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In order to recover the well-known interference pattern in the double slit experiment with massive electrons, one has to perform it in a vacuo. This is because, as far as I know, the interaction with the environment (e.g. air particles) performs a measurement on the quantum states of the propagating electrons and the interference pattern gets washed out.

Now, from a physical point of view: as an observer, I have no idea what interactions the electron wavefunction is having the various air particles. So how can this result in an observable effect such as having the interference pattern changed?

SuperCiocia
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1 Answers1

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  1. The interaction with the environment performs no measurement, it only may distort the wave-function.

  2. In order to observe that the pattern was damaged you don't need to have an idea of what interaction caused the damage. You need to have that idea if you study that specific interaction.

  3. An example of disturbing interaction with air particles: the collision with air molecules can slow down some of the electrons, while other electrons that didn't undergo collision keep their linear momenta. Then, if the electrons in the beam have different linear momenta, the wavelength of the beam isn't constant anymore, and the pattern of interference isn't clear anymore.

Good luck!

Sofia
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