- #1
barnflakes
- 156
- 4
Can someone help me prove that [itex]tr(\rho^2) \leq 1[/itex] ?
Using that [tex]\rho = \sum_i p_i | \psi_i \rangle \langle \psi_i |[/tex]
[tex]\rho^2 = \sum_i p_i^2 | \psi_i \rangle \langle \psi_i |[/tex]
[tex]tr(\rho^2) = \sum_{i, j} p_i^2 \langle j | \psi_i \rangle \langle \psi_i | j \rangle[/tex]
Where do I go from here? Thanks guys.
Using that [tex]\rho = \sum_i p_i | \psi_i \rangle \langle \psi_i |[/tex]
[tex]\rho^2 = \sum_i p_i^2 | \psi_i \rangle \langle \psi_i |[/tex]
[tex]tr(\rho^2) = \sum_{i, j} p_i^2 \langle j | \psi_i \rangle \langle \psi_i | j \rangle[/tex]
Where do I go from here? Thanks guys.