Abstract: Quantum constraint dynamics and tracking control strategy to stabilize the coherence of a decoherent system is applied to a dissipative qubit system at a finite temperature. By using a control field dependent on the dynamical state of the qubit through the constraint equations, we show that the quantum state of the qubit can be preserved within a finite time duration by the feedback effect of the qubit system. It is also shown that the temperature plays a negative role in the control strategy.

Keywords: 
• quantum constraint dynamics /
• control of the dissipative qubit /
• tracking control strategy /
• feedback effect from the qubit system