Double slit experiment with electrons

In summary, the conversation discusses the validity of using spin-aligned electrons in the double-slit experiment. The question was whether this would affect the interference pattern, and it was stated that it has no effect on the final result. However, this seems to contradict some course notes from UC Berkeley which suggest that a magnetic field in one path would change the spin and result in a different interference pattern. It is concluded that the two discussions are referring to different experiments.
  • #1
cygnet1
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In the double-slit experiment, without which-path information available, the diffraction pattern is usually shown as an even function with respect to the displacement from the midpoint of the slits: something like sin ay / y. (This is the case in Feynman's lectures, and many others.) The question was posed as to whether this result is valid for spin-aligned electrons. The most direct reply stated that it is indeed valid:
Originally Posted by Wallin
Can anyone direct me to any version of the double-slit experiment which used only electrons with aligned spin axes? If you can't direct me to an experiment, can you postulate how or if the double-slit experiment might be different using such electrons?

Thanks!
As has probably been stated (although not explicitly that I can see), using aligned spin electrons has no effect on the final result of interference (i.e. probability to find an electron at a certain position). This is analogous to using polarised light in a double-slit experiment. Sending the electrons through a slit has no effect on the spin of the electron.

This seems to contradict these UC Berkeley course notes, which state that if one of the paths is increased in length to make it out of phase from the other by 2∏ radians, then the interference pattern will go to zero, because the state function of the longer path will be multiplied by -1 (or exp i∏). It is stated in the notes that this effect was experimentally confirmed with neutrons (another fermion). This would not be the case for photons, which would constructively interfere.

If this is indeed correct, then wouldn't it also be true that if the electron source were symmetrically placed between the two slits, that there would be places in the diffraction pattern that would be different with photons?

So who's right? The Berkeley professor or Feynman?

Note: It appears the Berkeley notes refer to a magnetic field, B0, which may have something to do with it.
 
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  • #2
They are talking about different experiments.
In your quoted section they are talking about the probability of finding an electron at a particular place while in the notes, they are talking about finding a particular spin state at that place.
 
  • #3
Actually, I think I've answered my own question. The Berkeley lecture notes show a magnetic field in one path but not the other. It is that field that changes the spin and demonstrates the spin-1/2 nature of the fermions.
 

1. What is the double slit experiment with electrons?

The double slit experiment with electrons is a scientific experiment that demonstrates the wave-particle duality of matter. It involves firing electrons, which are particles, through two parallel slits and observing their interference pattern on a screen. This experiment helps to illustrate the strange behavior of quantum particles, which can exhibit both wave-like and particle-like properties.

2. Why is the double slit experiment with electrons important?

The double slit experiment with electrons is important because it challenges our understanding of the fundamental nature of matter. It shows that particles, like electrons, can behave like waves and exhibit interference patterns, rather than just following a predictable path like classical particles. This experiment has also paved the way for further research and developments in quantum mechanics and has led to new technologies such as electron microscopy.

3. Who first conducted the double slit experiment with electrons?

The double slit experiment with electrons was first conducted by physicist Clinton Joseph Davisson and Lester Germer in 1927. They were trying to observe the diffraction of electrons on a nickel crystal surface, and unexpectedly discovered the interference pattern which proved the wave-like behavior of electrons.

4. How does the double slit experiment with electrons differ from the classical double slit experiment?

The double slit experiment with electrons differs from the classical double slit experiment in that it involves subatomic particles, such as electrons, rather than larger objects like marbles or light. The classical experiment only shows a particle-like behavior, while the electron experiment also demonstrates the wave-like behavior of particles.

5. What are the implications of the double slit experiment with electrons?

The double slit experiment with electrons has significant implications for our understanding of the quantum world and the properties of matter. It challenges the classical view of particles as solid, predictable objects and instead shows that they can behave in unpredictable and wave-like ways. This has led to new theories and understandings in quantum mechanics and has advanced our knowledge of the fundamental building blocks of the universe.

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