Preserving quantum correlations in two superconducting qubits by applying time-dependent magnetic fields Y.Q. Zhang, Q.L. He, Q.X. Mu and J.C. Liu Eur. Phys. J. D, 66 8 (2012) 210 Published online: 16 August 2012 DOI: 10.1140/epjd/e2012-30105-6