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Bound Electrons and Spintronics

  1. Aug 1, 2003 #1
    I was recently reading an article about how quantum computer scientists have found a way to infuence the spin of electrons, http://www.aip.org/enews/physnews/2002/split/595-2.html,

    My question is, I know that for instance, if two electrons were in the same atom of ground state He, the electrons must have different spins, but because of the Heisenburg Uncertainty Principle, there is only a 50% chance that either electron has either spin. My question is, if these two electrons were taken away from the He atom and one was placed in a quantum computer where its spin was changed, the changing of its spin would not have any impact on the spin of the other electron would it? I mean, once the two electrons are taken away, they are no longer bound, are they?
  2. jcsd
  3. Aug 2, 2003 #2
    anybody know?
  4. Aug 3, 2003 #3
    I'm not sure in this particular case, but I think you mean quantum entanglement.
  5. Aug 3, 2003 #4
    correct, that's the right word, but my question is, are the electrons still entangled after they are separated?
  6. Aug 3, 2003 #5
    I don't know under what circumstances a pair of electrons will become entangled, but if we assume they are the moment they're removed I'm almost certain that they will stay that way forever.
  7. Aug 3, 2003 #6


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    Well basically what you're looking at is a case of two entangled electrons with opposite spin. Once they are removed from each other they are still entangled, so a measurement of one of them's spin will also detrmine the other ones spin, so they are still 'bonded'. However if you reverse the spin of one of the electrons without measuring it, they are still entangled. However, instead of the measuremnt of one electron defining the spin of the other electron as the opposite of that measurement, a measurment of one electron's spin will mean that the other one will have the same spin as the measured electron.

    In summary, they are still entangled and they both still have a 50-50 chance of having either spin, but this time when one is measured they both will have the same spin.
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