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.