Talk:Wave–particle duality/Archive 3

Wave-particle duality as MYTH
I added the link to paper Quantum mechanics: Myths and facts in the "External links". In this paper, the Wave-particle duality is taken as Myth. For more information read Quantum mechanics: Myths and facts. Lseixas 04:06, 24 December 2006 (UTC)


 * Yeah it's annoying how much this particular "meme" is propagated. Quantum entities are just that - entities that follow a particular set of rules based on quantized energy, the principle of least action, and various conservation laws.  They aren't waves or particles, however it sometimes does help to think of them as one or the other in certain limiting cases.  IMHO it's not myserious at all - it's just objects that obey math that we don't find intuitive.  I agree very strongly with the school of "shut up and calculate" :) - JustinWick 19:21, 22 January 2007 (UTC)


 * I, too, think of duality as somewhat mythical. Yet I use it all the time, since in optics all the progagation part acts like waves and all the absorption/detection part acts like particles.  So it's a useful myth. Dicklyon 21:47, 22 January 2007 (UTC)

The papers view that everything is waves is problematic in my view. Waves are medium phenomena (by definition, non particulate). However, one particular medium, the aether was laid to rest some while ago with the advent of Special Relativity. If waves exist, just what are they waving in? An alternative, is to simple state that everything is particles, but ones that obey non Newtonian laws of motion, as per L. Ballentine. It is an approach that seems to work. Kevin aylward 13:46, 10 September 2007 (UTC)


 * The idea that QM waves have a medium was laid to rest long ago, but that did not remove the need to treat particles as waves. QM waves propagate like light, at speed c, and relativity means there can be no medium for such waves. Dicklyon 16:57, 10 September 2007 (UTC)

But this is a meaningless statement. What do you actually mean by waves, if such a wave is not a disturbance in a medium? Please explain what such a wave physically is. Otherwise, all there is, is the word “wave”.

Additionally, as per the Ballentine view, physical waves are not needed in any QM explanation at all. That is, all observations can be consistently accounted for by the notion of discrete particles obeying non Newtonian mechanic. This is true for light, and for material particles, so the need to treat particles as waves has been removed by alternative arguments. Now apply Occams razor.

Secondly, on the country, SR explains exactly why that, in principle, an aether could exist, but that it can’t be observed as in a MMX experiment, e.g due to length contraction. The SR view is that, if it cannot be observed, than we can ignore it from our explanations. Einstein himself made this point.

Kevin aylward 09:14, 11 September 2007 (UTC)


 * Kevin, if you weren't such a twat, I'd think we would enjoy knocking back a few cold ones, doing some picking, and arguing over stuff like this ;-) Alfred Centauri 22:49, 11 September 2007 (UTC)

"What do you actually mean by waves, if such a wave is not a disturbance in a medium?"

it means that some solutions to Schrodinger's equation are what would typically be called wave equations, with characteristics like wavelength, frequency, phase and so on. 1Z 09:25, 11 September 2007 (UTC)

But that still doesn’t say really anything. I see it like this. We have two approaches to analysing the physical world, we can have a calculation model, that simple states what results of experiments are. That is, there is no one to one correspondence of what is written on paper to, that which is being modelled. The second, is that we make a statement that what is being modelled is physically real. That is we assume that there is a one to one correspondence with a mathematical symbol and some physical property such that we can claim that the wave is representing a real physical object. That is statements on the math are statements on the physical object. Of course, the math statement itself is not real in the true sense, its just lines on a bit of paper, but is is “as if” it is real. If you argue that a “wave” is just a solution to the SE, with characteristics, this is by definition, saying that the “wave” is a virtual, non physical mathematical construct. Therefor to then argue that the real physical world is all physical waves, doesn’t make sense to me.

The particle only view states that there are real, localised physical objects, made of some substance, that make patterns that are reminiscent of idealised waves when viewed from a distance. To make a statement that the physical universe is truly all *physical* waves, then one must, by assumption, have some physical material, with some properties that can manifest themselves as particles, e.g, sending a hump down a rope. Now this smells of an aether. The idea that we don’t physical move, e.g. substance at point x of wave goes up and down, when the disturbance goes left right, and its just an effect that moves, is an interesting idea, however, I don’t see that SE can be interpreted in that way.

So the question still remains, if the universe is all wave, what physically is the wave? Kevin aylward 15:11, 14 September 2007 (UTC)


 * But that still doesn’t say really anything. Can you really say what space time and matter are? What is the standard here? (And try actually answering the questions..)


 * We have two approaches to analysing the physical world. Actually we have three approaches:


 * empirical instrumental sufficiency, as per your first
 * stuctural/functional modelling isomorpohism (the structure of the theoretical model matches the structure of the "territory", the thing being modelled. "Black box" adequacy).
 * Full realism. Description of what something "really is", beyond merely structural corespondence.


 * It is also often argued that physics never reaches 3, so singling out waves as a special case where we do no know "what is waving" is meaningless. It is also often arged that there is no 3 to be reached, that everyhting is just pur structure; which would mean there is no more to a wave than structural properties like frequency and phase; there is nothing to "wave".


 * So there are your problem areas; you are siding with the more-than-structure people against the nothing-but-structure people wihout presenting an argument, or even being aware of the dispute And you are singling out waves a special and problematical case, when they may well be -- if the structure-only proponents are correct -- just a another example of an ungoroudned, abstract structure like eveything else in physics.


 * The point is that there are formal. "virtual" grounds for syaign something is a wave as opposed to a particle (or any number of other things). The structure that characterises a wave may be entirely abstract (as in a sine wave) or it may be possessed by some real entity. There are perfect, mathematical squares and there are real objects which are more-or-less square. 1Z 16:02, 14 September 2007 (UTC)


 * The particle-only view does not have to state any more than that there the entities that make up the world can modelled by delta functions. Having a precise position is just as much a formal property as having a wavelength. There is no magic to the particle-only view that allows it to answer the question: "what is particling" (at least in any way that the wave-only view can't. "Fundamental matter-energy" works either way).


 * To make a statement that the physical universe is truly all *physical* waves, then one must, by assumption, have some physical material, with some properties that can manifest themselves as particles, e.g, sending a hump down a rope. That is a very unclear statement. We can explain how particles (localised entities) arise formally out of waves -- and vice versa. (This is even possible in classical physics, via wave packets). Neither formal explanation invokes "stuff". That does no mean there is no "stuff". The point is that the situation is symmetrical, the playing field is level. The particle formalism does not supply a noumenal, non-structrual explanation as an added extra.1Z 16:20, 14 September 2007 (UTC)


 * If the universe is all particles, what are particles made of ? What is particling? 1Z 16:21, 14 September 2007 (UTC)


 * I agree, that is a question that remains. It's not clear, however, that it makes sense to expect the answer to be within the domain of stuff that we have previously known as "real".  There is no known way to relate the QM behavior of energy and matter to conventional stuff without some mystical level of "duality" or "randomness" or "non-causality."  That's life, whether you try to make explanations out of waves only or particles only or a more typical dualistic formalism.  But this is not really the place to discuss and debate these ideas.  The talk page is for talking about the article and how to improve it, which needs to be focused on what we can say that is supported by reliable sources. Dicklyon 15:21, 14 September 2007 (UTC)

Wave behavior of large objects
I recently deleted the last paragraph/sentence in the "Wave behavior of large objects" section.

"Whether objects heavier than the Planck mass (about the weight of a large bacterium) have a de Broglie wavelength is theoretically unclear and experimentally unreachable; above the Planck mass a particle's Compton wavelength would be smaller than the Planck length and its own Schwarzchild radius, a scale at which current theories of physics may break down or need to be replaced by more general ones."

1. The paragraph before this one in the section is pretty spectacular. Going to the Planck mass just weakens a potentially good argument about decoherence (which should be linked internally to Wikipedia def of decoherence).

2. I believe the deleted sentence to be logically flawed. (The de Broglie wavelength depends inversely on velocity. Where/why does the Compton wavelength enter the sentence? Slowing to pm/s velocities to measure fm de Broglie wavelengths of complex micron-sized objects seems adequate support for unreachability.

3. If it is meant as stated, it seems to be a bogus method of getting to Compton wavelengths and the Swartzchild radius. Why pick the Planck mass for any other reason?

4. The paragraph weakens an otherwise good article. Those who don't know any better won't get anything out of it. Those who do know, see something amiss.

5. I am concerned about the issue since I was planning on referencing the article in a general physics paper.

AQM2241 —Preceding unsigned comment added by Aqm2241 (talk • contribs)


 * If you're thinking about referencing a wikipedia article as a source, you'd better think again. Wikipedia should never be used as a source, though it can be helpful in finding sources.  If you find things that are not right, don't be surprised, but find a source for the right answer, fix it, and reference the source. Dicklyon 23:19, 16 June 2007 (UTC)

FULLERENE AND SCIENTIFIC RIGOR
I would like to know if the infamous fullerene experiment has been reproduced elswhere in the world by more mainstream scientists. —Preceding unsigned comment added by 70.81.162.66 (talk)

What do you mean by "mainstream scientists"? Are you suggesting that the IQOQI is not a reputable establishment and Anton Zeilinger is a charlatan? That would be funny. So giving you some credit, what are you saying? Frure (talk) 14:59, 7 November 2008 (UTC)

Duality expressed via uncertainty?
The article says:
 * Wave-particle duality is often expressed via the Heisenberg uncertainty principle

but it does not explain this. It doesn't say how this is expressed, only that it is expressed. How are HUPrinciple and WPDuality connected? For example, is it the inherent uncertainty in the momentum that makes the wave-particle is more wave-like, and the inherent uncertainty in the position that makes the wave-particle more particle-like? 145.97.205.193 05:56, 14 June 2007 (UTC)

All objects exhibit duality?
From my understanding, there isn't any actual proof of wave-particle duality on larger objects. The largest objects experimentally proven to exhibit such behavoir are fullerenes. The lead section leads readers to believe that all objects exhibit such behavoir. I propose the article to be reworded state this more clearly. For now, I'm putting the citation needed tag on such sentences. The discussion that spurred this can be found here. --Android Mouse 22:37, 19 June 2007 (UTC)


 * There is no reason to suppose that WP behaviour ceases at just the point where we cease to be able to observe it. The mechanism that might curtail it is wave function collapse, but that is a very ill-understood area. 1Z 00:13, 20 June 2007 (UTC)


 * Exactly. It's an ill-understood idea.  We're talking about quantum phenomena, and it's really not clear when messy compound objects are outside the realm to which QM ideas apply. Dicklyon 02:08, 20 June 2007 (UTC)


 * We can't draw a clear line between "realms. All systems are quantum systems. Classical-ish behaviour emerges from some of them. 1Z 07:49, 20 June 2007 (UTC)


 * Why won't you provide a reference in support of such strong claims when you make them? Dicklyon 17:40, 26 June 2007 (UTC)


 * I personally don't think a citaiton on those statements is really necessary. It can be found in almost any text.  &mdash; Laura Scudder &#9742; 23:05, 19 June 2007 (UTC)
 * So it's mostly accepted that wave-particle duality occurs in all objects, not just quantum? --Android Mouse 23:12, 19 June 2007 (UTC)
 * All the books I found talk about wave-particle phenomena as quantum effects. It makes no sense to talk about wave-particle duality outside the context of QM. Dicklyon 02:08, 20 June 2007 (UTC)


 * Exaclty what is the "context of QM"? 1Z 07:49, 20 June 2007 (UTC)


 * Hard to say. Probably it's the realm where "objects" display quantized behaviors such as wave-particle duality. Dicklyon 14:24, 20 June 2007 (UTC)


 * But (near enough) classical behaviour can be understood as emerging from quantum behaviour. But the quantum behaviour does not disappear. So in fact everything is in the "quantum context" and some things are also in a classical context (or at the classical limit). 1Z 16:51, 24 June 2007 (UTC)


 * So all quantum objects exhibit wave-particle duality, and a quantum object is an object that displays wave-particle duality? It seems then that "quantum object" is not a meaningful term then.  &mdash; Laura Scudder &#9742; 15:54, 21 June 2007 (UTC)


 * Yeah, I'm hoping someone will jump in with a sourced answer to this. I doubt that practioners of QM think that their methods apply to objects such as a "cheeseburger".  But if they do, I'd like to read where they say so. Dicklyon 23:57, 21 June 2007 (UTC)


 * There is a difference between saying, that for practical reasons, you wouldn't apply the Schrodinger equation to a cheeseburger; and saying that a Cheeseburger is some entirely different entity to the quarks and electrons that make it up 1Z 16:51, 24 June 2007 (UTC)


 * I'm not sure I see the difference. I don't deny that a cheeseburger is made up of atomic and subatomic particles.  But it seems to be clearly outside the domain to which QM applies, since it is not even possible to dilineanate what the cheeseburger is in terms of such constituents, and therefore to talk about a  cheeseburger as having wave properties or particle properties is absurd, even though its low-level constituents have such properties. Dicklyon 17:39, 26 June 2007 (UTC)


 * I don't think it's so well accepted, and prefer to see citations from more serious texts; but start with an "almost any" is OK, too. It's applicable to "quantum objects" whatever that means, sort of by definition; but what about big messy compound objects like cheeseburgers?  How can they be said to have a wave behavior?  Keep in mind that statements without citations are always fair game for removal (or revision with citation, more productively). Dicklyon 23:33, 19 June 2007 (UTC)


 * If Schrodinger's equation is applied to large objects in noisy environments, it doesn't predict wave-like behaviour in any classical sense, but it doesn't quire predict a single classical, positional universe, either. 1Z 00:13, 20 June 2007 (UTC)


 * And my point is that it's not clear that Shrodinger's equation is applicable outside the realm of QM. Dicklyon 02:08, 20 June 2007 (UTC)


 * Exactly what is the "context of QM"? S's E does not indicate its own limits. 1Z 07:49, 20 June 2007 (UTC)


 * Precisely the problem. I've yet to hear anyone propose a limit where things suddenly become "quantum objects" as opposed to "normal objects".  There's no point to the last sentence in the lead if we expect size limits to the theory.  &mdash; Laura Scudder &#9742; 15:54, 21 June 2007 (UTC)

I've been looking for a ref for this "all objects" concept, and having trouble finding it. Here are a bunch of books that mention "all objects" and "wave-particle", but as far as I can find, only one book on Data Compression (hardly a reliable source for this topic) makes the claim that all objects exhibit wave-particle duality. If we're going to emphasize all in the lead, we really need a reliable source. I'll take it out unless something can find one. Dicklyon 16:01, 24 June 2007 (UTC)

Here's a likely resolution: there seems to be lots of support for the idea that all particles are subject to wave–particle duality. This makes a lot more sense, since the the math suggests that as the wavelength gets very small the particle nature dominates, so things that can be considered to have a particle-like nature, which is what is suggested by "quantum object", I think, come within the theory. A cheeseburger is not a "particle" in this sense. Dicklyon 16:07, 24 June 2007 (UTC)
 * But a cheeseburger is composed entirely of particles. Why would an individual particle display duality but not a group of those same particles? --Android Mouse 17:01, 24 June 2007 (UTC)
 * Its particles will individually display wave-particle dualiity, because they are particles. I'm not familiar with a wave–group-of-particles duality, which is why I was questioning all this in the first place. But more to the point, it's not about what you or I think, but about what reliable sources say. Dicklyon 17:08, 24 June 2007 (UTC)
 * Don't photons exhibit duality both individually and as a large group? Also, I realize the article has to go off of reliable sources, I'm just asking out of curiosity. --Android Mouse 17:20, 24 June 2007 (UTC)
 * I'm not sure. Yes, I think it's likely, since coherently-behaving photons like in a laser are all in one quantum state, one wave function; but I'm not sure what particle aspect that would exhibit under such conditions.  Another example would be a Bose–Einstein condensate; one state, so probably it can be treated as one particle with one wave-function.  But here we're still talking of what I'd call "quantum objects", not objects of the "ordinary" sort.  The difference may well be just in how cleanly the "object" can itself be defined; a cheeseburger is constant giving off vapors and fumes of all sorts, and can't really be defined as distinct from the environment around it; such "ordinary" objects are not the things that quantum theory applies to.  Dicklyon 19:19, 24 June 2007 (UTC)

Why not say that: "according to quantum mechanics all objects can in principle exhibit wave particle duality" and then go on to qualify why in practice its difficult to detect inteference phenomena when the objects become large (i.e. decoherence etc.)? Count Iblis 20:31, 24 June 2007 (UTC)


 * So far, why not is easy: we don't know a source that claims that. They claim "all particles", not "all objects", as far as I can find. The lead already mentions the "conceptualization" that all objects in our universe exhibit properties...; isn't that plenty? Dicklyon 20:53, 24 June 2007 (UTC)


 * Basic Reference: P.A.M Dirac, the principles of quantum mechanics. Wave-particle duality is a consequence of the formalism of quantum mechanics which is assumed to be universally valid... Count Iblis 14:38, 26 June 2007 (UTC)


 * Over what universe or domain? Does it include cheeseburgers?  It means nothing. Dicklyon 15:08, 26 June 2007 (UTC)


 * That would be the universe. 1Z 15:20, 26 June 2007 (UTC)


 * Last I heard, we don't have ANY theory that can yet consistently describe the physics of the universe. At a large scale, where gravitational forces dominates, QM has little to say about how things are, since it has no gravity in the theory at all.  So I don't see why you say that.  Sources? Dicklyon 17:46, 26 June 2007 (UTC)


 * What do you consider objects to be made of? 1Z 21:10, 24 June 2007 (UTC)


 * Excellent rhetorical reductionist question! Dicklyon 22:20, 24 June 2007 (UTC)


 * To which the answer is? 1Z 23:25, 24 June 2007 (UTC)


 * Some objects are made of beef and cheese; others of sub-atomic particles. Just depends on what you have in mind by the too-general term "object". Dicklyon 03:45, 25 June 2007 (UTC)


 * Beef and cheese are made of..? 1Z 10:25, 25 June 2007 (UTC)

My two cents - There is a well-developed quantum mechanical theory of particles, and a well developed method of extending this theory to multiple-particle systems. A cheeseburger is a multiple-particle system, so in principle, there is a quantum mechanical description of it. This description is not at odds with any observations of the cheeseburger. In other words, quantum mechanics is consistent with the observed behavior of the cheeseburger. That is not to say that quantum mechanics is valid for the cheeseburger, for that we would need an experiment to detect, say, the wave nature of the cheeseburger, which is beyond present day technology. There may be a realm, presently beyond our ability to detect, at which quantum mechanics breaks down. Its hard to say (obviously). PAR 12:46, 25 June 2007 (UTC)


 * I disagree with your assertion that a cheeseburger is a multi-particle system. A fullerene molecule is a multi-particle system.  A cheeseburger is a real-world messy object that has no conceivable connection to the kinds of objects that you can describe in QM, in my opinion.  Your "in principle" is OK for the "conceptualization" line, but to say that a cheeseburger has wave properties or particle properties is a bit beyond what is supportable, isn't it? I'm not saying that QM breaks down, just that there are "objects" to which it applies and other "objects" that are just outside its domain. Dicklyon 17:55, 25 June 2007 (UTC)


 * If a fullerene particle doesn't exist in the real world,where does it exist?
 * Fullerenes certainly do exist in the real world, so I'm not sure what you're asking. Maybe whether they can be considered "particles" in the sense of QM?  Probably so, but I'm not clear on whether those results have been substantiated and duplicated, so there may remain some question even there. Dicklyon 18:50, 25 June 2007 (UTC)


 * I don't see why you think it is important that anything should be a "particle in the sense of QM" sinece QM is readily applicable to ensembles.1Z 20:30, 25 June 2007 (UTC)


 * I understand that QM applies to ensembles, but I would argue that it is absurd to try to treat a cheeseburger as an "ensemble of particles"; it's just not possible to take an ordinary messy object with all kinds of evaporation and stuff going on and force it into the mold of something that QM is applicable to. Dicklyon 17:46, 26 June 2007 (UTC)


 * If QM doesn't break down in some cases, in what sense does it fail to apply?1Z 18:30, 25 June 2007 (UTC)


 * It doesn't "fail"; it's just doesn't apply. Just like it doesn't apply to psychological concepts, linguistic concepts, farts, and other "objects" outside its domain. Dicklyon 18:50, 25 June 2007 (UTC)


 * With enough reduction, it could apply to all of those. It can't be practically applied to those domains because of the vast amount of detail involved in making the reductions. But that is not to say there are separate domains of objects, just different levels of complexity. 1Z 20:30, 25 June 2007 (UTC)


 * Do physicists really believe that? Find us a source. Dicklyon 20:38, 25 June 2007 (UTC)


 * For a start, there must be a page on reductionism. 1Z 22:50, 25 June 2007 (UTC)


 * I have no problem with reductionism, except when it's taken to ridiculous extremes or to the exclusion of more sensible approaches. Dicklyon 22:54, 25 June 2007 (UTC)

Forget the cheeseburger
Do physicists believe that the formalism of quantum mechanics is valid for macroscopic objects? Yes! The few physicists who work on alternative ideas know that if their ideas were proven to be correct then that would be "big news", while if quantum mechanics were shown to be universally valid, then that would not make headlines. The altenative ideas include e.g. the hypothesis by Penrose that gravity causes wavefunction collapse and that this is somehow important for consciousness.

This is why black hole evaporaton via the Hawking process is such a hot item in theoretical physics. If the Hawking radiation is really thermal in the sense that it doesn't contain informaton about the particles that formed the black hole, then the laws of quantum mechanics cannot be exactly valid. According to quantum mechanics the initial state of a collapsing gas cloud and the final state of the radiation and matter, that forms after the black hole (formed by a supernova of the star which was created by the gas cloud) evaporates, are related by a unitary transformation.

So, this article should not give the impression that physicists are neutral about the validity of quantum mechanics in the macroscopic world. If one could show that, in principle, wave particle duality does not hold for cheesburgers (via indirect means or using entirely theoretical arguments) then that would really be earthshattering news. Count Iblis 14:24, 26 June 2007 (UTC)


 * OK, I think that's equally absurd. What sense does it make to say a theory "does not hold" in a domain to which it is not applicable?  It's like proving that QM does not hold for Freudian psychology; makes no sense. Dicklyon 17:49, 26 June 2007 (UTC)


 * Actually, If I remember correctly, David Deutsch, who is a pioneer of the field of quantum computing, deviced a thought experiment involving a conscious entity simulated by a quantum computer. You could set up an interference experiment using that quantum computer where the conscious entity would evolve from one state to another state, but it can take two or more paths causing interference effects...


 * Anyway, if we say "QM does not hold" then that is not a trivial statement like "QM does not apply to Freudian psychology, Law, Theology, Rhetoric, etc.". What we mean is that a clear cut prediction of QM for the outcome of some experiment would be proven wrong if that experiment is actually performed, regardless of whether one can actually perform that experiment in practice. Quantum mechanics, of course, does not tell us whether Paris Hilton should have been sent to jail or not. :)  Count Iblis 19:04, 26 June 2007 (UTC)


 * Exactly, just as QM makes no predictions about cheeseburgers. Dicklyon 20:01, 26 June 2007 (UTC)

Nonsense. If QM is correct, it most certainly applies to cheeseburgers. A 1/4 pounder will have a wavelength of around 4.9e-33 when thrown at Paris Hilton at 1m/s.Kevin aylward 13:32, 10 September 2007 (UTC)


 * QM makes predictions about cheeseburgers in principle, but you wouldn't use it in practice. However, in-practice issues are not enough to found an ontology on. Different species is might have different limitations, but they live in the same universe with the same ontology. 1Z 07:44, 28 June 2007 (UTC)

Particle Only View
I have reinserted the Ballentine view, but corrected from my original. I see no reason for its deletion. It proposes a valid explanation as to the alleged wave-particle duality. Kevin aylward 13:26, 10 September 2007 (UTC)

If it is to stay, it should be balanced by the wave-only view as espoused by, for instance, Carver Mead. 1Z 22:25, 10 September 2007 (UTC)

I agree. The quote by Ballentine is not really very interpretable, and the interpretation that was there was unsourced. We've got a whole article about duality and a section on one guy who doesn't like it. I'm more with Carver Mead's side, since he can explain essentially all of electrodynamics by treating electrons purely as waves (but with charge quantized). I don't really see Ballentine's point, but I do very much see Mead's point. Dicklyon 23:05, 10 September 2007 (UTC)


 * I looked at the interview link (laputan) of Curver Mead. It seems to me that he was just saying the standard stuff, i.e. the wave of the SE, is the particle i.e. the shape of the wave function is the shape of the particle physically, like “ten foot electrons” with hills and valleys. Maybe I have misunderstood his view, but this particular well known idea is refuted by the Ballintine argument/experiment I cited below. If a photon is physically spread out, then it should trigger two detectors at once. Kevin aylward 19:45, 14 September 2007 (UTC)


 * You have misunderstood his view. Get the book.  Dicklyon 20:14, 14 September 2007 (UTC)


 * Then explain what you mean by the word "wave". What is waving? what physically is it?


 * [I assume this is an unsigned comment by Aylward]1Z 09:13, 12 September 2007 (UTC)

(c) Suppose, finally that the object emitted by the source S, is a single particle, and that |psi(x,t)|2 is the probability per unit volume that at time t the particl will be located within some small volume about the point x. since the particle cannot be in two places at once, the triggering of D1 and of D2 at the same time are mutually exclusive events. Thus, the probability of a coincidence will be zero, as shown in (c)

Although this experiment is practical and of considerable importance for the interpretation of quantum mechanics, it does not seem to have ever been performed for electrons or any massive particles. However, an analogues experiment has been done for photons by Clauser (1974 ) and the result is only consistent with interpretation (c)

The result is only consistent with (c) out of the intperpretation Ballentine chose to mention. The result is also consistent with an interpretations he chose not to mention; wave funciton collapse occurs randomnly on detection. Since the WF must become entirely localised at one of the detectors, the probability of coinididence is 0 as required.


 * Sure, and this is not in conflict with the quote. The mathematics of CI also effectively deny that there is a real physical wave. For example, the postulates of QM says the wave function is a mathematical function that gives the *probability* of finding a *particle* in a *volume*. Real, physical waves are not defined at all in the CI. Anyone that believes in a real probability current, has serious understanding issues, imo. Kevin aylward 07:46, 12 September 2007 (UTC)


 * The results of the experiment are consistent with interpretations where there is both a real physical wave and a real process of collapse. Whether you want to consider that a variation of the CI or something completely different is neither here no there; the point is that Ballentine has not exhastively shown that realism about waves is mistaken. He simply has not considered the full range of interpretations.1Z 09:13, 12 September 2007 (UTC)

Ballentine, of course, addresses other views in detail. In fact, very few text books address the interpretation of QM at all. However, it us a bit much to type out all the relevant quotes from his book that support the arguments here. I would suggest that you buy a copy. Its a great book. In fact, without the book, its hard to understand the full argument as to why callapse of the wave function is redundant. A key idea is occams razor. Like, remove any unnecessary assumptions, esspecially ones that can't be measured.

Secondly, until someone explains just what they mean by a “physical wave”, wave is just a meaningless word. For example, we know that water waves and their properties (refraction, diffraction etc), are not really due to water being a continuous substance with peaks and valleys, because it isn’t. Its made up of particulate molecules, and it is the interactions between molecules that, presumably at an approximate classical level of explanation, explains such apparent continuous wave phenomena. So for me, I don’t see true waves existing in the classical universe, so why should they exist in the quantum universe? Kevin aylward 10:43, 12 September 2007 (UTC)


 * If Ballentine addresses other views, you as an editor need to summarise them in order to make a good contribution to the article -- as well as representing a range of other opinion, for balance. I personally suspect that Ballentine's arguments are circular; the thinks collapse is redundant because he doesn't beleive in waves; and his argument against waves is based on disregrading collapse.1Z 15:50, 12 September 2007 (UTC)

Explanations are much simpler in the ensemble view. The issue here, as I have noted, you haven’t read the Ballentine book, so you only have limited idea of what the full Ballentine arguments for that are. By itself, this is reasonable, however, you can’t expect that I can copy all relevant information to eliminate all potential misunderstandings. One should appreciate that Ballentine, although not necessarily correct, has professional examined QM foundations in considerable detail, over 30+ years, so its unlikely that he will have missed any potential major refutations of his approach. Most of the editors here, like myself, are still only amateurs.Kevin aylward 15:13, 12 September 2007 (UTC)


 * If you cannot summarise LB's argument in a way that doesn't have obvious gaps, it would be better to just allude briefly to his conclusions. That would leave more room for other POVs.


 * As far as I am aware, LB's work has not been considered sufficently noteworthy for anyone to attempt to refute it. The Ensemble Interpretation is a dead duck for most physicists. 1Z 15:50, 12 September 2007 (UTC)

I don’t think most physicists even know about the Ballentine view. Most physicists don’t care about interpretations. I am sure that you can appreciate, to my knowledge, that around 90% of the worlds physicists are semiconductor physicists working at semiconductor manufactures, as that is actually were the real jobs and the readies are.

There is no realistic chance that Ballentines ensemble interpretation can be refuted as it is mathematical identical and equivalent in all ways with the CI as far as verifiable results go. The essence is simply that the state vector applies to ensembles, not to individual systems. To varify QM, one needs to do repeated experiments and see if the probabilities agree.

Despite what physicists say, in practise, they essentially use the EI unbeknown to them. The reality is that QM says not a lot about a single experimental run. You see, its all in the postulates, like, the *probability* of an observable being within a given range. To calculate and verify probabilities, you *must* run ensembles of experiments, like standard deviations to wit. There is no way to verify for example, a claim that the state vector refers to an individual system, because the postulates state that the result of any and all measurement must be a single eigen state with single eigen value. Any such claims to the single system are mere, experimentally unsupportable pontifications, imo. Kevin aylward 15:58, 14 September 2007 (UTC)


 * There is such a thing as a "wave equation" in maths even if the physical interpretation is unclear.

Yes, but it is meaningless to say that there exists, real, physical waves, if such physicality can’t even be described in even a basic sense. There is a claim that in QM, there are real physical waves. Well Habeas Corpus. What is this wave? Kevin aylward 15:13, 12 September 2007 (UTC)


 * What are these non-Newtonian dynamics? "What is X really" questions are hard to answer for any number of values

of X. But at least the wave realists have a predictive theory, and empirical resutls that conform to it.1Z 15:50, 12 September 2007 (UTC)


 * "So for me, I don’t see true waves existing in the classical universe, so why should they exist in the quantum universe?". That is a non-sequitur. Obviously, classical and quantum physics are different. Why shouldn't

that be one of the differences?

Oh dear, you miss the point. If classical waves are ultimately the result of particulate behaviour, i.e. true waves do not exist classicly, they are an illusion, then why should real waves magically appear in QM. Since QM can be explained from the particle point of view, why invent a truly new unit, the wave, which never previously existed even classically. Occams razor.


 * I haven't missed the point. You have made the same error again. Waves should non-magically appear in QM because QM is a different theory and that is one of the differences. There is nothing in CP to show that waves are absurd or impossible. There just happens not to be no such thing as a matter wave in CP, although there are energy

waves, as in Maxwell's EM theory. 1Z 15:50, 12 September 2007 (UTC)


 * The particle-only "explanation" of QM is a mere promissory note, since you have no maths to support it. S's E is a wave equation.1Z 15:50, 12 September 2007 (UTC)


 * Pardon again. I have no idea what you are on about here. The support is all in Ballentines text book. Every lock stock and barrel of QM is explained from the ensemble view point. Why don’t you get the book?


 * In any case, you are still not addressing the editorial issues, such as lack of balance. 1Z 11:19, 12 September 2007 (UTC)

This appears to be well accounted for by the other editors “balance” [unsigned comment presumably by KA]

No-one has so far added material to balance your contributions. Editors are suppsoed to balance their own contributions as far as they are able. 1Z 15:50, 12 September 2007 (UTC)

I am not saying the Copenhagen Interpertation is necessarily correct. However, it is clearly the case that it has not been disproved in any widely accepted fashion. 1Z 13:03, 11 September 2007 (UTC)


 * From the extended quote that Kevin added, it's clear that Ballentine's objections have little to do with what is meant by the wave nature of matter. He's saying that a photon is not a wave packet, and that's true, but it's not what duality of this article is about. Dicklyon 15:16, 11 September 2007 (UTC)

Of course it’s relevant to duality. Its fundermental. The wave packet is how one actually calculates all of the wave properties on an object. Without the existence of a wave packet, there would be no wave–particle duality at all, because there would be no wave like properties that would have caused the invention of the wave packet concept. It would all be de-facto particles. dah...Kevin aylward 07:46, 12 September 2007 (UTC)


 * Wave behaviour has an empirical foundation too.1Z 09:03, 12 September 2007 (UTC)

Yes, but invented when people did not know about molecules. After the fact, we now know that classical waves are pure fiction. Classical wave properties are strictly the result of particulate behaviour. There are no continuous disturbances in any real medium. Show me some empirical evidence that a continuous substance exits, as apart from an approximation to a continuous substance.


 * Objections to a theory are relevant if they are notable, but the PO section is not balanced or well-expressed. It should be called "controversy", for one thing 1Z 15:30, 11 September 2007 (UTC)


 * It should only be called controversy if there's a reliable source that says there's an active controversy. This sounds more like an item for interpretations of quantum mechanics. Dicklyon 15:39, 11 September 2007 (UTC)


 * There is an abundance of information on the controversy, see the Bohr-Einstein debate for instance. 1Z 09:03, 12 September 2007 (UTC)


 * I don't see why. interpretations of quantum mechanics is an overview page, it does not explain controversies in detail. And jsut about every aspect of QM is subject to active contorversy 1Z 16:03, 11 September 2007 (UTC)


 * That was just my idea of a better place. If you have a source discussing wave–particle dualiy as a controversy, you can talk about it.  My impression is rather that the "interpretation" of the duality is where the controversy is, or was; see  or . Dicklyon 16:49, 11 September 2007 (UTC)


 * There is controversy about where theory ends and interpretation begins, too. 1Z 18:54, 11 September 2007 (UTC)


 * Great; find a source about that controversy and let's mention it. Dicklyon 22:35, 11 September 2007 (UTC)

Ok, I will leave the Ballinine quote here for now. I think it is an important view on wave particle duality. I will wait for Dicklyons response as to the reasons why he claims that the actual nature of wave packet is irrelevant to wave particle-duality. It certainly has me banging my forehead on the wall.Kevin aylward 07:59, 12 September 2007 (UTC)


 * Ballentine says nothing about the "nature of the wave packet", since his "non-Newtownian dynamics"are unspecified. 1Z 09:03, 12 September 2007 (UTC)

Pardon? The experiment, which he is describing, says that the wave packet is most certainly not a real physical object that, for example, gets split in two. Therefore he is addresing the claimed true nature of the wave packet, that is, it is a virtual construct. The non-Newtonian dynamics are indeed specified, by the shrodinger equation, that is, the probability that a discrete particle will have a position and momentum within some range of values. Its not “his” mechanics, it’s, essentially, standard QM as far as the sums go Kevin aylward 10:23, 12 September 2007 (UTC)


 * His argument against a realistic interpretation of wave function is invalid for the reasons already given.  Solutions to the S.E are wave mechanics, at least as far as the mathematical form goes. (The question of the mathematical form is of course separate to the question of the ontological interpretation). A solution to the S.W.E is not "dynamics" in the sense Ballentine requires; it does not describe forces acting on a point particle causing it to swerve from a Newtonian course. 1Z 11:08, 12 September 2007 (UTC)

Ballentine On Wave packet
Ballentine continues, p.101, by describing a coincidence experiment. This apparatus consists of a source emitting particles described, by a wave packet towards a semitransparent, semireflecting barrier with transmitted and reflected being detected by D1 and D2, and the coincidence detector, C12. He notes:


 * (a) Suppose that the wave packet is the particle. Then since each packet is divided in half, according to the solution (4.4), the two detectors will always be simultaneously triggered by the two portions of the divided wave packet. Thus the records of D1, d2, C12 will be identical, as shown in (a)


 * (b) Suppose that the wave function of (4.4) is a physical field in ordinary space, but one that is not directly observable. However, it leads to observable effects through a stochastic influence on the detectors, the probability of a detector recording a count being proportional to the integral |psi(x,t)|2 over the active volume of the detector. Since the emission probability within an interval dt is p=rdt, and since the wave packet divides equally between the transmitted and reflected components, the probability of D1 recording a count during an interval dt is p/2, as is also the probability for D2. If two the detectors (and hence the two wave packets) are sufficiently apart, the triggering of D1 and of D2 should be independent events. Therefore the probability of a coincidence will be c =p2/4


 * (c) Suppose, finally that the object emitted by the source S, is a single particle, and that |psi(x,t)|2 is the probability per unit volume that at time t the particl will be located within some small volume about the point x. since the particle cannot be in two places at once, the triggering of D1 and of D2 at the same time are mutually exclusive events. Thus, the probability of a coincidence will be zero, as shown in (c)


 * Although this experiment is practical and of considerable importance for the interpretation of quantum mechanics, it does not seem to have ever been performed for electrons or any massive particles. However, an analogues experiment has been done for photons by Clauser (1974 ) and the result is only consistent with interpretation (c)

Thus the idea that the photon is a spread out “wave” in some manner is claimed to be refuted experimentally. The suggestion is that, just as the wave properties of light can be experimentally varified as the statistical nature of photonic laws of motion, the wave properties of material particles are explainable by the statistical nature of non-Newtonian laws of motion. Thus, the claim that there is no wave-particle duality, only particles. Kevin aylward 07:29, 12 September 2007 (UTC)


 * Don't think this belongs. Apart from anything else, it doesn't stand on its own. What is a reader supposed to make of being referred to equation 4.4? Or (a) ... as shown in (a)? William M. Connolley 10:42, 12 September 2007 (UTC)

This section was removed from the main page prior, however, you also removed a valid sub section, the particle only view. I have re-added it. If someone wants to put a wave only view in, fine. The above section forms an alternate to the overwhelming bias on the page that there is a wave-duality issue.

The wave function is pretty obvious in 4.4, but yes it is hard to be complete. Kevin aylward 15:57, 12 September 2007 (UTC)


 * Bias is dispoportionate over-or-under representation. It is perfectly legitimate for a most of a page to be devoted to the majority view on a subject. 1Z 16:02, 12 September 2007 (UTC)

What is a wave? What is a particle?
The article needs clear answers to theses questions. 1Z 23:59, 14 October 2007 (UTC)
 * Those answers should exist at wave and particle. --Michael C. Price talk 00:15, 15 October 2007 (UTC)


 * "Agreeing on a single, all-encompassing definition for the term wave is non-trivial". 1Z 10:47, 15 October 2007 (UTC)
 * I'm not disputing that, just questioning whether we need to repeat the same points *here*, when they should be covered somewhere else that we can link to. --Michael C. Price talk 11:06, 15 October 2007 (UTC)


 * That was a direct quote from wave. So it is not covered elsewhere, in a simple and clear way.1Z 11:11, 15 October 2007 (UTC)
 * That doesn't alter the fact that is where it should be covered, as I originally said. --Michael C. Price talk 11:38, 15 October 2007 (UTC)


 * That doesn't alter the fact that the lay reader is not going to be well informed, because the article plunges itno a discussion of W/P issues without laying out the groudn rules.1Z 14:30, 15 October 2007 (UTC)
 * If it is linked to, then why should the reader be confused? I do read the links on subjects I know little about. --Michael C. Price talk 08:27, 19 October 2007 (UTC)


 * The reader should be confused because there is not a clear explanation in the link, as I have demonstrated by direct quotation from it.1Z 14:29, 20 October 2007 (UTC)


 * If that's the case, then the logical next step would be to edit the wave and particle articles to make them better. --Steve 16:21, 20 October 2007 (UTC)
 * Exactly. --Michael C. Price talk 17:14, 20 October 2007 (UTC)


 * Yes, this article, along with several other linked ones, states that light (or matter) exhibits both wave-like and particle-like properties. The article mentions a couple of wave-like properties: diffraction and interference. It doesn't enumerate particle-like properties. The best it says is that particles exhibit Compton scattering. I looked at that article and it said that Compton scattering wasn't very wave-like, but was like a stream of particles, still with no explanation of why a wave couldn't do that, or what the heck a particle is. Furthermore, the article on subatomic particles simply enumerates them, and since particles supposedly exhibit wave-like properties, does that make a particle-like property a wave-like property? Qseep (talk) 06:00, 30 January 2009 (UTC)


 * The key particle-like property is quantized local interaction. For example, though groups of electrons can behave collectively as a wave, as in superconductors, when you split them up you find that you can't ever get a half of an electron; the charge is quantized.  Similarly with photons; they propagate as waves, but when they interact with matter, by changing the energy of an atom for example, the energy involved is always in discrete units proportional to the frequency; you can't absorb or emit a half photon.  Some would explain that purely in terms of waves as in Carver Mead's Collective Electrodynamics; it's hard to prove that something like Compton scattering can't be explained in terms of waves, but it has generally been interpreted as a particle-like behavior of photons; here particle means a little discrete thing that acts like a bouncing ball, basically. Dicklyon (talk) 06:40, 30 January 2009 (UTC)

All objects?
We've been over this before, but with no good resolution. Has anyone found a reliable source in support of the "all objects" assertion? I think it differs from de Broglie's "all matter". The matter that matters is the matter that's quantizable. The terms "objects" is just too vague, and tends to make popularizations go off on the deep end and talk about the wavelength of things that do not have a wave function per se. So let's stick to what's verifiable in reliable sources, OK? Dicklyon 18:06, 17 October 2007 (UTC)
 * Eh? "all matter" covers everything, including all objects.  What you mean by the "things that do not have a wave function per se" leaves me baffled, since everything can be ascribed a wavefunction.  According to de Broglie everything with a momentum has a wavelength.  Now what "things" don't possess momentum? --Michael C. Price talk 21:10, 17 October 2007 (UTC)


 * As mentioned in the article, a bacterium (for example) will have a de Broglie wavelength smaller than the Planck length, and most physicists agree that "space" isn't well-defined at that scale. I don't think the de Broglie hypothesis has even been formulated (let alone widely accepted by the physics community) in the Planck-length, quantum-gravity, string-theory regime.


 * Perhaps the article's opening could say, "According to traditional formulations of non-relativistic quantum mechanics, all objects...", or something like that.--Steve 21:43, 17 October 2007 (UTC)
 * Not just non-relativistic quantum mechanics: de Broglie is relativistically valid. --Michael C. Price talk 12:40, 19 October 2007 (UTC)
 * I think you didn't read what I said. I'm not talking about special relativity, I'm talking about general relativity and quantum gravity. Wavelengths smaller than the Planck length are quite possibly meaningless, and there's certainly no consensus among physicists in that regard. --Steve 15:49, 19 October 2007 (UTC)
 * I read exactly what you said: "non-relativistic quantum mechanics". You were talking about string theory/ QG elsewhere.--Michael C. Price talk 22:38, 19 October 2007 (UTC)
 * Regardless of what you understood me to have said, the point remains: You said above that "everything...has a [de Broglie] wavelength". According to string theory/QG, objects larger than the Planck mass do not. --Steve 03:38, 20 October 2007 (UTC)
 * No, not "according to string theory/QG". They are merely unfinished quantum theories about which no definitive statements can be made with complete confidence.  --Michael C. Price talk 06:45, 20 October 2007 (UTC)


 * Sure, it would say that; if we had a source. Dicklyon 00:44, 18 October 2007 (UTC)
 * Sources:
 * "Fundamental formulas of Physics" by Donald H Menzel gives the de Broglie wavelengths for electrons, protons and neutrons; protons and neutrons are composite particles.
 * Brian Greene, The Elegant Universe, page 104 "all matter has a wave-like character"
 * There are gizzilions of other sources, by reliable physicists, that ascribe wavelengths to even larger composite objects. --Michael C. Price talk 08:59, 19 October 2007 (UTC)
 * No argument that composite objects can be quantum objects. But I've searched and not been able to find anything about "all objects".  What about the object of my desire?  Too abstract to have a wavelength, I bet.  If Greene has it in his book, I can't find it; check here and maybe you can point it out, or quote it from your copy. Dicklyon 15:23, 19 October 2007 (UTC)
 * I'm happy to quote Greene as I have. "All matter" is sufficient for me.--Michael C. Price talk 15:28, 19 October 2007 (UTC)
 * PS I'd be interested to hear of what you consider a non-quantum object. --Michael C. Price talk 15:30, 19 October 2007 (UTC)
 * Well, the example I used before was a cheeseburger. There's just no way that such a messy object can be in the space things to which QM is applicable.  Even a bacterium is highly questionable, not just because it's wavelength would be so short, but because it is not really quantizable; it has molecules coming and going all the time, so there's no way to pin down what it is the degree of precision needed for QM to be applicable.  "All matter" is better, but it seems to leave out the pure-energy objects such as photons. Dicklyon 17:46, 19 October 2007 (UTC)
 * Again you claim that QM is not applicable to messy objects. Bollocks.  As for photons, I think no one doubts that they exhibit wave properties -- de Broglie extended the wave-particle-duality from photons to all matter.--Michael C. Price talk 22:42, 19 October 2007 (UTC)
 * QM applies to all matter and photons, yes. I don't mean to say that it doesn't apply to the matter in cheeseburgers.  But it's absurd to say that cheeseburgers have particle or wave properties, because QM doesn't apply to the cheeseburger as an object. Dicklyon 23:33, 19 October 2007 (UTC)
 * Still completely wrong. QM applies to everything.  --Michael C. Price talk 06:45, 20 October 2007 (UTC)
 * Sure it does, in a trivial sense. That doesn't mean that "everything" has a wavelength.  Dicklyon 07:04, 20 October 2007 (UTC)
 * Yes it does, since wavefunctions always come with complex phase factors. --Michael C. Price talk 07:06, 20 October 2007 (UTC)
 * But I still doubt that you'll find a physicist who says that a cheesburger has a wave function. I keep waiting for someone to find a source, but I don't see it. Dicklyon 07:08, 20 October 2007 (UTC)
 * If you need a source that specific then you are sadly deficient. You won't find a source that says that woolly mammoths had wavefunctions. Neither will you find a source that says they didn't have wavefunctions.  Work it out. --Michael C. Price talk 17:24, 20 October 2007 (UTC)


 * Obviously, nobody is asking for a source on wooly mammoths or cheeseburgers having wave functions. I'm asking for a source that implies they do by saying "all objects" in a way that does not exclude such messy non-quantizable objects. Dicklyon 17:38, 20 October 2007 (UTC)
 * There are no "non-quantizable objects". And look up quantum cosmology. --Michael C. Price talk 07:32, 21 October 2007 (UTC)
 * OK, good. What's your source for that? Dicklyon 08:06, 21 October 2007 (UTC)


 * Of course, having a (theoretical) WF, and displaying (empirically observable) wave behaviour are two different things. 1Z 14:35, 20 October 2007 (UTC)


 * Of course. But that's not what's at issue here. Dicklyon 17:38, 20 October 2007 (UTC)


 * Isn't it? What are your grounds for denying that a theoretical WF can be applied to macroscopic objects? 1Z 15:28, 21 October 2007 (UTC)


 * I'm not so much denying it as asking for a source for it. The only conditions I know of where QM applies to macroscopic objects in the sense of treating them as waves is when those "objects" are behaving coherently.  For example, the light in a laser, the collective electrons in a quantum Hall device, the bulk of a Bose–Einstein condensate, etc.  I've never heard a physicist claim that "all objects" have wave functions, but these examples do; and so far nobody has found a reference to that effect, so let's don't claim it. Dicklyon 15:45, 21 October 2007 (UTC)


 * There is a difference between "wave function" and "wave", too. Localised particles still have WFs. So the question of coherence is not particularly relevant. 1Z 19:05, 21 October 2007 (UTC)


 * All fundamental equations are quantum equations.--Michael C. Price talk 18:56, 21 October 2007 (UTC)

Redirect
Why, when I seek "Wave-particle duality", am I redirected to http://en.wikipedia.org/wiki/Talk:Wave%E2%80%93particle_duality ? I don't know what "%E2%80%93" represents, but if it's not a hyphen, it's wrong. Just look at the conversation on this talk page. Does anybody use any other character in that position than the hyphen? Of course not. Unfree (talk) 11:22, 24 December 2007 (UTC)


 * People don't usually bother to type the correct character for connecting two equal concepts, which is an en dash. The title is correct. Dicklyon (talk) 16:16, 24 December 2007 (UTC)

History
@XOR&#39;easter Your comments about wave-particle duality are interesting, but their place is not in the History section. TD (talk) 18:12, 3 September 2023 (UTC)


 * They're not my comments; I'm summarizing Feynman and Griffiths. Maybe there's a better place to put that summary, but the end of the "History" section seemed like not a bad place. The purpose of the section is to follow the development of the concept through history, and history eventually arrives in the modern era. XOR&#39;easter (talk) 18:16, 3 September 2023 (UTC)
 * You might be right. I won't object further on this point. TD (talk) 18:18, 3 September 2023 (UTC)

Wrongly deleted section
@Jähmefyysikko. You deleted the section "Wave particle duality, the quantum superposition principle and the Born rule" with this comment: "incoherent section". Where is the incoherence of this section? TD (talk) 20:11, 3 September 2023 (UTC)


 * All around. It has been discussed above. Jähmefyysikko (talk) 20:12, 3 September 2023 (UTC)
 * Where? I answered conclusively to all your objections, or those of others. TD (talk) 20:13, 3 September 2023 (UTC)
 * Let me suggest something. You say you have consensus on your favor, established by the silence of the editors who left this conversation. As a way of establishing how much support you have, let us wait and see whether some other editor wants to restore the section. Jähmefyysikko (talk) 20:17, 3 September 2023 (UTC)
 * I never said that there was a consensus in my favor, only that at present there wasn't any consensus against me (read the end of the section "Consensus?"). TD (talk) 20:22, 3 September 2023 (UTC)
 * So that wikipedians can make their own judgement, it would be better that they can find easily the disputed content. Deleting a content without reason is not correct. I recall you that I answered conclusively to all your objections.TD (talk) 20:27, 3 September 2023 (UTC)
 * To help the other editors make their own judgement, here's the diff.
 * The fact that you refuse to WP:HEAR my, XOR'easter's or Johnjbarton's objections does not mean that you have succesfully answered them. The section was a string of quotations with multiple mathematical notations mixed in and no common thread. Jähmefyysikko (talk) 20:47, 3 September 2023 (UTC)
 * I repeat that my notations are standard ones, like in almost all textbooks, that there is a common thread, and that my quotations are good references relevant to the point of this section. The argument WP:HEAR could be returned against you. TD (talk) 20:53, 3 September 2023 (UTC)
 * What objections have I not answered conclusively? TD (talk) 21:01, 3 September 2023 (UTC)
 * The section was a string of quotations with multiple mathematical notations mixed in and no common thread. Answering is not enough, you would need to address the problem. Jähmefyysikko (talk) 21:12, 3 September 2023 (UTC)
 * I addressed the problem: the common thread is given in the first quotation. I read carefully all the objections. I tried to understand all those points of view different from mine and to give rational answers. Hence WP:HEAR is not a good argument against me. TD (talk) 21:17, 3 September 2023 (UTC)
 * To mix mathematical notations is common use: "We shall often use the Dirac bra-ket notation: instead of $$(\phi_1,\phi_2)$$, we may write $$\langle 1 | 2 \rangle $$." (Steven Weinberg, The quantum theory of fields, p.49) TD (talk) 21:30, 3 September 2023 (UTC)
 * As you have said, you fail to see why others' would find your writing incomprehensible. This is part of WP:hearing. Others object to the unclear logic, you respond by telling it is clear to you. It is not constructive. Jähmefyysikko (talk) 21:25, 3 September 2023 (UTC)
 * I asked why it wasn't clear to them. I want to understand their point of view. It is constructive. TD (talk) 21:29, 3 September 2023 (UTC)
 * You see a "common thread" because you are reading your own writing. Three other editors have been explaining at length why the thread you see is not visible to anyone else. XOR&#39;easter (talk) 21:32, 3 September 2023 (UTC)
 * Three is not everyone. Why is this common thread not clear to you? TD (talk) 21:34, 3 September 2023 (UTC)
 * Three is ... everyone other than you who has taken the time to voice an opinion and wants to participate. I don't know how many different ways I can rephrase what I have already explained. XOR&#39;easter (talk) 21:50, 3 September 2023 (UTC)
 * What did you explain? TD (talk) 21:52, 3 September 2023 (UTC)
 * Is this your explanation?
 * "As I said: Superposability is only one aspect of states being elements in a vector space. Their first postulate is the latter, not the former, which they explicitly regard as a secondary consequence. Saying that Wave-particle duality is a consequence of the quantum superposition principle combined with the other principles of quantum mechanics just amounts to saying that wave-particle duality is a consequence of the principles of quantum mechanics. What does that contribute? Not a lot." (XOR&#39;easter  22:03, 31 August 2023 (UTC)) --TD (talk) 21:59, 3 September 2023 (UTC)
 * Please do not insert others' signatures, it is confusing and breaks the software. (It currently shows I am responding to XOR'easter) Jähmefyysikko (talk) 03:33, 4 September 2023 (UTC)

I am tired of this discussion. If you don't want to answer to my objections to your objections, you shouldn't delete this section. TD (talk) 22:10, 3 September 2023 (UTC)


 * Why is the burden on everyone else to prove to you that the section is not useful? XOR&#39;easter (talk) 22:13, 3 September 2023 (UTC)
 * I give good reasons. If you want to delete this section, give good reasons. What are your good reasons? TD (talk) 22:15, 3 September 2023 (UTC)
 * Can we just take it as read that I don't find any of your responses to any of my multiple criticisms satisfactory? XOR&#39;easter (talk) 23:00, 3 September 2023 (UTC)
 * Then explain. I'd like to understand your point of view. But I don't. This seems to be reciprocal. Discussions are intended to solve this kind of problem. TD (talk) 23:04, 3 September 2023

@Jähmefyysikko You deleted again this section, claiming that consensus is clear. Are you sure that there is a consensus about the arguments against this section? I listed them at the top of the section 'Summary of this discussion'. A few examples: Superposability is only a secondary aspect of states being elements in a vector space. XOR&#39;easter. Electrons are not particles. States interfere, not particles. Johnjbarton. --TD (talk) 04:49, 4 September 2023 (UTC)


 * Again, I remind you that Context is King. Johnjbarton wrote: The quantum equations of motion for electrons are wave equations and thus predict interference in agreement with experiment. Again we must conclude electrons are not particles. What he is saing is that electrons cannot be simple classical particles. Classical particles do not interfere. I think we can agree on such points on the talk page of Wave-particle duality. XOR'easter was also right in pointing out that postulate I contains more information than just the superposition principle. And yes, I am positive about the consensus, that was already discussed above. See for example this diff. Jähmefyysikko (talk) 06:56, 4 September 2023 (UTC)
 * JohnJBarton never gave such a precision about electrons not being classical particles. He repeatedly insisted that a quantum state can never be the state of a particle. If his thesis was that electrons are not classical particles, it wouldn't be an objection against this section, which is about quantum particles.
 * XOR'easter wrote that "superposability is a only one aspect of states being elements of a vector space". He wrote "vector space", not "Hilbert space". TD (talk) 08:02, 4 September 2023 (UTC)
 * You are repeating arguments that have been answered at length. Please stop reinserting the problematic material. Jähmefyysikko (talk) 11:00, 4 September 2023 (UTC)
 * You deleted again this section with the following reason : "Has been discussed on talk page at length." I recall you that the arguments against this section are usually ill-founded. I answered clearly to them. If you don't agree, please quote an argument against the present version of this section which is not ill-founded. TD (talk) 11:02, 4 September 2023 (UTC)
 * Still no common thread, multiple mathematical notations, random concepts thrown around; not useful for anyone. I will let the others continue from here. Jähmefyysikko (talk) 11:22, 4 September 2023 (UTC)
 * I repeat my answers: there is a common thread (the first quotation), multiple mathematical notations are common use (quotation from Weinberg). These are not random concepts, but clarifications on the subject (standard quantum mechanics on wave-particle duality) Not useful for any one is your opinion, how do you know? TD (talk) 11:27, 4 September 2023 (UTC)
 * Are you sure there is a consensus about all these ill-founded arguments? TD (talk) 11:21, 4 September 2023 (UTC)
 * I am sure there is consensus about this section not being useful. How different people approach that chaos of a text is up to them. Jähmefyysikko (talk) 11:24, 4 September 2023 (UTC)
 * How do you know there is a consensus? That this text is a chaos in only your opinion. It's not a conclusive argument. TD (talk) 11:31, 4 September 2023 (UTC)

Which slit section is marginal
I think the "Which slit" experiment is marginal. The standard explanation is that detecting an electron/photon removes coherence between the two parts, so statistically they don't interefere. If it was possible to make a coherent detector, i.e. one which led to a fixed phase shift, then interference is conserved. (Check the matrix elements if you are not sure.) I don't think such detectors exist beyond paper.

Ldm1954 (talk) 06:54, 4 September 2023 (UTC)


 * Do you assert that if we know through which slit the electron passes, we can still observe an interference pattern? TD (talk) 08:28, 4 September 2023 (UTC)
 * With a coherent detector -- which does not exist. As I said, check the matrix elements. Ldm1954 (talk) 08:36, 4 September 2023 (UTC)
 * What matrix? Could you give a reference about this? TD (talk) 08:38, 4 September 2023 (UTC)
 * Any QM text. Add exp(i*phi) to the Hamiltonian for one of the slits. Ldm1954 (talk) 08:51, 4 September 2023 (UTC)
 * All QM textbooks I know are in agreement with the Feynman lectures on this point. You disagree with Feynman. Please give a precise reference. What is a coherent detector? TD (talk) 08:55, 4 September 2023 (UTC)
 * Please do the math, it is a simple QM problem. You have to do the math to understand. Ldm1954 (talk) 08:59, 4 September 2023 (UTC)
 * What is the math you're talking about? Please be precise. I don't know what a coherent detector is. How could I do the math? Do you assert that Feynman, Cohen-Tannoudji and many others are wrong about a simple QM problem? TD (talk) 09:06, 4 September 2023 (UTC)
 * Solve for a Hamiltonian H for slit one, and H+exp(i*phi) for slit 2, where "phi" is constant and represents a fictitious coherent detector that shifts the phase but nothing else. You can solve this analytically in the absence of fields or potentials. This is undergraduate physics. Ldm1954 (talk) 09:08, 4 September 2023 (UTC)
 * No it isn't. A Hamiltonian for a slit is something I don't understand. The Hamiltonian is for the particle. H is an operator. exp(i*phi) is a complex number. How can we add an operator and a complex number? TD (talk) 09:13, 4 September 2023 (UTC)
 * Sorry, but Hamiltonian combine operators, vectors and scalars. For instance the Coulomb potential from a nuclear potential is a scalar. Please do some of the worked examples in QM texts. Ldm1954 (talk) 09:19, 4 September 2023 (UTC)
 * You're wrong. In QM a Hamiltonian is always an operator. The quantum representation of the Coulomb potential in the Schrödinger equation is an operator, not a scalar. What is the Coulomb potential from a nuclear potential. I never heard of such a thing? TD (talk) 09:23, 4 September 2023 (UTC)
 * @Ldm1954 On the contrary many sophisticated experiments have been done specifically verifying that "which slit" measurements always suppress interference. Please read the references. Johnjbarton (talk) 14:22, 4 September 2023 (UTC)
 * What has this to do with duality? IMHO, nothing as this is an issue of incoherence. Ldm1954 (talk) 14:29, 4 September 2023 (UTC)
 * The term is very ambiguous when applied outside historical context. According to Bhatta (2020) wave-particle duality is either considered in contemporary literature either (a) an outdated, irrelevant or incorrect concept, (b) something related to Born rule, (c) something related to complementary principle (probably there are other interpretations also). He points out that apart from these theoretical interpretations, there is also a tendency to label experiments as being about wave-particle duality: [...] wave–particle complementarity is still widely used in the experimental domain. For instance, the demonstration of wave–particle complementarity of photons by Grangier et al. is a well-known recent instance. Also, the demonstration by Scully and Walther has influenced a series of ‘which-path’ experiments that highlight the complex relation between duality and measurement. This vagueness is something the article has to live with. Jähmefyysikko (talk) 14:47, 4 September 2023 (UTC)
 * In which case this information must go into the lead, almost verbatim of what you wrote. It provides both crucial context, and is WP:NPOV to alternative views. I personally think the Pilot wave also goes in to be properly comprehensive. Also complimentarity. We don't have to believe all of them, but we should represent them. Take from my Sandbox? Ldm1954 (talk) 14:59, 4 September 2023 (UTC)
 * @Jähmefyysikko The Bhatta reference has two citations so we should double check any claims. Johnjbarton (talk) 15:11, 4 September 2023 (UTC)
 * Agreed. It seems to be a part of a dissertation, and such theses have varying quality. The journal is also subpar. What gives me some confidence on this author is the fact that a closely connected follow-up paper Bhatta 2021 was recommended for its literature survey in the Oxford Handbook of History of Quantum Interpretations. But Bhatta's thesis is about plurality, so the text tends to emphasize differences rather than unity of the concept. Imo, we may treat this as a possibly useful literature study about the usage of the term, and double-check all the claims from other sources. Such usage can be erroneous and not all authors should be treated with equal weight.
 * I still think we should pin down the various meanings of the term with some high-quality references. A better review could be BR Wheaton (2009) Wave-particle duality: a modern view in Compendium of Quantum Physics. I don't have much time this week to discuss, but I will get back to this next week. Jähmefyysikko (talk) 07:27, 6 September 2023 (UTC)
 * Unfortunately (from my point of view), both references mix up "duality" with "physical interpretations that may explain duality". The references explain to me why every editor wants to add their own interpretations of quantum mechanics to the duality article. We can't really organize the article around how each interpretation "explains" duality because every editor thinks their interpretation is standard. Johnjbarton (talk) 15:35, 6 September 2023 (UTC)
 * @Ldm1954 Duality is the observation of either wave or particle behavior depending on the experiment. Johnjbarton (talk) 15:15, 4 September 2023 (UTC)
 * If that is the definition, the "which slit" section is superfluous as it deals with loss of coherence during detection. If it is the wider definition of Bhatta, then it remains but then others such as the Pilot wave are in as well. The scope must be defined in the lead. If something is beyond the lead, then it does not belong.
 * This is an encyclopedia, not our personal opinions. As such it should represent fairly all views. We need a consensus on what is reasonable to include -- please note my deliberate use of the term reasonable, almost legalese. Ldm1954 (talk) 15:31, 4 September 2023 (UTC)
 * @Ldm1954 indeed, not our opinion. That is why the section includes reliable references. Johnjbarton (talk) 16:29, 4 September 2023 (UTC)