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Homework Help: QM: Commutator

  1. Feb 24, 2012 #1
    1. The problem statement, all variables and given/known data

    I want to find the commutator between the momentum operator p and σz, the third Pauli spin matrix. I am not quite sure how to get started on this one. Can I get a push in the right direction?

    For the record, I would say that it is zero since they act on different spaces. Is this correct?

    Best regards,
  2. jcsd
  3. Feb 27, 2012 #2
    I think it's important to specify a direction for the momentum operator. I think that, if it's x-momentum and z-spin and you measure x-momentum to be zero every time then you know that the spin vector is probably in the x direction telling you for sure that z-spin is zero, meaning they don't commute.
  4. Feb 27, 2012 #3
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