Quantum phase expectation values of a mesoscopic Josephson junction from quantum current measurements

摘要

A simple way to acquire information on the mean values of the phase operators sin #phi# and cos #phi# of an ultrasmall Josephson junction prepared in an arbitrary pure or not state is reported. Our proposal exploits the recently predicted occurrence of current spikes in the I-V characteristic of an mesojunction irradiated by a quantum single-mode low-intensity coherent electromagnetic field. A necessary condition for the validity of our treatment is presented and discussed.