gusucode.com > qit_matlab_0.10.0工具箱源码程序 > qit/@state/negativity.m
function N = negativity(s, sys) % NEGATIVITY Negativity of the state. % N = negativity(s, sys) % % Returns the negativity of the state s wrt. the partitioning % given by the listing of subsystems in the vector sys. %! A. Peres, "Separability Criterion for Density Matrices", PRL 77, 1413 (1996). %! M. Horodecki et al., "Separability of Mixed States: Necessary and Sufficient Conditions", Physics Letters A 223, 1-8 (1996). % Ville Bergholm 2008-2014 if (nargin < 2) error('Need the partitioning.') end s = ptranspose(s, sys); % partial transpose the state x = svd(s.data); % singular values N = (sum(x) -1) / 2;