Narrow Results

A system of a two level atom interacting with a multi-photon single mode of electromagnetic field and damped with a phase reservoir is considered. The squeezed coherent state is taken as initial field state. The exact solution of the master equation in the case of a high-Q cavity is found. The effects of phase damping on the temporal evolution of some quantitative entanglement measures between the states of the system are investigated.

The entanglement in a system of a single two-level trapped ion and a single-mode quantized field in a coherent state inside a phase-damped cavity is investigated. Analytic results under certain parametric conditions are obtained, by means of which we analyze the influence of dissipation on the atomic Fisher information and its marginal distribution. An interesting relation between the temporal entanglement sudden birth, sudden death, atomic Fisher information and the dissipation effect is observed.

We consider an application of the Burshtein equation to Jaynes–Cummings interactions possessing a field-noise modeled as the two-state random phase telegraph noise in the presence of two extra physical cases. These cases are the incorporation of respectively, (i) the atomic-noise regarded as phase damping and (ii) the Stark shift. We obtain the exact solutions to these systems to investigate the dynamical behavior of their entanglements. We observed those for the case (i), phase damping does not affect the field-noise-induced nonmonotonic behavior of the entanglement other than the amplitude of the entanglement and the optimal value of the mean dwell time at which the minimum entanglement occurs. Also, phase damping naturally accelerates the decoherence of the entanglement caused by the field-noise. For the case (ii), the Stark shift reduces the maximum value of the entanglement and induce more oscillations of the entanglement in time under the influence of the noise. This shift delays the time for the complete destruction of the entanglement and restrains the influence of the noise. We also consider the time-average of the entanglement as depending on the shift parameters. The average entanglement is a nonmonotonic function of these parameters.

The quantum nonlocal correlation between an atom and coherent field is described quantitatively in terms of multi-photon and phase damping processes. Especially, considering a two-level atom interacts with a single-mode quantized field in a coherent state inside a phase-damped cavity, and taking into account the number of multi-photon transitions and phase damping effect, the entanglement is investigated during the time evolution as a function of involved' parameters in the system. The results show that the enhancement of the transitions are very useful in generating a high amount of entanglement. Due to the significance of how a system is quantum correlated with its environment in the construction of a scalable quantum computer, the entanglement dynamics between the bipartite system with its environment is evaluated and investigated during the dissipative process. Finally, the physical interpretation of the correlation behaviors between the subsystems is explained through the statistical properties of the field.

An analytical description of a superconducting (SC) phase qubit coupled to a torsional resonator, which is damped by a dispersive reservoir, is presented based on the master equation. Therefore, the effect of the qubit phase damping on the dynamical behavior of the entanglement, purity loss and qubit inversion are investigated. It is found that the collapse and revival phenomena of qubit inversion are very sensitive not only to the damping parameter but also to the frequency detuning and the qubit distribution angle of the initial state. It is interesting to note that the purity of the state of the SC-qubit, which is measured by von Neumann entropy, can be completely lost due to the dispersive reservoir parameter. Because of the existence of dispersive reservoir, the von Neumann entropy cannot be a measure for the entanglement in open system. So, the negative eigenvalue of the partially transposed density matrix of qubit-resonator system is used to quantify the entanglement. For certain parameter sets, it is possible to control the degree and the dynamics of entanglement between the qubit and the torsional resonator.