Unambiguous discrimination of mixed states: A description based on system-ancilla coupling
Xiang-Fa Zhou, Yong-Sheng Zhang, Guang‐Can Guo · Physical Review A · 2007
We propose a general description for the unambiguous discrimination of mixed states according to the system-environment coupling, and present a procedure to reduce this to a standard semidefinite programming problem. In the two-state case, we introduce the canonical vectors and partly simplify the problem to the case of discrimination between pairs of canonical vectors. By considering the positivity of the $2\ifmmode\times\else\texttimes\fi{}2$ matrices, we obtain a series of new upper bounds for the total success probability, which depends on both the prior probabilities and specific state structures.