Anomalous decoherence effects in driven coupled quantum spin systems

We discuss anomalous decoherence effects at zero and finite temperatures in driven coupled quantum spin systems. By numerical simulations of the quantum master equation, it is found that entanglement dynamics of two coupled spin qubits is qualitatively affected by the noise strength. The effects of noise strength, the detuning and finite temperature of independent boson reservoirs on the steady state entanglement are addressed in detail. Pumped by an external field drive, non-trivial steady states can be found, the steady state entanglement increases monotonically up to a maximum at certain optimal noise strength and decreases steadily for higher values. Furthermore, increasing the detuning can not only induce but also suppress steady state entanglement, which depends on the value of noise strength. At last, we delimit the border between presence or absence of steady state entanglement in the related finite temperatures.