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## Main Question or Discussion Point

I have a question about density matrices. Is there a way to deduce the purity of the density matrix just by inspection?

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- Thread starter Lamont1986
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I have a question about density matrices. Is there a way to deduce the purity of the density matrix just by inspection?

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strangerep

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I don't think you can deduce it just by inspection. One needs to at leastI have a question about density matrices. Is there a way to deduce the purity of the density matrix just by inspection?

calculate [itex]\rho^2[/itex] and check that it has unit trace.

Cf. Ballentine pp 51-52.