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Singlet Pair Properties

  1. Oct 28, 2014 #1


    Staff: Mentor

    I just studied about the QM of singlet spin pairs. I have additional questions. Neither Wikipedia, nor past threads on this forum seem to address the questions.

    1) A pair of electrons forming a singlet pair A. Can the pair be split again into non-entangled electrons? If yes how; just hit it with a photon?

    2) Suppose we have two singlet pairs A and B. Can they be brought together without obeying the Fermi exclusion principle?

    3) Can we entangle pairs A and B into a quantum system with 4 electrons and 16 spin states?
  2. jcsd
  3. Oct 28, 2014 #2


    User Avatar
    Science Advisor

    1) Yes. Easiest is to measure the spin of one electron (along any axis).

    2) The exclusion principle always holds.

    3) Assuming we have a universal set of quantum gates with which to manipulate the spins, then we can put them into any state we like, such as the 4-particle GHZ state.
  4. Oct 28, 2014 #3


    Staff: Mentor

    Thank you Avodyne. Regarding Pauli Exclusion, I was wondering if a singlet pair can behave like a boson, even though the electrons are fermions.
  5. Oct 28, 2014 #4


    User Avatar
    2017 Award

    Staff: Mentor

    It can - superconductors or superfluidity of He3 work that way, for example. That does not violate the uncertainty principle - no two fermions have the same state.
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