gusucode.com > qit_matlab_0.10.0工具箱源码程序 > qit/@state/var.m
function x = var(s, A) % VAR Variance of an observable in the state. % x = var(s, A) % % Returns the variance of observable A in the state s. % A has to be Hermitian. % Ville Bergholm 2009 x = ev(s, A^2) - ev(s, A)^2;