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Quantum measurements have intrinsic properties which seem incompatible withour everyday-life macroscopic measurements. Macroscopic Quantum Measurement(MQM) is a concept that aims at bridging the gap between well understoodmicroscopic quantum measurements and macroscopic classical measurements. Inthis paper, we focus on the task of the polarization direction estimation of asystem of $N$ spins $1/2$ particles and investigate the model some of usproposed in Barnea et al., 2017. This model is based on a von Neumann pointermeasurement, where each spin component of the system is coupled to one of thethree spatial components direction of a pointer. It shows traits of a classicalmeasurement for an intermediate coupling strength. We investigate relaxationsof the assumptions on the initial knowledge about the state and on the controlover the MQM. We show that the model is robust with regard to theserelaxations. It performs well for thermal states and a lack of knowledge aboutthe size of the system. Furthermore, a lack of control on the MQM can becompensated by repeated "ultra-weak" measurements.

Robust Macroscopic Quantum Measurements in the presence of limited control and knowledge