Narrow Results

We examine the impact of the non-Markovian environment on the dynamical behavior of the quantum coherence and entropy squeezing considering a two-level atomic system (qubit) immersed in a reservoir with zero-temperature for two types of non-Markovian environments. We consider a cavity little off-resonance with the transition frequency of the qubit and the case of a non-perfect photonic band gap (PBG). We show that the amount of coherence is dependent on the structure of the environment and influenced through the memory effects. We obtain that the delay and revival of the coherence loss might take place by controlling the detuning of the cavity-qubit system. Whereas, a partial coherence trapping occurs in non-ideal PBG and the decrease of the gap width will destroy the coherence. On the other hand, we show the situation for which the squeezing is occurring and enhanced with respect to the main parameters for the system. Finally, we display the monotonic dependence of the quantum coherence and squeezing on the main model parameters.

The information theoretic concepts are crucial to study the quantum mechanical systems. In this paper, the information densities of ${𝒫}{𝒯}$-symmetric potential have been demonstrated and their properties deeply analyzed. The position space and momentum space information entropy is obtained and Bialynicki-Birula–Mycielski inequality is saturated for different parameters of the potential. Some interesting features of information entropy have been discussed. The variation in these entropies is described which gets saturated for specific values of the parameter. These have also been analyzed for the ${𝒫}{𝒯}$-symmetry breaking case. Further, the entropy squeezing phenomenon has been investigated in position space as well as momentum space. Interestingly, ${𝒫}{𝒯}$ phase transition conjectures the entropy squeezing in position space and momentum space.

In this paper, we quantitatively examine the dynamics of quantum resources, such as quantum coherence, degree of mixedness, fidelity, and the atomic entropy squeezing, in a quantum system of a two-level atom (TLA) driven by a phase noise laser (PNL) within the context of non-Markovian dynamics. The $l_1$ norm is used to quantify coherence, linear entropy to measure the degree of TLA mixedness, and entropy to detect the atomic squeezing. We demonstrate how these quantum resources can be controlled through a suitable selection of model parameters. Furthermore, we provide the optimal conditions required to manipulate these quantum resources based on changes in the damping coupling. Finally, we discuss the relationships among the quantum resources in the present quantum model.

In this contribution, a three level atom in interaction with a two-mode quantized electromagnetic field, initially prepared in an entangled two-mode coherent state, is considered. Through the elimination of an intermediate level using the adiabatic elimination method, a nonlinear Stark shift is introduced. The exact solution of the wave function in the Schrödinger picture is obtained. Some statistical aspects through the effective two-level atom interacting with the two-mode and multiphotons processess with the nonlinear Stark shift are presented. The results are employed to perform a careful investigation of the temporal evolution of the atomic inversion, entropy squeezing and variance squeezing. It has been shown that the system is sensitive to any change in the parameter representation of the Stark shift. General conclusions reached are illustrated by numerical results.

Normal squeezing, variance and entropy squeezing factors based on the Heisenberg uncertainty principle and Shannon information entropy theory, respectively, derived from the entangled states of two-mode coherent states in two-photon processes are numerically investigated through a previously developed generalized nonlinear Jaynes–Cummings two-level spin model. Numerical simulations are performed and discussed for two two-photon model Hamiltonians in both resonant and off-resonant states of the spin system with the bimodal cavity field.

A quantum model for the interaction between asymmetric two two-level atoms and an electromagnetic field is presented. The $k$-photon processes and atom–atom interaction are considered in this quantum model. The wavefunction for asymmetric case of the proposed model is obtained analytically. While, the explicit analytical formula of the wavefunction for symmetric case was calculated in previous works. Initially, the electromagnetic field is in the coherent state and two two-level atoms are identical in the excited states. For the proposed model, some statistical aspects are obtained, such as the linear entropy, atomic population inversion, entropy squeezing, atomic variance and von Neumann entropy. The evaluations of these statistical properties are discussed for the variation in the detuning parameters. Moreover, the nonclassical effects for atom–atom interaction are observed.

In this paper, the interaction between two trap ions with laser beam and electromagnetic field containing the Stark shift terms has been investigated. The analytical solution for the differential equations which describes the system Hamiltonian is obtained. The dynamical behavior for the entanglement, entropy squeezing and purity of system are discussed. Some important physical characteristics such as revivals and collapses for the occupation of the trapped ion, entanglement sudden death (birth) and single trapped ion entropy squeezing are discussed. In addition, the influence of Lamb–Dicke parameter and the initial states on the evolution of the entanglement, linear entropy are studied. Finally, some remarks about the obtained results are given briefly.

We propose a new approach for introducing the long-life information entropy of the interaction between atom and electromagnetic field. Our approach is based on a comparison of the initial state of the field. The field is initialized in Pólya state, negative hypergeometric state, generalized nonclassical state, phase-like state and generalized hypergeometric state. Dynamics of entropy squeezing are examined. It is shown that a long-time approximately steady nonclassical behavior of the system can be obtained using specific values of the parameters associated with the initial state of system. An application of the developed method to obtain the long-lived information from different models is given.

In terms of a new Hamiltonian we introduce a modified Jaynes–Cummings model to represent the interaction between a two-level atom and two electromagnetic fields injected simultaneously within a perfect cavity. The field–field interaction is assumed to be in the frequency converter form. Exact expressions of the dynamical operators is given by solving the equations of the motion in the Heisenberg picture. The entropy squeezing is examined in the framework of Shannon information entropy. Using the entropic uncertainty relation, one can be able to show that there is a new kind of quantum squeezing in the entropy.