Quantum entanglement in the system of a moving V-type three-level atom interacting with the SU（1,1）-related coherent fields

In a system with a moving V-type three-level atom interacting with the SU(1,1)-related coherent fields, we investigate the entanglement between the moving three-level atom and the SU(1,1)-related coherent fields by using the quantum-reduced entropy, and that between the SU(1,1)-related coherent fields by using the quantum relative entropy of entanglement. It is shown that the two kinds of entanglement are dependent on the atomic motion and exhibit the periodic evolution with a period of 2π/p. The maximal atom--field qutrit entanglement state can be prepared, and the entanglement preservation of the SU(1,1)-related coherent fields can be realized in the interacting process via the appropriate selection of system parameters and interaction time.     

SU(1,1)相干态与玻色-爱因斯坦凝聚相互作用系统中的量子纠缠

研究的系统为SU(1, 1)相干态和玻色-爱因斯坦凝聚体相互作用体系,在双光子跃迁过程中,分别用量子约化熵和量子相对熵研究了该系统中的SU(1, 1)相干态与凝聚体间的纠缠以及SU(1, 1)相干态的模间纠缠,分析了光场初始压缩因子、原子间相互作用对场-凝聚体间纠缠和模间纠缠的影响。     

SU(1,1)相干态与玻色-爱因斯坦凝聚相互作用系统中的量子纠缠

研究的系统为SU(1, 1)相干态和玻色-爱因斯坦凝聚体相互作用体系,在双光子跃迁过程中,分别用量子约化熵和量子相对熵研究了该系统中的SU(1, 1)相干态与凝聚体间的纠缠以及SU(1, 1)相干态的模间纠缠,分析了光场初始压缩因子、原子间相互作用对场-凝聚体间纠缠和模间纠缠的影响。     

Quantum treatment for two two-level atoms in interaction with an SU(1,1) quantum system

We consider the interaction between two identical two-level atoms prepared in superposition states and an SU(1, 1) quantum system prepared in the Perelemov coherent state. We determine the timedependent wave function through the Schrödinger equation for the resonance case, and, consequently, we obtain the density matrix. We consider the phenomenon of collapses and revivals of the atomic population inversion for different values of the parameters and show the coherent trapping. We investigate the entanglement in the system where we discuss the linear entropy for different values of the involved parameters and for some states. Finally we examine the second-order correlation function to distinguish between the classical and nonclassical behaviors. We show that the system is sensitive to the variation in both the Bargmann index k and the Perelomov coherent parameter μ, as well as the atomic phase parameters.     

Dynamics of a tri-beam laser interacting with a three-level atom

We investigate the dynamics of a tri-beam laser interacting with a closed three-level atomic system. The Bloch equations are obtained using Hesinberg??s equation of motion. The impact of the resulting parameters on the atomic occupation probabilities and information entropy is discussed. It is shown that the populations are affected by the detuning in different ways which are then compared in order to simulate realizations entanglement through the information entropy.     

Entropy squeezing and entanglement of the interaction between SU(1,1) and SU(2) quantum systems

The problem of the interaction between two quantum systems namely SU(1,1) and SU(2) is considered. Using the evolution operator technique, an exact solution of the wave function and consequently the density matrix are obtained. The entropy squeezing is examined and it has shown that, different values of the relative phase angle ? as well as the coupling parameter λ lead to different observation of the squeezing in the quadratures. In the meantime, we have shown that the entropy squeezing is also sensitive to the variation in the state angle θ, the detuning parameter Δ in addition to the excitation number m. Moreover, for a large value of the detuning parameter there is a weak entanglement between the atom and the quantum system and vice versa. Furthermore, we find that the Q-function is sensitive to the variation in the excitation number m in addition to the Bargmann index k where the nonclassical effect is pronounced for the even parity.     

Dynamics of a moving five-level atom interacting with cavity fields

We study the entanglement between a single five-level atom interacting with a one-mode cavity field in the case where the atomic motion is taken into account. The field entropy of this system is investigated under the nonresonant conditions. The effects of the detuning parameter and the atomic motion on the degree of entanglement are investigated. We show that both the detuning and atomic motion play important roles in the evolution of the von Neumann entropy and atomic populations.     

双模SU（1,1）相干态场与级联三能级原子相互作用的动力学

讨论了关联双模ＳＵ（１，１）相干态场与级联三能级原子的相互作用对原子动力学行为的影响，也研究了双模场的量广场的量子统计性质随时间的演化。通过数值计算，发现了一些新的演化规律。     

Quantum entanglement in the SU(1, 1)-related coherent fields interacting with a moving atom

The entanglement properties of the SU(1, 1)-related coherent fields interacting with a moving atom via the two-photon transition are investigated. We discuss the quantum entanglement between the SU(1, 1)-related coherent fields and the moving atom by using the quantum reduced entropy and that between the SU(1, 1)-related coherent fields by using the quantum relative entropy. It is shown that we can obtain the maximal entangled state between the fields and the moving atom and the high degree of entanglement between the SU(1, 1)-related coherent fields can be preserved for some choiced system parameters.     

虚光场对双模SU(1,1)相干态光场与原子玻色-爱因斯坦凝聚体相互作用系统中量子纠缠的影响

在双模SU(1,1)相干态光场和原子玻色-爱因斯坦凝聚体相互作用系统中, 应用全量子理论, 在非旋波近似下, 分别利用量子约化熵和量子相对熵, 研究了双模SU(1,1)相干态光场与原子玻色-爱因斯坦凝聚体间的量子纠缠和双模光场的模间纠缠, 讨论了虚光场、原子-场的耦合常数和光场参数对场-凝聚体原子纠缠和光场模间纠缠的影响.     

Dynamics of disordered interacting quantum systems

Starting from the Liouville-von Neumann equation for the state operator, a functional integral representation of the generating functional for time-temperature dependent Green's functions in interacting disordered quantum systems is constructed. In the framework of this method, quenched averages can be performed without introducing additional, unphysical degrees of freedom, like, e.g., in then-replica method. For interaction-free systems, the dynamical origin of the Schäfer-Wegner symmetry is pointed out. For interacting systems we derive a matrix field theory with a single matrix field, which includes all interaction effects without approximations.     

Peremolv SU(1,1)相干叠加态的二阶量子关联特性研究

本文首先讨论了Barut-GirardelloSU(1,1)相干叠加态在Bargmann指数k≠1/2时的二阶量子关联特性。发现随着Bargmann指数的增大,Barut-Girardello奇相干态呈现反关联的区域变大。然后提出并研究了PeremolovSU(1,1)相干叠加态。Peremolov奇相干态可呈现反关联,并且随着Bargmann指数的增加,反关联程度变弱,反关联区域变小。     

UNCORRELATED TWO-MODE SU(1,1) COHERENT STATES

We have constructed a new kind of two-mode bosonic realization of SU(1,1) Lie algebra, on the basis of which the SU(1,1) generalized coherent states in the two-mode Fock space are derived. These two-mode SU(1,1) coherent states, which are called uncorrelated two-mode SU(1,1) coherent states, include three special cases. For these states, we study the mean photon number distribution and their non-classical properties, which are photon anti-bunching, violations of Cauchy－Schwarz inequality and two-mode squeezing.     

Some studies of the interaction between two two-level atoms and SU(1,1) quantum systems

Herein, we present an approach to look for the best phenomenon to measure quantum correlation. The system of two isolated qubits each interacting with a single-mode cavity was theoretically created to study the quantum correlation. Some of the phenomena, such as the quantum discord and concurrence, were generated through such a system. The influences of initial state purity, qubit motion, and detuning parameters were discussed for the phenomena. These parameters for a specific value show that the behavior of phenomena are analogous. It is interesting to mention that some values of detuning undergo a sudden death of phenomena, and the quantum discord still captures the qubits quantum correlation. We predict that the quantum discord may be a better measure of quantum correlation than concurrence.     

Photoelectron ionization spectra in a system interacting with a neighbor atom

We study long-time photoelectron ionization spectra of a system interacting with a neighbor two-level atom under the influence of a laser field. The system has at least a ground state and a continuum of states that are free with respect to one electron. In a weak light field, a Fano resonance is revealed. Also we consider an atomic autoionization level of the system, which leads to two Fano resonances under the influence of a weak field.     

Nonlinear quantum optics in a waveguide: distinct single photons strongly interacting at the single atom level

We propose a waveguide-QED system where two single photons of distinct frequency or polarization interact strongly. The system consists of a single ladder-type three level atom coupled to a waveguide. When both optical transitions are coupled strongly to the waveguide's mode, we show that a control photon tuned to the upper transition induces a π phase shift and tunneling of a probe photon tuned to the otherwise reflective lower transition. Furthermore, the system exhibits single photon scattering by a classical control beam. Waveguide-QED schemes could be an alternative to high quality cavities or dense atomic ensembles in quantum information processing.     

Entanglement between two qubits interacting with a slightly detuned thermal field

In this paper, we investigate entanglement between two two-level atoms when they simultaneously interact with a single-mode thermal field in the strong-coupling regime. We show that a slight detuning between the atomic transition frequency and the field frequency might cause high entanglement between the atoms. More interestingly, if we choose the detuning appropriately, both atoms would somehow get entangled even when both atoms are initially in the excited state.     

Generation of two-mode SU(2) and SU(1,1) cat states in a two-dimensional anisotropic ion trap

A scheme is proposed for generating two-mode SU(2) and SU(1,1) cat states for an ion trapped in a two-dimensional (2D) anisotropic harmonic potential trap. In the scheme the ion is excited by two laser beams in the trap plane. After an interaction time, a measurement on the internal state collapses the ion motion onto a superposition of two SU(2) or SU(1,1) coherent states depending on the laser frequencies. This work was supported by the National Natural Science Foundation of China under Grant No. 60008003, Fujian Provincial Natural Science Foundation of China under Grant Nos. K20004 and F0110027, and Funds from Fuzhou University.