphic artist, obviously. --Steve (talk) 02:32, 12 July 2008 (UTC)
My apologies to Masud & Steve for the sig change - a copy & paste that somehow turned into a cut and paste.--Michael C. Price talk 03:25, 12 July 2008 (UTC)
No worries; there's a lot of text in the box now, and it is quite hard to parse. --Masud (talk) 05:53, 12 July 2008 (UTC)
Apologies for the false accusation. --Masud (talk) 05:53, 12 July 2008 (UTC)
What about having a mouse over effect, which pops up a note with a small description. When mediawiki supports JavaScript, that should not be a problem to implement.(07:27, 12 July 2008 (UTC))
In my opinion the formula of the template is somewhat misleading because standard deviations are mostly denoted by $\sigma_x$ in literature. Moreover, the term $\Delta x$ should be kept to denote finite resolutions (intervals), which are also used in the article of the Heisenberg principle. Actually, the inequality $\sigma_p\Delta x\geq \pi\hbar$ makes the differentiation of both quantities $\sigma_x$ and $\Delta x$ necessary and important. --Zetafun (talk) 12:17, 6 June 2010 (UTC)
The delta form is much more common, which is only misleading to someone who already understood it - in which case it isn't misleading, if you see what I mean. --Michael C. Price talk 09:16, 19 June 2010 (UTC)
Should we really prefer to support the common confusion about this important distinction (see talks), instead to promote the awareness between both of these measurement philosopies? I don't think so. --Zetafun (talk) 05:49, 21 June 2010 (UTC)
Anyone who wants can look up the details at the link immediately underneath. But to answer your question, Wikipedia does not promote ideas, it reports on them. And the most common ideas get the most representation. The delta symbols have iconic status in this regard. Look at any QM textbook and you will see the delta representation. And in the text you may see an explanation in terms of standard deviations. Why should we be different? --Michael C. Price talk 09:22, 21 June 2010 (UTC)

## Bose? Candlin?

Bose's paper founded quantum statistics. He was added to the QFT template, but I thought he was better off here. Candlin is a pet peeve--- Fermionic integration is a central tool in modern quantum theory, and it is half the path integral. There isn't a modern QM treatment that doesn't include it. But the inventor seems to have been completely ignored for some reason. Tentatively inserting these guys.Likebox (talk) 02:40, 26 October 2008 (UTC)

What about Paul Ehrenfest? shouldn't he also be included? Dauto (talk) 08:51, 23 February 2009 (UTC)
I wonder if Candlin shouldn't be moved to the QFT template? --Michael C. Price talk 09:22, 19 June 2010 (UTC)

## Quantum Nonlocality

I think Nonlocality deserves a place in Fundamental Concepts, even separately from Entanglement. I'm still working on improving the quality of the Quantum nonlocality article, but it is clearly an important notion and an active field of research, somewhat independently of entanglement.--Sabri Al-Safi (talk) 16:35, 12 April 2011 (UTC)

## A picture to replace the HUP?

True, the HUP a central feature of QM, but so is the SE, although why have an equation when we could have a picture?

I propose one of:

since they capture the very basics of QM, namely; wave-particle duality, the De Broglie momentum-wavelength relation, and do suggest the position of a particle is uncertain, and complete in black boxes to give a "mysterious feel" (at least IMO, maybe not, depends what you think...), which one learns in introductory QM. The second additionally has the SE and HUP so important in QM, which are more advanced...

If there are no objections I will replace with the second. If people don't like the colours I can just change to a simpler theme, but they don't have the same feel without the black background... M∧Ŝc2ħεИτlk 15:53, 4 January 2013 (UTC)

I personally have a hard time seeing it at 200px since there are some small features. a13ean (talk) 20:05, 4 January 2013 (UTC)
Presumably you refer to the second? If that's a problem I will default to the first (assuming no objections). M∧Ŝc2ħεИτlk 22:15, 4 January 2013 (UTC)
Particularly to the second but also to the first. On the monitor I'm using at the moment the thin line of the lambda in particular vanishes for the top one. Also the blue doesn't have much contrast against the black. As much as I also like the black background, I think a white one might be easier to see. We could also try to come up with something which has less fine features -- for example maybe just the waveform or something. a13ean (talk) 22:29, 4 January 2013 (UTC)

First, let's get the colours right (deleting symbols/equations is always easy, though I really would like to keep the De Broglie relation with the double-arrow there, since it shows momentum is not in one direction only, suggests the wavelength isn't well defined showing a span of position uncertainty and (with the equation) momentum uncertainty, and it's a very important equation learned before the HUP and SE). I had prepared an alternative similar colour scheme (a white background is a bit drab but I can live with it) which may be ok?

3. 4.

Better/worse? I think as a minimum of inclusion we should include the waveform and the particle; a waveform alone (a) looks too boring (b) emphasizes less on wave-particle duality. In the very, very last resort under strong consensus I'll reduce to a waveform alone but not yet.

P.S (forgot to change the text in the fourth image to curves... which presently renders in a not-nice default font... will fix later). Thanks for the continuous feedback, and much quicker than I expected. M∧Ŝc2ħεИτlk 23:55, 4 January 2013 (UTC)

As is usually the case, I have started a discussion... only to stall. Given that no-one has objected, I will replace the HUP with the 4th picture, and see what happens... M∧Ŝc2ħεИτlk 17:05, 2 February 2013 (UTC)

## New topic in concepts

Does anyone have any issues with the addition of Quantum entanglement to the concepts drop-down section? And an addition of the QM template on the entanglement page? Thanks
EzPz (talk) 02:30, 6 December 2013 (UTC)

Wow, amazing that it was missing until now. Yes, please do! --Nanite (talk) 10:05, 6 December 2013 (UTC)