利用concurrence作为纠缠度量,研究了 z 方向非均匀磁场中双量子比特的海森堡 XYZ 模型及其基态纠缠在不同参数范围内的性质,通过计算得出了临界磁场值,讨论了平均磁场和临界磁场与量子相变的关系,分析了两个相邻量子位自旋 z 分量 J z 的相互作用和各向异性参数 γ B 、 γ J 对海森堡模型热纠缠的影响,通过绘制图像说明了各向异性、自旋耦合参数 J z 和热纠缠之间的关系。研究结果表明:在双量子比特系统中,对于有效的温度 T ,当耦合参数 J z =0时,随着 γ J 的增加,临界磁场 Bc 减小,纠缠逐渐消失;但是当耦合参数 J z >0时,对各向异性参数 γ B 、 γ J 取合适的值,随着 J z 的增加,纠缠度达到最大值的磁场范围和温度范围都变大,且纠缠得到有效增强。

Herein, we study the Heisenberg two-qubit XYZ chain in a z -directional non-uniform magnetic field by considering concurrence to be the entanglement metric. Further, we explore the properties of ground-state entanglement in different parameter ranges, calculate the critical magnetic field value, and discuss the relations between the average/critical magnetic fields and the quantum phase transition. We also analyze the interaction of the two adjacent qubits of the z -component J _z of the spin and investigate the influences of the anisotropy parameters γ _B and γ _J on the thermal entanglement of the Heisenberg model. The relations among the anisotropy, coupling parameter J _z , and thermal entanglement can be better illustrated by drawing images. The results denote that in a two-qubit system at an effective temperature T , the critical magnetic field B_c decreases and the entanglement gradually disappears as γ _J increases when the coupling parameter J _z is equal to 0. However, when the coupling parameter J _z is greater than 0, the ranges of magnetic field and temperature with the maximum degree of entanglement increase with increasing J _z for appropriate values of the anisotropy parameters γ _B and γ _J , effectively enhancing the entanglement.