Talk:Quantum mechanics

Density function image

I've made a newer version of the density function image, i think it should replace the old one.

Hydrogen

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)

Nature of "Random" Side Note

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)

Simple Introduction

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)

Walter Ernhart Planck

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.

Fundamental

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)

Question (from comments)

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)

C.S. Lewis, once again

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)

Did C.S. Lewis have religious objections to indeterminism?

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)

Roll back recent vandalism

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)

Nonlocality proven?

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)

For a more accessible and less technical introduction to this topic, see Introduction to quantum mechanics.

"Quantum theory"

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

Conan O'Brien and Jim Carrey Discuss Quantum Mechanics

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)

Awkward phrasing?

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)

Glitch

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)

Need for Section on The Philosophy of the Coppenhagen Interpretation of QM

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)

TeraProofs

I have once again removed a link to TeraProofs. It has now been added twice [1] [2] 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)

"Quantum mechanics" vs. "quantum physics"

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)

Recent Edits

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)

Blur intrinsic?

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)

quantum aspects

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)

please have a look at quantum tunneling

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)

Article Needs Improvement

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)

Minimise

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

Edit Summary Mistake

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)

Many worlds and multiverse

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)

Bell inequality and local realism

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)

Fork

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

Quantum biology in the introduction

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)

False dichotomy

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)

Expanded utility of Quantum Mechanics

"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)

GUT and ToE

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)

Intended readership for introductory QM articles - discussion

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)

Error has crept in

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)

Perhaps good idea to have wikipedia entries for the operators.

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