On the Optimality of Square Root Measurements in Quantum State Discrimination

Understand

Distinguishing assigned quantum states with assigned probabilities via quantum measurements is a crucial problem for the transmission of classical information through quantum channels.

• Measurement operators maximizing the probability of correct discrimination have been characterized by Helstrom, Holevo and Yuen since 1970's.
• On the other hand, closed--form solutions are available only for particular situations enjoying high degrees of symmetry.
• As a suboptimal solution to the problem, measurement operators, directly determined from states and probabilities and known as square root measurements (SRM), were introduced by Hausladen and Wootters.