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Qubit spin convention

  1. Feb 27, 2013 #1
    This is a bit embarrassing, but by convention does [itex]|0> = (1,0)^T[/itex] and
    [itex]|1>=(0,1)^T[/itex], where we are in the basis of the eigenvectors of [itex]\sigma_{z}[/itex]?
  2. jcsd
  3. Feb 27, 2013 #2


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    The notation is a bit misleading, since [itex]|0\rangle[/itex] is most commonly used to denote the ground state of a system. However, in the absence of an external field, both spin states have the same energy. The justification for using the notation is the convention that in a communications protocol, one state must be chosen to signal binary 0 vs binary 1 for the other state. There's no particular reason to choose one over the other, but indeed the spin up state is conventionally chosen to be the off bit, see http://en.wikipedia.org/wiki/Qubit#Physical_representation
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