Possible explanation for the wave-particle duality ?

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vanhees71

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Of course, theories change with new observations, but that really occurs rarely. In the case of quantum theory nothing has changed since 1925 (or if you wish from 1948 when renormalized perturbative relativistic qft has been established).

According to quantum theory we don't treat electrons as waves but the probability amplitudes (wave functions) as waves. This is THE important difference between classical field theory descriptions and quantum theory. So far there is no classical field-theoretical model describing matter and interactions in a way consistent with the observations. As long as we don't have such a model for electrons that is (at least as) good as quantum theory, I'd vote for using quantum theory!
 
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Of course, theories change with new observations, but that really occurs rarely. In the case of quantum theory nothing has changed since 1925 (or if you wish from 1948 when renormalized perturbative relativistic qft has been established).

According to quantum theory we don't treat electrons as waves but the probability amplitudes (wave functions) as waves. This is THE important difference between classical field theory descriptions and quantum theory. So far there is no classical field-theoretical model describing matter and interactions in a way consistent with the observations. As long as we don't have such a model for electrons that is (at least as) good as quantum theory, I'd vote for using quantum theory!
I was thinking of practical uses such as, in the case of electrons,electron diffraction to determine things such as crystaline structure. Do the workers in these fields consider the probability amplitudes as waves or do they consider the electrons as waves or does it make no difference? I don't know the answer (will try to find out) but if both approaches give equally succesful results I guess they would use the simplest approach.
 
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No, physics is about observations and their description in mathematical theories (or more modestly models) that link observations to general principles that were established by earlier observations.


I was simply pointing out my disbelief that mathematics is somehow the building block of physical reality. To me, it's just a very successful model and considering the history of physics, better, more encompassing ones will replace the current ones in the future.



So what is the observation that establishes the idea that "electrons have frequencies and wavelengths". If you refer to the functioning of the electron microscope, it is understandable by standard modern quantum theory. There is no need for wave-particle duality as in the double-slit experiment!

I was specifically referring to some specific frequencies needed for the operation of MRI scanners(I myself am alive because of existence of such MRI scanners). But all of the TV, radio and satellite communications utilize the electromagnetic frequencies and wavelengths of the electrons that comprise these fields.

When you say that the operation of the electron microscope is understandable by the standard modern quantum theory you do realize that you use the word 'understand' to denote 'shut up and calculate' understanding, and not understand as in 'electrons are waves and have wavelengths, let me draw them for you on the blackboard' type of understanding, right?


Now, if someone were to draw the 'electron wavelengths and frequencies are the classical limiting case' card, I would not know what to say.
 

vanhees71

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Admittedly, the intuitive picture built by quantum theory is pretty abstract, but it's the most successful picture we have about the physical world today. Of course, there's always the possibility that one day we find an even more comprehensive description of Nature, but so far there's nothing in sight. Also MRI is a nice example for the application of quantum theory.
 
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Electrons have frequencies and wavelengths and some critical medical devices rely on this feature to save lives.
That's the whole point of what Vanhees and I have been saying - they don't.

Under some circumstances that behave LIKE they do - that's it - that's all.

This has been known since QM was developed in the 1920's - nearly a century ago - yet for some reason misconceptions still remain.

Thanks
Bill
 
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I was simply pointing out my disbelief that mathematics is somehow the building block of physical reality.
Its beyond me why people get caught up in this semantic dead end. Physical theories are mathematical models. Its relation to reality, whatever reality is, there is no agreement on that by a long shot, is a philosophical issue - not physics.

Euclidean geometry taught at high school is a good example. It's a model of how point and lines behave. But the definition of points and lines it uses is simply a conceptualization. Points are supposed to have no size - lines no breath. Such don't exist - but as conceptualizations they are applicable in many contexts.

We as humans are able to do something truly wonderful - abstract away inessentials - develop theories based on those abstractions - then apply them to actual situations. The ancient Greeks did this with geometry - realizing the key entities were these abstract things points and lines. Modern physics simply carries on the tradition.

Thanks
Bill
 
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Do the workers in these fields consider the probability amplitudes as waves or do they consider the electrons as waves or does it make no difference? I don't know the answer (will try to find out) but if both approaches give equally succesful results I guess they would use the simplest approach.
Both approaches do NOT give equally successful results. That's why QM was invented in the 1920's and De-Broglies matter waves abandoned.

For example try deriving QFT from De-Broglies matter waves, electron spin, all sorts of stuff is NOT explainable within that very limited paradigm. QM is much richer, and when you understand it, conceptually simpler - but it requires greater effort to do that.

As you will find in Ballentine QM is developed from just 2 axioms, rather than de-Broglies ad-hoc hypothesis. Its much more elegant and far reaching.

Thanks
Bill
 
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Both approaches do NOT give equally successful results. That's why QM was invented in the 1920's and De-Broglies matter waves abandoned.

For example try deriving QFT from De-Broglies matter waves, electron spin, all sorts of stuff is NOT explainable within that very limited paradigm. QM is much richer, and when you understand it, conceptually simpler - but it requires greater effort to do that.

As you will find in Ballentine QM is developed from just 2 axioms, rather than de-Broglies ad-hoc hypothesis. Its much more elegant and far reaching.

Thanks
Bill
I'm referring to the practical application of QM. To those non theoreticians who actually use some or more of the results of the theory in their everyday work. Depending on what they do they would need a certain amount of knowledge but how many would need to be familiar with,for example, QFT?
I don't know the answer but as an example consider a lens designer .I'm guessing such a person would use ray and wavefront optics in their work.Simple stuff but still probably useful.
 
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I don't know the answer but as an example consider a lens designer .I'm guessing such a person would use ray and wavefront optics in their work.Simple stuff but still probably useful.
I think the answer to your question would be found in the textbooks they use.

Thanks
Bill
 
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Maui said:
Electrons have frequencies and wavelengths and some critical medical devices rely on this feature to save lives.

That's the whole point of what Vanhees and I have been saying - they don't.

Under some circumstances that behave LIKE they do - that's it - that's all.


That's kind of funny but i think i can mostly agree. And this seems to be the whole point of treating all of reality(physical matter, 3d space, radiation - visible or not, etc. other constituents) as fields and their classical limit as 'the universe'(where the wave-particle duality makes sense and where the 'under some circumstances' requirement' is fulfilled.). Obviously, in the quantum realm there is no wave-particle duality as pretty much all systems are undefined or ill-defined unless some special conditions are met. I do not know why anyone would question that, i know i wouldn't.
 
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Its beyond me why people get caught up in this semantic dead end. Physical theories are mathematical models. Its relation to reality, whatever reality is, there is no agreement on that by a long shot, is a philosophical issue - not physics.
But mathematical models of what, then?
 
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But mathematical models of what, then?
Of abstractions.

Simply go back to Euclidean geometry.

A point is defined as having no size, a line no width. They don't exist - but no one seriously doubts (with caveats from relativity) the results being true. Its used all the time in engineering, surveying, kinematics, all sorts of things without any trouble or questions that its not dealing with reality or whatever. My father used to like laying cement around the house - he would lay out string with pegs and model the strings as lines and pegs as points to do his calculations. The diagrams he drew were not the string and pegs - he abstracted away the inessentials and represented them by the points and lines of Euclidean geometry. That wasn't the reality - it was a conceptual model - but basically - so what?

Now I cant get into the mind of my dad, but he was a very practical minded electrical engineer - but I suspect he would have given you a rather strange look if you said the diagrams he drew wasn't the reality - of course it isn't - but it simply doesn't matter.

Thanks
Bill
 
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stevendaryl

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This is bog standard QM - nothing to do with fields.

Also Vanhees is talking about the formalism of QM. That, for a long time now, independent of any interpretation, has shown the wave-particle duality is well - wrong.
I don't agree that wave-particle duality is wrong. I guess it depends on whether you take the phrase as a precise theory, or as simply a description of quantum behavior. As the latter, it seems pretty appropriate. In a diffraction experiment, both particle-like behavior and wave-like behavior are involved. The diffraction pattern seems very wave-like, with interference and so forth. But the individual dots appearing on a photographic plate are particle-like.
 
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I don't agree that wave-particle duality is wrong. I guess it depends on whether you take the phrase as a precise theory, or as simply a description of quantum behavior. As the latter, it seems pretty appropriate. In a diffraction experiment, both particle-like behavior and wave-like behavior are involved. The diffraction pattern seems very wave-like, with interference and so forth. But the individual dots appearing on a photographic plate are particle-like.


I think he was saying the wave-like behavior does not exist as such but is present in special cases. As in - ghosts do not exist but ghost-like behavior can be observed in some specific cases. Which also begs the layman's question - if it walks like a duck and talks like a duck... (by popular opinion) in qm it seems to not be a duck.
 
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Perhaps wave function collapse can be identified as an unreal conceptual mathmatical response to what is, in fact, an observational collapse from the observing photons present, or reality, into the observing photons past, or unreality, whilst intuitatively understanding, if that is allowed on this forum, that at each ongoing, immeasureable discrete point in time of the collapse, the observing photons temporal position will adjust to be always in the present, or a state of awareness or conciousness, whilst the observed photon will adapt spacial positional change and create time as it moves into the observing photons past as information which can only be realised in the observing photons present.
 

DevilsAvocado

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In our 3 dimensional space what really happens is not that the particle goes through two slit at the same time and it interferes with itself, it passes only one slit and doesn't interfere with anything, its just the possible paths that are limited for it, and it simply does not cover those places that are impossible for it to go through.
Okay, so what happens to your "3D probability grid" when we close one slit? And the particle goes thru the one left open? What "signaling system" will change the state of "the grid"? To produce the non-interference single-slit pattern?
 

DevilsAvocado

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The little youtube movie is astonishingly misleading, although usually Lewin's lectures on YouTube are excellent. Lewin doesn't do a specifically quantum-theoretical experiment here (except in the sense that (nearly) everything "classical" is understood as an approximation to something that can be also described by quantum theory).
Besides Walter Lewin, professor emeritus of MIT, it looks like you are also on collision course with PF Mentor ZapperZ ...

= a very dangerous mission :biggrin:

In quantum theory the single-particle wave function however has a probabilistic meaning and does not describe some kind of smearing of the single particle it is describing.
Okay, so which slit is the single electron going through? :tongue2:

And what's you comment on papers like this:

(my bolding)
http://pra.aps.org/abstract/PRA/v49/i5/p4243_1 said:
Two-photon interference in a standard Mach-Zehnder interferometer

A pair of light quanta with different colors (155.9-nm difference in center wavelength) generated from parametric down-conversion was injected collinearly into one input port of a Mach-Zehnder interferometer. Coincidence interference behavior was studied over a wide range of optical path differences of the interferometer. A measurement of 75% interference visibility with oscillation of the pump frequency for a large optical path difference of the interferometer (43 cm) is the signature of a quantum two-photon entangled state, which reflects both particle and wave nature of the light quanta in one experiment.

DOI: 10.1103/PhysRevA.49.4243
 

DevilsAvocado

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That's why QM was invented in the 1920's and De-Broglies matter waves abandoned.
Stop!! :surprised Someone need to hurry to NYC and tear down this faulty plaque!

800px-Bell_Labs_APS_plaque_west_side_of_Westbeth_door_jeh_edited.jpg


And reclaim the 1937 Nobel Prize in Physics for the Davisson–Germer experiment, and to be absolute safe we should also reclaim the 1997 & 2001 Nobel Prize in Physics, since these are also closely related to the Bose–Einstein condensate, and the cranky non-existing "matter waves"!! :grumpy:


P.S: Contemporary papers in Nature, like this; Coherent control of optical information with matter wave dynamics, should of course also be banned!!


(:smile::biggrin:o:)) <-- Three Wise Guys that matters!
 

DevilsAvocado

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I was specifically referring to some specific frequencies needed for the operation of MRI scanners(I myself am alive because of existence of such MRI scanners).
Wow, thank god you're alive! :thumbs:

This is probably the best argument I've seen on PF in a long time, but as you see, it doesn't bite on the "Beholders of the Truth". Yes, you are alive, but still very wrong! :smile:

Sometimes I get tired... QM works prefect... mathematically... the seventeen (17!) interpretations seems not to do as well...

I like this picture:

400px-Dualite.jpg


The solid cylinder would be the mathematics of QM, the circle the deterministic complex waviness nature, and the rectangle the measurement of quantized probabilities. And people are fighting on what is, or isn't, if it's real, or not – still in the end, everybody get exactly the same results in experiments... and predictions.

Perhaps it's only one "thing"... who knows...
 
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I don't agree that wave-particle duality is wrong.
I don't want to get into a semantic discussion about it.

My view is simply as per the FAQ of this forum:
https://www.physicsforums.com/showthread.php?t=511178
'Secondly, in quantum mechanics, the description and properties of light has only ONE, single, consistent formulation, not two. This formulation (be it via the ordinary Schrodinger equation, or the more complex Quantum Electrodynamics or QED), describes ALL characteristics of light – both the wave-like behavior and the particle-like behavior. Unlike classical physics, quantum mechanics does not need to switch gears to describe the wave-like and particle-like observations. This is all accomplished by one consistent theory.

So there is no duality – at least not within quantum mechanics. We still use the “duality” description of light when we try to describe light to laymen because wave and particle are behavior most people are familiar with. However, it doesn't mean that in physics, or in the working of physicists, such a duality has any significance.'

This is the sense I mean its wrong, I am pretty sure its the sense Vanhees means its wrong; its a concept that is a hindrance once you learn the full quantum machinery - at best its a concept only useful as a motivation in explaining that machinery - and only in some treatments - it's not even mentioned in Ballentine - and I am pretty sure the above reason is why.

Thanks
Bill
 
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Perhaps wave function collapse can be identified as an unreal conceptual mathmatical response to what is, in fact, an observational collapse from the observing photons present, or reality, into the observing photons past, or unreality, whilst intuitatively understanding, if that is allowed on this forum, that at each ongoing, immeasureable discrete point in time of the collapse, the observing photons temporal position will adjust to be always in the present, or a state of awareness or conciousness, whilst the observed photon will adapt spacial positional change and create time as it moves into the observing photons past as information which can only be realised in the observing photons present.
Can't say I follow what you are saying.

But it needs to be pointed out if wavefunction collapse occurs at all is very interpretation dependent.

In many cases, the system being measured is destroyed in which case collapse is a non issue, and when it isn't destroyed you can look upon the observation as a filtering type measurement which is the same as a state preparation procedure - it was in some other state that you may have not even known and you have prepared it in another state - so it changed during that - nothing really to worry about especially if you associate a state with a preparation procedure - which is the modern view.

Thanks
Bill
 
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Besides Walter Lewin, professor emeritus of MIT, it looks like you are also on collision course with PF Mentor ZapperZ
I suspect not.

After all Zapper wrote the FAQ about the wave particle duality that I quoted.

Rest assured if I didn't think Zapper correct, I would have contacted him about his FAQ entry.

But he isn't, and in fact explains it so well I find myself linking to it.

Thanks
Bill
 
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Stop!! :surprised Someone need to hurry to NYC and tear down this faulty plaque!
Why - its not inconsistent with anything I said.

De-Broglie came up with his matter wave theory about 1923. But things moved fast and it was abandoned when Matrix Mechanics, Dirac's Q numbers, and Schrodinger's wave mechanics (which is a generalization of the matter wave concept coming out of a question someone asked Schrodinger - if you have waves you need a wave equation - he found one) were discovered about 1925-1926. Of those Dirac's Q numbers were in fact more general than the other two. But things moved fast, exactly as that plaque said, and Dirac used his Q numbers to develop his transformation theory in about 1927, which is basically QM as we know it today. He showed the 3 formulations were really 3 different aspects of this one theory:
http://cerncourier.com/cws/article/cern/28693
'However, this general formulation allowed him to go much further. With it, he was able to develop his transformation theory, which showed explicitly (see P Dirac 1927 in Further reading) how it was possible to relate a range of different formulations of quantum mechanics, all of them equivalent in their physical consequences, such as Schrödinger's wave equation and Heisenberg's matrix mechanics. This was an astonishing achievement, which led to a deeper understanding of quantum mechanics and its use. This transformation theory was the pinnacle of Dirac's development of quantum mechanics since it unified all proposed versions of quantum mechanics, as well as giving rise to a continuum of other possible versions. In later life Dirac considered this transformation theory to be his own as no other quantum mechanician had found any hint of it. Altogether, Dirac's quantum mechanics takes a simple and beautiful form, with a structure showing elegance and economy of concept, and linked directly with the classical theory. It showed us a new aspect of our universe, both profound and perplexing in its new concepts, and certainly unexpected.'

Within a very short number of years De-Broglies matter waves was consigned to the dustbin of history and simply an interesting historical interlude.

Of course it does not mean it wasn't crucial to QM's development - and the confirmation of wave like aspects in experiments not worthy of a Nobel prize - it was - but in 1927 a much more general theory was developed that did away with this wave-particle duality stuff - exactly as Zapper explained in the FAQ's.

Of course Dirac got a Nobel prize for his magnificent accomplishment as well.

Thanks
Bill
 
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DevilsAvocado

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This is the sense I mean its wrong, I am pretty sure its the sense Vanhees means its wrong; its a concept that is a hindrance once you learn the full quantum machinery - at best its a concept only useful as a motivation in explaining that machinery - and only in some treatments - it's not even mentioned in Ballentine - and I am pretty sure the above reason is why.
Well, actually it is, and maybe this explains some "interpretational disagreements"...

(my bolding)
Quantum Mechanics - A Modern Development - Leslie E. Ballentine said:
The phenomenon of diffraction scattering is not peculiar to electrons, or even to elementary particles. It occurs also for atoms and molecules, and is a universal phenomenon (see Ch. 5 for further discussion). When first discovered, particle diffraction was a source of great puzzlement. Are “particles” really “waves”? In the early experiments, the diffraction patterns were detected holistically by means of a photographic plate, which could not detect individual particles. As a result, the notion grew that particle and wave properties were mutually incompatible, or complementary, in the sense that different measurement apparatuses would be required to observe them. That idea, however, was only an unfortunate generalization from a technological limitation. Today it is possible to detect the arrival of individual electrons, and to see the diffraction pattern emerge as a statistical pattern made up of many small spots (Tonomura et al., 1989).
As I understand Zz, he removes this incompatibility by clearly stating that; "in quantum mechanics, the description and properties of light has only ONE, single, consistent formulation, not two, [... which ...] describes ALL characteristics of light – both the wave-like behavior and the particle-like behavior".

Whilst Ballentine reduces the whole thing to 'statistics', i.e. there is no wave-like behavior in the single particle, but only in the ensemble.

To me, this is a huge difference, since now we are not talking formalism or foundation, but interpretations, which is a completely different enchilada.

(Do I need to say that Ballentine is a prominent advocate of the ensemble interpretation?)

Maybe he is right!?

Well, here we go...

"There are many difficulties with the idea, but the killer blow was struck when individual quantum entities such as photons were observed behaving in experiments in line with the quantum wave function description. The Ensemble interpretation is now only of historical interest." -- John Gribbin

"[...] the notion that probabilistic theories must be about ensembles implicitly assumes that probability is about ignorance. (The 'hidden variables' are whatever it is that we are ignorant of.) But in a non-deterministic world probability has nothing to do with incomplete knowledge, and ought not to require an ensemble of systems for its interpretation" -- David Mermin


Question: What would happen if the world only was made of only "Ballentineists"? Would we have the electron microscope and neutron diffraction then? And would that be a better world??


P.S: If one would like to quote Zz in favor of "smearing" and simultaneous wave-like/particle-like behavior, that shouldn't be a problem either:

[PLAIN said:
https://www.physicsforums.com/showthread.php?t=511179]It[/PLAIN] [Broken] turns out that the picture of electrons moving in circular orbits around the nucleus isn’t correct either(*). The solution here is the implementation of Quantum Mechanics via the Schrödinger Equation and the concept of wavefunction. By applying such formalism, the “electron” occupies a volume of space simultaneously, so that it is “smeared” in a particular geometry around the nucleus.
 
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DevilsAvocado

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I suspect not.
There must be some misunderstanding...

[PLAIN said:
http://physicsandphysicists.blogspot.com/2013/01/misconception-of-heisenberg-uncertainty.html]Misconception[/PLAIN] [Broken] of the Heisenberg Uncertainty Principle - The Video

Back in 2006, I wrote an entry on the misconception of the Heisenberg Uncertainty Principle. I used light going through a single slit to illustrate what the HUP really is.

Now, I've found a video illustrating JUST THAT!

https://www.youtube.com/watch?v=a8FTr2qMutA

I hope that with the video, what I was trying to explain is even clearer than before.

Zz.
 
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