How much a Quantum Measurement is Informative?

TL;DR

This paper investigates the informational power of quantum measurements, defining it as the maximum classical information extractable, and explores its properties, additivity, and analytical calculation in symmetric cases.

Contribution

It introduces the concept of informational power as a measure of quantum measurement informativeness and analyzes its properties and calculation methods.

Findings

Informational power is additive and equals the classical capacity of a quantum-classical channel.

Symmetry in measurements allows analytical derivation of informational power.

The paper provides examples illustrating the calculation of informational power.

Abstract

The informational power of a quantum measurement is the maximum amount of classical information that the measurement can extract from any ensemble of quantum states. We discuss its main properties. Informational power is an additive quantity, being equivalent to the classical capacity of a quantum-classical channel. The informational power of a quantum measurement is the maximum of the accessible information of a quantum ensemble that depends on the measurement. We present some examples where the symmetry of the measurement allows to analytically derive its informational power.