Trade-off between information and disturbance in qubit thermometry

TL;DR

This paper investigates the fundamental balance between information gain and disturbance in qubit thermometry using quantum estimation theory, identifying optimal measurements and conditions for efficiency.

Contribution

It explicitly characterizes efficient measurements in qubit thermometry for various disturbance measures and establishes commutativity as a necessary condition for efficiency.

Findings

Efficient measurements vary with the disturbance measure chosen.

Commutativity between measurement operators and the equilibrium state is necessary for efficiency.

The study provides explicit forms of optimal measurements for different disturbance metrics.

Abstract

We address the trade-off between information and disturbance in qubit thermometry from the perspective of quantum estimation theory. Given a quantum measurement, we quantify information via the Fisher information of the measurement and disturbance via four different figures of merit, which capture different aspects (statistical, thermodynamical, geometrical) of the trade-off. For each disturbance measure, the efficient measurements, i.e. the measurements that introduce a disturbance not greater than any other measurement extracting the same amount of information, are determined explicitly. The family of efficient measurements varies with the choice of the disturbance measure. On the other hand, commutativity between the elements of the probability operator-valued measure (POVM) and the equilibrium state of the thermometer is a necessary condition for efficiency with respect to any figure of disturbance.