Information capacity of quantum observable

Abstract

In this paper we consider the classical capacities of quantum-classical channels corresponding to measurement of observables. Special attention is paid to the case of continuous observables. We give the formulas for unassisted and entanglement-assisted classical capacities $C,C_{ea}$ and consider some explicitly solvable cases which give simple examples of entanglement-breaking channels with $C<C_{ea}.$ We also elaborate on the ensemble-observable duality to show that $C_{ea}$ for the measurement channel is related to the $\chi$-quantity for the dual ensemble in the same way as $C$ is related to the accessible information. This provides both accessible information and the $\chi$-quantity for the quantum ensembles dual to our examples.

13 pages. New section and references are added concerning the ensemble-observable duality

References in corpus (4)

• Remarks on the classical capacity of quantum channel
• Informational power of quantum measurements
• Optimal signal states for quantum detectors
• Entropy reduction of quantum measurements

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