We investigate the phenomenon of sudden transition between classical and quantum decoherence in the study of quantum discord for a dissipative cavity QED system, which consists of two noninteracting two-level atoms, each trapped in a dissipative cavity. It is found that the quantum discord between two atoms, which are prepared initially in the X-type quantum states, is not destroyed by the dissipation of the cavities for a finite time interval and the stationary quantum discord can arise in the interaction of atoms with cavities as the time approach to infinite. The transition time is sensitive to the initial state parameter of the two atoms and the mean photon number of the coherent field. Interestingly, the quantum discord between the two atoms is completely unaffected by the dissipation of the cavities if we choose the suitable value of the ratio, which depends on the decay rate of two cavities and the atom-field coupling constant.
We investigate the behavior of quantum steering for a pair of quantum qubits described by the Heisenberg model with external magnetic field and in equilibrium with a reservoir at temperature T . Generally, the steerable weight, which is used to identify the steerability, is suppressed by thermal fluctuations. When the magnetic field is vanishing, the steerable weight behaves like the quantum entanglement. When the magnetic field is not zero, the steerable weight is dramatically different from the other quantities used to identify the quantum correlations between the two spins, i.e., the concurrence, quantum discord and coherence. In the strong magnetic field limit, all of the other quantities we studied are vanishing for the Ising model, while steerable weight tends to one. This demonstrates that the strong transverse magnetic field is helpful to preserve the quantum steerability of the Ising model.
We study the dynamics of quantum discord and entanglement between a superconducting qubit and a data bus, which is driven by a controllable time-dependent electromagnetic field, in the presence of phase decoherence and find that the quantum discord and entanglement remain at a stationary non-zero value for long time evolution. It is shown that the amount of stationary quantum discord and entanglement can be enhanced by applying the time-dependent electromagnetic field. stationary quantum discord, stationary entanglement, time-dependent electromagnetic field
We propose a scheme of entanglement transfer through two independent arrays of cavities coupled by optical fibers when each of the cavities contains a single two-level atom. We study the entanglement dynamics of the transferred states and find the explicit expression for the density matrix and concurrence. It is shown that the amount of the transferred entanglement has a direct connection with the target states and the lengths of the arrays of cavities. Moreover, the influence of the initial states and the length of the arrays of cavities on the phenomenon of entanglement sudden death is also investigated.
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