The double slit experiment

[minkwe]

I'm sure it will be momentum transfer by Duane's quantum rule. Does anyone have a copy of this paper, or is Minkwe so sure of his theory that he can dismiss the synopsis of Katherine Thomas as being wrong without knowing any of the details of the experiment or the theory behind it?

So rather than wait for my answer, you would assumed I wasn't aware of the details of an experiment which I brought to your attention? But I see that you now have access to the paper and can read it for yourself. Hopefully you will tell me what aspect of the *results* of that experiment (as opposed to the opinion of the authors) is mysterious and cannot be explained classically.

[minkwe]

The conclusion:

As an alternative to a quantum mechanical description of the slits, our results show that a classical description of the slits according to Einstein’s original viewpoint of the thought experiment is still possible. In that case one has, however, to assume a delocalized nonclassical interaction.

In other words, a classical explanation is possible, but it needs non-locality.

Richard, not only is that statement self-contradictory it doesn't add anything to the discussion. If it needs non-locality, it is not classical. Besides, I already pointed out in my post of the experiment that the authors prefer a mystical explanation.

The authors of the very first paper John cited also make claims about the results which a detailed evaluation of the results reveal to be false. It is naive to simply point to the opinion of the authors, which I already mentioned in my original post about the experiment, as "proof" that non-locality is the only explanation. Look at the results and convince yourself that it is impossible to explain it as I've done, before you jump on the "non-locality" bandwagon. Unless you are already on it or it's sibling ("non-realism").

You actually have to think carefully about their arguments, and ask hard questions of whether their results justify the conclusions, and whether they are making syllogistic fallacies of reasoning about the results. E.g. Do they make conclusions about all possible local explanations based on the failure of a halfhearted attempt at one specific classical explanation? etc. Unfortunately, critical thought is seriously lacking in science these days, hence the proliferation of mysticism like "non-locality".

A simple question I've been asking, lifts the veil just a little bit: Does anyone suggesting that this experiment is "non-local" believe that the dynamics of Newton's cradle is a non-local phenomenon?

[gill1109]

Sorry folks on my way to Copenhagen and then on to Sweden and Germany. You can email me if anything exciting comes up.

[jreed]

You actually have to think carefully about their arguments, and ask hard questions of whether their results justify the conclusions, and whether they are making syllogistic fallacies of reasoning about the results. E.g. Do they make conclusions about all possible local explanations based on the failure of a halfhearted attempt at one specific classical explanation? etc. Unfortunately, critical thought is seriously lacking in science these days, hence the proliferation of mysticism like "non-locality".

Yes, I have to agree with Minkwe on this. After looking at the paper, they assume that the classical description must involve scattering at only one of the atoms, either Hydrogen or Deuterium in the H-D molecule. However this neglects the molecular bond that holds this molecule together. When you scatter from one atom, the other one must also be involved. The results of the experiment show this and it shouldn't come as a big surprise or proof of some strange non-locality effects.

Now, back to the original two slit experiment. I'm trying to understand how the two slit assembly interacts as a whole with each scattered electron using classical ideas. If we are talking about vibrational normal modes of the assembly, this means that either each scattered electron must excite certain modes, or all the modes are already there due to random vibrations of the assembly. Am I correct so far?

[Ben6993]

I have now read the fascinating Schmidt et al paper as best I can (I am not a physicist).

The use of a fast moving beam of HD molecules as a slit is a delightful idea! Against a static mass of helium acting as the particles. I followed a lot of it but note the conclusions on trust. I originally assumed that the non-classical non-local aspect would be concerned with a particle transferring momentum to the whole framework of a double slit mechanism and was almost disappointed that it just seems to mean that the H and the D in one molecule were sharing the transferred momentum of one particle (a helium atom). That seems more local than non-local. But I may be misreading/misunderstanding.

I assume that two simultaneous and parallel beams of HD were used in the experiment, making two slits. I wonder what the diffraction pattern would be for a one-slit experiment. That would be using just one beam of HD. I do not suppose one could send one He atom at a time through two slits in this experiments. Could one slit be blocked off with the equivalent of a soft curtain [as in Richard Gill's suggestion]. One could fire two slits at the He mass and make one slit miss, assuming the He could be maneuvered out of the way of the second slit. But I am probably missing something here. I view two slits in a metal plate as an interacting whole. But are the two slits in Schmidt et al interacting with one another? I have a very naive view of the molecules in a metallic plate with two slits somehow interacting with one another differently to a plate with one slit. But the interactions are always local, with neighbours. For example, a vibrating string has neighbouring bits of string having movement influenced by their immediate neighbours.

[minkwe]

Ben,
Your understanding of the Schmidt experiment is correct.

As concerns your question about the original double slit experiment, I believe the normal modes already exist in the atomic motions.

Metallic plates can be thought if as a closed-packed lattice of netal atoms (there are no molecules in metals). Other types of solids have molecules though.

[Ben6993]

Thank you Michel.

A point about implications of the Schmidt et al experiment. If quantisation of linear momentum is caused by interaction between one atom and one molecule, and I can accept that, why is there an interference pattern at the screen? The use of the term 'free floating' HD molecules implies no coordination and no group action of the double slits? Does not an interference pattern at the screen require all the interactions to somehow be coordinated to combine correctly at the screen. (I think that the Schmidt experiment does not actually use a screen, but never mind.) Something has to coordinate all the interactions else the screen would not show interference?

[minkwe]

Hi Ben,
The key is that though each particle impinges on a specific molecule at a time, different particles impinge on different molecules at different times, at different points in their vibrational cycles, thus transferring different amounts of momentum. The diffraction pattern is therefore a sort of "histogram" of momentum transferred. The particles could be said to be sampling the "allowed" momentum transfers to the molecules. Even for fixed slits, there is no group action. Different particles simply sample different points in the vibrational cycle.

The type of coordination you are thinking about is not necessary. Remember that for this experiment, there was no screen, the pattern was calculated from the momentum transferred. For the double slits, the fact that the slits are fixed, and the particles have fixed momentum prior to the slits, and the slits have the same dynamics all the time, is enough coordination. But each particle only interacts with a given atom, transfers only an "allowed" amount of momentum. The angle it leaves the slit is a function of the momentum transferred. Different particles do the same thing. At the end you look at the histogram of angles leaving the slits and find that there are more particles heading in some directions -- ie, certain values of momentum transfers are more preferable than others, hence the bright regions vs the dark regions. This is why it may appear as though the pattern is random until you have collected a large number of particles.

[gill1109]

Hi Ben,
The key is that though each particle impinges on a specific molecule at a time, different particles impinge on different molecules at different times, at different points in their vibrational cycles, thus transferring different amounts of momentum. The diffraction pattern is therefore a sort of "histogram" of momentum transferred. The particles could be said to be sampling the "allowed" momentum transfers to the molecules. Even for fixed slits, there is no group action. Different particles simply sample different points in the vibrational cycle.

Ah, the memory loophole.

[minkwe]

Hi Ben,
The key is that though each particle impinges on a specific molecule at a time, different particles impinge on different molecules at different times, at different points in their vibrational cycles, thus transferring different amounts of momentum. The diffraction pattern is therefore a sort of "histogram" of momentum transferred. The particles could be said to be sampling the "allowed" momentum transfers to the molecules. Even for fixed slits, there is no group action. Different particles simply sample different points in the vibrational cycle.

Ah, the memory loophole.

Gill's response was a masterpience of inability/unwillingness to understand physics. Not unlike the earlier attempt viewtopic.php?f=6&t=51&start=20#p2025

[gill1109]

Hi Ben,
The key is that though each particle impinges on a specific molecule at a time, different particles impinge on different molecules at different times, at different points in their vibrational cycles, thus transferring different amounts of momentum. The diffraction pattern is therefore a sort of "histogram" of momentum transferred. The particles could be said to be sampling the "allowed" momentum transfers to the molecules. Even for fixed slits, there is no group action. Different particles simply sample different points in the vibrational cycle.

Ah, the memory loophole.

To expand on this: consider N two-slit experiments each in a different laboratory and each with N=1 particle.

According to QM, if we superimposed the arrival positions of all the. n particles, we would see the interference pattern. But not according to the "memory loophole" explanation given here.

[minkwe]

To expand on this: consider N two-slit experiments each in a different laboratory and each with N=1 particle.

According to QM, if we superimposed the arrival positions of all the. n particles, we would see the interference pattern. But not according to the "memory loophole" explanation given here.

What memory loophole explanation? Did Gill even bother to read the explanation?

[gill1109]

To expand on this: consider N two-slit experiments each in a different laboratory and each with N=1 particle.

According to QM, if we superimposed the arrival positions of all the. n particles, we would see the interference pattern. But not according to the "memory loophole" explanation given here.

What memory loophole explanation? Did Gill even bother to read the explanation?

Momentum *transfer*. Momentum is conserved. What the particles lose, the slits gain, and vice versa. The "pattern" takes time to become established, since first an equilibrium needs to have been reached.

There exist many such "memory solutions" to the two slit "paradox".

[minkwe]

To expand on this: consider N two-slit experiments each in a different laboratory and each with N=1 particle.

According to QM, if we superimposed the arrival positions of all the. n particles, we would see the interference pattern. But not according to the "memory loophole" explanation given here.

What memory loophole explanation? Did Gill even bother to read the explanation?

Momentum *transfer*. Momentum is conserved. What the particles lose, the slits gain, and vice versa. The "pattern" takes time to become established, since first an equilibrium needs to have been reached.

There exist many such "memory solutions" to the two slit "paradox".

So instead if actually reading and understanding it, Gill prefers to imagine what it might be talking about. It is very easy to verify by actually reading the explanation that there is no such thing as memory needed. So again anyone who does not understand it should read it carefully and ask specific questions rather than pretend to criticise and make obviously false snark remarks about things they do not understand.

[gill1109]

Anyone who thinks someone else misunderstood something, should kindly point that out.

Alternatively they could continually make aggressive and personal remarks aimed at disparaging the character / intelligence / motivation of other forum participants. Such behaviour reflects painfully on their own character.

[Joy Christian]

Alternatively they could continually make aggressive and personal remarks aimed at disparaging the character / intelligence / motivation of other forum participants. Such behaviour reflects painfully on their own character.

HaHaHa... You are funny, Mr. Kettle. Er... Mr. Pot. Very funny.

[minkwe]

Anyone who thinks someone else misunderstood something, should kindly point that out.

We have twice observed in this thread already that Gill has, without understanding my explanation, snarkly attacked it as:
1) exploiting non-locality loophole
2) exploiting memory loophole
Claims which are not only clearly false, but he should have known were false had he read the explanation. So again if Gill does not understand anything in the explanation, I would gladly dumb it down for him. Smart-arse snark remarks like "Ah, the memory loophole" don't work when you have no clue what you are talking about.

[gill1109]

Anyone who thinks someone else misunderstood something, should kindly point that out.

We have twice observed in this thread already that Gill has, without understanding my explanation, snarkly attacked it as:
1) exploiting non-locality loophole
2) exploiting memory loophole
Claims which are not only clearly false, but he should have known were false had he read the explanation. So again if Gill does not understand anything in the explanation, I would gladly dumb it down for him. Smart-arse snark remarks like "Ah, the memory loophole" don't work when you have no clue what you are talking about.

Rules:
The short set of rules of this board are:

1. Impolite behavior is NOT to be tolerated

4. No flaming

5. No derogatory personal comments about anyone; stick to the physics

10. And... the most important rule; Have Fun!

[gill1109]

Alternatively they could continually make aggressive and personal remarks aimed at disparaging the character / intelligence / motivation of other forum participants. Such behaviour reflects painfully on their own character.

HaHaHa... You are funny, Mr. Kettle. Er... Mr. Pot. Very funny.

Glad it amused you, Mr Kettle! You must agree that one should respond to the content of postings, not on imagined aspects of the character or intelligence or competence of the person who posted the message you are responding to. It is difficult, I know. Especially if you perceive problems with the content.

Yours
Mr. Pot.

[FrediFizzx]

OK guys, let's get back on topic.