Generalized measurement postulate
= Generalized measurement postulate
A generalized quantum measurement is specified by operators $M_i$ satisfying $\sum_iM_i^\dagger M_i=I$. On input $\rho$, outcome $i$ has probability $\operatorname{Tr}(M_i^\dagger M_i\rho)$ and conditional state $M_i\rho M_i^\dagger/\operatorname{Tr}(M_i^\dagger M_i\rho)$.