Pretty good measurement
= Pretty good measurement
{title2=PGM}
{wiki}
For ensemble $\{p_j,\rho_j\}$ with average $\bar\rho=\sum_jp_j\rho_j$, the pretty good measurement has $M_j=\bar\rho^{-1/2}p_j\rho_j\bar\rho^{-1/2}$ on the support of $\bar\rho$.