#### entropy1

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Is it correct that a linear combination of pure states is another pure state?

Can pure (and mixed) states only be expressed in density matrices?

Is a pure state expressed in a single density matrix, whereas mixed states are expressed in a linear combination of several density matrices? Since a pure state is a single density matrix, a linear combination of density matrices would be a linear combination of pure states, and hence a pure state. I don't understand.

I hope someone likes to illuminate me on the matter. Thanks.