M. Hashem

Entanglement and purity loss for the system of two 2-level atoms in the presence of the Stark shift

In this paper, we have presented an analytic solution for two 2-level identical atoms interacting with a single-mode quantized radiation field, taking into account the level shifts produced by Stark shift. We assume that the two atoms are initially prepared in the exited state and the field in a coherent state. We investigate the purity loss of the system and bipartite partitions of the system. The effects of the Stark shift on the purity loss of the system and different bipartite partitions of the system (field-two atoms, atom-(field+atom)) through the tangles are considered. In particular, the effect of the Stark shift on the amount of entanglement between atoms and field is evaluated by the negativity.

Stationary discord and non-local correlations via qubit damping

By using quantum discord (QD), measurement induced non-locality (MIN) and negativity (QE), quantum correlation and entanglement are investigated for two qubits in two different cases for the initial two qubit Werner states, taking into account the influence of qubit damping. It is shown that there is no asymptotic decay for MIN while asymptotic decay exists for QD and QE. Quantum correlations cannot be strengthened by introducing the damping. The appearance time of stationary correlations gets shorter with the increase in the damping parameter. Finally, a uniform damping qubit can affect the stationary correlations when the qubits are initially in an entangled state.

Influence of the phase damping for two-qubits system in the dispersive reservoir

An analytical solution of the master equation for two qubits-field system in the dispersive reservoir are investigated, the qubits are initially in werner states. Under the influence of the damping we investigate the quantum correlation in a two-qubit based on measurement-induced disturbance (MID). We compare MID and entanglement measured by negativity and illustrate their different characteristics. We find the effect of damping on MID is weaker than negativity. Negativity will experience a sudden transition but this will not happen for MID.

Control of purity and entanglement for two spatially two-separated qubits via phase damping

Control of purity and entanglement of two two-qubits dispersively coupled to a field with a reservoir are investigated. Initially the qubits are entangled, while the field is either in a coherent state or a statistical mixture of two coherent states. For an alternative entanglement measure we calculate the negativity of the eigenvalues of the partially transposed density matrix. A measure related to the mutual entropy, namely the index of entropy, is employed to measure the entanglement. Its results agree well with the negativity. It is found that the entanglement and purity have strong sensitivity to phase damping. The asymptotic behaviour of the states of the field, the two two-qubits, and the total system fall into mixed states.

Quantum entanglement in a system of two moving atoms interacting with a single mode field

We investigate the quantum entanglement in a system of two moving atoms interacting with a single mode field. An analytical solution for this system is obtained when both atoms are initially in the excited state and the field is in a coherent state. We study the effects of atomic motion and other parameters on the entanglement of the system and different bipartite partitions of the system (field–two atoms, atom–(field+atom)) through the tangles. The effect of atomic motion on the amount of entanglement between atoms and the field is also evaluated through the negativity. The results show that atomic motion leads to the periodic death and anabiosis of the entanglement between two moving atoms, and the time of the death and the amplitude of the anabiosis of the entanglement between two moving atoms depend on the coupling constant of two moving atoms and the parameter of the mode field.

Quantum phase properties and Wigner function of two 2-level atoms in the presence of the Stark shift for the Tavis–Cummings model

An analytical solution for two identical 2-level atoms interacting with a single-mode quantized radiation field in the presence of the Stark shift is obtained. Both atoms are prepared initially in the excited state and the field in a coherent state. The phase distribution, phase variance and Wigner function are investigated. The influence of the Stark shift on the Wigner function and the phase properties is analysed.

The behavior of the generated quantum correlations in two-SC-qubit system strongly coupled with a SC cavity in the presence of local noise

An analytical solution of the master equation that describes two charge superconducting qubits interacts with a single microwave cavity field mode within dispersive approximation and dissipation region of the qubit damping. Quantum correlations of a general two-qubit state (non-X-state) are studied by using three different quantum correlation quantifiers: measurement-induced non-locality, geometric quantum discord and logarithmic negativity. It is shown that the quantum correlations are sensitive to the choice of the parameters of the qubit dissipation rate, coherent state intensity and the initial qubit distribution angle. The generated oscillatory behavior of quantum correlations is different and more prominent as the noise rate decreases at the considered period of time.