Solution
= Solution
Tracing out $B$ gives $\rho_A=I/2$. Its <Von Neumann entropy> is $-\operatorname{tr}\rho_A\log_2\rho_A=1$, and $\operatorname{tr}\rho_A^2=1/2$, so it is mixed.
= Solution
Tracing out $B$ gives $\rho_A=I/2$. Its <Von Neumann entropy> is $-\operatorname{tr}\rho_A\log_2\rho_A=1$, and $\operatorname{tr}\rho_A^2=1/2$, so it is mixed.