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Inspection of the Density Matrix

  1. Mar 31, 2010 #1
    I have a question about density matrices. Is there a way to deduce the purity of the density matrix just by inspection?

  2. jcsd
  3. Mar 31, 2010 #2


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    Science Advisor

    I don't think you can deduce it just by inspection. One needs to at least
    calculate [itex]\rho^2[/itex] and check that it has unit trace.
    Cf. Ballentine pp 51-52.
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