Comment on "Continuous simultaneous measurement of position and momentum of a particle"

Abstract

In a recent paper, [Gampel, F. and Gajda, M., Phys. Rev. A 107, 012420, (2023)], the authors claimed they are proposing a new model to explain the existence of classical trajectories in the quantum domain. The idea is based on simultaneous position and momentum measurements and a "jump Markov process". Consequently, they have interpreted the emergence of classical trajectories as sets of detection events. They successfully implemented the model for a free particle and for one under a harmonic potential. Here, we show that the continuous observation limit is a realization of a coherent semiclassical expansion; Also, as has already been demonstrated, the jump process is not necessary and is not observable. In other words, the collapse, as they propose, is a non-go theorem; even if it is real, it can not be measured under the needed assumptions to obtain Newtonian classical dynamics.