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1.
LING Yin-Sheng 《理论物理通讯》2008,50(12):1295-1298
Use Jordan-Wigner transformation the eigenstates and eigenenergies of live qubits XX chain including external magnetic field are obtained. The concurrences Co,1 and Co,2 of ground state are obtained. For the ferromagnetic, when [(√5 - 1)/2]|J| 〈 B ≤ |J|, the values of C0,1 and C0,2 are the same. The C0,2 is easily broken by temperature. 相似文献
2.
CAO Min LING Yin-Sheng ZHU Shi-Qun 《理论物理通讯》2009,51(5):811-814
We calculate the eigenvalues and eigenvectors of a five-qubit isotropic Heisenberg model in an external magnetic field, and give analytical results for the concurrence of two nearest-neighbor qubits. A magnetic field can eliminate degeneration and change the ground state of the system. Therefore increasing the value of the magnetic field can induce entanglement in a certain range both for the antiferromagnetic and ferromagnetic case. 相似文献
3.
LING Yin-Sheng 《理论物理通讯》2007,48(6):1017-1020
Using Jordan-Winger transformation and finite Fourier transformation, the Hamiltonian of XX chain can be transformed to the diagonal form. If the total qubits number N=odd, the
internal energy
U, and correlation function
Gzz in thermal
equilibrium can be calculated. Then the pairwise concurrence and the
critical value βcr can be calculated. For N≥5 XX
chains, there are pairwise concurrences in thermal equilibrium for
antiferromagnetic and ferromagnetic cases when β>βcr. 相似文献
4.
We calculate the concurrence of all pairwise entanglement of
Heisenberg XX open chain with single system impurity in three-qubit
and four-qubit cases, and find that the impurity parameter Ji has
great effect on pairwise entanglement. Choosing the proper parameter
Ji, we can obtain the maximal pairwise entanglement of the
nearest qubits and make the non-nearest qubits entangle. 相似文献
5.
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Tc随着J的增大而降低, 次近邻格点间纠缠存在的临界温度Tc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. 相似文献
6.
We show that although we cannot distil a singlet from many pairs of bound entangled states, the concurrence and the tangle of two entangled quantum states are always strictly larger than those of one of them, even both entangled quantum states are bound entangled. We present a relation between the concurrence and the fidelity of optimal teleportation. We also give new upper and lower bounds for concurrence and tangle. 相似文献
7.
8.
9.
The concurrence vectors are proposed by employing the fundamental representation of A
n Lie algebra, which provides a clear criterion to evaluate the entanglement of bipartite systems of arbitrary dimension. Accordingly,
a state is separable if the norm of its concurrence vector vanishes. The state vectors related to SU(3) states and SO(3) states are discussed in detail. The sign situation of nonzero components of concurrence vectors of entangled bases presents
a simple criterion to judge whether the whole Hilbert subspace spanned by those bases is entangled, or there exists an entanglement
edge. This is illustrated in terms of the concurrence surfaces of several concrete examples.
相似文献
10.
HE Zheng-Hong XIONG Zu-Hong HU Dong-Mei 《理论物理通讯》2007,47(5):811-815
Quantum teleportation is investigated by using the entangled states of two-qubit Heisenberg XX chain in an external uniform magnetic field as resources in the model of Milburn's intrinsic decoherence. Though intrinsic decoherence on quantum entanglement and quantum teleportation exerts different effects in different initial systems, proper magnetic fields and probabilities of different eigenstates in the initial states can weaken the effects. 相似文献
11.
In this paper,we study the quantum phase transition and the effect of impurity on the thermal entanglement between any two lattices in three-qubit Heisenberg XX chain in a uniform magnetic field.We show that the quantum phase transition always appears when impurity parameter is an arbitrary constant and unequal to zero,the external magnetic field and impurity parameters have a great effect on it.Also,there exists a relation between the quantum phase transition and the entanglement.By modulating the temperature,magnetic field and the impurity parameters,the entanglement between any two lattices can exhibit platform-like behaviour,which can be used to realize entanglement switch. 相似文献
12.
Based on algebraic dynamics and the concept of the concurrence of the entanglement, we investigate the evolutive properties of the two-qubit entanglement that formed by Heisenberg XXX models under a time-depending external field. For this system, the property of the concurrence that is only dependent on the coupling constant J and total values of the external field is proved. Furthermore, we found that the thermal concurrence of the system under a static random external field is a function of the coupling constant J, temperature T, and the magnitude of external field. 相似文献
13.
14.
Pair coherent state, is a state of a two-mode radiation field that is known as a state with non-gaussian wave function. In this paper, study on the pair coherent state, we notice that with superposition of two first terms of this states, one two-qubits formed. Because of the importance of two-qubits in theory of quantum entanglement, with two different measures with the title of concurrence and D-concurrence, we have studied the amount of entanglement and
discussed its details. At the end, we describe these measures for pair coherent states as a function of the amplitude of the SU(2) coherent states. 相似文献
15.
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. 相似文献
16.
通过计算比特数n不大于6海森堡XX链中的两体纠缠,发现只有当n为奇数时,最近邻纠缠在磁场为零时才出现下凹现象.当n为4或6时,非最近邻纠缠在磁场两边对称;当n为5时,非最近邻纠缠在磁场两边则不对称. 相似文献
17.
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. 相似文献
18.
An important property of entanglement: pairwise entanglement that can only be transferred by an entangled pair 总被引:1,自引:0,他引:1
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Based on the calculation of all the pairwise entanglements in the n (n ≤ 6)-qubit Heisenberg XX open chain with system impurity, we find an important result: pairwise entanglement can only be transferred by an entangled pair. The non-nearest pairwise entanglements will have the possibility to exist as long as there has been even number of qubits in their middle. This point indicates that we can obtain longer distance entanglement in a solid system. 相似文献
19.
两原子与数态场相互作用系统中纠缠的调控 总被引:1,自引:1,他引:0
通过计算并发度研究了两个处于初始激发态的两能级原子与数态场相互作用系统的纠缠动力学特性,并讨论了场的光子数、原子和场的失谐量以及原子操作对并发度的影响。结果表明当不存在原子操作时,两原子之间的纠缠出现突然产生现象,并且可以通过调节光子数和原子与场的失谐量来控制产生纠缠的阈值时间和纠缠的最大值。当存在原子操作时,两原子之间的纠缠随着时间的演化可以立即产生,而且通过对经典场的操作和控制可以实现两原子之间纠缠的调控。 相似文献