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Doubble slit experiment getting bigger

  1. Mar 3, 2015 #1
    If we increase the mass of the particle beeing fired at the slots, at what point will the standard experiment break down and become just small pellets beeing fired and classical physics will apply?
    Theoretically say we increase one Planck unit at A time.
    Or, just is there A limit to the mass/size that governs the mind boggling doubble slit exp.?
    Txs from A Non-physicist
  2. jcsd
  3. Mar 3, 2015 #2
    This is a very important and deep question. Therefore the answer is not easy.
    Im principle, you should be able to perform a double slit experiment even with tennis balls, but this does not happen because as the object gets bigger and bigger a process called decoherence starts to destroy quantum effects.
    There is no clear and sharp limit between the classical and the quantum world, and my question to your answer is that the size of the object is limited by how good and isolated is your experiment.
    e.g. To my knowledge, the record ad the moment is held by the group of Marcus Arndt in Vienna, who has performed the double slit experiment with relatively big objects: organic molecules with about 60 atoms and mass >500 atomic units.
  4. Mar 3, 2015 #3


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    Staff: Mentor

    Something that very few treatments of the double-slit experiment mention: the interference pattern is not a simple yes-no thing that's either there or not depending on the experiment.

    In an ideal thought experiment in which the sizes of the slits and the positions of the detectors and screen are arranged just so, and the incoming particles are properly isolated from the environment between emission and detection, the interference pattern will be bright and there won't be any contribution from particles that didn't self-interfere (that is, "behaved like particles"). In principle this would work even with tennis balls.

    In practice, it is impossible to build this perfect experimental setup, so we never get a truly perfect interference pattern. As we move further away from the ideal the interference pattern gets weaker and weaker as we get more contributions from particles that don't self-interfere. So there's no single point at which the experiment breaks down: as Matteo137 says, it depends on how good and isolated your experiment is.
  5. Mar 4, 2015 #4
    Thank U for clearifying my thoughts. It is very hard to phrase a proper question in QM, when my deeper knowledge of the subject is rather .....shallow.
    Keep up the good flow.):):
  6. Mar 4, 2015 #5
    Txs matteo137. U keep up your good postings and I will enjoy reading....Thomas
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