Measurement Induced Dephasing and Suppression of Persistent Current in a Lattice Ring

We investigate the effect of measurement on the persistent current density in a lattice ring penetrated by an Aharonov-Bohm flux and coupled to a quantum dot which is continuously monitored by a point contact detector. It is demonstrated by explicit analysis of the time-evolution of current density that the persistent current in the lattice ring is suppressed completely due to dephasing of quantum states induced by an analogous which-way-measurment that whether or not the electron is localized on the quantum dot. Practical experiments to observe the measurment induced dephasing is proposed.