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Decoherence suppression of a dissipative qubit by the non-Markovian effect

We evaluate exactly the non-Markovian effect on the decoherence dynamics of a qubit interacting with a dissipative vacuum reservoir and find that the coherence of the qubit can be partially trapped in the steady state when the memory effect of the reservoir is considered. Our analysis shows that it is the formation of a bound state between the qubit and its reservoir that results in this residual coherence in the steady state under the non-Markovian dynamics. A physical condition for the decoherence suppression is given explicitly. Our results suggest a potential way to decoherence control by modifying the system-reservoir interaction and the spectrum of the reservoir to the non-Markovian regime in the scenario of reservoir engineering.