多光子过程中相位退相干时两原子布局数反转

利用全量子理论的方法,研究了存在相位退相干时多光子T-C模型中两个二能级原子与二项式光场相互作用系统中两原子的布居数反转。讨论了相位退相干系数、二项式光场系数、最大光子数、跃迁光子数对原子布居数反转的影响。结果表明：相位退相干减少了原子布居数反转的振幅、破坏了原子的量子特性。改变跃迁光子数,可以改变原子间布居数反转演化周期及演化强度。当二项式光场的最大光子数增大时,原子布居差的崩塌-回复现象就会逐渐消失。相位退相干因子不变时, 二项式光场从相干态过渡到数态过程中,原子布居的振荡频率由大变小,周期性的崩塌与回复现象逐渐消失。     

多光子过程中相位退相干时两原子布局数反转

利用全量子理论的方法,研究了存在相位退相干时多光子T-C模型中两个二能级原子与二项式光场相互作用系统中两原子的布居数反转。讨论了相位退相干系数、二项式光场系数、最大光子数、跃迁光子数对原子布居数反转的影响。结果表明：相位退相干减少了原子布居数反转的振幅、破坏了原子的量子特性。改变跃迁光子数,可以改变原子间布居数反转演化周期及演化强度。当二项式光场的最大光子数增大时,原子布居差的崩塌-回复现象就会逐渐消失。相位退相干因子不变时, 二项式光场从相干态过渡到数态过程中,原子布居的振荡频率由大变小,周期性的崩塌与回复现象逐渐消失。     

虚光场对玻色-爱因斯坦凝聚体与二项式光场相互作用系统中光场压缩性质的影响

在二项式光场和二能级原子玻色-爱因斯坦凝聚体相互作用系统中, 应用全量子理论, 分别在旋波近似和非旋波近似下, 研究了光场的压缩特性以及原子本征频率、原子-光场的耦合系数、光场参数以及虚光场对系统光场压缩特性的影响. 研究表明, 光场的两个正交分量均被周期性压缩, 光场压缩持续时间与原子的本征频率有关, 压缩深度与二项式光场概率分布参数和虚光场有关, 光场与原子的耦合系数决定了光场涨落的崩塌-回复频率. 关键词： 量子光学 玻色-爱因斯坦凝聚 虚光场 光场压缩     

Critical behavior of geometric measure of quantum discord when approaching the critical points via different paths

We investigate the critical behavior of geometric measure of quantum discord (GMQD) in a one-dimensional transverse XY spin chain. The critical and the scaling behavior of the ground state GMQD are investigated both at the multi-critical and Ising critical points. Our results show that the behavior of GMQD at muti-critical point (MCP) has close relation with the path, which is determined by the parameter α, that approaching the MCP. For α < 2, the GMQD and its first derivation show oscillation behavior. For α ≥ 2, no oscillation behavior is observed. This indicates that the GMQD can not describe exactly the multi-critical point of the XY model. However, at the Ising critical point, the path parameter has no influence on the critical behavior. The GMQD (first derivation of GMQD) shows peaks (dips) and indicates exactly the position of Ising critical point. The results also show that the path parameter influences much to the scaling behavior near the MCP, but less to that of Ising critical point. Our results may provide reference to the exploration of relationships between GMQD and quantum phase transitions.     

二项式光场与级联三能级原子在非旋波近似下相互作用的量子特性

利用全量子理论,在非旋波近似下,对与级联型三能级原子相互作用的二项式光场的光场压缩效应和原子布居几率进行了精确求解.讨论了二项式光场参量η对光场压缩效应的影响,同时也讨论了二项式态光场的最大光子数M对原子布居几率的影响.数值计算结果表明:随着二项式光场参量η的增大,光场压缩效应的持续时间先增大后减小.在非旋波近似下,由于虚光子的影响,光场压缩效应的演化曲线出现了“小锯齿状”的振荡;随着二项式光场的最大光子数M的增大,原子布居几率回复塌缩周期逐渐增大,并且原子布居几率在塌缩区不能完全塌缩,而是出现了“小锯齿状”的振荡.另外文中也讨论了非旋波项对系统量子特性的影响.     

Pairwise Quantum Discord for a Symmetric Multi-Qubit System in Different Types of Noisy Channels

We study the pairwise quantum discord (QD) for a symmetric multi-qubit system in different types of noisy channels, such as phase-flip, amplitude damping, phase-damping, and depolarizing channels. Using the QD and geometric quantum discord (GMQD) to quantify quantum correlations, some analytical and numerical results are presented. The results show that, the QD dynamics is strongly related to the number of spin particles N as well as the initial parameter ?? of the one-axis twisting collective state. With the number of spin particles N increasing, the amount of the QD increases. However, when the amount of the QD arrives at a stable maximal value, the QD is independence of the number of spin particles N increasing. The behavior of the QD is symmetrical during a period 0 ≤ ?? ≤ 2π. Moreover, we compare the QD dynamics with the GMQD for a symmetric multi-qubit system in different types of noisy channels.     

超几何光场态与二能级原子相互作用中原子反转的演化及光场的反聚束效应

研究作为二项式态单参数推广的超几何态与二能级原子的强度耦合相互作用．讨论了原子反转的动力学演化以及光场的反聚束效应．     

高Q Kerr介质腔中二项式光场与原子相互作用

应用全量子理论研究了在高Q Kerr介质腔中, 二能级原子与二项式光场相互作用系统中原子行为和光场的量子特性. 采用数值计算的方法, 详细讨论了光场参量和Kerr效应对原子布居反转和平均光子数的影响.研究发现当二项式光场处在中间态时, 在考虑Kerr效应的条件下,原子布居振荡加剧, 回复时间变短, 系统内平均光子数减少.     

Influence of the virtual photon field on the squeezing properties of atom laser

This paper investigates the squeezing properties of an atom laser without rotating-wave approximation in the system of a binomial states field interacting with a two-level atomic Bose--Einstein condensate. It discusses the influences of atomic eigenfrequency, the interaction intensity between the optical field and atoms,parameter of the binomial states field and virtual photon field on the squeezing properties. The results show that two quadrature components of an atom laser can be squeezed periodically. The duration and the degree of squeezing an atom laser have something to do with the atomic eigenfrequency and the parameter of the binomial states field, respectively. The collapse and revival frequency of atom laser fluctuation depends on the interaction intensity between the optical field and atoms. The effect of the virtual photon field deepens the depth of squeezing an atom laser.     

Nonclassical Properties for Two Coupled N-Two-Level Atom and a Single Two-Level Atom Under an External Magnetic Field

We study the interaction between a single two-level atom and N two-level atoms under the effect of a uniform magnetic field. The exact solution is obtained and the expectation value of the time-dependent quantum operators calculated using the Block state (the generalized coherent state). We discuss numerically the atomic inversion where the phenomenon of collapse and revival is observed. The change in the value of the atomic angle plays a role in variance squeezing, where it is pronounced for ?? = π/3. Entropy squeezing is discussed and occurred in the first quadrature. The degree of entanglement through linear entropy is examined where the system shows partial entanglement and at a certain value of parameters displays nearly maximum entanglement.     

Entangled spin states of a Bose condensate in an electromagnetic field

We consider the formation of entangled quantum states for an atomic Bose condensate interacting with an external electromagnetic field in a single-particle state under conditions of change in various regimes for exchange interaction processes. These states of the Bose system have high phase coherence and are accompanied by the generation of squeezed states of a new type in terms of the parameters defined by a combination of transition operators for the condensate atoms and external-field photons with an appropriate polynomial deformation of the algebra SU(2). We show that localized quantum structures corresponding to stable elementary excitations of the atoms and the field in the condensate can be formed in principle. We also analyze the purely quantum effects of collapse and revival for the level populations of the Bose condensate and the change in atomic statistics as well as determine the conditions for the formation of superstructure of these unsteady states for the Bose system.     

薛定谔猫态的产生与探测及其对Jaynes-Cummings模型的影响

利用大失谐情况下的简并喇曼过程和双光子Jaynes-Cummings模型来产生电磁场中的宏观量子叠加态,即薛定旋风谔猫态,并探讨如何用零频检测的方法来探测这些态。研究了当电磁场初态为薛定谔猫态时,对强度耦合的Jaynes-Cummings模型中原子反转的崩塌与再生现象的影响,将在以相干态为初态所产生的原子反转的崩塌区产生不同程度的再生现象。 关键词：     

Thermo Vacuum State for Describing the Density Operator of Photon-subtracted Squeezed Chaotic Light

For the density operator describing s?photon-subtracted squeezed chaotic light (PSSCL) we search for its thermo vacuum state (a pure state) in the real-fictitious space. We find that it reduces to a thermo vacuum state of squeezed chaotic light when s = 0, and to a thermo vacuum state of the optical negative binomial field when no squeezing. The new thermo vacuum state simplifies calculating photon number average, quantum fluctuation and Mandel’s Q parameter of PSSCL. Using the method of integration within ordered product (IWOP) of operators we also derive the normalization coefficient and explicitly analytical expressions of Wigner function for PSSCL.     

Quantum Discord of Two-Qubit Thermal State in Hydrogen Atom

The geometric measure of quantum discord (GMQD) is used to study the quantum correlation in a two-qubit thermal state in hydrogen atom. External magnetic field can destroy the initial symmetry of the state and further change its degeneracy structure. The dependence of the quantum correlation on temperature and magnetic field is discussed.     

含高阶项Trapped离子振动态的崩塌-回复特性

解析分析了“捕陷”离子在驻波光场作用下的动力学。离子的量子平均能量随时间的变化呈现崩塌 -回复的特征 ,表明这个系统的振动态具有压缩效应。哈密顿量中的高阶项使得离子平均能量呈现不规则的崩塌 -回复 ,严重抑制离子的振动态的相干性。     

压缩态光场变耦合系数双光子J-C模型性质

讨论了初始光场为压缩态、原子-光场耦合系数随时间变化情形下双光子过程J-C模型的量子统计性质。具体研究了双光子过程中原子布居数反转、光场的压缩等随时间的演化性质,讨论了初始光场的压缩系数、压缩相位及耦合系数变化快慢对这些性质的影响。研究结果表明,初始光场的压缩系数增大,崩塌和回复的频率增大,回复值减小。当原子-光场耦合系数变化缓慢时,崩塌和回复现象被延迟。而光场逐渐失去压缩性质;而当耦合系数变化较快时,崩塌和回复现象被加速,而光场压缩量将产生振荡,压缩效应将反复出现。     

Dynamical Properties of Some Statistical Quantities for a Quantum System in Generalized Negative Binomial States

We estimate the quantum state of a qubit and a quantized radiation field yielding a generalized negative binomial distribution (GNBD). We give an explicit form for various generalized negative binomial states associated to superposition, even, odd, and q-deformed states. We investigate the dynamical properties of the Mandel parameter as a quantifier of the statistical properties for the radiation field corresponding to its dynamics. We obtain the quantum Fisher information based on the estimation of the atomic state and compare it with the Mandel parameter for different instances of the GNBD. The link between the statistical quantities for different parameters of the GNBD is explored.     

Reduction of quantum phase fluctuations in intermediate states

Recently we have shown that the reduction of the Carruthers-Nieto symmetric quantum phase fluctuation parameter (U) with respect to its coherent state value corresponds to an antibunched state, but the converse is not true. Consequently reduction of U is a stronger criterion of nonclassicality than the lowest order antibunching. Here we have studied the possibilities of reduction of U in intermediate states by using the Barnett-Pegg formalism. We have shown that the reduction of phase fluctuation parameter U can be seen in different intermediate states, such as binomial state, generalized binomial state, hypergeometric state, negative binomial state, and photon added coherent state. It is also shown that the depth of nonclassicality can be controlled by various parameters related to intermediate states. Further, we have provided specific examples of antibunched states, for which U is greater than its Poissonian state value.     

二项式光场与级联三能级原子在非旋波近似下相互作用的量子特性

利用全量子理论,在非旋波近似下,对与级联型三能级原子相互作用的二项式光场的光场压缩效应和原子布居几率进行了精确求解.讨论了二项式光场参量η对光场压缩效应的影响,同时也讨论了二项式态光场的最大光子数M对原子布居几率的影响.数值计算结果表明:随着二项式光场参量η的增大,光场压缩效应的持续时间先增大后减小.在非旋波近似下,由于虚光子的影响,光场压缩效应的演化曲线出现了"小锯齿状"的振荡;随着二项式光场的最大光子数M的增大,原子布居几率回复塌缩周期逐渐增大,并且原子布居几率在塌缩区不能完全塌缩,而是出现了"小锯齿状"的振荡.另外文中也讨论了非旋波项对系统量子特性的影响.     

Entanglement and Measurement-Induced Disturbance About Two-Qubit Heisenberg XYZ Model

By taking into account the nonuniform magnetic field, quantum correlation behaviors measured by concurrence and measurement-induced disturbance (MID) about a two-qubit anisotropic Heisenberg XYZ model are investigated in detail. We mainly concentrate on the differences between the entanglement and MID with the changes of different self and external control parameters. It is found that the ground state of entanglement exists the revival phenomenon, while this revival phenomenon is not included in MID. This difference is also appeared in the case of the finite temperature. Moreover, we give out the reason why the ground state entanglement and MID can behave very differently, which the former occurs the revival phenomenon whereas the latter does not. Through studying the effects about different parameters on C and MID, it presents that their magnitudes can be evidently enhanced by properly tuning B, b or adjusting the temperature. It also shows the situation which the entanglement is symmetrical with J _z while MID is monotonically decreased from one constant value.