Information gain versus coupling strength in quantum measurements

TL;DR

This paper explores how the information gained from quantum measurements depends on the interaction strength between the system and the measuring device, revealing monotonic and complementary behaviors in qubit systems.

Contribution

It introduces a method to calculate information gain as a function of coupling strength and demonstrates its monotonic increase and complementarity in specific measurement directions.

Findings

Information gain increases monotonically with coupling strength.

Measurement along one axis reduces information gain along the orthogonal axis.

Complementarity of information gain in different measurement directions.

Abstract

We investigate the relationship between the information gain and the interaction strength between the quantum system and the measuring device. A strategy is proposed to calculate the information gain of the measuring device as the coupling strength is a variable. For qubit systems, we prove that the information gain increases monotonically with the coupling strength. It is obtained that the information gain of the projective measurement along the x-direction reduces with the increasing of the measurement strength along the z-direction, and a complementarity of information gain in the measurements along those two directions is presented.