Abstract: In this paper, problems of compensation for purity of particle in a mixed state and counteraction against decoherence process are investigated. A new method utilizing an assistant particle and its interactions with the target particle to compensate purity and coherence is proposed. Compensations for two different situations are considered: purity compensation for the target particle in a mixed state and counteraction against decoherence process. Conditions of the assistant particle for each situation are obtained. System numerical simulations are done to validate the validity of the method proposed.

Key words: quantum control, decoherence control, purity compensation, coherence compensation, particle interaction