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1.
In this paper, we study a Hamiltonian system constituted by two coupled two-level atoms (qubits) interacting with a nonlinear generalized cavity field. The nonclassical two-qubit correlation dynamics are investigated using Bures distance entanglement and local quantum Fisher information under the influences of intrinsic decoherence and qubit–qubit interaction. The effects of the superposition of two identical generalized coherent states and the initial coherent field intensity on the generated two-qubit correlations are investigated. Entanglement of sudden death and sudden birth of the Bures distance entanglement as well as the sudden changes in local Fisher information are observed. We show that the robustness, against decoherence, of the generated two-qubit correlations can be controlled by qubit–qubit coupling and the initial coherent cavity states. 相似文献
2.
We study the dynamics evolution of a two-qubit Heisenberg XXX spin chain under a time-dependent rotating magnetic field. Based on the
algebraic structure of the non-autonomous system, the exact solution of the Schrödinger equation is obtained by using the method of algebraic dynamics. Based on the time-dependent analytical solution, we further study the entanglement evolution between the two coupled spins for different initial states, and find that the entanglement is determined by the coefficients of the initial state and the coupling constant $J$ of the system. 相似文献
3.
我们研究了含时旋转磁场中海森堡XXX模型下的双量子比特的动力学演化情况.基于此非自治系统的代数结构,我们用代数动力学方法求得了系统的精确解析解.在此基础上,进一步研究了在不同初态下系统的纠缠测度随时间的演化,发现纠缠测度由系统的初态的系数和耦合强度决定. 相似文献
4.
F. Kheirandish S. J. Akhtarshenas H. Mohammadi 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2010,57(1):129-140
Entanglement dynamics of an open two-qubit anisotropic
XY Heisenberg system is investigated in the presence of an
inhomogeneous magnetic field and spin-orbit interaction. We
suppose that each qubit interacts with a separate thermal
reservoir which is held in its own temperature. The asymptotical
and the dynamical behavior of entanglement are analyzed. To
distinguish between entanglement induced by the environment and
entanglement due to the presence of inter-qubit interaction, the
effects of spin-orbit parameter D and temperature difference
parameter ΔT on the entanglement of the system have been
investigated. We show that for a fixed set of the system
parameters, entanglement can be produced just by adjusting the
temperature difference between the reservoirs. The size of this
entanglement, which is induced by temperature difference of
reservoirs, increases as the spin-orbit parameter D increases.
Also we find that, this environment induced entanglement can be
improved if the qubit influenced by the weaker magnetic field is
in contact with the hotter reservoir, i.e. indirect geometry of
connection. In this case, the amount of asymptotic entanglement
increases as D increases. Regardless of the geometry of
connection, increasing D causes the appearance of entanglement
in the larger regions of TM-ΔT plane, therefore
entanglement can exist in higher temperatures and temperature
differences. Furthermore, increasing D enhances the amount of
entanglement in these regions. We also show that the state of the
system can be found in the maximally entangled state for the case
of zero temperature reservoirs and large amount of the spin-orbit
parameter. 相似文献
5.
We study the dynamics of entanglement in a two-qubit system interacting with a squeezed thermal bath via a dissipative system-reservoir interaction with the system and reservoir assumed to be in a separable initial state. The resulting entanglement is studied by making use of concurrence as well as a recently introduced measure of mixed state entanglement via a probability density function which gives a statistical and geometrical characterization of entanglement by exploring the entanglement content in the various subspaces spanning the two-qubit Hilbert space. We also make an application of the two-qubit dissipative dynamics to a simplified model of quantum repeaters. 相似文献
6.
Bing Xie G. R. Zeng Hui Pan Zisheng Wang 《International Journal of Theoretical Physics》2016,55(3):1474-1491
The time-dependent Pancharatnam phase and the quantum correlations are studied for the two-qubit system in correlated dephasing environment. We find that in both X-state and Y-state, the rapid changes of the time-dependent Pancharatnam phase are intrinsic in the died and alive phenomena of quantum entanglement described by the concurrence under the exactly same parameters, while the slow changes of the time-dependent Pancharatnam phase correspond to the sudden death of entanglement. The results show that the time-dependent Pancharatnam phase includes the information of quantum correlations. 相似文献
7.
Li-Tuo Shen Zhen-Biao Yang Mei Lu Rong-Xin Chen Huai-Zhi Wu 《Applied physics. B, Lasers and optics》2014,117(1):195-202
We study the ground states of the single- and two-qubit asymmetric Rabi models, in which the qubit–oscillator coupling strengths for the counterrotating-wave and corotating-wave interactions are unequal. We take the transformation method to obtain the approximately analytical ground states for both models and numerically verify its validity for a wide range of parameters under the near-resonance condition. We find that the ground-state energy in either the single- or two-qubit asymmetric Rabi model has an approximately quadratic dependence on the coupling strengths stemming from different contributions of the counterrotating-wave and corotating-wave interactions. For both models, we show that the ground-state energy is mainly contributed by the counterrotating-wave interaction. Interestingly, for the two-qubit asymmetric Rabi model, we find that, with the increase in the coupling strength in the counterrotating-wave or corotating-wave interaction, the two-qubit entanglement first reaches its maximum and then drops to zero. Furthermore, the maximum of the two-qubit entanglement in the two-qubit asymmetric Rabi model can be much larger than that in the two-qubit symmetric Rabi model. 相似文献
8.
9.
We investigate the entanglement of a two-qubit anisotropic Heisenberg XY chain in thermal equilibrium at temperature T in the presence of an external magnetic field B along the z axis. By means of the combined influences of anisotropic interactions and a magnetic field B, one is able to produce entanglement for any finite T, by adjusting the magnetic field strength. This contrasts with the isotropic interaction or the B = 0 cases, for which there is no entanglement above a critical temperature T(c) that is independent of the external B field. 相似文献
10.
The Berry phase in a composite system induced by the time-dependent interaction is discussed. We choose two coupled spin-1/2 systems as the composite system: one of the subsystems is subjected to a static magnetic field, and the coupling parameters between two spins are controllable in time. We show that the time-dependent interaction can induce the Berry phase in a similar way as that a spin-1/2 system (qubit) is driven by an effective time-dependent magnetic field. Furthermore, using two consecutive cycles with opposite directions of both the static magnetic field as well as opposite signs of the coupling parameters, a nontrivial two-qubit unitary transformation purely based on Berry phases can be constructed. 相似文献
11.
Critical entanglement and geometric phase of a two-qubitmodel with Dzyaloshinski--Moriya anisotropic interaction 下载免费PDF全文
We consider a two-qubit system described by the Heisenberg
XY model with Dzyaloshinski--Moriya (DM) anisotropic interaction
in a perpendicular magnetic field to investigate the relation
between entanglement, geometric phase and quantum phase transition
(QPT). It is shown that the DM interaction has an effect on the
critical boundary. The combination of entanglement and geometric
phase may characterize QPT completely. Their jumps mean that the occurrence
of QPT and inversely the QPT at the critical point at least
corresponds to a jump of one of them. 相似文献
12.
G. Lagmago Kamta A. Y. Istomin A. F. Starace 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,44(2):389-400
We study systematically the entanglement of a two-qubit
Heisenberg XY model in thermal equilibrium in the presence of an
external arbitrarily-directed static magnetic field, thereby
generalizing our prior work [G. Lagmago Kamta, A.F. Starace, Phys.
Rev. Lett. 88, 107901 (2002)]. We show that a magnetic field
having a component in the xy-plane containing the spin-spin
interaction components produces different entanglement for
ferromagnetic (FM) and antiferromagnetic (AFM) couplings. In
particular, quantum phase transitions induced by the magnetic
field-driven level crossings always occur for the AFM-coupled
qubits, but only occur in FM-coupled qubits when the coupling is of
Ising type or when the magnetic field has a component perpendicular
to the xy-plane. When the magnetic field has a component in the
xy-plane, the cut-off temperature above which the entanglement of
both the FM- and AFM-coupled qubits vanishes can always be
controlled using the magnetic field for any value of the XY coupling
anisotropy parameter. Thus, by adjusting the magnetic field, an
entangled state of two spins can be produced at any finite
temperature. Finally, we find that a higher level of entanglement is
achieved when the in-plane component of the magnetic field is
parallel to the direction in which the XY exchange coupling is
smaller. 相似文献
13.
M. Ban 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2010,58(3):415-421
Decoherence of interacting two qubits placed
under the influence of a common environment
is studied by means of the quantum master equation,
where the two qubits interact with each other
via the XY-coupling and the two-qubit system
has the dephasing coupling with the environment.
It is shown that when the asymmetry of the
interaction between the two-qubit system and environment
is not small,
the qubit-qubit interaction significantly affects
the dephasing of the two-qubit system.
To examine such an interaction effect,
the decay of two-qubit entanglement is calculated.
It is found that the qubit-qubit interaction makes not only
the decay of entanglement small
but also the period of the oscillatory behaviour short. 相似文献
14.
The entanglement between two stationary qubits is a kind of valuable quantum resources in quantum information or quantum network. This paper investigates the time evolution of the entanglement between two atoms, which are initially prepared in the Bell states and each of which interacts with its own cavity field in the identical and non-identical double damping Jaynes-Cummings (J-C) system. It mainly considers the effect of the atomic spontaneous decay Γ and the decay of cavity field κ on the two-qubit entanglement in such system. While causing the decay of entanglement, Γ and κ can also play a positive role in the entanglement evolution, which may imply a way to better control and maintain the entanglement. What is more, the rules governing the transfer of entanglement between two-qubit subsystems in strong coupling regime are finally studied by taking Γ and κ into consideration. 相似文献
15.
The effect of Dzialoshinski-Moriya (DM) interaction on thermal entanglement of a two-qubit XXZ spin chain in a homogenous magnetic field is investigated. It is found that the DM interaction can enhance thermal entanglement. When D is large enough, the entanglement can exist for larger temperatures and strong magnetic field. 相似文献
16.
We investigate a Heisenberg spin cluster with two particles controlled by a time-dependent magnetic field. The system is controlled by tuning the amplitude, frequency, and interaction time of the three-step time-dependent magnetic field. Then we solve the time-dependent Schrodinger equation of the two-particle system, and obtain the time evolution operator. By the three-timestep interaction, the wavefunction evolves from the initial state to the final state, and the total evolution operator can be expressed as a product of the three evolution operators. By adjusting the physical parameters, the key two-qubit logic gate, the C-Not gate, can be realized physically. 相似文献
17.
Dynamics of entanglement protection of two qubits using a driven laser field and detunings:Independent and common,Markovian and/or non-Markovian regimes 下载免费PDF全文
Preventing quantum entanglement from decoherence effect is of theoretical and practical importance in the quantum information processing technologies.In this regard,we consider the entanglement dynamics of two identical qubits where the qubits which are coupled to two independent(Markovian and/or non-Markovian) as well as a common reservoir at zero temperature are further interacted with a classical driving laser field.Then,we study the preservation of generated two-qubit entanglement in various situations using the concurrence measure.It is shown that by applying the classical driving field and so the possibility of controlling the Rabi frequency,the amount of entanglement of the two-qubit system is improved in the off-resonance condition between the qubit and the central cavity frequencies(central detuning) in both non-Markovian and Markovian reservoirs.While the central detuning has a constructive role,the detuning between the qubit and the classical field(laser detuning) affects negatively on the entanglement protection.The obtained results show that long-living entanglement in the non-Markovian reservoir is more accessible than in the Markovian reservoir.We demonstrate that,in a common reservoir non-zero stationary entanglement is achievable whenever the two-qubit system is coupled to the reservoir with appropriate values of relative coupling strengths. 相似文献
18.
Dynamic evolution of entanglement is studied for coupling two-qubit system in non-Markov environment in terms of concurrence.
We find that the degree of entanglement depends on the initial quantum state of the system and the interaction between the
two-qubit system and the environment. When the interaction between the qubits and the environment is completely symmetric,
especially, the environment has no effect on the entanglement, where the decoherence is entirely resulted from the interaction
between qubits. By controlling the coupling way of the interaction, thus, one may avoid the entanglement sudden death (ESD). 相似文献
19.
Entanglement in a two-qubit Heisenberg XXZ chain with different Dzyaloshinskii-Moriya couplings and an inhomogeneous magnetic field 下载免费PDF全文
Ground state entanglement and thermal entanglement of a two-qubit Heisenberg XXZ chain in the presence of the different Dzyaloshinski-Moriya interaction and inhomogeneous magnetic field are investigated.By the concept of concurrence, we find that the inhomogeneity of the magnetic field may make entanglement last for a long time and the critical temperature is dependent on Jz and b. The entanglement can be increased by increasing the temperature in some cases. We also find that the x-component parameter Dx has a higher critical temperature and more entanglement for a certain condition than the z-component parameter Dz. 相似文献
20.
研究了热平衡温度,自旋交换相互作用,Dzyaloshinskii-Moriya(DM)相互作用及外加非一致性磁场对两比特海森堡XYZ自旋链量子系统的热纠缠与局域量子不确定度的影响,对比分析了并发度量子纠缠与局域量子不确定度描述自旋链系统量子关联的差别.结果表明自旋链系统的量子纠缠在热平衡温度,DM相互作用及外加磁场的非一致性参数的变化情况下均会出现纠缠突然死亡的再生现象,而自旋链系统的局域量子不确定度随着这些参数呈连续变化现象.并且,自旋交换相互作用,DM相互作用及外加横向磁场作用强度较小时,他们的变化对自旋链系统的量子纠缠与局域量子不确定度的影响有着明显的差别. 相似文献