gusucode.com > qit_matlab_0.10.0工具箱源码程序 > qit/+invariant/max_concurrence.m
function C = max_concurrence(c) % MAX_CONCURRENCE Maximum concurrence generated by a two-qubit gate. % C = max_concurrence(U) % gate % C = max_concurrence(c) % canonical invariants % % Returns the maximum concurrence generated by the two-qubit % gate U, starting from a tensor state. % % Alternatively, U may be given in terms of a vector of three % canonical local invariants. %! B. Kraus and J. I. Cirac, "Optimal creation of entanglement using a two-qubit gate", PRA 63, 062309 (2001). % Ville Bergholm 2006-2010 if (size(c, 2) == 4) % gate into corresponding invariants c = invariant.canonical(c); end temp = circshift(c, [0, 1]); C = max(abs(sin(pi*[c-temp, c+temp])), [], 2);