Quantum probabilities with ordinary objects

This is a video comment on a point mentioned by professor Leonard Susskind in his sixth Stanford lecture on Quantum Mechanics (www.youtube.com/watch?v=tKbzlOU_ETk at minute 12:00) that it is quite hard to think of a classical setup which gives the same probability distribution as polarized photons. This video gives a proposal for such a setup, where ordinary needles steered by a pilot-wave are shot towards a wire-grid. Technical knowledge of quantum amplitudes is necessary to follow this video.

The videoscript is available at http://commonsensequantum.blogspot.com/2009/01/quantum-probabilities-with-ord...

Category:

Science & Technology

Tags:

• quantum
• mechanics
• physics
• probabilities
• louis
• de
• broglie
• david
• bohm
• pilotwave
• pilot-wave
• bohmian
• leonard
• susskind
• stanford
• lecture
• photon
• polarization
• polarizer

[upisoft2]

Unfortunately there is nothing quantum about your *experiment*. In order to create quantum representation with a spinning needle you must somehow change the plane of rotation of the needle when it passes through the net. In your experiment the angle is unchanged. If you put second net tilted exactly the same angle as the first net, it will still stop some of the needles that first net let pass through. Not quite like photon going through polarizer.

[ArjenDijksman]

@upisoft2 That's a good point that you raise. My explanation in this video is concerned about the probability distribution of the measurement results, which are definitely quantum probabilities. It is not concerned about how the needle is affected by the passage through the grid. That's another question. You can imagine that the angle will be changed when it touches one of the wires, and one can thus design a mechanism that will be analogous to a polaroid filter.

[upisoft2]

@ArjenDijksman The little problem is that the needle has to be affected when it does not touch any of the wires. anyway I think you have misunderstood the professor. It is obvious that one can create a system that can give statistical results. After all the statistics were there long before QM. He was talking about QM properties that cannot be reproduced easily on large scale.

[ArjenDijksman]

@upisoft2 I recommend you listen to Susskind's lecture. He's talking about quantum probability distribution of which he doesn't know any classical analogue. Such particle statistics have never been encountered in scientific investigation before the advent of QM.

[myclicks]

Is it the only way to explain the wire-grid polarizer? You can't explain by using electromagnetics, wave reflection and interference?

[ArjenDijksman]

You can explain it using electromagnetism and (better!) quantum mechanics. But this is a mechanical model that comes close to it. One must be aware that this is only an analogy, which gives a partial insight of what happens. In real experiment, the electrons of the wire-grid play an important role. That's not modeled in this analogy.

[myclicks]

Thank you for your kind reply. But now I suspect classical electromagnetism alone cannot explain the wire-grid polarization. Because even the wires reflect some of the incident wave, there is still huge a portion of the wave leaking through between wires. The grid now becomes a diffraction grating, therefore you should expect to see wave on the other side of the grid. Could you explain that?

[martendijksman]

Wat een goede opname!

[aboabdalla12]

nice idea