Bell态原子与双模纠缠相干光场相互作用的场熵演化特性

运用全量子理论研究了初始处于Bell态(对称迭加态或反对称态)的两原子与双模纠缠相干光场相互作用系统中场熵的演化特性. 分析了光场强度、光场纠缠度及原子间相互作用强度对场熵演化特性的影响. 结果表明：原子初态处于反对称态时,场熵始终为零;原子初态处在对称迭加态时,增大光场强度场熵的时间演化曲线逐渐变成较规则的振荡曲线,原子间的相互作用强度对双原子间纠缠度有显著的非线性调制作用.     

Bell态原子与双模纠缠相干光场相互作用的场熵演化特性

运用全量子理论研究了初始处于Bell态(对称迭加态或反对称态)的两原子与双模纠缠相干光场相互作用系统中场熵的演化特性. 分析了光场强度、光场纠缠度及原子间相互作用强度对场熵演化特性的影响. 结果表明：原子初态处于反对称态时,场熵始终为零;原子初态处在对称迭加态时,增大光场强度场熵的时间演化曲线逐渐变成较规则的振荡曲线,原子间的相互作用强度对双原子间纠缠度有显著的非线性调制作用.     

Bell态原子与双模纠缠相干光场相互作用的场熵演化特性

运用全量子理论研究了初始处于Bell态(对称迭加态或反对称态)的两原子与双模纠缠相干光场相互作用系统中场熵的演化特性. 分析了光场强度、光场纠缠度及原子间相互作用强度对场熵演化特性的影响. 结果表明：原子初态处于反对称态时,场熵始终为零;原子初态处在对称迭加态时,增大光场强度场熵的时间演化曲线逐渐变成较规则的振荡曲线,原子间的相互作用强度对双原子间纠缠度有显著的非线性调制作用.     

Bell态原子与双模纠缠相干光场相互作用的场熵演化特性

运用全量子理论研究了初始处于Bell态(对称迭加态或反对称态)的两原子与双模纠缠相干光场相互作用系统中场熵的演化特性. 分析了光场强度、光场纠缠度及原子间相互作用强度对场熵演化特性的影响. 结果表明：原子初态处于反对称态时,场熵始终为零;原子初态处在对称迭加态时,增大光场强度场熵的时间演化曲线逐渐变成较规则的振荡曲线,原子间的相互作用强度对双原子间纠缠度有显著的非线性调制作用.     

Bell态原子与双模纠缠相干光场相互作用的场熵演化特性

运用全量子理论研究了初始处于Bell态(对称迭加态或反对称态)的两原子与双模纠缠相干光场相互作用系统中场熵的演化特性. 分析了光场强度、光场纠缠度及原子间相互作用强度对场熵演化特性的影响. 结果表明：原子初态处于反对称态时,场熵始终为零;原子初态处在对称迭加态时,增大光场强度场熵的时间演化曲线逐渐变成较规则的振荡曲线,原子间的相互作用强度对双原子间纠缠度有显著的非线性调制作用.     

Bell态原子与双模纠缠相干光场相互作用的场熵演化特性

运用全量子理论研究了初始处于Bell态(对称迭加态或反对称态)的两原子与双模纠缠相干光场相互作用系统中场熵的演化特性. 分析了光场强度、光场纠缠度及原子间相互作用强度对场熵演化特性的影响. 结果表明：原子初态处于反对称态时,场熵始终为零;原子初态处在对称迭加态时,增大光场强度场熵的时间演化曲线逐渐变成较规则的振荡曲线,原子间的相互作用强度对双原子间纠缠度有显著的非线性调制作用.     

两二能级原子在共同环境下的量子关联动力学

通过精确求解带有偶极-偶极相互作用的两个二能级原子与一个共同热库相互作用模型, 得到了两原子间量子纠缠和量子失谐(quantum discord)的解析表达式. 综合考虑了环境的非马尔可夫效应、原子间的偶极-偶极相互作用以及原子的本征频率同腔模中心频率之间的失谐量对两原子间量子纠缠和quantum discord的影响. 研究显示: 在非马尔可夫机制下, 且原子的本征频率与腔模中心频率是共振时, 当两原子初态处于纠缠态时, 原子间偶极-偶极相互作用可以显著抑制包括量子纠缠和quantum discord等量子关联的衰减, 更特别的是, 如果原子的本征频率同腔模中心频率有一定的失谐时, 利用原子间偶极-偶极相互作用可大大地延长两原子退纠缠的时间; 当两原子初态处于可分离态时, 从短时间来看, 原子间偶极-偶极相互作用可以提高量子纠缠和quantum discord振荡的振幅,而在长时间极限下, 原子间偶极-偶极相互作用不会改变量子纠缠和quantum discord达到的稳定值. 最后, 讨论了原子间偶极-偶极相互作用对量子纠缠和quantum discord动力学不同的影响. 关键词： 量子纠缠 量子失谐 共同环境 偶极-偶极相互作用     

Bell态原子与双模纠缠相干光场双光子相互作用系统的量子纠缠

运用全量子理论和数值计算的方法,借助于原子的量子约化熵研究了初始处于Bell态|β00>和| β10>的两原子与双模纠缠相干光场双光子相互作用系统中两原子与双模光场之间纠缠的演化特性.分析了光场强度、光场纠缠度及原子间相互作用强度对原子熵演化特性的影响.结果表明:随着双模光场的平均光子数的增大,原子熵的时间演化曲线逐渐变为规则振荡;增大原子间的相互作用强度,原子熵的振荡频率和振幅都减小;改变双模光场的纠缠度,原子熵的振荡频率和振幅都不发生改变.     

系统-环境初始关联对纠缠动力学的影响

研究了存在偶偶相互作用的两个二能级原子与共同单洛伦兹热库相互作用模型下的两体间的纠缠动力学行为。主要考虑了原子系统与环境存在初始关联时,两原子间的偶偶相互作用对纠缠动力学的影响,可以发现:偶偶相互作用一定时,马尔科夫环境下初始关联使原子与热库间的纠缠比原子间的纠缠衰减得慢,非马尔科夫环境下初始关联使原子间的振荡减弱;另外在马尔科夫热库中,随着偶偶相互作用的增强,两原子纠缠可以得到提升,而在非马尔科夫热库中,随着偶偶相互作用的增强,原子间及原子与热库间最终保持较大纠缠值。     

Bell态原子与双模纠缠相干光场相互作用的纠缠特性

运用Negativity熵研究了Bell态原子与双模纠缠相干光场相互作用系统中两个全同二能级原子之间的纠缠演化特性.分析了光场强度、光场纠缠度及原子间相互作用强度对纠缠的影响.结果表明:原子处于|β11〉时,两原子始终处于最大纠缠态;原子处于|β00〉时,初始纠缠的两原子始终较长时间处于退纠缠状态;原子处在|β10〉时,增大双模光场的平均光子数可以明显增大两原子之间的纠缠度并保持较大的纠缠状态;原子初态处在|β01〉时,原子间的相互作用强度对双原子间纠缠度有较显著的非线性调制作用.     

压缩真空态中原子与场的量子纠缠和量子discord

在压缩真空库中,研究了原子与场的相互作用下二比特体系的量子discord和量子纠缠的动力学行为.重点分析了原子的初始态系数和压缩真空库的压缩系数对量子纠缠和量子discord的影响.通过数值分析我们得到,随着原子的初始态系数和压缩真空库的压缩系数值的增加,量子纠缠和量子discord都会减小,但量子纠缠比量子discord减小的更快一些.最后研究了在原子的初始态系数和压缩真空库的压缩系数的值相同的情况下,量子discord比量子纠缠存在的时间更长些.     

在不同初态下Dzyaloshinskii-Moriya相互作用及内禀退相干对海森伯系统的量子纠缠的影响

研究了存在内禀退相干时,对于不同的系统初态,具有DM相互作用和各向异性的三粒子XXZ海森伯模型的对纠缠动力学特性.得出了一些结论:系统的对纠缠度与各向异性参数?无关,但内禀退相干对系统的纠缠有明显的抑制作用;在内禀退相干存在时,若系统初态为纠缠态,选择合适的DM相互作用的参数,系统的对纠缠有一个非零的稳定值;系统初态为分离态时,系统的对纠缠会随时间震荡衰减,并且每次震荡会出现纠缠突然死亡现象,系统的对纠缠最终达到解纠缠状态.因此,选择合适的系统初态和DM相互作用参数可以有效地控制系统的对纠缠.     

Entanglement of two atoms in two-mode Raman coupled model with intrinsic decoherence

Considering intrinsic decoherence, the two-atom two-mode Raman coupled model is investigated in this paper. Utilizing the constants of motion in this model, we obtain the analytic expressions of the density operator of the system for investigating the entanglement of two atoms. The speed of entanglement decay increases with the increasing of the coupling coefficient of one atom. The difference between the oscillation periods when the initial state parameter of atomic subsystem belongs to two intervals becomes smaller with the increasing of the coupling coefficient of one atom. The increasing of the initial photon number of the second field can hasten the vanishing of entanglement of atomic subsystem. The robustness of atomic entanglement against decoherence depends on the interval of the initial state parameter of atomic subsystem.     

Entangling Two Multi-atomic Clusters Through a Cavity Field

Two atomic clusters, which have NA and Ns two-level atoms, respectively, are placed in a cavity but separated spatially. There is no direct interaction between the atoms. All the atoms interact with a single-mode of the cavity field. Quantum entanglement between the two atomic clusters is investigated for various initial states of the two atomic clusters and the field. When the cavity field is initially in a Fock state, we find that the time evolution of entanglement quasi-periodically oscillates regardless of the initial states of atoms. The oscillation period increases as the initial photon number increases. When all the atoms in both of the atomic clusters are initially in the excited state, we show that there is no entanglement between the atomic clusters with NA = NB = 1 regardless the initial state of the cavity field. However, when either NA or NB is larger than one, we find that the entanglement always exists even for a strong thermal field. In cases with different initial states of the atomic clusters, we notice that the entanglement becomes stronger as number of the atoms increases. When all the atoms in both of the clusters in the ground state, we also find that the entanglement can be enhanced even by a thermal field. We also notice that a single qubit can be entangled with multi-atoms which are initially in the ground state by the cavity field initially being in vacuum, thermal, coherent, and squeezed states.     

Dynamics of entanglement in one-dimensional Ising chains with two- and three-body interactions

The evolution of entanglement in a one-dimensional Ising chain with both two-body and three-body interactions, under two types of initial states, is numerically simulated. We analyse three problems concerning the dynamics of pairwise entanglement: (i) the possibility of generating large entanglement from an initial separable state by the use of a selective irradiation scheme; (ii) the effect of three-body interaction on the generation of entanglement from an initial separable state; (iii) the effect of three-body interaction on the decay of the entanglement from a state with only (m,n)-pair maximal entangled, and the rest in product form. It is shown that a large pairwise concurrence C_mn can be obtained when the resonant, transverse radio-frequency fields are selectively switched on from the mth to nth spins. Three-body interaction will decrease the oscillation amplitude of the nearest neighbour concurrence, while the oscillation amplitude of remote pairwise concurrence will be greatly increased with the consideration of three-body interactions. For an initial (m,n)-pair maximal entangled state, a slow decay of the pairwise concurrence C_mn is found with the introduction of three-body interactions.     

Entanglement Dynamics of Two V-type Atoms with Dipole–Dipole Interaction in Dissipative Cavity

In this work, a coupled system of two V-type atoms with dipole–dipole interaction in a dissipative single-mode cavity, which couples with an external environment, is studied. The analytical solution of this model is obtained by solving the time dependent Schrodinger equation after Hamiltonian of dissipative cavity is diagonalized by introducing a set of new creation and annihilation operators according to Fano theorem. It is also discussed in detail how the entanglement dynamics of different initial states are influenced by the cavity-environment coupling, the spontaneously generated interference (SGI) parameter, and the dipole–dipole interaction between two atoms . The results show that the SGI parameter has different effects on entanglement dynamics under different initial states. Namely, the SGI parameter will increase the decay rate of the initially maximal entangled state and reduce that of the initially partial entangled state. For the initially product state, the larger SGI parameter corresponds to the more entanglement generated. The entanglement monotonically decreases under the weak cavity-environment coupling, while the oscillation of entanglement will occur under the strong cavity-environment coupling. The larger the dipole–dipole interaction is, the slower the entanglement decays and the more the entanglement will be generated. So the dipole–dipole interaction can not only protect and generate entanglement very effectively, but also enhance the regulation effect of the SGI parameter on entanglement.     

Entanglement dynamics of two qubits coupled by Heisenberg XY interaction under a nonuniform magnetic field in a spin bath

This paper investigates the entanglement dynamics of a Heisenberg XY model for a two-spin system in the presence of a nonuniform magnetic field.The master equations and the concurrence evolution equations for the initial α state are derived and analysed.It is shown that for the symmetric initial α state,only the nonuniform field can play a role in entanglement dynamics while the uniform field and the bath will not play such a role.For the asymmetric α state,the nonuniform field leads to the beat pattern oscillation of the concurrence evolution.The inhomogeneity of the field can enhance the entanglement by suppressing the decoherence effects of both the spin-orbit interaction and the spin bath.     

混合态下运动原子与相干态光场相互作用的量子纠缠

利用负熵方法,研究了混合态运动原子与相干态光场相互作用系统的量子纠缠特性,讨论了原子初态、场模结构参数、相干场平均光子数、失谐量、跃迁光子数等物理参量对系统纠缠度的影响。结果表明：考虑原子运动时,系统纠缠度在整个时域范围内出现了规则的周期振荡。原子初态趋于纯态时系统纠缠度较高。随着相干场平均光子数的增大,系统纠缠度的峰值逐渐变小,规则振荡的周期不变。随着跃迁光子数的增大,系统纠缠度的峰值逐渐变大,振荡变得越来越快。随着失谐量的增大,系统纠缠度的峰值逐渐变小。     

Asymptotic Entanglement Sudden Death in Two Atoms with Dipole–Dipole and Ising Interactions Coupled to a Radiation Field at Non-Zero Detuning

We investigate the time evolution and asymptotic behavior of a system of two two-level atoms (qubits) interacting off-resonance with a single mode radiation field. The two atoms are coupled to each other through dipole–dipole as well as Ising interactions. An exact analytic solution for the system dynamics that spans the entire phase space is provided. We focus on initial states that cause the system to evolve to entanglement sudden death (ESD) between the two atoms. We find that combining the Ising and dipole–dipole interactions is very powerful in controlling the entanglement dynamics and ESD compared with either one of them separately. Their effects on eliminating ESD may add up constructively or destructively depending on the type of Ising interaction (Ferromagnetic or anti-Ferromagnetic), the detuning parameter value, and the initial state of the system. The asymptotic behavior of the ESD is found to depend substantially on the initial state of the system, where ESD can be entirely eliminated by tuning the system parameters except in the case of an initial correlated Bell state. Interestingly, the entanglement, atomic population and quantum correlation between the two atoms and the field synchronize and reach asymptotically quasi-steady dynamic states. Each one of them ends up as a continuous irregular oscillation, where the collapse periods vanish, with a limited amplitude and an approximately constant mean value that depend on the initial state and the system parameters choice. This indicates an asymptotic continuous exchange of energy (and strong quantum correlation) between the atoms and the field takes place, accompanied by diminished ESD for these chosen setups of the system. This system can be realized in spin states of quantum dots or Rydberg atoms in optical cavities, and superconducting or hybrid qubits in linear resonators.     

混合态下运动原子与相干态光场相互作用的量子纠缠

利用负熵方法,研究了混合态运动原子与相干态光场相互作用系统的量子纠缠特性,讨论了原子初态、场模结构参数、相干场平均光子数、失谐量、跃迁光子数等物理参量对系统纠缠度的影响。结果表明：考虑原子运动时,系统纠缠度在整个时域范围内出现了规则的周期振荡。原子初态趋于纯态时系统纠缠度较高。随着相干场平均光子数的增大,系统纠缠度的峰值逐渐变小,规则振荡的周期不变。随着跃迁光子数的增大,系统纠缠度的峰值逐渐变大,振荡变得越来越快。随着失谐量的增大,系统纠缠度的峰值逐渐变小。