How is the measurement done for the double slit experiment?

[brajesh]

TL;DR Summary

How is the measurement done for the double slit experiment? Is it active or passive?

How is the measurement of which path the particle took done for the double slit experiment?
When electrons are being sent through the slit. Or when photons are being sent through the slit.

Is it an active process or a passive process?

I haven't seen an explanation for this and perhaps this will help me understand the collapse of the wave better.

 

[anuttarasammyak]

I do not know report of the experiments. I have an idea of experiment to set two magnetic meters near the slits to measure magnetic field generated by passing electron, though I do not know it is achievable and practical. Magnetic field measurement would make wavefunction collapse to disturb interference pattern at the screen.

 

[Nugatory]

How is the measurement of which path the particle took done for the double slit experiment?

There is no such thing as “the” double slit experiment. There are many ways of demonstrating quantum interference, and they’re different in their details. Furthermore, popular treatments often are describing experiments that haven’t been done; they say “when we have a detector...” when they mean “we haven’t actually tried it, but if we had a detector...”. So if you want specifics about how the which path measurement is done, you have to find the description of a specific experiment to know what was done in that experiment.

Probably the most common approach is to just block one of the slits so that we know which slit a particle passed through - had to be the open slit. A more interesting approach with photons is to put polarizing filters behind the slits and rotate them in and out of alignment. When both filters are aligned vertically there’s no way of knowing which slit any photon passed through and the interference pattern forms. When one filter is turned to a horizontal position, then the vertically polarized photons will have gone through one slit and the horizontally polarized ones through the other slit, and the pattern does not form.

 

[DrChinese]

Is it an active process or a passive process?

To add to Nugatory's excellent answer:

It can be either active or passive.

Active: block a slit entirely.

Passive: place polarizers over the slit. The relative alignment of the polarizers determines whether there is (or not) interference. Regardless of orientation, a photon passes through a polarizer. Here are the specifics:

https://sciencedemonstrations.fas.h...-demonstrations/files/single_photon_paper.pdf