Constraint Dynamics and Tracking Control to Coherence of aThermal Dissipative Qubit

Abstract

Constraint dynamics and tracking control strategy to stabilize thecoherence of a decoherent system is applied to a dissipative qubitsystem at a finite temperature. By using a control field dependenton the dynamical state of the qubit via the constraintequations, we show that the coherence of the qubit can be preservedwithin a finite time duration by the feedback effect of the qubitsystem. It is also shown that the temperature plays a negative roleto this coherence control strategy.