Success probabilities for universal unambiguous discriminators between unknown pure states

Abstract

A universal programmable discriminator can perform the discrimination between two unknown states, and the optimal solution can be approached via the discrimination between the two averages over the uniformly distributed unknown input pure states, which has been widely discussed in previous works. In this paper, we consider the success probabilities of the optimal universal programmable unambiguous discriminators when applied to the pure input states. More precisely, the analytic results of the success probabilities are derived with the expressions of the optimal measurement operators for the universal discriminators and we find that the success probabilities have nothing to do with the dimension d while the amounts of the copies in the two program registers are equal. The success probability of programmable unambiguous discriminator can asymptoticly approach to that of usual unambiguous discrimination (state comparison) as the number of copies in program registers (data register) goes to infinity.