The double slit experiment

[jreed]

Again, I don't know were you got the idea of "excitation" in anything I said. Please read the link I gave about normal modes. Every physical object has normal modes and pay attention to what I'm actually saying as opposed to what you imagine I might be saying. You still haven't pointed to any "trouble" in my explanation. I genuinely want to explain the details and answer all your questions but you will have to read what I actually write.

Let's go over this again. You seem to think that saying "it's a normal mode" explains everything, but that doesn't explain anything for me. Again I ask the question: A normal mode of what? We could have vibrational modes of the plate with the slits or electromagnetic normal modes as in a microwave resonant cavity. Which one is it? Or maybe there's some normal mode I don't know about. After all I only have a Ph.D. in physics and a degree from MIT but maybe I missed something. I'm trying to understand what you're talking about, but so far it doesn't make sense.

[minkwe]

Let's go over this again. You seem to think that saying "it's a normal mode" explains everything, but that doesn't explain anything for me. Again I ask the question: A normal mode of what

Then ask a specific sensible question that you don't understand, because your question, "normal mode of what?" is anything but. I already told you the normal modes OF THE SLIT SYSTEM. You have to ask a specific question to get a specific answer.

We could have vibrational modes of the plate with the slits or electromagnetic normal modes as in a microwave resonant cavity. Which one is it?

I didn't say anything about a microwave resonant cavity? I'm talking about the coupled vibration of the atoms which make up the slit system.

After all I only have a Ph.D. in physics and a degree from MIT but maybe I missed something. I'm trying to understand what you're talking about, but so far it doesn't make sense.

Is that all you have? I thought you had more than that? You still haven't pointed out one thing that doesn't make sense. Instead, you are all over the place, talking about excitations by electrons, microwave resonance, MIT, Ph.D. etc.

1) quanta/particles can transfer momentum to the walls if the slits.
2) The amount of momentum transferred, determines the angle of deflection of the particle.
3) Transfered momentum is quantized. Therefore the particles are deflected into discrete directions.
4) The allowed directions are determined by the relationship between the normal modes if the slit system and the frequency of the quanta/particle.
5) Since different slit systems have different normal modes, the diffraction patterns are different.
6) The pattern produced, and the slit system producing it have a dual relationship. They can be expressed as Fourier transforms of each other.

Which of these points don't you understand and need clarification for? Which of these points do you claim is "trouble", or does not make sense?

[jreed]

We could have vibrational modes of the plate with the slits or electromagnetic normal modes as in a microwave resonant cavity. Which one is it?

I didn't say anything about a microwave resonant cavity? I'm talking about the coupled vibration of the atoms which make up the slit system.

Good! Now we're making some progress. So we're talking about vibrational modes of the plate system. The idea here is that the electron excites a normal mode of this system. If it didn't excite a mode there wouldn't be an interaction, and therefore no scattering. I don't suppose you can accept that however, based on your comments on an earlier posting.

[minkwe]

The idea here is that the electron excites a normal mode of this system.

Nope, that is not the idea, the electron doesn't excite a normal mode. Momentum is transferred between the particle and the atoms in the slit and the amount of momentum transferred is related to the vibrational modes of the system, it is not the electron causing the vibrations. Again, I'm talking of momentum transfer, not excitation.

If it didn't excite a mode there wouldn't be an interaction, and therefore no scattering.

If there is no momentum transfer there will be no scattering, there will be no reflection, there will be no optical phenomena. Yet I won't say photons "excite" a mirror and that's why you have reflection. If you want to call momentum transfer , "excitation" then go ahead, I won't.

I don't suppose you can accept that however, based on your comments on an earlier posting.

Call it "excitation" if you want. I'm talking about momentum transfer.

[gill1109]

The idea here is that the electron excites a normal mode of this system.

Nope, that is not the idea, the electron doesn't excite a normal mode. Momentum is transferred between the particle and the atoms in the slit and the amount of momentum transferred is related to the vibrational modes of the system, it is not the electron causing the vibrations. Again, I'm talking of momentum transfer, not excitation.

If it didn't excite a mode there wouldn't be an interaction, and therefore no scattering.

If there is no momentum transfer there will be no scattering, there will be no reflection, there will be no optical phenomena. Yet I won't say photons "excite" a mirror and that's why you have reflection. If you want to call momentum transfer , "excitation" then go ahead, I won't.

I don't suppose you can accept that however, based on your comments on an earlier posting.

Call it "excitation" if you want. I'm talking about momentum transfer.

Momentum transfer which occurs from the electron to the whole screen with the two slits, in a way which depends on the geometry of the whole thing. Thus momentum transfer at split A depends on whether slit B is open or closed. I suppose Michel thinks of the screen as a solid piece of metal with two slits cut in it ... you don't open or close them, you just replace a piece of metal with two slits by a piece of metal with one slit. I think we need to refine the experiment by hanging curtains behind the two slits which can be independently drawn and opened. So the two slits are always there but one can be blocked by a further piece of material which does not actually contact the thing with the slits in it.

[FrediFizzx]

Somebody didn't even read the experiment paper.

[gill1109]

Somebody didn't even read the experiment paper.

Which paper do you mean?

[gill1109]

There is an excellent description of a refined double slit experiment (due to Wheeler) in chapter 14 of "Speakable and unsoeakable". Michel's "solution" no longer works. Seems no-one read that paper.

[minkwe]

Momentum transfer which occurs from the electron to the whole screen with the two slits

When Richard stands on the beach, his whole body instantaneously interacts with sand that is why he is able to stand. It's only the head that is unable to peek above the sand covering it.

Thus momentum transfer at split A depends on whether slit B is open or closed.

Richard is unable to walk through walls, because the atoms in his body know instantaneously that there is no opening there. Richard is able to bounce on a trampoline but not on a concrete floor because the atoms in his feet interact with the whole trampoline and know instantaneously on contact that the trampoline is flexible

[gill1109]

Michel, you are resorting to personal abuse. And talking nonsense. Your fun analogies don't work.

On the positive side, see chapter 14 of "Speakable and Unspeakable". It's called "de Broglie–Bohm, delayed-choice double-slit experiment, and density matrix". The delayed-choice double-slit experiment was invented by J.A. Wheeler. It totally destroys your argument.

Have you read chapters 13, and 16 of "Speakable and Unspeakable" yet? They totally destroy all your arguments about CHSH, Bell and all that. They bring in statistics. They build the bridge between theory and experiment.

[minkwe]

On the positive side, see chapter 14 of "Speakable and Unspeakable". It's called "de Broglie–Bohm, delayed-choice double-slit experiment, and density matrix". The delayed-choice double-slit experiment was invented by J.A. Wheeler. It totally destroys your argument.

Have you read chapters 13, and 16 of "Speakable and Unspeakable" yet? They totally destroy all your arguments about CHSH, Bell and all that. They bring in statistics. They build the bridge between theory and experiment.

Richard, this thread is not about CHSH and Bell. If you have an example of a double-slit experiment which is mysterious and can not be explained classically. Post it like John did, and state exactly the mystery that can not be explained. Then we can have a constructive discussion about it. Reference the paper with the experimental results, and say exactly what you believe is mysterious about it, then we can talk. Anything else will be simply ignored.

[jreed]

Nope, that is not the idea, the electron doesn't excite a normal mode. Momentum is transferred between the particle and the atoms in the slit and the amount of momentum transferred is related to the vibrational modes of the system, it is not the electron causing the vibrations. Again, I'm talking of momentum transfer, not excitation.

Ok, I understand now. The momentum of a phonon of the slit assembly is absorbed or emitted by the electron and this changes its momentum in a way to cause the pattern we see on the screen. I can agree with that. I don't have any problems with the rest of the interpretation of this experiment. In the literature there were some arguments raised about this exact same experiment and the same problem in the 1960s when Lande's book came out. See Nature, 193, pages 1276-1277 and Nature, 195, pages 1088-1089.

[gill1109]

Nope, that is not the idea, the electron doesn't excite a normal mode. Momentum is transferred between the particle and the atoms in the slit and the amount of momentum transferred is related to the vibrational modes of the system, it is not the electron causing the vibrations. Again, I'm talking of momentum transfer, not excitation.

Ok, I understand now. The momentum of a phonon of the slit assembly is absorbed or emitted by the electron and this changes its momentum in a way to cause the pattern we see on the screen. I can agree with that. I don't have any problems with the rest of the interpretation of this experiment. In the literature there were some arguments raised about this exact same experiment and the same problem in the 1960s when Lande's book came out. See Nature, 193, pages 1276-1277 and Nature, 195, pages 1088-1089.

Yes this is so easy to understand. The phonon belongs to the slit assembly. It is therefore non-local. The interaction of particle with whichever slit it passes through, is different, depending on whether the other slit is there or not.

That is why we have to forget the traditional two-slit experiment and move on to John Wheeler's delayed choice double-slit experiment and variants. There are always two slits open. Sometimes a curtain is dropped behind one of them or the other, sometime not. So there is no way a phonon can "communicate" from one slit to another, whether the other is open or not.

[minkwe]

Yes this is so easy to understand. The phonon belongs to the slit assembly. It is therefore non-local.

Richard, you are very funny. Every particle belongs to the universe, therefore all interactions with particles are non-local.

Now, back to more serious stuff. What did you say was mysterious about Wheelers thought experiment? If you have a citation of ractual results we can evaluate, that will be nice also.

[minkwe]

See Nature, 193, pages 1276-1277 and Nature, 195, pages 1088-1089.

Thanks for the articles, I'll check them out.

Nature 193, 1277 (31 March 1962) | doi:10.1038/1931277a0
http://www.nature.com/nature/journal/v1 ... 1277a0.pdf

Nature 195, 1088 - 1089 (15 September 1962); doi:10.1038/1951088a0
http://www.nature.com/nature/journal/v1 ... 1088a0.pdf

On initial reading of the abstract of the second one, if it represents Lande correctly, appears to suggest that Lande's theorem included action-at-a-distance with the "whole apparatus", different from what I'm talking about:

ATTENTION has been directed to persistent questions of interpretation in quantum physics by the recent exchange of views1 on the subject between Dr. H. V. Stopes-Roe and Prof. A. Landé. To Prof. Landé's picture2 of the particle as permanently localized phenomenon, influenced through action-at-a-distance by the extended structure of a measuring instrument, Dr. Stopes-Roe understandably objects that a necessarily detailed and 'suitable interpretation of the collective action of the apparatus' has not been provided. Prof. Landé's failure to furnish such an interpretation is equally understandable, since any interpretational superstructure in physics that lacks roots in the underlying mathematical formalism (cf. the luminiferous ether) tends sooner or later to be viewed as excess ideological ballast.

I'll have to read them more carefully to see the similarities and differences between Lande's theory and my explanation.

Have you ever wondered why the Fourier transform of the box function, is the single slit diffraction pattern, and the Fourier transform of the double box function is exactly the double slit diffraction pattern, etc? Actually it should be the triangle function which is just a convolution of the box function.

[gill1109]

I have a personal eBook copy of "Speakable..." so if anyone wants to see one or the other chapter, they can email me ... but I would prefer they bought it and read all of it.

[jreed]

I'll have to read them more carefully to see the similarities and differences between Lande's theory and my explanation.

Have you ever wondered why the Fourier transform of the box function, is the single slit diffraction pattern, and the Fourier transform of the double box function is exactly the double slit diffraction pattern, etc? Actually it should be the triangle function which is just a convolution of the box function.

The Fourier transform of a box function is the sync (sin(f)/f) function. The Fourier transform of two boxes is the convolution of two sync functions. That's what the two slit response looks like.

I think you'll find Lande's explaination of this experiment is similar to yours.

[jreed]

Yes this is so easy to understand. The phonon belongs to the slit assembly. It is therefore non-local.

Richard, you are very funny. Every particle belongs to the universe, therefore all interactions with particles are non-local.

Now, back to more serious stuff. What did you say was mysterious about Wheelers thought experiment? If you have a citation of ractual results we can evaluate, that will be nice also.

Wheeler's thought experiment is no longer just a thought experiment. It has been done. Here's a reference for the actual experiment:

http://en.wikipedia.org/wiki/Delayed_ch ... experiment

[minkwe]

What did you say was mysterious about Wheelers thought experiment? If you have a citation of actual results we can evaluate, that will be nice also.

Wheeler's thought experiment is no longer just a thought experiment. It has been done. Here's a reference for the actual experiment:
http://en.wikipedia.org/wiki/Delayed_ch ... experiment

Do you find anything mysterious in the experiment?

http://dx.doi.org/10.1016/j.phpro.2010.09.024

We present a computer simulation model of Wheeler’s delayed choice experiment. The model is solely based on experimental facts and does not rely on concepts of quantum theory or probability theory. We demonstrate that it is possible to give a particle-only description of Wheeler’s delayed choice experiment which reproduces the averages calculated from quantum theory and which does not defy common sense.

[Ben6993]

Richard wrote:

I have a personal eBook copy of "Speakable..." so if anyone wants to see one or the other chapter, they can email me ... but I would prefer they bought it and read all of it.

Bell's Chapter 16 seems to start on page 149 at http://bookre.org/reader?file=635185&pg=149
Bertlmann's socks and the nature of reality

Page 149 of the website index is easily locatable. The actual image of this page of the book is not numbered but must be p139.
Not sure if it is a complete chapter.