Entangling and decohering influence of noisy perturbations. Stochastic anti-resonance in the time evolution of interacting qubits

We study the entanglement evolution of two coupled qubits in interaction with an external environment and in the presence of an external magnetic field with a stochastic component. The results show the expected degradation of entanglement due to the noise. The new effect is that the time of disentanglement depends in a non-monotonous way on the strength of the noise. We find that it is shortest for an intermediate strength value of the latter. This we call "stochastic anti-resonance". Our results could lead to a better undestanding of noisy perturbations and their role for optimal designing of quantum devices.