01581nas a2200169 4500008003900000245006600039210006600105260001200171300001100183490000700194520107400201100001801275700001701293700002201310700002401332856005501356 2010 d00aMulticopy programmable discrimination of general qubit states0 aMulticopy programmable discrimination of general qubit states c10/2010 a0423120 v823 aQuantum state discrimination is a fundamental primitive in quantum statistics where one has to correctly identify the state of a system that is in one of two possible known states. A programmable discrimination machine performs this task when the pair of possible states is not a priori known but instead the two possible states are provided through two respective program ports. We study optimal programmable discrimination machines for general qubit states when several copies of states are available in the data or program ports. Two scenarios are considered: One in which the purity of the possible states is a priori known, and the fully universal one where the machine operates over generic mixed states of unknown purity. We find analytical results for both the unambiguous and minimum error discrimination strategies. This allows us to calculate the asymptotic performance of programmable discrimination machines when a large number of copies are provided and to recover the standard state discrimination and state comparison values as different limiting cases.1 aSentís, Gael1 aBagan, Emili1 aCalsamiglia, John1 aMuñoz-Tapia, Ramon uhttp://link.aps.org/doi/10.1103/PhysRevA.82.042312