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In an electron double slit experiment, let's put two charged plates behind the slits in an attempt to move the pattern up and down on the the screen.

What will happen? Will it just shift the interference pattern on the screen or washes it out completely?

If it washes it out, what's the minimal field that doesn't affect the pattern? Since I don't believe the electron double slit experiment was performed in an environment where all fields were exactly zero, but they still managed to get the pattern.

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  • $\begingroup$ This wikipedia article on the double-slit experiment answers this question for you, but you might be interested in this part in particular (with the corresponding paper): "if one does not insist that the method used to determine which slit each photon passes through be completely reliable, one can still detect a (degraded) interference pattern." - elearning.physik.uni-frankfurt.de/data/FB13-PhysikOnline/… $\endgroup$
    – D. W.
    Commented Jul 14, 2014 at 15:42
  • $\begingroup$ I'm always a little bit astonished reading an article about an experiment and to read incidentally that it is a theoretical "experiment". $\endgroup$
    – HolgerFiedler
    Commented Jul 15, 2014 at 15:50

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If we can neglect the internal modes of the charged plates, they merely modify the potential in which electrons propagate, i.e., the potential of the slits. Depending on configuration it may change the interference pattern, but it does not destroy the interference.

On the other hand, if the plates have their own modes, they may cause dephasing and/or decoherence and destroy the interference. This is also the case, if electrons are coupled to electromagnetic field and can lose/absorb energy or simply be scattered by photons.

It is necessary to note that the double slit experiment is a thought experiment - although it has been realized literally, the relevant phenomena can be studied in many physical situations and configurations. E.g., the destruction of the interference picture has been extensively analyzed in solid-state Aharonov-Bohm interferometers.

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https://commons.m.wikimedia.org/wiki/File:Moellenstedt_biprisma_voltage_shadow.JPG It shows the influence of an electrical field to fringes.

https://commons.m.wikimedia.org/wiki/File:Moellenstedt_biprisma_schematic_arrangement.JPG This shows how experiment with electrons was arranged in generally.

As a result you may find out that the potential of the material which forms the slits is responsible for changes in fringes dimensions. Ergo can we say that the potential is responsible for the fringes at all?

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  • $\begingroup$ Can you link the Wiki article that uses these pictures? $\endgroup$
    – Calmarius
    Commented Jul 15, 2014 at 14:55
  • $\begingroup$ @Calmarius: G. Möllenstedt und H. Düker: Beobachtungen und Messungen an Biprisma-lnterferenzen mit Elektronenwellen. In: Zeitschrift für Physik. Nr. 145, 1956, S. 377-397. I'm sorry. It's in German. And the source is protected. If you are familiar with German you can read my excerpt Elektronenbeugung $\endgroup$
    – HolgerFiedler
    Commented Jul 15, 2014 at 15:38
  • $\begingroup$ Sorry I don't understand German... So is the point of your image is that they focused an electron beam using EM field and they still got fringes? $\endgroup$
    – Calmarius
    Commented Jul 16, 2014 at 11:22
  • $\begingroup$ @Calmarius Möllensted et all uses a pointlike electron source and let the electrons through the biprisma. Electrons got deffracted from the wire. This time the electric potential was zero. Increasing the potential the frings changes. That is what they saw. The conclusion that the electric fields of the surface electrons of the wire and the electric field of the electron beam make a discrete EM field. And this field - even with external zero potential - is responsible for fringes. Last sentence is my conclusion and don't belive in it. $\endgroup$
    – HolgerFiedler
    Commented Jul 16, 2014 at 18:36

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