TransWikia.com

How does Bohmian mechanics explain the effect of information in the double-slit experiment?

Physics Asked by David Spector on September 26, 2021

De Broglie and David Bohm found a method (1952) that explains the double-slit experiment and its variations, which are so central to QM, in an intuitive way without appeal to probability, wave-function collapse, the "measurement problem", or invoking the consciousness of the experimenter. Although recognition of Bohm’s work was not timely for sociological reasons, John Bell praised it as early as 1987.

I can almost understand that the experimental configuration can determine a nonlocal equation that guides the path of particles through the apparatus, such that blocking one slit causes the interference pattern to disappear, but I don’t understand at all how detecting which slit the particle went through (in such a way that the motion of the electron is not disturbed) can also cause the pattern to disappear. Can someone please try to explain this latter effect, using the Bohmian interpretation, and using a minimum of mathematics?

ADDED:

In Bohm’s 1952 paper, part I, page 174, he says that measuring which slit the particle went through (WWM) disturbs the trajectory of the particle, causing the pattern to disappear. He further says that being able to measure WW without disturbing the particle would cause the interference pattern to be seen. This, however, is not what is observed in actual experiments. The following reference implies there is a Bohmian explanation: https://advances.sciencemag.org/content/5/6/eaav9547.full#:~:text=In%201991%2C%20Scully%2C%20Englert%2C%20and%20Walther%20%28SEW%29%20proposed,to%20the%20correlations%20between%20particles%20and%20the%20detectors .

One Answer

Since I'm not getting any answers (possibly because Bohmian mechanics are still being ignored by physicists?), I thought I'd post my own answer, based on Observing momentum disturbance in double-slit “which-way” measurements, a link to which paper is in my question.

It turns out that those physicists who have been speculating that information is at the heart of QM, and that particles turn into waves and then back to particles again in the double-slit experiment are probably wrong, as theory and experiment have confirmed Bohmian mechanics in this 2019 paper.

In particular, there is no need for esoteric discussions about abstract information, wave-like or probabilistic eigenstates, or any kind of nondeterminism in the particle's trajectory.

The paper shows that the momentum transfer to the particle from any apparatus to measure its location relative to the slits is nontrivial, and that there is a linear relationship between the degree of certainty of the position measurement and the degree to which the interference pattern disappears, which depends on the degree of momentum transfer only.

To put this in simple language, measuring the position of a tiny particle is similar to blocking one of the slits. It causes the interference pattern to disappear, in direct relationship with the degree of blockage. This blockage is to be understood to affect the path of the particles exactly as though the wave function were a nonlocal force (Bohm called it the quantum potential). The nonlocal nature of this guiding force implies that closing a slit (or measuring the passage of the particle) instantly changes the nonlocal quantum force field associated with the experimental configuration, which in turn changes the degree to which particles are gradually pushed into an interference pattern.

Remarkably, there is no all or nothing effect at work here, no need for mysticism or ambiguity, non nondeterminism, no need to imagine a "wave function collapse" into classical eigenstates, and no need to worry about Heisenberg's Uncertainty Principle, which still holds for all measurements.

To the extent that we believe in Occam's Razor, then, Bohmian mechanics would appear to be a more correct, intuitive, explanatory, and practical interpretation of QM than Bohr's orthodox Copenhagen Interpretation, at least when applied to the double-slit experiment, which is considered to be quintessential.

If I have made any mistakes in my question or this answer, I ask that they be corrected here, as this seems to be an important understanding in physics today.

Answered by David Spector on September 26, 2021

Add your own answers!

Ask a Question

Get help from others!

© 2024 TransWikia.com. All rights reserved. Sites we Love: PCI Database, UKBizDB, Menu Kuliner, Sharing RPP