Talk:Quantum mechanics/Archive 7

This is an archive of past discussions about Quantum mechanics. Do not edit the contents of this page. If you wish to start a new discussion or revive an old one, please do so on the current talk page.

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I zapped several crufty and/or downright crackpotterly links from the "External links" section. Misinformation does not need the implied endorsement and the added publicity that our "encyclopedia" provides. For a dress-down of the Hindu "Vedanta" flavor of pseudophysics, see Alan Sokal's article "Pseudoscience and Postmodernism: Antagonists or Fellow-Travelers?" (2006). Anville 19:19, 2 June 2006 (UTC)

We need some people who are comfortable with this topic to describe these interpretations of QM. RK 19:15, 17 June 2006 (UTC)

• Interpretation of quantum mechanics

Isn't "Quantum Physics" or "Quantum Theory" a more appropriate title, with "Quantum mechanics" linked to this article? The application of quantum theory to, say, electromagnetic fields surely isn't in the domain of "mechanics," at least not as understood by the college student who is introduced to mechanics and electromagnetism as separate subjects. Quantum theory has much broader scope than mechanics; surely the Wikipedia naming conventions aren't so deferential to commonly familiar terms that we should apply such a misnomer to this article. (?!?)

In general, with respect to those who have undertaken the difficult task of contributing, this article is a sprawling, incoherent mess. Perhaps it would be appropriate to give a concise introduction to the theory with clear links to articles at several levels of sophistication. Technically sophisticated readers will benefit little from wordy paragraphs or sentences which begin with "An equation known as the Schroedinger Equation...," while novices can hardly be expected to follow the equations and mathematically rigorous language which is sorely needed in this article. As it stands, this is hardly a "technical" article, as implied by the statement at the top.

Is there any hope that a group of concerned physics professors from major universities will take responsibility for maintaining this important page???

Gnixon 23:59, 23 July 2006 (UTC)

Please append your edits to the end of the page --Ancheta Wis 01:20, 24 July 2006 (UTC) moved

I was under the impression that causality (cause begets effect) does not apply as definitely in the quatum realm as it does in the classical, that effects can chronologically preceed their supposed causes. After watching The Elegant Universe and doing some brief reading on the subject, this was one of the things that I gathered. It is, to me, interesting enough to include on the QM page, if accurate. Though, since I have no formal experience with QM I did not want to add it to the article without backing. --HantaVirus 14:47, 27 July 2006 (UTC)

Under the discussion of entanglement under "Quantum mechanical effects" the issue of the violation of special relativity is not handled with much care. "If quantum mechanics is correct, entangled particles can display remarkable and counter-intuitive properties. For example, a measurement made on one particle can produce, through the collapse of the total wavefunction, an instantaneous effect on other particles with which it is entangled, even if they are far apart. (This does not conflict with special relativity because information cannot be transmitted in this way.)" August 2nd 2006 11:13 PST. This last statment is simply false and was the major issue posed to Bohr by Einstein. The thought experiment goes something like this: Imagine two particles with known opposite spin (because of a paramagnetic effect or whatever). Both particles have underknown spin until one is measured, then the other is instantaniously known, before information (which can't travel faster than the speed of light, no matter what the article claims) can travel to the other particle, thus violating SR. A few experiments have been preformed, but nothing conclusive has come from any of them, and this remains a major question in QM from my understanding. I would hope this could be corrected by someone with a little more technical background than myself.

No, I'm pretty sure you cannot transmit information via QM entanglement. Unless you are the particle in question and the information you are transmitting is your unknown state. What I mean is that an experimenter cannot use entanglement to transmit arbitrary information faster than light. Even if, at some level, in order to make things work out, it seems that some "information" must be moving faster than light, it is not information that we can ever use. It is certainly not information that would allow someone to violate special relativity (send information beyond a light cone, predict the future, etc.) and it is not transmitted by a wave or particle as far as we know, so it doesn't violate relativity. A faster-than-light quantum entanglement "radio" can never exist. And I've never heard that that is somehow a controversial issue or that any physicists disagree that QM cannot transmit information faster than light. I'm not a physicist, but I've asked a couple of them about it and this is what I was told. Xezlec 16:43, 5 August 2006 (UTC)

No information can be transmitted by Bell states without classical communication. Though the quantum state is changed by the measurement of the first particle(collapse of wavefunction), there is no observable change in the state unless the measurement outcome is first communicated to the second particle.Waxigloo 17:43, 26 August 2006 (UTC)

To avoid repeating the same text again, I am putting a link to my comment about Schrödinger's cat: [[1]]. David R. Ingham 20:50, 23 August 2006 (UTC)

See also Introduction to quantum mechanics#Quantum entanglement which is only about locality. Bohr's answer to Einstein, that 'what is described is a system', means that no new info is transmitted (it's the same system). --Ancheta Wis 21:42, 23 August 2006 (UTC)

I wish that the articles on quantum theories were more clear on terminology, so that it is more clear what is a subset of what. The lead section should make it clear what quantum mechanics is in relation to quantum field theory, quantum electrodynamics, and quantum physics in general. In general, if several meaning are attached to a word, the lead sections should discuss the various meanings, and which is retained in wikipedia. The articles should then be consistent with these definitions.

I see the following inconsistencies:

• quantum mechanics was said to be a subset of quantum field theory in the lead section of quantum mechanics, while the introduction section of the article suggests that (relativistic) quantum mechanics is synonym with quantum field theory. I have now changed the lead section to distinguish the 2 uses of the "quantum mechanics" words
• if (relativistic) quantum mechanics is a synonym of quantum field theory, as the introduction section says, shouldn't the two articles be merged ? Why does the "quantum field theory" articles says that it is the application of quantum mechanics to fields ?

I see different options here:

1. consider that "quantum mechanics" has 2 meanings. We would thus split / merge the current quantum mechanics page into "quantum field theory", and a new "non-relativistic quantum mechanics". The "quantum mechanics" page would then be a disambiguation page with links to both articles.
2. consider that "quantum mechanics" has 1 main meaning, as a synonym of quantum physics or quantum field theory. In that case, I'm not sure how to position it compared to quantum field theory: shouldn't the article be merged with quantum field theory ?
3. consider that "quantum mechanics" has 1 main meaning, as a synonym for non-relativistic quantum theory. I'm not sure this is really the most common meaning though. If it is, then we should clearly say it in the lead section of the quantum mechanics article, and change its "introduction" section.
4. We could also use the otheruses4 template to say :"This article is about non-relativistic quantum mechanics. For relativistic quantum mechanics, please see quantum field theory". This is the option I prefer. We should then need to make sure that the article discusses non-relativistic quantum mechanics only.

Whatever we choose, there would be some work to verify that the use of the 'quantum mechanics' word is consistent throughout wikipedia. I have added the merge tag to help resolve this issue. Pcarbonn 06:03, 29 August 2006 (UTC)

Quantum mechanics and quantum field theory are different subjects and are taught as such at colleges/universities. QM is non-relativistic, the fields are not quantised and the particle number is fixed. In QFT all these restrictions are lifted. --Michael C. Price ^talk 08:04, 29 August 2006 (UTC)

So, you choose option 3 or 4, is that it ? Pcarbonn 20:50, 29 August 2006 (UTC)

3, although an important qualification is that "quantum mechanics" means "non-relativistic, classical field quantum theory". --Michael C. Price ^talk 21:10, 29 August 2006 (UTC)

Disagree: I do not approve of a merge. They are not the same thing. Waxigloo 18:48, 29 August 2006 (UTC)

So, which option do you choose ? Or you don't see a problem with the lead section and the last paragraph of the "introduction" section? Pcarbonn 20:50, 29 August 2006 (UTC)

Sorry; I forgot to say-- I think I agree with option 4. Limiting this article to non-relativistic QM and putting a link at the top for QFT seems to be the most informative and accurate thing to do.Waxigloo 00:59, 30 August 2006 (UTC)

Thank you for your feedback. I agree that a merge with quantum field theory does not make sense, so I removed the tag.

Reason for the split tag: In addition to the proposals above, I propose to create a quantum theory article, and move some of the general content of the quantum mechanics article to it (I suspect that some statements made in the quantum mechanics article apply to all quantum theories).Pcarbonn 06:16, 30 August 2006 (UTC)

What do you propose: that "quantum theory" includes "quantum field theory" and "quantum mechanics" plus some other stuff? --Michael C. Price ^talk 07:41, 30 August 2006 (UTC)

yes, indeed, it would be an overview of all quantum theories, and could explain some common features of them (eg. duality of wave and particles). I've created a stub already (see quantum theory). Alternatively, the article could be called quantum physics. I suspect that some people (and the current version of the article) use "quantum mechanics" to mean "quantum physics" in general, for historical reason (quantum mechanics was first, right ?). Hence the confusion. Pcarbonn 11:04, 30 August 2006 (UTC)

Sounds a good plan. I suggest that quantum theory redirect to quantum physics (or vice versa) -- ah I see you're already done that. Keep the article brief (as it is already) and have QM, QFT, etc as main articles within. --Michael C. Price ^talk 12:02, 30 August 2006 (UTC)

I don't think the content should be removed. Also, I think the reasons for removing it is false.

After the revert, I'm going to add a ref to what Hawking thinks on the subject of Einstein's "dice" quote.

I think it very much does belong here. Quantum Mechanics has it's opponents. And those reasons are valid reasons. Some of those reasons are religious. I'm a religious man myself, I put the section in on Miracles, because I'm actually reading the book now. Contrary to C.S. Lewis, I believe in quantum mechanics, almost religiously so. But I think that the other viewpoints are important to providing a NPOV. McKay 23:31, 18 September 2006 (UTC)

The Einstein quote, which is often misused and misunderstood (as it was here), is not a "religious objection" that Einstein had. I have even seen arguments that Einstein was not even all that Hell-bent on the necessity of determinism, and that that quote has been played up beyond all fairness proportional to the seriousness with which Einstein said it, and the stock he put in it. But we can assume he meant it: i.e., QM is incomplete because he felt the universe ought to be deterministic. Fine.

But Einstein was some sort of pantheist-thingummy, if I have understood him correctly. He was certainly not a dogmatic believer in any religion (on the contrary). So really, while the "dice" quote does represent some of the reservations he had about QM, they are reservations he had on aesthetic grounds, and from his sharp instinct for physical truth, not religious inclinations. There is no way that it can be accurately termed a "religious objection".

Note that I am not disputing that Einstein said the "dice" thing (so simply providing links to quote sites is unnecessary) - I am disputing that he meant it as a "religious objection". Byrgenwulf 06:24, 19 September 2006 (UTC)

Yes, Einstein was not Jewish (except by heritage). His religous beliefs were not judeo-christian. But he did have religous beliefs. saying "he had reservations on atheistic grounds" is false. I will admit that this quote is oft used incorrectly. But not in the manner in which you speak. It is oft used to establish that he was Jewish, or Christian or something. He did not believe in this manner, but he did "believe in Spinoza's God who reveals himself in the orderly harmony of what exists, not in a God who concerns himself with fates and actions of human beings." His statement that he disliked QM because he felt that it was out of the orderly harmony of the universe, is most definitely a religous statement. Without further evidence that it wasn't religous grounds, I think that your claims that it wasn't religious is dubious. McKay

• I said "aesthetic" not "atheistic". Byrgenwulf 14:48, 19 September 2006 (UTC)

About the "religious objections" section in general, then...I do agree that giving coverage to all viewpoints is important, of course. But, it should be remembered that C.S. Lewis was a professor of English, not of physics. He happens to be a real scholar, one for whom I have some respect, even; but by adding English professors' criticisms of things like Heisenberg's uncertainty principle, I very much fear we are opening the flood gates for other people to come and add their own particular "religious objections" to QM, which will no doubt also be objections raised by non-experts, and in the end the article will be bogged down by this. The bottom line is that people have "religious objections" to all forms of science, and QM is no exception; the "religious objections" to QM that I have seen are not even taken as seriously, as, for example "intelligent design".

Is every science article now to include a "religious objections" section? And "objections" from what religion? All the religions that "object"? Just how respectable do the "objections" have to be, before they can be included? For I very much doubt that Prof. Lewis knew exactly what he was talking about, and was rather just deciding what he thought the scientists meant by "Heisenberg uncertainty" - but an English professor, no matter how respectable, is simply not qualified to make pronouncements like that, I don't think. Byrgenwulf 06:24, 19 September 2006 (UTC)

I would say that if the religous objections are notable, then they should be included. Some Joe Schmoe's comments are not notable, but Prof. Lewis's, I would claim are. Sure, his claims were objections to what he thought scientists meant, but according to the book, he was actually correct in what he thought that scientists meant. He was opposed to the indeterminstic nature of the universe. Which is basically the point of Quantum Mechanics. Evolution has a religious objections section. While he is an "english professor" he is also a popular religionist. What he says on the matter of religion is notable. And he had a religious objection to QM. That's kinda like saying McKay 14:04, 19 September 2006 (UTC)

What Lewis said is notable in Lewis' article. If Lewis were famed for having objected to Heisenberg's Uncertainty Principle (or, more specifically, claiming it is merely an epistemic limitation on human beings but not an indicator of how the world "really is"), then it could be included here. But that isn't what Lewis is noted for, either: does the Lewis article have a section on "how quantum mechanics differs from Lewis's ideas on the world"? No. The exact interpretation of Heisenberg's Uncertainty Principle is also a far more subtle and intricate matter than simply dismissing it as "a limit on how accurately humans can know the world", because a statement like that carries a host of implications for how the rest QM is viewed, but which are not properly worked through in the article as it stands, so the matter is left dangling, a little like your post above.

Also, the "indeterministic nature of the universe" is not "the point" of QM. "The point" of QM is that it is the best theory of motion that we humans have at the moment.

Here's an idea. In the "philosophy" subsection of the article, whether the question of determinism is discussed, why not include a sentence like "Some Christian writers, such as C.S. Lewis (reference), share the view that the QM is incomplete, because notions of indeterminism do not agree with their religious beliefs"? That way, the point is covered, in such a way as Lewis is cited as one key example, but it doesn't open the gates to infinitely many more people making the same point and bogging down the article in unnecessary ancillary discussion. Byrgenwulf 14:48, 19 September 2006 (UTC)

I like that suggestion. I still think that Einstein's should be similarly included as well. But this is a good start. McKay 06:14, 21 September 2006 (UTC)

OK, let me try to clear some things up here. Lewis' objection is not a "religious objection": it is a philosophical objection, but the philosophical position which Lewis adopted stems from his religious outlook. Einstein's God/dice quote is not a religious objection either, because the philosophy of Spinoza (or more generally a belief in pantheism and cosmic order) is not a religion.

Also, Einstein was not "objecting" to quantum mechanics. QM works: we know this because we are writing an Internet-based encyclopaedia, which uses technology based on quantum mechanical principles (like electron tunneling). I cannot speak for Lewis in this regard, but from what I know of him he was not a complete fool, so I don't think he was actually "objecting" to QM either.

The real question here is whether QM is a complete theory or not. Einstein (and apparently Lewis) felt that it was not; although Einstein relaxed his objections later in his life. It is also a question of the philosophical interpretation of the uncertainty principle. These are not religious in nature, and nor are they real "objections" to quantum mechanics: they are objections to particular understandings of what quantum mechanics is.

Religious beliefs may have inspired Lewis' comment, and so did Einstein's personal philosophy inspire his, but it would be grossly inaccurate to class comments of these sorts as "religious objections to quantum mechanics".

I trust my recent revision will be acceptable. Byrgenwulf 17:04, 21 September 2006 (UTC)

The footnote [2] right after the comment about lewis leads to a hawking page that doesn't reference lewis. The citation should be to one of lewis's books, probably Miracles chapter 3. This needs to be fixed.

Wow. The paragraph in Lewis' book, Miracles, that sparked this discussion of Lewis has been terribly misunderstood.

First, there is the idea that his philosophical objection to QM stems from his religious beliefs. That is ridiculous. Simply notice that the pages preceding this paragraph of discussion were dedicated to constructing an argument against naturalism (material monism) based on QM. Lewis had just finished drawing philosophical implications of QM that supported his religious beliefs. That would all be very pointless if Lewis felt his religious beliefs negated the possibility of QM.

This brings us very nicely to the second misunderstanding, which is that Lewis is even definitively objecting to QM. He's not even so much objecting to QM as he is expressing his reservations over putting much stock in his argument from QM. Let's look at the paragraph.

There are actually two "objections." This first of these objections is the one cited previously, that the motion of particles is not random and lawless but merely incalculable. Read more carefully. At best all he is really saying here is that his philosophical sensibilities, so to speak, lend him to wonder if this so-called objection is actually what experts really mean by their theories. (Note his humility). My best guess as to what his philosophical ground for this reservation actually is is that QM possibly undermine the law of causation's implication that an effect cannot exceed its cause, that order can't spontaneously arise from chaos. However, this is purely speculative on my part. Hey, I like exploring possibilities. Sue me.

The second objection made is not even itself philosophical but practical. We've seen theory topple theory, only itself to be soon toppled. The fickleness of science seemed to Lewis good reason to not put all of his eggs in the quantum mechanical basket. This apprehension is one that fades in time as QM prevail.

Thus, it is obvious that Lewis did not propose any substantive objection to QM. He is simply disowning his previous argument, as he said he would at the outset of his discussion of QM (I'm aware that Lewis presents his previous argument in a way that suggests it is not his, but he doesn't cite anyone else). However, in Lewis another issue is raised that I'm interested in. Aside from philosophy waged against QM, what about philosophy that follows from it. One criticism of Lewis is that he was an English professor offering his opinion of physics. However, he offers his understanding of QM and then draws out his philosophy accordingly. Such is the work of philosophers. Physicists would be very helpful if they would temper us non-experts' understanding of these physics, rather than trying isolate each discipline from one another.

I encourage you to read Lewis' argument against naturalism from QM, if for no other reason than because it's fairly intriguing. Essentially, it goes as such:

(1)Naturalism claims that nature is a systematic totality and every event within her "interlocks" with everything else, including the movements of particles. There is nothing beyond her--no doors to be opened.

(2)Apparently these particles don't move in accordance with the general laws of nature, but rather move randomly and indeterminately. The determinate laws of motion we observe are actually normative renderings of an underlying sea of randomness.

(3)This indeterminate realm cannot be integrated into the naturalist's understanding of nature. QM are antithetical to the naturalist understanding of nature as systematic. The random motion of particles is not itself natural, but rather sub-natural, admitting something other than that which is natural.

(4)Naturalism collapses if all of nature's events arise from what is subnatural. The possibility of a supernatural is then unscathed by such a crippled philosophy.

So now I ask what someone well-studied in QM would have to say about this line of thought, even though I've completely digressed from the original topic. Progress can't be stifled by topics, you know. Okay, that's just an attempt at justifying my bringing up of what I'm interested in ...

Stephen Howard 06:09, 18 October 2006 (UTC)

Altered religious to philosophical per Stephen Howard. --Ancheta Wis 10:17, 14 December 2006 (UTC)

Let me repeat a quote from Steven Weinberg with which, in my experience, at least most field theorist and experimentalists agree.

Physics Today, April 2006, "Weinberg replies", p. 16,

... but the apparatus that we use to measure these variables—and we ourselves—are described by a wave function that evolves deterministically. So there is a missing element in quantum mechanics: a demonstration that the deterministic evolution of the wave function of the apparatus and observer leads to the usual probabilistic rules [Copenhagen interpretation].

QM, as a microscopic theory, is fully tested and is deterministic, in the sense that whenever it is possible to do an unambiguous and purely quantum mechanical calculation of how a something evolves, QM always gives a unique and correct state vector. There are empirical rules, that have not yet been fully justified theoretically, for using classical approximations in quantum experiments. So one can say that it is intuition and classical physics that introduce the probabilities into QM and not the theory in isolation.

It is a matter of choice whether to take the state vector, that we cannot directly observe, as reality or to insist that reality must have a direct correspondence to our intuition and perceptions. It is the nature of physics that its concepts tend to evolve away from intuition and direct experience, so to me the former is the more obvious choice.

Some, such as Roger Penrose, and many Wikipedia editors still believe that wave function collapse is a fundamental process that goes on in nature. My view is that this is a sort of "quantum Lamarckism" that accepts the results of QM without really accepting its content. David R. Ingham 21:58, 19 October 2006 (UTC)

It seem that what he was objecting to was QM with the Copenhagen Interpretation, as that was all that was available? In that case, he won his point with the EPR paper, if my vague understanding of the Copenhagen Interpretation is right. David R. Ingham 15:30, 22 October 2006 (UTC)

Roger Penrose in The Road to Reality points out that the term "second quantized" is confusing. That makes " first quantized" too misunderstood to be in the first paragraph. David R. Ingham 05:35, 30 September 2006 (UTC)

The present first paragraph makes me wish I had been more attentive to my watch list. QM is a specific theory (Schrödinger and Heisenberg) that includes whatever are meant by first and second quantization. It has relativistic and non-relativistic forms. The current relativistic form is called quantum field theory. It is not just a replacement for classical mechanics, but for all classical physics, including E & M. The only other quantum physics that I know of is "the old quantum theory", which may still be used as an approximation. David R. Ingham 05:51, 30 September 2006 (UTC)

I think I catch what you're saying, but I'll bet noone understands better what you mean than you, perhaps you should be WP:BOLD, and make the change yourself. If someone doesn't like it, it will get reverted, no harm done. Please, make this article better. McKay 05:58, 30 September 2006 (UTC)

I reverted to the best version I could find in the history, Revision as of 23:25, 16 June 2006 by Keenan Pepper. The "first quantization" idea is not appropriate to mention here. "Second quantization" means the use of raising and lowering operators to account for particles appearing and disappearing. This happens if QFT, but it also happens purely within the non-relativistic many body Schrödinger equation. When one describes a solid or a nucleus with the Schrödinger equation, phonons (particles of sound, called vibrational excitations in nuclear physics) appear as collective behavior. These are created and annihilated the same way that photons are in quantum electrodynamics. Penrose says the term "second quantization" is confusing.

Secondly, I have never heard the term QM used anywhere else to single out only non-relativistic quantum physics, excluding QFT. Schrödinger and Heisenberg knew that the real world is relativistic, but did not yet see how to do relativistic quantum calculations, which is well known to be quite tricky. David R. Ingham 19:48, 30 September 2006 (UTC)

See how 1st, 2nd and 3rd quantisation are defined at quantum theory. --Michael C. Price ^talk 03:31, 1 October 2006 (UTC)

The Dirac and Klein-Gordon equations are relativistic quantum mechanical model, that is not a QFT, but simply the tree-level result of QED. Relativistic QM and QFT are not necessarily the same thing.Jameskeates 11:16, 2 November 2006 (UTC)

Penrose makes a big issue of the fact that a state is described by a function of the coordinates of all the particles and not by a wave function for each particle. This is how the extra variable that describe quantum entanglement come in. David R. Ingham 06:03, 30 September 2006 (UTC)

"probability distributions" is mentioned too early. These issues are related to classical approximations rather than to quantum theory proper. David R. Ingham 06:20, 30 September 2006 (UTC)

I think we need a page like History of quantum mechanics...Thoughts? --HappyCamper 02:00, 7 October 2006 (UTC)

Yes it is a large subject and different people are interested in the theory itself and its history. David R. Ingham 21:09, 19 October 2006 (UTC)

If you have view on this please go to Wikipedia:Articles_for_deletion/Quantum_theory and cast your vote. --Michael C. Price ^talk 06:02, 20 October 2006 (UTC)

That statment was wrong. End of story Kevin aylward 24th Oct 2006

"It should be stressed that the electron itself is not spread out over such cloud regions. It is either in a particular region of space, or it is not."

Is this really correct? How can single photons interfere with themselves, then, as they do in two-slit experiments? Also, it seems to conflict with the following -- from Physics Web:

"Quantum particles such as electrons can be in a superposition of two or more quantum states. This means that an electron can, for instance, be in two places at the same time." (from http://physicsweb.org/articles/news/4/1/7)

I'm just a lowly English grad student, so I don't feel qualified to make the change myself. But then, I've been reading about quantum mechanics since I was in the fourth grade, and I've never heard anyone suggest that, prior to decoherence, there's any such thing as an "electron itself" that "is either in a particular region of space, or... is not." There's only a quantum wave function that dictates the odds of an interaction taking place at a particular location. Am I wrong? Solemnavalanche 05:03, 6 November 2006 (UTC)

I'm writing a Wikipedia article about the classical/quantum mechanical rigid rotor and need the canonical quantization rule. My first idea was to link to this article, but what a terrible article this is! In it I found for instance the following gibberish: If you take one apple, and add another apple, how many apples do you have? In other words, you have two apples. In other other words, the possible states are points in the projectivization of a Hilbert space.

I did not find the quantization rule or the time-dependent Schrödinger equation! It is really a shame that this important topic is covered so poorly. P.wormer 86.81.145.23 17:01, 17 November 2006 (UTC)

• I'm a bit concerned that you may be proposing to violate the original research rule! You need to find a source that is better than another Wikipedia article or a response on a talk page. In any case, the phrase you quote appears to be recent vandalism, and I have removed it. --David Woolley 19:23, 17 November 2006 (UTC)

• The addition of quantization rules or time-dependent Schrodinger equation add nothing to the understanding of the physics. For most people reading these articles, adding a bunch of equations is NOT helpful. As physicists sometimes we forget that most people do not even understand the basics of high school algebra anymore; at least thats what ive learn from teaching in college.

these things can be looked up in any introductory text book on quantum or modern physics; they should have been one of the first things taught. Often times they are listed at the back cover or appendix for easy referal. --Blckavnger 21:10, 17 November 2006 (UTC)

• • I'm a relative Wikipedia newby, but I seem to remember to have read in one of the help files that the whole spectrum of knowledge is to be covered in Wikipedia: from high school kids to postdocs. They all should find something useful. Anyway some of the existing math articles do have a very high level. If Wikipedia should not cover what is in textbooks, then most of the science articles that I've seen so far can be deleted.

  Further I wonder what you mean by 'understanding physics' when you say that knowing/being able to understand the time-dependent Schrodinger Equation does not add anything to this understanding. Do you say the same about Newton's second equation? Or any other mathematical description of physics?

  P.wormer 12:06, 18 November 2006 (UTC)

  • • Actually, for an overview article, like this, there should be nothing in it that is not in a textbook! For a deeper level physics article, there shouldn't be anything that isn't in a reputable physics journal. However, the textbook may be a graduate level one, and there is a need to keep the size of the article down, whilst, at the same time, avoiding using simplifications, that appear in popular science and undergraduate texts, as though they were the whole truth. -- David Woolley 17:53, 19 November 2006 (UTC)

My main concern is someone is using Wikipedia as a reference for scientific research, as was the original discussion; but i see i wasnt making this clear. Maybe in the future this may become acceptable, but i would consider this unacceptable. While talking with other people in my field, they would also find this unacceptaple. Wiki should be for introductory information, especially in such broad topics as quantum mechanics or general relativity. Its in my humble opinion that more technical matter should be reserved for more specific, technical articles like say Quantum Zeno Effect or Binary Black Hole calculations.

Also, i do not believe that writing down a bunch of equations adds to the physics, understanding including F=ma. This opinion comes from my experience in teaching physics. I feel students dont quite understand the meaning behind the formula without elaboration and experience. They usually just echo back the equation to me. They usually cannot answer basic conceptually questions (i.e. if i apply a force thats twice as big as the first time, should the new acceleration by twice the original acceleration?)That doesnt mean we shouldn't write equation downs but ,I believe that for wiki we should keep them only to general and important equations. Specifically in this case, we shouldnt list all versions of the Schroedinger equation. One generic version of Schodinger is fine and i think the form of the time-dependent Schrodinger equation is not as illuminating.

But again this is my opinion; if everyone else thinks that it would be appropriate i would happily withdraw my comments. Sometimes when you get into a research area its hard sometimes to find an outside perspective. --Blckavnger 16:59, 20 November 2006 (UTC)

A wonderful introduction to the basic aspects of quantum mechanics is suddenly interrupted with this:

It should be noted, however, that in quantum mechanics, "random" has come to mean "random for all practical purposes," and not "absolutely random." Those new to quantum mechanics often confuse quantum mechanical theory's inability to predict exactly how nature will behave with the conclusion that nature is actually random.

This is incorrect and misleading. It is factually incorrect because the most widely held interpretation, the so called orthodox interpretation of QM, says the exact opposite of this. Namely, the state of the system is completely described by the quantum state or wave function and that results of measurements are truly random. In fact, the article directly contradicts this assertion at the bottom of the page, and gives a more thorough treatment of the history behind this issue. It may be that some sneaky bastard was trying to subtly advocate non-local hidden variable theories (in which case he needs to advocate it in plain language, in an appropriate place), or simply that someone not familiar with QM and the interpretations tried to sound smart. Either way this note should be removed entirely, or replaced with a reference to the more extensive discussion. Like this:

It should be noted that, according to the most widely held interpretation, the word "random" does not merely indicate ignorance of the prior state of the system, but that results of measurements in quantum mechanics are truly random (see below for details).

Note the intentional omission on the unsubstantiated claim about misconceptions of new students. It is far more likely, in any case, that those new would not assume true randomness. Because either is unprovable, and because its irrelevant, it should be removed.

The point here is not to start a flame war over which interpretation is right, or which interpretation SHOULD be dominant. The point is not to subtly ignore one or the other interpretation like some kind of propaganda war to win adherents. There is room for a logically argument about randomness here, but it is inappropriate to put it in a side note.

Iterating the problems here in power point form,

• The statement is wrong.
• The statement omits the fact that this issue is interpretation dependent.
• The statement over simplifies without hinting that it is doing so.
• In context of competing interpretations, it makes an assertion with no support.

It would truly be an embarrassment to have this error in a featured article. Please fix it.

EvanR 04:19, 13 October 2007 (UTC)

This bit in the article troubles me, but I'm just short of bold enough to remove it myself:

Dr. Walter Ernhart Planck's "proton collapse" experiment cast doubt upon the distribution of protons in an atom and temporarily cast doubt upon the Rutherford model (1924)

Can anyone verify this or remove it if needed? Thanks, Figma 05:48, 12 January 2007 (UTC)

Removed in lieu of a citation. --Ancheta Wis 06:26, 13 January 2007 (UTC)

Thanks for getting rid of that. I have searched for any information on a "Walter Ernhart Planck", and have turned up nothing but outright copies of this Wikipedia article on various paranormal, occult and New Age websites. --Swwright 07:17, 13 January 2007 (UTC)

Someone seems to have edited a paragraph or two with a "snoop dogg" filter. I'm not all that wiki-literate, or I would fix it myself.

Quantum mechanics is a more fundamental theory than Newtonian mechanics and classical electromagnetism, in the sense that it provides accurate and precise descriptions for many phenomena that these "classical" theories simply cannot explain on the atomic and subatomic level.

Surely the thing that makes it more fundemental (rather than simply correct when these other theroies are wrong) is that these other theories can be derived from QM as emergent results. —The preceding unsigned comment was added by Paul Murray (talk • contribs) 03:51, 16 January 2007 (UTC).

- 'more fundamental' is inaccurate: unfortunately in relativity and QM, it is all too common, not only for newspaper articles, but even book-selling Ph.D's from Ivy-league schools to make Relativity and QM more interesting through dramatic, artistic license. For decades I've read fundamentally inaccurate articles on Relativity that make it sound like the build up to World War I. Similar license is taken with QM. The assassination of Arch Duke Ferdinand had nothing to do with either theory.

Statements like 'Relativity overthrew Newton' sound cool, but are woefully inaccurate. On the contrary, both QM and Relativity were developed, and continue to be developed with the correspondence principle; that is, the new theory must fit in with the old. All three have their regions of dominance - Relativity's is near light-speed travel, QM's is the microscopic, and Newtonian is the everyday world that we experience with our naked senses.

The two new theories are actually drenched with Newtonian Mechanics within their equations and their development; [equal and opposite] and [f = ma] survive within the equations of the modern branches and they were motivating factors in developing the equations. Schrodinger's equation, for instance, was developed with the use of the Hamiltonian (Newtonian Mechanics). In the case of Relativity, space and time have been changed, but after consistency of light-speed establishes a new topology, 'local physics' (Newtonian Mechanics) is the guiding factor in it's development.

Every time a result in the modern branches is confirmed, Newtonian physics is confirmed with it in that Newtonian Mechanics is an intrinsic part of of the modern branches. In fact, due to non-linearity, positive results for Relativity empirically establish Newton's equations to a degree that would otherwise be profoundly difficult or impossible with the reality of limited technology.

Accurately, the context in which Newton's equations now exist has undergone extensive and radical changes, but they are more established now than 150 years ago.

At most, 'on equal footing; with respective domains of dominance'. But considering that Newtonian permeates the modern branches, but not visa versa, I would suggest that Newtonian seems to be more fundamental. I'm not sure, however, how important that is: the key point is the importance of a genuine, in-depth understanding of the modern theories. While there are radical changes in parts of the whole, the whole tends to merely be refined, with most of it remaining in tact. 66.245.28.149 17:14, 4 July 2007 (UTC)

Another inequality is the fact that Newton came before both Einstein and Planck; they will always remain indebted to him, and their writings reflect this. Ancheta Wis 01:18, 5 July 2007 (UTC)

Quantum mechanics is a fundamental branch of theoretical physics with wide applications in experimental physics that replaces classical mechanics and classical electromagnetism at the atomic and subatomic levels. It is the underlying mathematical framework of many fields of physics and chemistry, including condensed matter physics, atomic physics, molecular physics, computational chemistry, quantum chemistry, particle physics, and nuclear physics. Along with general relativity, quantum mechanics is one of the pillars of modern physics.

There is a simple algebraic way to derive the values of Planck's quantum of action and of energy from the equations of Newtonian physics. There is a slightly more complicated way to derive the value of the quantum of energy WITHOUT using either h or the frequency. Is anyone out there interested?

glird@bellsouth.net (Dr. G. I. Lebau) User:Gimmetrow 03:53, 16 March 2007 (UTC)

Nobody is interested, because your claim is patently false. It cannot be possible to derive the value of Planck's quantum of action nd engery from the equations of Newtonian physics, since the equations of Newtonian physics alone CANNOT give the correct curve for blackbody radiation. Why, they can't even give the equations for describing simpler electromagnetic phenomena, since these are invariant under the Poincare group, NOT under Galilean transformations. 99.130.73.126 (talk) 00:59, 17 February 2009 (UTC)

There was a long discussion (see archive 7) about whether it was appropriate to include C.S. Lewis' opinion here.

I'm a great fan of Lewis, but I will say that it struck me as odd to see his opinion in this article. At the same time, I think the question he raised--the difference between the epistemic and ontological views of the Heisenberg Uncertainty Principle--is something many of us are puzzled by. (I can remember asking the question in High School, although not with such big words :-).)

So here's a suggestion: rephrase the paragraph to something like this:

At first glance, it is unclear whether the Heisenberg uncertainty principle is actually a matter of ontological indeterminacy, or if it is merely an epistemic limitation. Many writers outside of physics have raised this question, such as C.S. Lewis, who was a professor of English. [Add correct ref here--see below re current ref] This viewpoint is closely related to hidden variables theories of quantum physics. The Bohr-Einstein debates provide a vibrant critique of the Copenhagen Interpretation from an epistemological point of view.

I would do that edit, but I know I'm out of my depth here. And in any case, the "at first glance" would have to be countered by the opposite view (since clearly most physicists seem to believe that the H.P. is an actual indeterminacy, i.e. there are no hidden variables). So something would need to be added to the above paragraph beyond what I've written. It might start out

However, most physicists believe that the Heisenberg uncertainty principle really does reflect a true indeterminacy in the world, not just a limitation on what an observer can learn.

Also, the footnote on the C.S. Lewis quote is wrong, as was also pointed out in archive 7. Unfortunately, I don't know how to fix that. —The preceding unsigned comment was added by Mcswell (talk • contribs) 23:38, 17 January 2007 (UTC). ar? The Lewis reference is still wrong, and I'd love to know what the real sources are, but I agree it doesn't belong here. 70.94.45.243 21:52, 5 February 2007 (UTC)

The C.S. Lewis reference has been wrong for nearly a year. If it's still like this in a week or so, I'm going to yank it and replace it with a direct quote in which Heisenberg says pretty much the same thing. (In his essay "The Physicists Conception of Nature" he says basically that the laws of QM deal not with the particles themselves but with our knoweldge of the particles. a better citation here would be http://www.nd.edu/~hps/documents/Camilleri%20-%20Myth%20of%20Copenhagen-ND.pdf and see page 20.) —Preceding unsigned comment added by 71.198.73.112 (talk) 08:27, 4 December 2007 (UTC)

The claim that "The writer C. S. Lewis viewed quantum mechanics as incomplete, because notions of indeterminism did not agree with his religious beliefs" struck me as mighty suspicious considering that C.S. Lewis was not a determinist. It was determinism that did not agree with his religious beliefs (belief in free will and all that) not indeterminism. And the reference attached to the questionable C.S. Lewis claim does not even mention C.S. Lewis? And it's been like this for how long? Over a year (from what I've read above)? And it's been known to be wrong for how many months? The link http://www.nd.edu/~hps/documents/Camilleri%20-%20Myth%20of%20Copenhagen-ND.pdf does not appear to mention Lewis either. Either we find real source for this C.S. Lewis claim or we yank it out. Wade A. Tisthammer (talk) 19:26, 29 March 2008 (UTC)

For some strange reason, it has not been completely yanked. But it is high time, since Lewis as a philologist and later a theologian, not a physicist or philosopher. His opinions concerning the underlying epistemology and ontology are far inferior to those of a real philosopher, such as Jacques Maritain. Maritain covered this at least obliquely in http://www2.nd.edu/Departments/Maritain/etext/range01.htm#p3 which deserrves mention at least here, if not in the article itself. 99.130.73.126 (talk) 01:23, 17 February 2009 (UTC)

I see changes made by http://en.wikipedia.org/wiki/Special:Contributions/75.66.122.180 on 24 January 2007 are article vandalism. I'm not sure how changes can directly be rolled back, but that should probably be done. 128.111.53.203 00:43, 24 January 2007 (UTC)

Is done. --Van helsing 10:35, 24 January 2007 (UTC)

I noticed some vandalism on this article today, editing in the introduction with 'Quantum mechancis is the study of the relationship of people of the same sex [gay lovers]. - Psuedodynamic —Preceding unsigned comment added by Psuedodynamic (talk • contribs) 16:39, 11 October 2007 (UTC)

I rolled back some vandalism. Dauto (talk) 22:08, 6 January 2009 (UTC)

This comment is addressed to whoever made a recent edit in the article on Quantum Mechanics, in the "Philosophical consequences" section, working from cacheng.unige.ch at L'Université de Genève.

The matter of nonlocality is not quite settled, contrary to the assertion made in the recent edit. I happen to agree with the "nonlocality" view, but there are still highly-reputed physicists who are working to construct a viable hidden-variable theory (cf. Scarani and Gisin, at http://arxiv.org/abs/quant-ph/0110074 -- unless I am totally mis-understanding that paper). The assertion about the proven status of nonlocality, has no citation to back it up, and appears therefore to be personal opinion. Please undo this change.

If you disagree or have more recent knowledge, please reply; I would dearly love to have citations to back up the nonlocality view. Thank you. — SWWright^Talk 00:06, 21 February 2007 (UTC)

Here are a few comments. Honestly I haven't read the whole paper, but here's my understanding of what i've read: firstly, they admit that Bell's theorem excludes any sort of hidden-variable theory; instead, they propose something they call "hidden communication". <quote>the correlations are not entirely pre-established at the source; but they admit the existence of some form of communication between the particles [...]</quote>

Furthermore, Scarani and Gisin also admit that their theory violates special relativity: <quote>Therefore the model must single out the frame in which the hidden communication occurs</quote>.

IMHO, nonlocality is not seriously disputed anymore. - Saibod 11:32, 19 March 2007 (UTC)

The reason to desire locality is that according to special relativity, nothing can travel faster than the speed of light. The EPR paradox is an illustration of how quantum mechanics is incompatible with this idea. The paper you refer to invokes the EPR paradox to motivate a search for alternative theories to quantum mechanics but at the same time is willing to accept 'superluminal' signaling, i.e. faster than light communication. So it still does not have locality in the conventional sense of the word. Since non locality is generally accepted, lets leave it in for now. --V. 02:16, 1 March 2007 (UTC)

No, actually the EPR paradox is *not* incompatible with special relativity. See EPR_Paradox#Locality_in_the_EPR_experiment. The "spooky action at a distance" is instantaneous, but it is impossible to transfer information, thus there is no violation of causality. There are severe misconceptions about this in the section on relativity and QM about this, and especially in the main article on relativity and QM itself. I'm going to try and correct these. - Saibod 11:32, 19 March 2007 (UTC)

?? {{nofootnotes}} {{seeintro}}

I propose that quantum theory, currently a disambiguation page, be merged here. Comments? --Smack (talk) 06:59, 26 February 2007 (UTC)

Anyone care to comment on this? Does any of it make sense, or is it just babble? Jouster 17:45, 27 February 2007 (UTC)

They are babbling, in that neither of them has any idea what he is saying ... but to my semi-educated ear they appear to have talked to a genuine physicist while scripting their lines, because some of it actually makes sense. — SWWright^Talk 06:46, 28 February 2007 (UTC)

I cannot help but feel that

Some fundamental aspects of the theory are still actively studied. A common misconception is that Einstein was a part of it. However this is not true. Physicists begged him to join them in the quest but he did not accept these offerings because he said, "God does not roll dice".

sounds like a middle-school book report. Anyone else agree? Jouster 14:29, 3 March 2007 (UTC)

also inaccurate, Einstein certainly made some notable contributions to the field of QM (like spontaneous emission), he just did not subscribe to the Copenhagen interpretation. this is what the "god does not throw dice" referred to.--V. 19:28, 3 March 2007 (UTC)

Would anyone care to make the appropriate changes, then? I don't have any substantive expertise in the subject. Jouster 20:04, 3 March 2007 (UTC)

Question. Can by some quantum glitch, fluctuation, matter appear from nothing for a long amount of time? Ozone 19:28, 19 March 2007 (UTC)

I'v often thought that such occurances would be possible yet infitismally improbable, If you affix a transdimentional lorentziean wormhole to a cetain point of matter that matter would in theory take place in a shift into another dimention, apparently gone, and after the gravity of the other universe diminishes the gravity of the previous universe would in theory 'pull' the matter in reverse through the same wormhole. If I'm mistaken please email me at dylan.s.94@hotmail.com, I'm only a 13 y/o kid from SD, I want to be proven wrong. P.S. the time shift of a lorentzian worm hole could change the outcome, also entropy would grow if the matter was doubled into the same area. —The preceding unsigned comment was added by 216.254.231.173 (talk) 01:07, August 23, 2007 (UTC)

I'm not sure, but I'd say that it can, with exceedingly low probability. --Smack (talk) 05:28, 20 March 2007 (UTC)

Define "from nothing". Conservation dictates that you can't create matter or energy from, strictly speaking, "nothing", so if that's what you mean, the answer would seem to be, "No." On the other hand, entangled quantum states, blah blah blah, energy at a distant point coalescing into matter somewhere else would seem quite possible, if, again, stupendously-improbable. Jouster  (whisper) 19:30, 20 March 2007 (UTC)

That's how the universe started according to quantum cosmology.1Z 19:52, 20 March 2007 (UTC)

Jouster: We have the uncertainty principle for energy and time. --Smack (talk) 05:21, 21 March 2007 (UTC)

I understand the concept, at least on a basic level, of the uncertainty principle. I do not understand, however, how uncertainty allows for violation of conservation. This is almost certainly my own shortcoming, as I know very little about physics beyond Newtonian. Jouster  (whisper) 08:19, 21 March 2007 (UTC)

This isn't vanilla quantum mechanics. See string theory landscape and cosmic inflation. 1Z 11:49, 21 March 2007 (UTC)

Thank you. Damn, all the good ideas have been taken Peterdjones, 1Z. Ozone 20:55, 21 March 2007 (UTC)

Guys, remember this page is just for discussing the article. For general questions, I recommend choosing someone from this page and posting the question on their user page. Gnixon 01:43, 13 July 2007 (UTC)

I agree with the user (just below) saying that there ought to be a Wikipedia entry about the Coppenhagen Interpretation of QM -- or a section in this entry on the Coppenhagen philosopy of QM.

http://en.wikipedia.org/w/index.php?title=User:Michael_D._Wolok&action=edit

The Coppenhagen interpretation of QM says that nothing EXISTS in the world such as position and mometum -- NOT UNTIL A SENTIENT BEING MAKES A MEASUREMENT. It is not that there is uncertainty, it is that such a thing does not exist. The sentient creature capable of measurement does a GOD-LIKE act of CREATION when s/he/it performs the measurement and COLLAPSES the wavefunction. Prior to the measurement, yes, the wavefunction was "in a superposition of states" but what EXISTED was indeed that wavefunction. The wavefunction (by multiplying itself by its complex conjugate) becomes a probability distribution, but the WAVEFUNCTION ITSELF IS WHAT EXISTS in the world. The wavefunction exists in the world whether or not a mind ever existed, whether or not a measurement is ever made, whether or not the wavefunction ever gets collapsed by a creature wishing to do his/her God-like act of creating a magnitude into the world. So, Einstein, you focused only on what did NOT exist in the world without a mind -- which is what so riled you up about those Coppenhagen folks. But Einstein, you forgot that the Coppenhagen folks were just as vehement about the wavefunction EXISTING independent of any mind (like you greatly prefer) as they were about the magnitudes NOT existing until a mind collapsed the wavefunction. In short, Einstein saw the glass as half empty and then totally forgot that he was focused on only half of the glass. Another summary: as idealist (non-existence without mind) as the Coppenhagen folks were about magnitudes (position, momentum etc), those same Coppenhagen folks were total realists about the wavefunction's ontological status.

A BONUS ON UNDERSTANDING BAYESIAN STATISTICS

To the Sampling Theory statistician, the truth is a pure number. The unknown parameter, if given an audience with God, could be stated as e.g. 3.452. The data, however, are random variables. To the Bayesian, just the opposite is true. The Bayesian says, "waddaya mean my data are random variables? I got 2.17. What's random about that?" To the Bayesian, the parameter, the truth, is a probability density function. There are many implications for statistics, terminology, and computation procedure, but here the philosophy part of the Sampling Theory - Bayesian dichotomy is aided by a one-to-one correspondence of the Bayesian with the Coppenhagen interpretation of QM. When the Bayesian says "I got 2.17! What's random about that?", that is isomorphic to the Coppenhagen QM'er saying "That was the measurement result. I collapsed the wavefunction." When a Bayesian talks about the parameter, the truth being a probability density function, that is isomorphic to the Coppenhagen QM'er saying that "what really exists in the world is the wavefunction". When the Coppenhagen QM'er talks of this wavefunction being in a superposition of states, that is isomorphic to the Bayesian talking about the prior distribution on the parameter. Bayesian statistics may seem weird (in some ways: truth is a probability density function) but in other ways not (which I can't go into). But clearly the Bayesian Statistician's isomorphic ontology with the Coppenhagen QM'er makes Bayesian Statistics in a sense, well, sensible. Sampling Theory statistics is Newtonian; Bayesian Statistics is specifically Coppenhagen QM.199.196.144.11 19:24, 21 March 2007 (UTC)

There is an article on the Copenhagen interpretation, although I don't knwo whether it is philosophical enough for you.1Z 20:04, 21 March 2007 (UTC)

I have once again removed a link to TeraProofs. It has now been added twice [2] [3] by two different IP addresses, but both editors used very similar wording. Is this an attempt to bump the PageRank for the site, perhaps, or is TeraProofs legit? Jouster  (whisper) 07:34, 17 May 2007 (UTC)

Removed another link. Jouster  (whisper) 21:45, 21 May 2007 (UTC)

Jouster: Teraproofs.com actually has quantum mechanics related proofs and solutions that can be hard to find.

The preceding comment was added by Leiding (contribs); I don't really see what this adds to the conversation, and the promotion of TeraProofs seems to be the user's only agenda. I'm ignoring him. Jouster  (whisper) 12:31, 24 May 2007 (UTC)

I have read the wikipedia rules, and will no longer post links to my website. To my knowledge, all links that I have posted have been removed. At the time I posted them I was unaware that this was not kosher.--Leiding 13:56, 24 May 2007 (UTC)

Thank you for your response. I'm happy we could work this out constructively! Welcome to the site, and I'm excited to see what sort of constructive edits someone with your extensive knowledge can add! Jouster  (whisper) 01:12, 25 May 2007 (UTC)

I have looked over the recent edits, and none of them seem to be an improvement, so I am reverting.1Z 11:37, 3 June 2007 (UTC)

The addition

"They are both supported by rigorous and repeated experiment, but in certain ways they appear to lead to contradictory results".

..simply repeats what was said before.

"The modern world of physics is notably founded on two tested and demonstrably sound theories of general relativity and quantum mechanics —theories which appear to contradict one another."~

This sentence was deleted

"Einstein himself is well known for rejecting some of the claims of quantum mechanics."

and replaced with a para about the EPR paradox: but Einstein had objections other than those in the EPR paper.

This sentence is misleading:

"As practical matter, this is not a cause for much concern, as the gravitational force from a single particle is so small to be negligible"

This is misleading, quantum gravity is of great concern in cosmology. 1Z 11:37, 3 June 2007 (UTC)

Reading over my version I realize that actually it wasn't an improvement. My original hope was to make it clearer that there are not really contradictions between relativity and QM, but I didn't put that across very well. I guess it's more of a point about how science works in general (e.g. Newtonian physicists isn't "wrong" as it still is valid in appropriate limits). Your further edits have definitely been in the right direction. --shoyer 10:50, 7 June 2007 (UTC)

Neither relativity nor quantum theory are in conflict with any experiments, however they do conflict in the sense that attempts to unify them (quantum gravity) have so far failed. That's a confusing point, so don't feel bad about trying to clarify it. Gnixon 01:35, 13 July 2007 (UTC)

The Overview states, "For instance, electrons may be considered to be located somewhere within a region of space, but with their exact positions being unknown. Contours of constant probability, often referred to as "clouds" may be drawn around the nucleus of an atom to conceptualize where the electron might be located with the most probability. It should be stressed that the electron itself is not spread out over such cloud regions. It is either in a particular region of space, or it is not. Heisenberg's uncertainty principle quantifies the inability to precisely locate the particle."

It may be a problem of language, but if one cannot state exactly where an electron 'is', how can one assert that "the electron itself is not spread out over such cloud regions?" The blur of an electron's position may be an artefact of what is capable of observation, but equally it may reflect a bluriness in the extent to which the particle is localized at any given time.

I don't think so. Consider the processes internal conversion and electron capture. They occur when an electron (usually a K-shell electron) is actually inside the nucleus. The nucleus can't interact with part of an electron. The probability of interaction varies with the probability of the electron being inside the nucleus - heat up Be-7 (which decays by K-capture) a few thousand degrees and the half-life increases, because you've ionized away the electrons from the K-shell. Philip Trueman 13:58, 17 June 2007 (UTC)

In the most widely held interpretation of quantum mechanics, the electron's location is represented by a wave function, and it does not 'have' a specific position until one carries out the act of measuring its position. At the time of measurement, all interpretations agree that the probability of finding the electron in a given position is equal to the (square of the) wave function's (absolute) value at that position. The sentence in the article (bolded above) puts it quite poorly. Gnixon 01:23, 13 July 2007 (UTC)

Broadly speaking, quantum mechanics incorporates four classes of phenomena that classical physics cannot account for: (i) the quantization (discretization) of certain physical quantities, (ii) wave-particle duality, (iii) the uncertainty principle, and (iv) quantum entanglement. Each of these phenomena will be described in greater detail in subsequent sections.

Does this include: quantum superposition and: Bose-Einstein condensation? &#151; Xiutwel ♫☺♥♪ (talk) 11:24, 21 August 2007 (UTC)

Dear friends and colleagues, could you please have a look at the article quantum tunneling? Since a while, this article is abused for publicity for a paper that is overrated and not really on topic. Thanks, Frau Holle 17:52, 8 September 2007 (UTC)

I just took a look at this article, and got stopped at the very first sentence:

In physics, quantum mechanics is the study of the relationship between energy quanta (radiation) and matter, in particular that between valence shell electrons and photons.

The first clause is fairly worthless as a definition of quantum mechanics, and the second clause is downright silly. It sounds like someone read Feynman's QED and doesn't know the difference between quantum mechanics and quantum electrodynamics. Sheeesh.

If this opening sentence is any indication of the quality of the rest of the article, I think this article needs a LOT of work, preferably by someone who knows something about quantum mechanics.63.24.97.203 (talk) 03:10, 5 February 2008 (UTC)

agree with some of your comments, there is an urgent need for openning out this definition and stablishing the differences from quantum electrodynamics. Missingdata1 (talk) 15:14, 14 May 2008 (UTC)

Planck is minimised in the "History" paragraph to put Einstein in a good light.

— Preceding unsigned comment added by 217.41.51.240 (talk) 13:16, 27 March 2008 (UTC)

I mistakenly hit the enter key instead of the pipe key, what I meant to type was "Changed "Maxwell's laws" to "Maxwell's laws" in order to correctly link to the desired article" 4RM0 (talk) 11:29, 4 July 2008 (UTC)

I changed the edit by User 217.235.189.135 because an interpretation is not an application. Moreover, reference to the Many-worlds interpretation is already made in the section on Philosophical implications, where also the connection with multiverse is laid. I don't mind a reference to the multiverse hypothesis (which is hardly a physical theory), even though, given its origin, it can hardly be an application of quantum mechanics (however, the multiverse hypothesis might be thought to be supported by quantum mechanics).WMdeMuynck (talk) 21:02, 24 August 2008 (UTC)

In a recent edit by User: Mrvanner a cautious claim with respect to the meaning of the Bell inequalities as regards local realistic theories has been replaced by a definitive one. In view of the ongoing discussion in the scientific literature on the question whether contextualism could save local realism I think this edit to be premature. In my view the more cautious version is preferable because it does not make an unjustified statement. Since it is not my intention to defend in Wikipedia views I have defended in the scientific literature I have not undone the edit. I would appreciate if someone who is acquainted with Wikipedia policy could explain this policy as regards the question of majority and minority views in scientific matters.WMdeMuynck (talk) 10:29, 1 September 2008 (UTC)

Could someone please decide what is the appropriate treatment for quantum parallelism. — RHaworth (Talk | contribs) 05:52, 9 February 2009 (UTC)

Recent edits to the introduction have presented a quantum explanation for biological processes as fact. This is new research that has not gained wide acceptance. In any case it does not belong in the introduction, which should summarise the article; the link between biology and quantum mechanics is not discussed in the article, nor are there any citations for editors to check. Midnight Madness (talk) 01:55, 23 February 2009 (UTC)

Seems to me quantum mechanics has so many established routine practical applications that it's ridiculous to include something so speculative as quantum biology as the only example in the introduction. Basically, any time someone's building something with microscopic specs and wants a precise answer to a simple question, the thing to do is download a QM software package and simulate the thing. This is true for designing drugs, fuel cells, many many other things. Hinting at this instead of some nebulous biology would be a big upgrade. And further: why isn't this mentioned anywhere in the article??

Also, just as a matter of tone, quantum mechanics is something so prevalent in popular culture as a "mystery" that I think wikipedia owes it to its readers to be as concrete as possible on the topic whenever possible. (I was directed to this page from Roger Ebert's blog-review of Watchmen, for example.) There's this popular conception that quantum mechanics is something that no one understands, and it seems to me it would really help public understanding of QM if the article could evidence its routine and practical side.--72.93.169.60 (talk) 18:47, 20 March 2009 (UTC)

Some other science articles are starting to produce introductory versions of themselves to make them more accessible to the average encyclopedia reader. You can see what has been done so far at special relativity, general relativity and evolution, all of which now have special introduction articles. These are intermediate between the very simple articles on Simple Wikipedia and the regular encyclopedia articles. They serve a valuable function in producing something that is useful for getting someone up to speed so that they can then tackle the real article. Those who want even simpler explanations can drop down to Simple Wikipedia. I propose that this article as well consider an introductory version. What do you think?--Filll 22:40, 12 December 2006 (UTC)

there already is an introduction to quantum mechanics article. --Blckavnger 22:51, 12 December 2006 (UTC)

Then it needs to be linked in a way that is parallel to the other science articles.--Filll 23:04, 12 December 2006 (UTC)

It used to be that way. --Ancheta Wis 10:10, 14 December 2006 (UTC)

It is good now. There are 7 such articles at the moment.--Filll 15:07, 14 December 2006 (UTC)

• I have added a link to the "Introduction to quantum mechanics" page in the "see also" section. Lowri (talk) 09:57, 17 July 2008 (UTC)

I just want to point out that the link to the simpler version of quantum mechanics, "the introduction to quantum mechanics" is obscured or overwhelmed by the box above it. I totally missed it and would not be aware of it if I had not been reading this discussion. Would it be a good idea to place it a few more lines down out of the "shadow" of the box at the top of the page (so it can be seen)? For myself I understood most of what I read but if I wanted simpler explanations elsewhere it would be good to know that this is available. Ti-30X (talk) 03:24, 6 May 2009 (UTC)

At the risk of sounding picky, I have to point out oneother area where the simple introduction now current has room for improvement. Specifically, the article says:

Classical physics can be derived as a good approximation to quantum physics, typically in circumstances with large numbers of particles. Thus quantum phenomena are particularly relevant in systems whose dimensions are close to the atomic scale, such as molecules, atoms, electrons, protons and other subatomic particles. Exceptions exist for certain systems which exhibit quantum mechanical effects on macroscopic scale; superfluidity is one well-known example.

But this is misleading, since even the existence of crystalline solids, or any other solid based on a crystalling structure (such as metals), is a quantum phenomenon. It had been completely unexplained until the invention of quantum mechanics made modern Solid State theory possible. Until then, it was a challenging paradox, since we have long had a theory that classical central forces cannot form a stable solid. So the wording should be changed to reflect this. 99.130.73.126 (talk) 00:52, 17 February 2009 (UTC)

The assertion is made here (and elsewhere) that Quantum mechanics (QM, or quantum theory) is a branch of physics dealing with the behavior of matter and energy on the minute scale of atoms and subatomic particles. "Macroscopic" is even defined as a term to emphasise the distinction. This serves to reinforce the widely held popular misconception that Quantum Theory is the theory of the small. Would it not be better to rather state that QT was discovered FROM a study of the small, and lead to a radical reappraisal of the nature of ALL physical reality, a reapraisal that is continuing to the present day... The point need to be made early that Quantum theory is a revolution in physics, not a discovery in some domain of physics. Classical physics can then be defined as the prevailing description physical reality prior to the quantum revolution, and that the relationship of classical physics to the quantum viewpoint is still a matter of active research. It is really quite unjustified and unphysical to give a special STATUS to size (length measures). The simple reason that quantum physics BECAME APPARENT at small sizes is that unclassical physical effects may be magnified more at smaller scales of distance. An analogy would be Einstein's theory of relativity (special or general), where relativistic effects may be considerably more apparent at higher energies or unusual conditions such as nuclear physics or cosmology. Likewise to describe macroscopic quantum effects as "exceptions" is to reinforce a false dichotomy. In the case of relativity, it the fundamental constant c that makes relativistic effects more apparent at higher energies. But it would be wrong to give the impression (say) that relativity is safely relegated to corrections for very high energy particles. For example the computers that calculate GPS coordinates from orbiting space craft routinely must make significant relativistic corrections. Similarly it is the size of physical constants that determines how apparent quantum effects will be in the macroscopic world, not the physical size of the world itself, per se. —Preceding unsigned comment added by Kaonyx (talk • contribs) 01:20, 11 May 2009 (UTC)

"Quantum mechanics is essential to understand the behavior of systems at atomic length scales and smaller."

This statement implies quantum mechanics is only an atomic science. Quantum Mechanics applies to any square integrable system with a fixed uncertainty measurement, for example, economics.

Matt Young —Preceding unsigned comment added by 76.205.133.32 (talk) 04:54, 21 May 2009 (UTC)

I added more specific credentials for Hawkins and Whitten. —Preceding unsigned comment added by DanielGlazer (talk • contribs) 05:04, 5 June 2009 (UTC)

The section "Attempts at a unified theory" talks about merging all forces of nature and has quantum gravity as the "main article", so I replaced a reference to 'Grand unified theory' with 'Theory of everything'. Anyway, I think that someone up to the task should merge the current content of said section with "Relativity and quantum mechanics". Furthermore "Attempts at a unified theory" should then talk about the Grand unified theory, having it as the main article.--Tycho (talk) 23:25, 4 July 2009 (UTC)

• Ok, did it myself. It still needs some work though.--Tycho (talk) 00:31, 6 July 2009 (UTC)

For a variety of reasons, there are currently two different introductory articles on Quantum Mechanics on Wikipedia (in addition to the Quantum mechanics article itself):

• Introduction to quantum mechanics, which aims to be accessible to those with a command of high school algebra, but which has been criticised for going into too much technical detail and mathematics for an introductory article.
• Basic concepts of quantum mechanics, a more descriptive article with less mathematical detail, but which has been criticised for going too much into the history and a lack of mathematical detail.

Arguably this is at least one too many introductory articles, and various ways of dealing with this issue (by merging, moving content, deleting, etc.) have been suggested without ever coming to a consensus view. Possibly the problem is that we haven't yet answered the more fundamental question: what level(s) of readership should the introductory article(s) be targeted at?

This discussion has been raised in order to generate a consensus view on this issue, which can then inform discussion of what to do with the articles. In order to avoid having the same discussion taking place on three different talk pages, please direct all comments to Talk:Basic concepts of quantum_mechanics#Intended readership for introductory QM articles - discussion. Djr32 (talk) 11:20, 25 October 2009 (UTC)

Note that line 8 under "Quantum mechanics and classical physics" says: "… have already been mentioned above in the remarks on the Einstein-Podolsky-Rosen paradox."

This is actually the first mention of this paradox in the article, so the original allusion should be edited back in.

196.21.89.242 (talk) 10:25, 3 November 2009 (UTC) John Watterson

John, you can be bold and contribute to the article as well. --Ancheta Wis (talk) 13:13, 3 November 2009 (UTC)

Like the position operator, impulse operator, Hamiltonian, spin etcetera. 88.159.72.240 (talk) 12:59, 19 November 2009 (UTC)

By accident I took a look at this article and I'm a bit upset about the referencing used. The main problems are:

• Links to just any website found. This may be a GeoCities sitem or "Ellies Crystal Metaphysical and Science Website".
• Anonymous essays and forum postings (e.g. on reddit)
• Literatur reference not given by author, title, ISBN, and page but as uncommented deep links into Google Books.

This all makes the referencing look like a bad joke. Giving no inline references and just stating which books have been used would be more sincere.

--Pjacobi (talk) 15:39, 20 November 2009 (UTC)

This was rather disgusting indeed, so I spent 10 minutes on it.

I did not check the sources however. I Hope I didn't make any mistakes. DVdm (talk) 14:33, 21 November 2009 (UTC)

Is there anyone who has the time and interest to read an obscure old physics journal article to help explain Schrödinger's cat, or knows secondary sources to refer to?

The Wikipedia article reads or has recently read totally differently from the way I read Schrödinger's article in which the cat example was used. The article says that the example was made in jest, while I read it literally. David R. Ingham (talk) 06:26, 6 December 2009 (UTC)

This section is grotesquely long, could somebody more familiar with the subject cut it down a bit? Zazaban (talk) 20:35, 24 December 2009 (UTC)

As scientists generally regard the term "mechanics" as a deprecated term and prefer to use "physics" instead (correct me if I'm wrong, this is the view held at Stanford), I think we should consider changing the name of the article accordingly. GarconDansLeNoir 16:19, 1 June 2007 (UTC)

IMHO mechanics is that part of physics that deals with point particles, in contrast to field theory which deals with fields. Also, doesn't "quantum mechanics" more refer to the theoretical foundation of operators and Hilbert space, while "quantum physics" is a very broad term encompassing all physics on atomic scales? Just my personal impression, might as well be biased. - Saibod 09:07, 2 June 2007 (UTC)

As a grad student in chemistry (specializing in quantum), I think this is a non-issue. I have not observed any discussion in the "scientific culture" to which I belong regarding the distinction between "quantum mechanics" and "quantum physics." Of course, as a student I am more concerned with learning it than what it is called. Any more thoughts?--Leiding 15:05, 4 June 2007 (UTC)

The "mechanics" part of "quantum mechanics" is a pain in the ass. QM tends to be used to refer generally to any kind of quantum physics, even if that's not quite accurate. I agree the language is bad, but I think it would be needlessly confusing to Wikipedia's audience if we changed the article's name (presumably by moving this article to "quantum physics" and redirecting "quantum mechanics" there since that's what everyone would look for). Gnixon 01:40, 13 July 2007 (UTC)

I see it as quantum theory which is founded on a description of physical systems by vectors in a Hilbert space which undergo unitary time evolution. It can be viewed as a framework for theories, rather than a theory itself. When quantum theory is applied to systems whose degrees of freedom correspond to what would classically be covered by mechanics (i.e. the position and momentum of an object) the result is quantum mechanics. When quantum theory is applied to dynamics which include fields the result is quantum field theory and so on. Personally, I would like to see quantum theory used when the general theory is meant, whereas quantum mechanics and quantum field theory should refer to the "application" of quantum theory to mechanics and field theory, respectively. I emphasize, however, this is merely my opinion. 69.140.13.88 (talk) 23:11, 6 January 2010 (UTC)Nightvid

User:DVdm The original formulation seems to me to be better because Einstein's ideas differed markedly from Planck's. Where Planck saw quantization as a property of the interaction between atom and electromagnetic field, was Einstein's idea that it is a property of the field alone. Nowadays (rightly or wrongly) Einstein's idea is universally accepted.WMdeMuynck (talk) 10:34, 22 January 2010 (UTC)

Ok, can live with that. DVdm (talk) 11:11, 22 January 2010 (UTC)

Someone recently reinserted the name Abdus Salam in the list of physicists who developed electroweak theory. I was curious how this name was left out, and why the name "Carl Jamieson" was a redlink. As far as I can tell, there is no such (famous) physicist. It appears that this edit was the culprit and was an act of vandalism. It is sad that such an error could persist in an article of this importance for half a year! It appears to have gone undetected for so long because someone else was in the middle of a bunch of edits at the time. CosineKitty (talk) 02:05, 17 February 2010 (UTC)

I've made a newer version of the density function image, i think it should replace the old one.

Yey or ney? —Preceding unsigned comment added by PoorLeno (talk • contribs) 22:54, 16 August 2008 (UTC)

I really like your new graphic and would like to see it in the article. However, what would be very cool is to go through the derivation. The only example on the page is the very simple 1-D point. Going through Hydrogen's derivation would be a great addition. Speedplane (talk) 17:42, 30 June 2009 (UTC)

The derivation is unfortunately a little complicated, possibly too complicated for a wiki article. One of the better explanations is here: [4] StuartH (talk) 04:29, 24 March 2010 (UTC)

Hi. I made some changes to the page yesterday that were rapidly reversed and treated as vandalism. I'm new to wikipedia, so forgive me if I've gone about making the changes in the wrong way. I intend to re-introduce them gradually, subject to getting advice to the contrary through this discussion page. By way of background, I have a PhD in quantum theory, so I know something about the topic.

The first sentence on the page currently reads as follows, with my comments inserted: 'Quantum mechanics (QM) is a set of scientific principles [this is un-necessarily vague- quantum mechanics is a branch of physics] describing the known behavior of energy and matter [QM does not describe all the known behavior, although it does describe most of it. Also, it describes those behaviors more accurately than any other collection of theories, so that ought to be made clear] that predominate [the words 'that predominate' are superfluous] at the atomic and subatomic scales. QM gets its name from the notion of a quantum [that is not a helpful explanation- its like saying that classical mechanics gets its name from the notion of classicism], and that quantum value is the Planck constant [plank's constant is not 'the quantum value', it is just the ratio of energy to frequency of a single photon]. Given the reasons I've stated here I will edit the first sentence accordingly unless someone talks me out of it.

Best wishes —Preceding unsigned comment added by 81.129.41.235 (talk) 20:22, 25 February 2010 (UTC)

Hi! This is an unfortunate welcome to Wikipedia. What happened here was understandable but not very friendly. I did not revert your edit, but the reason was probably because somebody saw an IP address edit (81.129.41.235), coupled with a large section of text changed. We are swamped with people vandalizing Wikipedia articles, and 9 times out of 10, it is someone editing with an IP address. I also notice that at least half of the edits made by IPs are vandalism. The amount of change you made all at once, along with the IP address was (unfairly) a red flag that caused this immediate knee-jerk reaction. Take a look at how your edit looks to people like me who are on the lookout for vandalism: diff. They see lots of stuff changed, the fact that you removed references (the "Tag"). Here are some ideas you can try to avoid the knee-jerk reaction:

1. Make a few uncontroversial and minor edits first.
2. Type in an explanation in the "edit summary" box when you commit the change, so people understand where you're coming from.
3. If you want to make lots of changes, try discussing here what you want to do first and see if there is any objection to it. Wait 3 or 4 days for long-time contributors to have a chance to find it and weigh in.
4. Create a named account for yourself. If you do, put a sentence or two on your new account's user page, so your user name isn't a "redlink". (Yes, this is dumb, but it is a red flag that makes the old-timers instinctively suspect vandalism.)

I'm sorry if this was off-putting, and we could definitely use more people like you here! CosineKitty (talk) 02:42, 26 February 2010 (UTC)

The introductory paragraph includes the statement, "The name derives from the observation that some physical quantities—such as the energy of an electron—can be changed only by set amounts". This is only true of bound electrons in atoms and molecules (and their ions), free electrons are in the continuum and their energy can take any value.

"The name derives from the observation that some physical quantities —such as the energy of an electron bound into an atom or molecule— can be changed only by discrete amounts".

Note also that I changed "set amounts" to "discrete amounts". I find this a better description because of the equivalence of 'quantization' and 'discreteness'.

I would just make the change myself, but this being the introduction of an important article I would welcome any comments before doing so.

--DJIndica (talk) 15:48, 4 May 2010 (UTC)

I think changing "set amounts" into "discrete amounts" is an improvement.WMdeMuynck (talk) 09:45, 5 May 2010 (UTC)

To quote: "The wave–particle duality of energy and matter at the atomic scale provides a unified view of the behavior of particles such as photons and electrons."

I'm a working physicist and a native English speaker and I don't understand what that's supposed to mean. I can guess, and all of my guesses have the statement as being incorrect in one sense or another. We could say "Quantum field theory provides a unified description of the behavior of particles such as photons and electrons". Bkalafut (talk) 10:48, 27 June 2010 (UTC)

Also, why is the somewhat archaic "wavefunction" the preferred term here instead of state vector, which could be wikilinked to Quantum_state?Bkalafut (talk) 10:53, 27 June 2010 (UTC)

As an armchair physicist i.e. the sort who would actually read the wiki page, I have never heard of 'state vector' but I am very familiar with the word and concept of 'wavefunction'. —Preceding unsigned comment added by 88.104.101.94 (talk) 20:43, 15 September 2010 (UTC)

While we have Introduction to quantum mechanics, it seems to me that the article would also benefit from an outline in the style of Category:Outlines. We might also want one in the style of Category:Indexes of articles. I just wanted to see if one already exists or if anyone is going to object to this as overkill. I think it is justified because of the set of prerequisites and specialized topics in QM.--Brazmyth (talk) 11:44, 3 July 2010 (UTC)

Why would anyone think a citation is needed at the end of the philosophical implication section, where it talks about returning a system to a previous state? This is just an obvious statement. Even if it had never been said before it is self evidently true. —Preceding unsigned comment added by 88.104.101.94 (talk) 20:49, 15 September 2010 (UTC)

It is because WP reports it as if it were gossip.--76.202.117.22 (talk) 15:16, 16 September 2010 (UTC)

The product "iPhone" is based on a quantum physics patent owned by Dr. David VanKoevering. This patent has been intentionally omitted from iPhone technology credits. —Preceding unsigned comment added by 76.224.0.78 (talk) 05:40, 6 December 2010 (UTC)

A photo of scientists who made important contribution needs to be add. Here is the file:

File:12 Quantum Mechanic Masters.jpg

—Preceding unsigned comment added by 71.49.192.141 (talk) 07:55, 14 December 2010 (UTC)

Many physicists from stuying quantum physics have supported idealism (that the universe is mental) this includes James Jeans, Arthur Eddington, Werner Heisenberg, Erwin Schrödinger, Louis de Broglie, Max Planck, Wolfgang Pauli, Amit Goswami etc.

A website explains some of it here. Can something be added to the article about quantum physics and idealism?

http://faculty.virginia.edu/consciousness/home.html

86.10.119.131 (talk) 21:31, 18 December 2010 (UTC)

It is probably better to add it to philosophy of physics. --Ancheta Wis (talk) 22:34, 18 December 2010 (UTC)

It seems that idealism is linked to scientists studying quantum mechanics, not to quantum mechanics itself. I second Ancheta, attach it to philosophy of physics. The Cap'n (talk) 17:30, 22 February 2011 (UTC)