Thermal Entanglement of an XY Two-Qutrit Spin Chain with Dzialoshinski-Moriya Interaction

The effect of Dzialoshinski-Moriya (DM) interaction on thermal entanglement of an XY two-qutrit spin chain is investigated. We find that DM interaction and the anisotropy parameter can enhance quantum thermal entanglement to a maximal value individually. However, when both of them take large values, the entanglement is not enhanced, but is destroyed. Our analysis will shed some light on the understanding of the effect of the DM interaction on thermalentanglement of an XY two-qutrit spin chain.     

Thermal Entanglement of a Two-Qubit XXZ Heisenberg Chain with Dzialoshinski-Moriya Interaction

The effect of DziaJoshinski-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.     

Thermal Entanglement of a Two-Qubit XXZ Heisenberg Chain with Dzialoshinski-Moriya Interaction

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.     

三比特铁磁质海森堡自旋链模型的热纠缠

本文对带Dzyaloshinskii-Moriya(DM)相互作用的铁磁质海森堡XXZ自旋链模型在磁场中的热纠缠进行了详细地计算和分析.通过画图发现铁磁质模型的热纠缠远大于反铁磁质模型的热纠缠.同时发现外磁场B,耦合系数J_Z和DM相互作用D都可以有效地控制纠缠和临界温度T_C.该结论为实验上利用海森堡XXZ模型的纠缠特性进行隐形传态提供了很好的理论依据.     

三比特铁磁质海森堡自旋链模型的热纠缠

本文对带DM相互作用的铁磁质海森堡XXZ自旋链模型在磁场中的热纠缠进行了详细地计算和分析. 通过画图发现铁磁质模型的热纠缠远大于反铁磁质模型的热纠缠. 同时发现外磁场 ,耦合系数 和DM相互作用 都可以有效地控制纠缠和临界温度 . 该结论为实验上利用海森堡XXZ模型的纠缠特性进行隐形传态提供了很好的理论依据.     

Thermal Entanglement in Two-Qutrit Heisenberg XX Chain with Different Dzyaloshinskii-Moriya Interaction and Nonuniform Magnetic Field

The effects of the different Dzyaloshinskii-Moriya (DM) interaction on thermal entanglement of a two-qutrit Heisenberg XX spin chain in a nonuniform magnetic field are investigated. Our results imply that the x-component DM interaction plays a central role in enhancing quantum entanglement and it has a higher critical temperature than the z-component DM interaction. The entanglement can be tunable controlled by changing the multiple of the magnetic fields B1 and B2 . Also we found that different DM interaction are competitive to each other in some conditions.     

Thermal Entanglement in Two-Qutrit Heisenberg XX Chain with Different Dzyaloshinskii-Moriya Interaction and Nonuniform Magnetic Field

The effects of the different Dzyaloshinskii-Moriya (DM) interaction on thermal entanglement of a two-qutrit Heisenberg XX spin chain in a nonuniform magnetic field are investigated. Our results imply that the x-component DM interaction plays a central role in enhancing quantum entanglement and it has a higher critical temperature than the z-component DM interaction. The entanglement can be tunable controlled by changing the multiple of the magnetic fields B₁ and B₂. Also we found that different DM interaction are competitive to each other in some conditions.     

Ground-State and Thermal Entanglement in Three-Spin Heisenberg-XXZ Chain with Three-Spin Interaction

The entanglement properties of a three-spin X X Z Heisenberg chain with three-spin interaction are studied by means of concurrence of pairwise entanglement. We show that ground-state pairwise entanglement, pairwise thermal entanglement, or quantum phase transition is not present in antiferromagnetic spin chain. For the ferromagnetic case, quantum phase transition takes place at △ = 1 for anisotropic interaction and at some values of three-spin coupling strength, and pairwise thermal entanglement increases when the value of J/T increases and with anisotropic interaction and three-spin interaction decrease. In addition, we find that increasing the anisotropic interaction and the three-spin interaction will decrease critical temperature.     

三量子位和四量子位Heisenberg XY链中的纠缠与自旋压缩(英文)

研究了三量子位和四量子位Heisenberg XY链中的基态纠缠与自旋压缩,给出了纠缠C和自旋压缩参数ξ2的解析表达式.结果表明,当外部磁场B大于某一临界值Bc时,纠缠与自旋压缩等价,即纠缠意味着自旋压缩,反之亦然.对三量子位情形,Bc=J[(4-3γ2)1/2-1];对四量子位情形,Bc可以通过数值方法进行求解.     

非均匀外磁场下海森堡自旋链的热纠缠

研究了两量子比特海森堡XXX自旋链处于x方向的非均匀磁场时系统的纠缠特性,并用负度N来度量.得到N的解析表达式,并在此基础上进行数值计算.仔细讨论了均匀磁场B、非均匀磁场b、温度T和自旋耦合系数J对纠缠度N的影响.结果表明:N会随着■和T的增大而减小,但会随着J的增大而增大.同时,增大的J和b还会使临界磁场■和临界温度T_th变大,从而使系统中热纠缠存在的磁场范围和温度范围都变大.这一点在较大磁场和较高温度下需要纠缠具有实际意义.由此,我们可以通过调节B、b、T和J来控制热纠缠,这对固态系统中通过构建和选择参数调整系统的纠缠度具有一定的作用和意义.     

含三体相互作用的海森堡自旋链纠缠研究

研究了含三体相互作用的海森堡自旋链的能级和相应本征态的纠缠情况,详细分析了含有三个粒子的海森堡自旋链的纠缠,发现所有的纠缠态都为W态。给出三粒子海森堡自旋链在温度为零时的基态纠缠,发现反铁磁自旋链的基态不随各向异性、耦合强度等参数发生变化,铁磁自旋链的基态纠缠随各向异性因子和三自旋耦合项而改变。讨论了三比特自旋链在低温时的热纠缠,给出纠缠度表达式及其随温度、各向异性因子和耦合强度的变化关系。     

非匀强磁场中双量子位Heisenberg XY链的基态纠缠和热纠缠(英文)

研究了非匀强磁场中各向异性Heisenberg XY链的基态纠缠和热纠缠.结果表明对双量子位情形,纠缠与格点间耦合常数J、外部磁场B、各向异性参数γ和b的正负无关.对绝对零度情形,我们给出了纠缠C的解析表达式,并指出临界磁场Bc随磁场各向异性参数b的增大而增大.对有限温度情形,我们给出了γ=0时C的解析表达式和γ≠0时的数值模拟结果,结果发现引进非匀强磁场可以使纠缠在某些区域明显增大;同时我们还指出当γ=0时,纠缠存在的临界温度Tc仅是b的增函数,而当γ≠0时,它却由B和b共同决定.     

Disentanglement of Two Qubits Coupled to an XY Spin Chain at Finite Temperature

The disentanglement evolution of bipartite spin-1/2 system coupled to a common surrounding XY chain in transverse fields at nonzero temperature is studied in this letter. The dynamical process of the entanglement is numerically and analytically investigated. We find that thermal effects can enhance disentanglement if the entangled initial state of the central spins does not in the decoherence free space. The critical phenomenon of quantum phase transitions reflected in the disentanglement can be washed out by the thermal effect eventually.     

Effect of Dzialoshinski-Moriya interaction on thermal entanglement of a mixed-spin chain

The effect of Dzialoshinski-Moriya (DM) interaction on thermal entanglement of a mixed-spin chain in an external magnetic field is investigated. It is found that DM interaction may enhance quantum thermal entanglement to a maximal value even though the magnetic field plays a positive role in shrinking thermal entanglement in the mixed-spin chain. Furthermore, the effect of inhomogeneity of the magnetic field on quantum entanglement is analyzed. Our analysis will shed some light on the understanding of the effect of the DM interaction on thermal entanglement of a mixed-spin chain. Supported by the National Natural Science Foundation of China (Grant No. 60573008) and Anhui Foundation for Young Teachers (Grant No. 2008jq1025zd)     

Ground-State and Thermal Entanglement in Three-Spin Heisenberg-XXZ Chain with Three-Spin Interaction

The entanglement properties of a three-spin X X Z Heisenberg chain with three-spin interaction are studied by means of concurrence of pairwise entanglement. We show that ground-state pairwise entanglement, pairwise thermal entanglement, or quantum phase transition is not present in antiferromagnetic spin chain. For the ferromagnetic case, quantum phase transition takes place at A = 1 for anisotropic interaction and at some values of three-spin coupling strength, and pairwise thermal entanglement increases when the value of J/T increases and with anisotropic interaction and three-spin interaction decrease. In addition, we find that increasing the anisotropic interaction and the three-spin interaction will decrease critical temperature.     

Quantum Communication in Spin Chain with Multiple Spin Exchange Interaction

The transmission of quantum states in the anisotropic Heisenberg XXZ chain model with three-spin exchange interaction is studied. The average fidelity is used to evaluate the state transfer. It is found that quantum communication can be enhanced by the anisotropic coupling and multiple spin interaction. Such spin model can reduce the time required for the perfect state transmission where the fidelity is unity. The maximally entangled Bell states can be generated and separated from the whole quantum systems.     

Entanglement and Fidelity of a Spin Ladder with Dzyaloshinsky-Moriya Interaction

The spin ladder with Dzyaloshinsky-Moriya interaction is investigated by using the quantum renormalization-group method. The entanglement and fidelity are periodic functions of the time and oscillate between zero and one. The oscillation period decreases with either the interaction in the spin ladder or the
Dzyaloshinsky-Moriya interaction increasing. When the system relates to the environment, both entanglement and fidelity oscillate with a damping rate related to intrinsic decoherence rate, the interaction in the spin ladder, and the Dzyaloshinsky-Moriya interaction.     

次近邻相互作用对Heisenberg XX链纠缠影响的研究

研究了存在次近邻相互作用(耦合)时Heisenberg XX链的纠缠特性. 结果表明对近邻格点, 随着耦合常数J的变化, 次近邻相互作用的存在可能使其纠缠度增大或者减小; 而对次近邻格点, 引进次近邻相互作用却可以产生纠缠, 并且使其随着|J|的增大而增大. 近邻格点间纠缠存在的临界温度T_c随着J的增大而降低, 次近邻格点间纠缠存在的临界温度T_c随着|J|的增大而升高. 此外对纠缠W态的制备, 次近邻相互作用的存在还使得三量子位情形时W态产生的时刻改变, 而对于四量子位情形却没有影响.     

Thermal Spin Squeezing as a Signature of Thermal Global Entanglement in Heisenberg Models

We study thermal spin squeezing (TSS) and thermal global entanglement (TGE) in a general Heisenberg spin chain, in the presence of Dzyaloshinskii-Moriya interaction and an external magnetic field. We derive an inequality associating the squeezing parameter and the global concurrence, which establishes (TSS) as a signature of (TGE). The inequality reduces to equality for particular symmetric chains which also associates TSS with bipartite entanglement in such systems. We also check the results by presenting two numerical examples.