Sudden death and rebirth of Entanglement for Different Dimensional Systems driven by a Classical Random External Field

The entangled behavior of different dimensional systems driven by classical external random field is investigated. The amount of the survival entanglement between the components of each system is quantified. There are different behaviors of entanglement that come into view decay, sudden death, sudden birth and long-lived entanglement. The maximum entangled states which can be generated from any of theses suggested systems are much fragile than the partially entangled ones. The systems of larger dimensions are more robust than those of smaller dimensions systems, where the entanglement decay smoothly, gradually and may vanish for a very short time. For the class of $2\times 3$ dimensional system, the one parameter family is found to be more robust than the two parameters family. Although the entanglement of driven $2 \times 3$ dimensional system is very sensitive to the classical external random field, one can use them to generate a long-lived entanglement

A treatment of the quantum partial entropies in the atom-field interaction with a class of Schrodinger cat states

This communication is an enquiry into the circumstances under which entropy and subentropy methods can give an answer to the question of quantum entanglement in the composite state. Using a general quantum dynamical system we obtain the analytical solution when the atom initially starts from its excited state and the field in different initial states. Different features of the entanglement are investigated when the field is initially assumed to be in a coherent state, an even coherent state (Schrodinger cate state) and a statistical mixture of coherent states. Our results show that the setting of the initial state and the Stark shift play important role in the evolution of the sub-entropies and entanglement.Comment: 12 pages, 3 figures, Accepted for publication in International Journal of Quantum Information Jan. (2005

Multi-Qubit Dynamical Quantum Search Algorithm with Dissipation

We invoke an efficient search algorithms as a key challenge in multi-qubit quantum systems. An original algorithm called dynamical quantum search algorithm from which Grover algorithm is obtained at a specified time is presented. This algorithm is distinguished by accuracy in obtaining high probability of finding any marked state in a shorter time than Grover algorithm time. The algorithm performance can be improved with respect to the different values of the controlled phase. A new technique is used to generate the dynamical quantum gates in the presence of dissipation effect that helps in implementing the current algorithm.Comment: 19 pages, 7 figure

Entanglement manipulation for mixed states in a multilevel atom interacting with a cavity field

We derive an explicit formula for an entanglement measure of mixed quantum states in a multi-level atom interacting with a cavity field within the framework of the quantum mutual entropy. We describe its theoretical basis and discuss its practical relevance (especially in comparison with already known pure state results). The effect of the number of levels involved on the entanglement is demonstrated via examples of three-, four- and five-level atom. Numerical calculations under current experimental conditions are performed and it is found that the number of levels present changes the general features of entanglement dramatically.Comment: 10 pages, 3 figure

Wigner function of noisy accelerated two-qubit system

In this manuscript, the behavior of the Wigner function of accelerated and non-accelerated two qubit system passing through different noisy channels is discussed. The decoherence of the initial quantum correlation due to the noisy channels and the acceleration process is investigated by means of Wigner function. The negative (positive) behavior of the Wigner function predicts the gain of the quantum (classical) correlations. Based on the upper and lower bounds of the Wigner function, the entangled initial state loses its quantum correlation due the acceleration process and the strengths of the noisy channels. However, by controlling the distribution angles, the decoherence of these quantum correlation may be suppressed. For accelerated state, the robustness of the quantum correlations contained in the initial state appears in different ranges of the distribution angles depending on the noisy type. For the bit phase flip and the phase flip channels, the robustness of the quantum correlations is shown at any acceleration and large range of distribution angles. However, the fragility of the quantum correlation is depicted for large values for strength of the bit flip channel. Different profiles of the Wigner function are exhibited for the quantum and classical correlations, cup, lune, hemisphere

Wigner function of accelerated and non-accelerated Greenberger Horne Zeilinger State

The Wigner function's behavior of accelerated and non-accelerated Greenberger Horne Zeilinger (GHZ) state is discussed. For the non-accelerated GHZ state, the minimum/maximum peaks of the Wigner function depends on the distribution's angles, where they are displayed regularly at fixed values of the distribution's angles. We show that, for the accelerated GHZ state, the minimum bounds increases as the acceleration increases. The increasing rate depends on the number of accelerated qubits. Due to the positivity/ negativity behavior of the Wigner function, one can use it as an indicators of the presences of the classical/quantum correlations, respectively. The maximum bounds of the quantum and the classical correlations depend on the purity of the initial GHZ state. The classical correlation that depicted by the behavior of Wigner function independent of the acceleration, but depends on the degree of its purity

Effect of an External Magnetic Field on Some Statistical Properties of the 2+1 Dirac-Moshinsky Oscillator

The 2+1 Dirac-Moshinsky oscillator ( 2+1 DMO ) is mapped into the generalized Jaynes-Cummings model (GJCM), in which an external magnetic field is coupled to an external isospin field. The basic equations of model are analytically solved, where the coherent state is considered as an initial state. The obtained results show that the strength of the magnetic field and the coupling parameter of the isospin field play important roles on some statistical properties such as entanglement, population inversion and degree of coherence. It has been shown that these parameters play a rule to increase entanglement and show the collapses and revivals phenomenon.Comment: 21 pages, 8 figures. arXiv admin note: text overlap with arXiv:1812.0026

Wigner distribution function of atomic system interacts locally with a deformed cavity

Wigner distribution function of atomic system interacts locally with a deformed cavity is discussed. It is shown that, the deformed cavity has a destructive effect on the Wigner distribution function, where it decreases as one increases the deformation strength. The upper and lower bounds of the Wigner distribution function depends on the initial state settings of atomic system (entangled/product), the initial values of the dipole-dipole interaction's and detuning parameters, and the external distribution weight and the phase angles. The possibility of suppressing the decay induced by the deformed cavity may be increased by increasing the dipole's strength or the detuning parameter. We show that the distribution angles may be considered as a control external parameters, that maximize/ minimize the Wigner distribution function. This means that by controlling on the distribution angles, one can increase the possibility of suppressing the decoherence induced by the deformed cavity

Generation of maximally entangled states of two cavity modes

In this letter we present a scheme for generating maximally entangled states of two cavity modes which enables us to generate complete set of Bell basis states having rather simple initial state preparation. Furthermore, we study the interaction of a two-level atom with two modes of electromagnetic field in a high Q cavity. The two-level atom acts as a control qubit and the two mode electromagnetic field serves as a target qubit. This simple system of quantum electrodynamics provides us experimentally feasible universal quantum logic gates.Comment: 10 page

Aspects of a Two-Level Atom in Squeezed Displaced Fock States

This paper presents some results on some aspects of the two-level atom interacting with a single-mode with the privileged field mode being in the squeezed displaced Fock state (SDFS). The exact results are employed to perform a careful investigation of the temporal evolution of the atomic inversion, entropy and phase distribution. It is shown that the interference between component states leads to non-classical oscillations in the photon number distribution. At mid revival time the field is almost in the pure state. We have briefly discussed the evolution of the Q function of the cavity field. The connection between the field entropy and the collapses and revivals of the atomic inversion has been established. We find that the phase probability distribution of the field reflect the collapses and revivals of the level occupation probabilities in most situations. The interaction brings about the symmetrical splitting of the phase probability distribution. The general conclusions reached are illustrated by numerical results