Fidelity of asymmetric dephasing channels

We study the properties of the fidelity of one-qubit operations in a noisy channel and reveal its properties in dependence on coupling to the outer environment. We show that for an asymmetric qubit-environment coupling, the fidelity can be improved by a tuning of the external parameters acting on the qubit energy splitting. In particular, for the case of a spin qubit, the fidelity can be improved by an appropriate tuning of the external magnetic field. We observe that within tailored parameter regimes, the fidelity (typically being oscillatory) evolves monotonically and remains significant in the long-time regime, for both an environment prepared in vacuum and coherent states. This result holds true also for the entanglement fidelity of the two-qubit system.