In this paper the time evolution of von Neumann entropy as a measure of entanglement between a two-level atom and the photonic coherent states in a cavity is studied. The atom-photon interaction occurs in the presence of a centrosymmetric medium which makes the photonic cavity mode couple with itself via the third order susceptibility. In the present system the atom-photon interaction is assumed to follow the linear Jaynes-Cummings model while the photonic selfcoupling is due to presence of a centrosymmetric medium and occurs via the third order susceptibility. After calculating the time-evolution operator, the von Neumann entropy, as a function of time, is determined. It is shown that an increase of photonic self-coupling leads to decreasing of entanglement. Furthermore, the role of atom-photon detuning on the entanglement behavior is also addressed.
Abstract Optical tomography is a widely used method for estimating complex information. It provides a monotonic relation between the coherent field states density and their corresponding probability distributions. This approach is critical for validating any quantum information processing system’s implementation. This paper explores the optical tomography and coherence dynamics for a cavity interacting with two two-level atoms having time-dependent locations. We analyze the dynamics of the photon-field states, as two moving atoms enter a cavity filled with two superposed coherent states. The von-Neumann entropy dynamics illustrates how interaction couplings between the two atoms and cavity can give rise to entangled states under the effects of the atom-field couplings and the time-dependent atomic location parameter. Aside from coherence, the interactions between the cavity and atoms are essential for producing nonclassical proprieties in optical tomography. Furthermore, we investigate the dynamics of optical tomography densities with respect to the couplings between atoms and photons for time-dependent atomic location. Our results show that the couplings between atoms and cavity not only accelerate but also improve the processes involved in generating nonclassical optical tomography and coherence dynamics.
We investigate the quantum entanglement dynamics of two coupled harmonic oscillators with a time-dependent interaction. Using the Lewis-Riesenfeld invariant method, we derive the exact analytical wave functions without any perturbative or adiabatic approximations and combine this with a phase-space analysis using the Wigner function to provide a complete description of the system's quantum state evolution. We obtain general expression form for the purity and the linear entropy
SL=1−P for arbitrary excitation numbers
(n,m), allows a systematic study of entanglement for a large class of quantum states. We show that the entanglement dynamics is very sensitive to the interplay between the detuning parameters
θ and
ϑ2, the frequency parameter
β0 and the coupling strength
ε: the increase of detuning takes the system from slow irregular oscillations to fast and regular periodic behavior, and the stronger coupling systematically enhances both the amplitude and the average value of the linear entropy. Most importantly, for the resonance case
ω1=ω2=1 and strong couplings
ε≈0.99, the system shows robust undamped synchronized periodic oscillations of the linear entropy for all quantum states considered, indicating preserved quantum coherence without saturation. Our findings demonstrate that linear entropy is a sensitive and practical entanglement witness, and we establish explicit analytical relations between the coupling parameters of the system and its entanglement properties, which are directly relevant to quantum information processing and the control of quantum correlations in continuous-variable systems.
In this paper, we present some properties through two two-level atoms interacting with a two-mode quantized cavity field. We study this system in the presence of detuning parameter, Kerr nonlinearity, Stark shift, relative phase and intensity-dependent atoms-field coupling. Also, the coupling parameter is modulated to be time dependent. The exact solution of this model is given by using the Schrődinger equation when the atoms and the field are initially prepared in superposition states and coherent states, respectively. We employed the results to calculate some aspects such as linear entropy, total atomic inversion and cross-correlation function.
We investigate the quantum entanglement of systems of coupled harmonic oscillators on the basis of thermo-field dynamics (TFD). For coupled harmonic oscillators at equilibrium, the extended entanglement entropy is derived using the TFD method, and it is demonstrated to be controlled by temperature and coupling parameters. For non-equilibrium systems, in addition to temperature and coupling parameters, the time dependence of the extended entanglement entropy is calculated in accordance with the dissipative von Neumann equation, and the dissipative dynamics of the systems of coupled harmonic oscillators is discussed. Consequently, based on TFD, the physical parametrization of the entanglement entropies is confirmed in both the equilibrium and non-equilibrium cases of harmonic oscillator systems by means of the laws of thermodynamics.
We study the quantum entanglement of systems of coupled harmonic oscillators on the basis of thermo-field dynamics (TFD).For coupled harmonic oscillators at equilibrium, the extended entanglement entropy is derived using the TFD method, and it is demonstrated to be controlled by temperature and coupling parameters.For non-equilibrium systems, in addition to temperature and coupling parameters, the time dependence of the extended entanglement entropy is calculated in accordance with the dissipative von Neumann equation, and the dissipative dynamics of the systems of coupled harmonic oscillators is discussed.Consequently, based on TFD, the physical parametrization of the entanglement entropies is confirmed in both the equilibrium and nonequilibrium cases of harmonic oscillator systems by means of the laws of thermodynamics.