entvn.m

计算冯。诺易曼熵的程序

function x = entVN(p)

% ENTVN   von-Neumann entropy
% requires: nothing
% author: Toby Cubitt
%
%     ENTVN(RHO) gives the von-Neumann entropy of density matrix RHO
%     (note: this is NOT the entropy of the reduced density matrix)


e = eig(p);
x = -e'*log2(e+(e==0));