On the role of the measurement apparatus in quantum measurements

TL;DR

This paper investigates how the outcomes of quantum measurements can be influenced by the state of the measurement apparatus, highlighting the robustness of certain measurement bases and the manipulability under different interaction models.

Contribution

It introduces models of quantum measurement involving decoherence and compares robustness versus manipulability of outcomes depending on the interaction type.

Findings

Measurement outcomes along the pointer basis are robust against bath state variations.

Heisenberg interactions allow significant manipulation of measurement results by changing the bath state.

Long interaction times are crucial for obtaining measurement outcomes in the models studied.

Abstract

We study the extent to which the outcomes of a quantum measurement can be manipulated by changing the state of the measurement apparatus. The measurement process is modeled as decoherence induced by the experimenter, to gain knowledge about a particular system. The measurement apparatus is assumed to contain a large number of degrees of freedom, and the measurement outcomes are obtained by looking at the long interaction time limit. We study two cases which show contrasting behaviour. With a fixed axis coupling, the measurement is performed along the pointer basis with a high degree of robustness, for a wide variety of bath states. In a second model with Heisenberg interactions, the measurement outcomes can be altered considerably by changing the state of the bath.