I Why does "wave particle duality" not exist anymore?

[Blue Scallop]

Because photons, for example, are NOT waves and they are NOT particles. They are quantum objects. That's really all there is to it.

For photons with lots of energy and smaller wave length.. does it mean the energy is stored in a smaller region of probability? how is the energy stored?

 

[Mentz114]

For photons with lots of energy and smaller wave length.. does it mean the energy is stored in a smaller region of probability? how is the energy stored?

Photons are not localizable so there is no formal 'region of probability' for the position.

Photon detectors react to the electric field component $\vec{E}$ of the photon. The probability of detection is proportional to $E^2$.
This is a simplification, naturally.

 

[f95toli]

Again: The idea behind wave-particle duality was to explain quantum phenomena (observable facts!) with classical means. The very people who brought up these ideas (Einstein, Bohr, de Broglie, Sommerfeld et al) were very much aware of the fact that it was not a complete and consistent picture. There is no observed fact which in any way is consistent with wave-particle duality, and due to that modern QT has been discovered. To answer your questions:

I believe you are missing the point a bit. The reason why some people (especially experimentalists, including me) still use the "particle-wave duality concept" when describing and thinking about experiments is NOT because we think this somehow describes reality, but because it is often a good "handwavy" way of modelling/explaining results; a good example would say be experiments on electron quantum optics where we frequently think of single electrons as "waves".
To me the the duality is a bit like the Bloch sphere; it is a useful way of thinking of certain situations, but electrons are no more particles/waves than spin 1/2 systems (in my case qubits) are arrows in a sphere.

 

[vanhees71]

That's fine. You have some qualitative intuition how waves behave, and the Schrödinger equation is an equation leading to waves. You shouldn't however call this wave-particle duality anymore. The meaning of the waves is given by Born's rule, i.e., by the probabilistic interpretation.

For the Bloch sphere you don't run into such heuristical quibbles because spin 1/2 is specifically quantum theoretical without any reference to (false or at least inaccurate) classical heuristics!

The main problem in learning QT is not in the mathematical formalism but to develop an intuition for phenomena we have no every-day experience for.

 

[Dadface]

The assumption that the expression "wave particle duality" should not be used any more depends on ones definition of the expression. To me it seems that in the wider world of physics outside of this forum the expression is still widely used including, it seems, by giants in the world of quantum optics such as Zeilinger and Aspect. has anyone told them that they should not be using the expression?
I think one way to get everyone on the same page would be to reach a decision on how "wave particle duality" should be defined and perhaps a good start on that would be to clarify any definitions of "waves" and definitions of "particles".

 

[Blue Scallop]

The assumption that the expression "wave particle duality" should not be used any more depends on ones definition of the expression. To me it seems that in the wider world of physics outside of this forum the expression is still widely used including, it seems, by giants in the world of quantum optics such as Zeilinger and Aspect. has anyone told them that they should not be using the expression?
I think one way to get everyone on the same page would be to reach a decision on how "wave particle duality" should be defined and perhaps a good start on that would be to clarify any definitions of "waves" and definitions of "particles".

According to Demystifier: "The problem with "wave-particle duality" is the duality part. It is, of course, true that we need both the concept of wave and concept of particle to understand modern quantum physics. But it is not true that we need duality. Wave and particle are not dual to each other.".

Now according to merriam Webster dictionary:

www.merriam-webster.com/dictionary/dualityCached
Define duality: the quality or state of having two parts — duality in a sentence.

http://www.collinsdictionary.com/dictionary/english/dualityCached
Duality definition: A duality is a situation in which two opposite ideas or feelings exist at the same time.

What is the real definition of "duality"? Based on the definitions, are or aren't wave and particles dual to each other? Based on the above two definitions. Don't wave and particle exist at the same time?

If they are not really dual to each other, then I can agree with PF we must rid the world of wave-particle duality... because it's not really dual.

 

[phinds]

@Blue Scallop I think you are misunderstanding the way "duality" was used in this context 90 years ago. It just meant that what are now recognized as "quantum objects" (not waves or particles at all) were somehow BOTH at the same time (which we now understand is not the case)

As @Nugatory once said:

Although it's a popular metaphor and an OK visualization tool, "wave/particle duality" isn't a solid enough idea to build new theories on top of - it's more a user-friendly approximation of what quantum mechanics really says. Pillows are fuzzy, and tables have four legs, but when you encounter a sheep (which is fuzzy like a pillow and has four legs like a table) you aren't going to find the concept of "table/pillow duality" very helpful.

 

[Blue Scallop]

@Blue Scallop I think you are misunderstanding the way "duality" was used in this context 90 years ago. It just meant that what are now recognized as "quantum objects" (not waves or particles at all) were somehow BOTH at the same time (which we now understand is not the case)

As @Nugatory once said:

Ok. I'll join the PF movement to rid the world of wave-particle duality then.
Where will we make our first protest.. at the white house? maybe Trump can tweet "ban wave-particle duality"! Haha..

 

[Charles Link]

It would seem that to understand in any depth the objection to the idea of wave-particle duality, it might require a very in-depth understanding of quantum field theory. As I once heard an older physics professor tell a student, "A physicist needs to learn to make certain approximations". Some of the things that get taught at the lower levels may not always be completely precise, but one can only teach the subject at the level off understanding that they have. The present generation of quantum physicists may be giving a thumbs-down on "wave-particle duality", but I don't think I have a good enough understanding of quantum field theory to understand the difference in what is being offered as a replacement.$\\$ Editing: And the video that @atyy supplied is excellent, thank you. I watched it in its entirety. The results of the single photon experiments including the delayed choice experiment were quite remarkable. One of the questions that arises from this is if the quantum theory had the tools to predict these results, or was it necessary to make a few changes to the theory? At the end of the lecture, Dr. Alain Aspect mentioned the concept of entanglement, but he did not expound upon it.

 

[weirdoguy]

Ok. I'll join the PF movement to rid the world of wave-particle duality then.
Where will we make our first protest.. at the white house?

Stop thinking it's only "PF movement". You simply won't find it most of the textbooks on quantum mechanics.