Process POVM

• Authors: ZIMAN Mário
• Year of publication: 2009
• MU Faculty or unit: Faculty of Informatics
• Description: We shall introduce the mathematical framework for the description of measurements of quantum processes. Using this framework the process estimation problems can be treated in the similar way as the state estimation problems, only replacing the concept of positive operator valued measure (POVM) by the concept of process POVM (PPOVM). In particular, we will show that any measurement of qudit channels can be described by a collection of effects (positive operators) defined on two-qudit system. However, the effects forming a PPOVM are not normalized in the usual sense. We will briefly demonstrate the usage of this formalism on three particular examples: 1) equivalence of perfect channel discrimination with specific unambiguous state discrimination 2) unambiguous comparison of unitary channels 3) MaxEnt for process estimation from incomplete data In conclusion, we shall discuss the limitations of the PPOVM framework.

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