gusucode.com > qit_matlab_0.10.0工具箱源码程序 > qit/@state/ev.m
function x = ev(s, A) % EV Expectation value of an observable in the state. % x = ev(s, A) % % Returns the expectation value of observable A in the state s. % A has to be Hermitian. % Ville Bergholm 2008 if is_ket(s) % state vector x = s.data' * A * s.data; else % state operator x = trace(A*s.data); end x = real(x); % Hermitian observable