Tight bounds on accessible information and informational power

摘要: The accessible information quantifies the amount of classical that can be extracted from an ensemble quantum states. Analogously, informational power by a measurement. For both quantities, we provide upper and lower bounds depend only on dimension system, prove their tightness. In case symmetric informationally complete (SIC) ensembles measurements, stronger are provided tightness proved for qubits qutrits. From our bounds, notice, perhaps surprisingly, statistics generated SIC or measurements in arbitrary dimension, though optimal tomographic purposes, fact never contain more than just one bit information, rest being constituted completely random bits. On other hand, obtain explicit strategy beating so-called pretty-good extraction mutual measurements.