The bipartite and tripartite entanglement in a three-qubit Heisenberg XY model with a nonuniform magnetic field is studied. There are two or four peaks in the concurrence of the bipartite entanglement when the amplitu...The bipartite and tripartite entanglement in a three-qubit Heisenberg XY model with a nonuniform magnetic field is studied. There are two or four peaks in the concurrence of the bipartite entanglement when the amplitudes of the magnetic fields are. differently distributed between the three qubits. It is very interesting to note that there is no tangle of tripartite entanglement between the three qubits when the amplitudes of the magnetic fieMs are varied. However, the variation of the magnetic field direction can induce the tangle. The tangle is periodic about the angle between the magnetic field and the z axis of the spin.展开更多
The bipartite entanglement of the two- and three-spin Heisenberg model was investigated by using the concept of negativity. It is found that for the ground-state entanglement of the two-spin model, the negativity alwa...The bipartite entanglement of the two- and three-spin Heisenberg model was investigated by using the concept of negativity. It is found that for the ground-state entanglement of the two-spin model, the negativity always decreases as B increases if △ 〈γ- 1, and it may keep a steady value of 0.5 in the region of B 〈 J[（△＋ 1）2 -γ^2]^1/2 if △ 〉γ-1, while for that of the three-spin model, the negativity exhibits square wave structures if γ=0 or△=0. For thermal states, there are two areas showing entanglement, namely, the main region and the sub-region. The main region exists only when △ 〉 △c （△c =γ- 1 and （γ^2 - 1）/2 for the 2- and 3-spin model respectively） and extends in terms of B and T as A increases, while the sub-region survives only when γ≠0 and shrinks in terms of B and T as △ increases.展开更多
This paper investigates bipartite entanglement of a two-qubit system with anisotropic couplings under an inhomogeneous magnetic field. This work is mainly to investigate the characteristics of a Heisenberg XYZ chain a...This paper investigates bipartite entanglement of a two-qubit system with anisotropic couplings under an inhomogeneous magnetic field. This work is mainly to investigate the characteristics of a Heisenberg XYZ chain and obtains some meaningful results. By the concept of negativity, it finds that the inhomogeneity of magnetic field may induce entanglement and the critical magnetic field is independent of Jz. The inhomogeneous magnetic field can increase the value of critical magnetic field Bc. It also finds that the magnetic field not only suppresses the entanglement but also can induce it to revival for some time.展开更多
This paper investigates the bipartite entanglement of a two-qubit Heisenberg XXZ chain under an inhomogeneous magnetic field. By the concept of negativity, we find that the inhomogeneity of the magnetic field may indu...This paper investigates the bipartite entanglement of a two-qubit Heisenberg XXZ chain under an inhomogeneous magnetic field. By the concept of negativity, we find that the inhomogeneity of the magnetic field may induce entanglement and the critical magnetic field is independent of Jz. We also find that the entanglement is symmetric with respect to a zero magnetic field. The anisotropy parameter Jz may enhance the entanglement.展开更多
We investigated the quantum entanglement in spin-1 Heisenberg XY chain for two-spin-qutrit and multi-particle systems. As a measure of the entanglement, the negativity of this state was analyzed as a function of the t...We investigated the quantum entanglement in spin-1 Heisenberg XY chain for two-spin-qutrit and multi-particle systems. As a measure of the entanglement, the negativity of this state was analyzed as a function of the temperature and the magnetic field. We gave some numerical results and discussed them in detail. We found that the negativity increases monotonously with the coupling constants |J1| and |J2|, and it showed a symmetry with respect to the point of J1=0 and J2=0. In addition to the above features, there is evidence that the critical temperature is independent of the length of the chain.展开更多
基金The project supported by the Specializcd Research Fund for the Doctoral Program of Higher Education under Grant No. 20050285002 . It is a pleasure to thank Xiang Hao, Jian-Xing Fang and Yin-Sheng Ling for their useful and extensive discussions about the topic.
文摘The bipartite and tripartite entanglement in a three-qubit Heisenberg XY model with a nonuniform magnetic field is studied. There are two or four peaks in the concurrence of the bipartite entanglement when the amplitudes of the magnetic fields are. differently distributed between the three qubits. It is very interesting to note that there is no tangle of tripartite entanglement between the three qubits when the amplitudes of the magnetic fieMs are varied. However, the variation of the magnetic field direction can induce the tangle. The tangle is periodic about the angle between the magnetic field and the z axis of the spin.
基金National Natural Science Foundation of China(10547008)
文摘The bipartite entanglement of the two- and three-spin Heisenberg model was investigated by using the concept of negativity. It is found that for the ground-state entanglement of the two-spin model, the negativity always decreases as B increases if △ 〈γ- 1, and it may keep a steady value of 0.5 in the region of B 〈 J[（△＋ 1）2 -γ^2]^1/2 if △ 〉γ-1, while for that of the three-spin model, the negativity exhibits square wave structures if γ=0 or△=0. For thermal states, there are two areas showing entanglement, namely, the main region and the sub-region. The main region exists only when △ 〉 △c （△c =γ- 1 and （γ^2 - 1）/2 for the 2- and 3-spin model respectively） and extends in terms of B and T as A increases, while the sub-region survives only when γ≠0 and shrinks in terms of B and T as △ increases.
文摘This paper investigates bipartite entanglement of a two-qubit system with anisotropic couplings under an inhomogeneous magnetic field. This work is mainly to investigate the characteristics of a Heisenberg XYZ chain and obtains some meaningful results. By the concept of negativity, it finds that the inhomogeneity of magnetic field may induce entanglement and the critical magnetic field is independent of Jz. The inhomogeneous magnetic field can increase the value of critical magnetic field Bc. It also finds that the magnetic field not only suppresses the entanglement but also can induce it to revival for some time.
文摘This paper investigates the bipartite entanglement of a two-qubit Heisenberg XXZ chain under an inhomogeneous magnetic field. By the concept of negativity, we find that the inhomogeneity of the magnetic field may induce entanglement and the critical magnetic field is independent of Jz. We also find that the entanglement is symmetric with respect to a zero magnetic field. The anisotropy parameter Jz may enhance the entanglement.
文摘We investigated the quantum entanglement in spin-1 Heisenberg XY chain for two-spin-qutrit and multi-particle systems. As a measure of the entanglement, the negativity of this state was analyzed as a function of the temperature and the magnetic field. We gave some numerical results and discussed them in detail. We found that the negativity increases monotonously with the coupling constants |J1| and |J2|, and it showed a symmetry with respect to the point of J1=0 and J2=0. In addition to the above features, there is evidence that the critical temperature is independent of the length of the chain.
