Dynamics by measurement: Aharonov’s inverse quantum Zeno effect

The quantum Zeno effect is known as the inhibition of a system's reversible dynamics by frequent measurements. Aharonov and Vardi [Phys. Rev. D 21, 2235 (1980)] proposed a scheme intimately related to the quantum Zeno effect. They showed that, by performing a dense sequence of measurements along a presumed path, the system is found to follow this---arbitrarily chosen---trajectory. The proof was based on the von Neumann projection hypothesis. In this paper we investigate whether this effect still holds if we model a realistic measurement process instead of the artificial instantaneous von Neumann collapse. We test the orientation of the Bloch vector of a two-level system using a third level and resonance fluorescence as the measuring apparatus. Therefore we are able to use a dynamical collapse governed by the three-level master equations. We show that a sequence of orientation measurements designed to monitor a particular trajectory indeed induces a dynamics exactly along this trajectory.