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Can macroscopic objects interfere with themselves like quantum particles?

  1. Aug 31, 2011 #1
    Consider this experiment...

    A satellite is put into orbit around mars and the date of the experiment is set for when mars is directly opposite the sun from earth. This puts it about 21 light minutes away from earth. Assuming there are no aliens watching it is absolutely impossible for any observations to be made until the experiment is over. On board this satellite is an electron gun aimed at a pair of slits, as in the classic double slit experiment. If there were a photographic plate behind the slits there would be an interference pattern, but instead there are 2 detectors. If detector A is triggered the satellite launches a missile which goes into orbit traveling from east to west. If detector B is triggered the missile is launched into orbit traveling from west to east. Since no observation of the experiment can possibly be made for 21 minutes the two states should exist in superposition until it is observable. Before that time has expired the 2 possible missile paths cross and the missile "interferes" with itself, just like the electron would have done at the photographic plate.

    So when the results of the experiment are observable from earth does the experimenter see a missile orbiting mars in one direction or other? Or may he see a debris field where the missile impacted itself after traveling both ways around the planet? Or in this instance would "interference" mean something other than an impact, and what would it be?
  2. jcsd
  3. Sep 1, 2011 #2


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    If you are able to shield the macroscopic object from the environment (heat bath, thermal photons, ... ) in order to avoid decoherence - yes; afaik the largest objects for which interference has been shown is C60 fullerene, but I may be wrong.
  4. Sep 1, 2011 #3


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    I think the "record value" was published in Nature Communications this year.

    See S. Gerlich et al., "Quantum interference of large organic molecules", Nature Communications 2, 263;

    The article is free to read. They claim to see interference for objects up 60 Angström in size. For comparison: depending on the definition of size, C60 has a diameter of 7 or 10 Angströms.
  5. Sep 1, 2011 #4
    Hi, mrspeedybob.

    In your configuration, let |A> be probability amplitude for electron to come into detector A. Similarly |B> be probability amplitude for electron to come into detector B. Probability we detect missile going one way is <A|A>. Probability we detect missile going the other way is <B|B>. <A|A> + <B|B> = 1. The magnitudes of <A|A> and <B|B>
    are determined by close investigation of the configuration.

  6. Sep 1, 2011 #5

    Vanadium 50

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    An intelligent observer is not a feature of QM. You're not starting from a good spot.
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