Time-dependent Coupling Effect Research Articles

Classical and quantum correlations between two qubits interacting with a field in thermal spin states

In this manuscript, we introduce a quantum physical model consisting of two-atom system that interact with a quantized field initially prepared in the thermal spin states (TSSs). We study the effect of the main parameters of the model on the dynamical behavior atom–atom coherence, atoms-field entanglement, atom–atom entanglement and classical correlation. We show how the quantumness measures can be influenced by the spin number and thermal noise in the absence and presence of time-dependent coupling effect. We obtain that, despite the destructive influence of thermal noise, a considerable amount of coherence, entanglement and classical correlation still remain during the time evolution according the values of spin number. The results also show that the TSSs can offer the advantage of generating the maximal amount of coherence, entanglement and classical correlation during the dynamics.

Quantum correlation and statistical properties in semiconductor microcavities with time-varying coupling effect

In this manuscript, we show how the photon-exciton entanglement and distribution of photons depend on the main parameters of the physical model in the semiconductor microcavities without and with of the time-dependent coupling effect (TDCE). We examine the dynamics of the quantum entanglement and photon statistics by considering the time variation of the coupling between the excitons and photons in weak excitation regime of quantum well confined in a semiconductor microcavity. We show that the manipulation and control of the degree of the entanglement and statistical distribution of photons in the presence of the TDCE can be benefited by a convenient choice of the strength field and the rate of the excitonic spontaneous emission.

Quantum correlations and quantum Fisher information of two qubits in the presence of the time-dependent coupling effect

In this paper, we consider two separate Jaynes–Cummings (JC) nodes with a nonidentical qubit-field system in the presence of dissipation terms. We reveal the influence of the time variation of the coupling terms on some important measures when the qubits are immersed in a vacuum. The density matrix for the two qubits initially in Bell states are obtained. The dynamical behavior of the quantum discord (QD), classical correlation (CC), qubit-qubit entanglement, and quantum Fisher information (QFI) is investigated. We explore the relationship among QD, CC, qubit-qubit entanglement, and QFI in the absence and presence of the dissipation effect during the time evolution. Furthermore, we show the main optimal conditions for obtaining a high level of correlation and coherence between the two qubits.

Entanglement and photon statistics of two dipole–dipole coupled superconducting qubits with Kerr-like nonlinearities

The engineering of Kerr and time-dependent coupling interactions is of great attention for treating quantum information in quantum systems and for investigating the collective behavior of large numbers of interacting particles in a cavity-qubit network. In this manuscript, we investigate the time evolution of the entanglement and some nonclassical properties of two superconducting qubits interacting with a single-mode field in the presence of a Kerr-like medium and dipole–dipole interaction without and with time-dependent coupling effect. We show that a slight alteration in the interaction, detuning, and Kerr parameters might cause a change in the entanglement of subsystem states during the evolution. By taking into account the influence of the different physical parameters, we show the statistical distributions produced in the photons of the single mode field through the calculation of the Mandel’s parameter. Finally, we find that the time-dependent Mandel’s parameter not only provide the statistical properties of the field, but also include the information of quantum entanglement for the subsystem states.

Physical and nonclassical properties of the interaction between a four-level atom and field in coherent state of Morse potential

The quantum system of the field initially defined by the k-photon-added Morse potential coherent states (MPCSs) of the radiation field interacting with a four-level atom (FLA) was studied. The physical and non-classical properties of the field defined by the MPCS system were quantified using the Mandel parameter. The effect of time-dependent coupling (TDC) on the atomic speed was examined. Moreover, the dynamic properties of the non-local correlation between the FLA and MPCS radiation field were studied and compared with those of the geometric phase. We also investigated the influence of the initial interaction conditions and different system parameters on the evolution of the non-local correlation, Mandel parameter, and geometric phase. The relationships between the geometric phase, Mandel parameter, and non-local correlation with TDC were explored.

Effect of Time Dependent Coupling on the Dynamical Properties of the Nonlocal Correlation Between Two Three-Level Atoms

In this article, we present the analytical solution for the pair of entangled two three-level atoms in the cascade configuration with and without the atomic motion effect. The effects of time dependent coupling and photon multiplicity on the evolution of the nonlocal correlation between the two atoms are examined. It is shown that the amount of atom-atom entanglement increases for one photon transition when the atomic motion effect is considered. Also, the entanglement between the two atoms decreases by increasing the photons multiplicity when the time dependent coupling effect is ignored. Finally, the results explored very important phenomena such as entanglement sudden death and entanglement sudden birth.

Foundation Differential Settlement Included Time-dependent Elevation Control for Super Tall Structures

Due to the time-dependent properties of materials, structures, and loads, accurate time-dependent effects analysis and precise construction controls are very significant for rational analysis and design and saving project cost. Elevation control is an important part of the time-dependent construction control in supertall structures. Since supertall structures have numerous floors, heavy loads, long construction times, demanding processes, and are typically located in the soft coastal soil areas, both the time-dependent features of superstructure and settlement are very obvious. By using the time-dependent coupling effect analysis method, this paper compares Shanghai Tower's vertical deformation calculation and elevation control scheme, considering foundation differential settlement. The results show that the foundation differential settlement cannot be ignored in vertical deformation calculations and elevation control for supertall structures. The impact of foundation differential settlement for elevation compensation and pre-adjustment length can be divided into direct and indirect effects. Meanwhile, in the engineering practice of elevation control for supertall structures, it is recommended to adopt the multi-level elevation control method with relative elevation control and design elevation control, without considering the overall settlement in the construction process.

Quantum Transfer Energy and Nonlocal Correlation in a Dimer with Time-Dependent Coupling Effect

The presence of coherence phenomenon due to the interference of probability amplitude terms, is one of the most important features of quantum mechanics theory. Recent experiments show the presence of quantum processes whose coherence provided over suddenly large interval-time. In particular, photosynthetic mechanisms in light-harvesting complexes provide oscillatory behaviors in quantum mechanics due to quantum coherence. In this work, we investigate the coherent quantum transfer energy for a single-excitation and nonlocal correlation in a dimer system modelled by a two-level atom system with and without time-dependent coupling effect. We analyze and explore the required conditions that are feasible with real experimental realization for optimal transfer of quantum energy and generation of nonlocal quantum correlation. We show that the enhancement of the probability for a single-excitation transfer energy is greatly benefits from the combination of the energy detuning and time-dependent coupling effect. We investigate the presence of quantum correlations in the dimer using the entanglement of formation. We also find that the entanglement between the donor and acceptor is very sensitive to the physical parameters and it can be generated during the coherent energy transfer. On the other hand, we study the dynamical behavior of the quantum variance when performing a measurement on an observable of the density matrix operator. Finally, an interesting relationship between the transfer probability, entanglement and quantum variance is explored during the time evolution in terms of the physical parameters.

Realistic Quantum Control of Energy Transfer in Photosynthetic Processes

The occurrence of coherence phenomenon as a result of the interference of the probability amplitude terms is among the principle features of quantum mechanics concepts. Current experiments display the presence of quantum techniques whose coherence is supplied over large interval times. Specifically, photosynthetic mechanisms in light-harvesting complexes furnish oscillatory behaviors owing to quantum coherence. In this manuscript, we study the coherent quantum energy transfer for a single-excitation and nonlocal correlation in a dimer system (donor+acceptor) displayed by two-level systems (TLSs), interacting with a cavity field with a time-dependent coupling effect considering the realistic situation of coupling between each TLS and the cavity field. We analyze and explore the specific conditions which are viable with real experimental realization for the ultimate transfer of quantum energy and nonlocal quantum correlation. We show that the enhancement of the probability for a single-excitation energy transfer greatly benefits from the energy detuning, photon-number transition, classicality of the field, and the time-dependent coupling effect. We also find that the entanglement between the donor and acceptor is very sensitive to the physical parameters and it can be generated during the coherent energy transfer.

Nonclassical properties and purity of a qubit system in photon-added squeezed thermal states with time-dependent coupling effect

The degree of purity and nonclassical properties for a two-level system interacting with a photon-added squeezed thermal field (PASTF) are described in terms of the physical parameters involved in the whole system state with and without time-dependent coupling effect. Specially, we investigate the influence of the squeezed parameter and photon-added number on the behavior of the linear entropy and the Mandel's parameter. We find that for each value of the photon-added number, there exist critical value of the squeezed parameter for which the linear entropy is maximal and the statistical properties get farther from the trivial case. Moreover, we show that the presence of the time-dependent coupling effect may increase the periodicity time and lead to quench oscillations of the Mandel's parameter during the evolution. Finally, we exploit an interesting relationship between the linear entropy and the Mandel's parameter in terms of the physical parameters.

Measures of nonclassicality for a two-level atom interacting with power-law potential field under decoherence effect

In this paper, we propose a useful quantum system to perform different tasks of quantum information and computational technologies. We explore the required optimal conditions for this system that are feasible with real experimental realization. We present an active way to control the variation of some measures of nonclassicality considering the time-dependent coupling and photon transition effects under a model that closely describes a realistic experimental scenario. We investigate qualitatively the quantum measures for a two-level atom system interacting with a quantum field initially defined in a coherent state in the framework of power-law potentials (PLPCSs). We study the nonlocal correlation in the whole system state using the negativity as a measure of entanglement in terms of the exponent parameter, number of photon transition, and phase damping effect. The influences of the different physical parameters on the statistical properties and purity of the field are also demonstrated during the time evolution. The results indicate that the preservation and enhancement of entanglement greatly benefit from the combination of the choice of the physical parameters. Finally, we explore an interesting relationship between the different quantum measures of non-classicality during the time evolution in the absence and presence of time-dependent coupling effect.

Entanglement, nonclassical properties and geometric phase of Raman photon pairs in the presence of time-dependent coupling

In this paper, we develop the model of the four-level double Raman pairs by exploiting the required optimal conditions for this system that are feasible with real experimental realization. We investigate qualitatively the entanglement, statistical properties, and geometric phase for the pair of Stokes and anti-Stokes photons in the presence of the time-dependent coupling effect. We show that these quantifiers are very sensitive to the change of the Rabi frequency and time, exhibiting substantial phenomena that are depending on the kind of coupling between the atom and photons. Finally, we explore the relationship between the quantum quantifiers in terms of the physical parameters with and without time-dependent coupling effect.

Effect of the time-dependent coupling on a superconducting qubit-field system under decoherence: Entanglement and Wehrl entropy

The dynamics of a superconducting (SC) qubit interacting with a field under decoherence with and without time-dependent coupling effect is analyzed. Quantum features like the collapse–revivals for the dynamics of population inversion, sudden birth and sudden death of entanglement, and statistical properties are investigated under the phase damping effect. Analytic results for certain parametric conditions are obtained. We analyze the influence of decoherence on the negativity and Wehrl entropy for different values of the physical parameters. We also explore an interesting relation between the SC-field entanglement and Wehrl entropy behavior during the time evolution. We show that the amount of SC-field entanglement can be enhanced as the field tends to be more classical. The studied model of SC-field system with the time-dependent coupling has high practical importance due to their experimental accessibility which may open new perspectives in different tasks of quantum formation processing.

The Effect of Time-Dependent Coupling on Non-Equilibrium Steady States

Consider (for simplicity) two one-dimensional semi-infinite leads coupled to a quantum well via time dependent point interactions. In the remote past the system is decoupled, and each of its components is at thermal equilibrium. In the remote future the system is fully coupled. We define and compute the non equilibrium steady state (NESS) generated by this evolution. We show that when restricted to the subspace of absolute continuity of the fully coupled system, the state does not depend at all on the switching. Moreover, we show that the stationary charge current has the same invariant property, and derive the Landau-Lifschitz and Landauer-Buttiker formulas.