Continuous measurements in a composite quantum system and possible exchange of information between its parts

Abstract

We study the influence of a continuous measurement in a composite quantum system C on the evolution of the states of its parts. It is shown that the character of the evolution (decoherence or recoherence) depends on the type of measured quantity and on the initial state of the system. A number of conditions under which the states of the subsystems of C decohere during the measuring process are established. We propose a model of the composite system and specify the observable the measurement of which may result in the recoherence of the state of one of the subsystems of C. In the framework of this model we find the optimal regime for the exchange of information between the parts of C during the measurement. The main characteristics of such a process are computed. We propose a scheme of detection of the recoherence under the measurement in a concrete physical experiment.