title: Time-resolved measurement of a charge qubit.
abstract: We propose a scheme for monitoring coherent quantum dynamics with good time-resolution and low backaction, which relies on the response of the considered quantum system to high-frequency ac driving. An approximate analytical solution of the corresponding quantum master equation reveals that the phase of an outgoing signal, which can directly be measured in an experiment with lock-in technique, is proportional to the expectation value of a particular system observable. This result is corroborated by the numerical solution of the master equation for a charge qubit realized with a Cooper-pair box, where we focus on monitoring coherent oscillations.
authors.affiliation: Institut für Physik, Universität Augsburg, Universitätsstrasse 1, D-86135 Augsburg, Germany.
authors.forename: Georg M
authors.initials: GM
authors.lastname: Reuther
authors.forename: David
authors.initials: D
authors.lastname: Zueco
authors.forename: Peter
authors.initials: P
authors.lastname: Hänggi
authors.forename: Sigmund
authors.initials: S
authors.lastname: Kohler