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1.
Chun-Lei Jiang Mao-Fa Fang Yao-Hua Hu 《International Journal of Theoretical Physics》2009,48(6):1672-1677
The thermal entanglement of a Two-qubit anisotropic Heisenberg XYZ chain in thermal equilibrium at temperature T in the presence of external magnetic field is investigated, the combined influence of anisotropic interaction and the inhomogeneous
magnetic field on the thermal entanglement of the system is examined. Our results show that, the thermal entanglement can
be produced at any finite T by adjusting the magnetic field strength, and the critical magnetic field ε for which the concurrence C vanishes is increased by introducing the interaction of the z-component of two neighboring spins J
z
, and by the increasing of the anisotropic parameter γ. 相似文献
2.
Bipartite entanglement of a two-qubit system with anisotropic couplings under nonuniform magnetic fields 下载免费PDF全文
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. 相似文献
3.
Thermal entanglement in two-qutrit spin-1 anisotropic Heisenberg model with inhomogeneous magnetic field 下载免费PDF全文
Erhan Albayrak 《中国物理 B》2010,19(9):90319-090319
The thermal entanglement of a two-qutrit spin-1 anisotropic Heisenberg XXZ chain in an inhomogeneous magnetic field is studied in detail. The effects of the external magnetic field (B), a parameter b which controls the inhomogeneity of B, and the bilinear interaction parameters Jx=Jy≠Jz on the thermal variation of the negativity are studied in detail. It is found that negativity N decreases when the values of magnetic field, inhomogeneity b and temperature are increasing. In addition, N remains at higher temperatures for higher values of Jz and lower values of B and b. 相似文献
4.
Xiu-Xing Zhang Xun-Chang Yin Guang-Hou Sun Chuan-Jia Shan 《International Journal of Theoretical Physics》2010,49(7):1507-1515
We investigate the pairwise thermal entanglement of the extended XY model with three spin interactions and external filed
on zig-zag lattice. The influences of three spin interactions J
2 and external field λ on the thermal entanglement of the nearest neighbor (NN) and next nearest neighbor (NNN) spins are considered. It is found
that J
2 and λ suppress both the maximal value and the critical temperature of the NN entanglement C
12. However, when it comes to the NNN entanglement C
13, there exists a critical value of J
2 above which both the maximal entanglement and the critical temperature can be enhanced by J
2 for a fixed external field. With J
2 fixed, the effect of λ on C
13 are different for different values of J
2. For J
2<1, λ suppresses both T
C
and the maximal values of C
13. For J
2≥1, λ enhances the maximal values of C
13 while decreases the critical temperature. These results show that one is able to get the entanglement wanted by properly
controlling the values of the three spin interactions J
2 and the external field λ. 相似文献
5.
6.
E. Albayrak 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,72(4):491-496
The thermal entanglement of a two-qubit anisotropic Heisenberg XXZ
chain with Dzyaloshinskii-Moriya (DM) interaction in an
inhomogeneous magnetic field was studied in detail. The effects of
the DM parameter, external magnetic field (B), a parameter b
which controls the inhomogeneity of B and the bilinear
interaction parameters Jx = Jy ≠ Jz (the anisotropic case) on
the concurrence (C) was formulated and studied in detail. The
behaviors of the concurrences for the cases between (J = Jz = 1) and
(J = -1,Jz = 1) and, (J = Jz = -1) and (J = 1,Jz = -1) at the ground
state and at the thermal equilibrium are exactly the same. It was
found that for the antiferromagnetic (AFM) case the entanglements
persist to higher temperatures in comparison with the ferromagnetic
(FM) case. In addition, the AFM case presents a special point at
which the nonzero concurrences are all equal at some special
temperatures. The further properties will be given in the text. 相似文献
7.
E. Rastelli A. Tassi 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,3(3):341-347
Ferromagnetic spin chains of a hexagonal lattice coupled by a weak antiferromagnetic interaction J1 develop a helix arrangement if the intrachain antiferromagnetic NNN exchange J2 is sufficiently large. We show that the classical minimum energy spin configuration is an umbrella when an external magnetic field is applied. The scenario is dramatically changed by quantum fluctuations. Indeed we find
that the zero point motion forces the spins in a plane containing the magnetic field so that classical expectation is deceptive
for our model. Our result is obtained by controlled expansion in the low field-long wavelength modulation limit.
Received: 9 September 1997 / Revised: 15 October 1997 / Accepted: 17 November 1997 相似文献
8.
The thermal entanglement in a two-qubit Heisenberg XXZ spin chain is investigated under a single pulse magnetic field Bsinθ. The paper shows that the greater the contribution of the inhomogeneity on the exchange interaction, the higher thermal entanglement will be attained at the fixed temperature except the case that $\theta=2k\pi+\frac{3}{2}\pi$ . J z significantly disturb the thermal entanglement in uniform case. When the structure of the spin system are given, changing the external magnetic field B can induce controllable entanglement. Our study may provide a useful tool to change the entanglement of spin chain system. 相似文献
9.
Teleportation and thermal entanglement in two-qubit Heisenberg X Y Z spin chain with the Dzyaloshinski-Moriya interaction and the inhomogeneous magnetic field 下载免费PDF全文
This paper studies the average fidelity of teleportation and thermal entanglement for a two-qubit Heisenberg X Y Z chain in the presence of both an inhomogeneous magnetic field and a Dzyaloshinski-Moriya interaction. It shows that for a fixed Dz, the increase of bz will broaden the critical temperature at the cost of decreasing the thermal entanglement. And it can modulate the inhomogeneous magnetic field and the Dzyaloshinski-Moriya interaction for the average fidelity of teleportation to be optimal. 相似文献
10.
Pairwise thermal entanglement in a three-qubit Heisenberg XX model with a nonuniform magnetic field and Dzyaloshinski-- Moriya interaction 下载免费PDF全文
Pairwise thermal entanglement in a three-qubit Heisenberg XX model is investigated when a nonuniform magnetic field and the Dzyaloshinski-Moriya interaction are included. We find that the nonuniform magnetic field and Dzyaloshinski-Moriya interaction are the more efficient control parameters for the increase of entanglement and critical temperature. For both the nearest neighbour sites and the next nearest neighbour sites, the magnetic field can induce entanglement to a certain extent and the Dzyaloshinski-Moriya interaction can enhance the entanglement to a stable value. The steady value of the nearest neighbour site entanglement C 12 is larger than the next nearest neighbour site entanglement C 13 . An interesting phenomenon is that the entanglement curve of C 12 appears a peak value when the Dzyaloshinski-Moriya interaction is considered in a nonuniform magnetic field. 相似文献
11.
Guo-Hui Yang Xiang Yang Miao Jun Feng Zhang 《International Journal of Theoretical Physics》2009,48(9):2570-2578
We report the transfer fidelities of two-qubit pure state via a two-qubit Heisenberg XYZ spin model under a nonuniform magnetic field. It shown us that not only the average fidelity can be enhanced evidently but
also the ideal fidelity region can be broadened by introducing the interaction of z component of two neighboring spins J
z
. Decreasing the anisotropy parameter γ also can improve F
a
and result in ideal fidelity. Our study on the average fidelity of this quantum channel system also shows that for any finite
value of temperature T we can obtain the ideal average fidelity by improving the inhomogeneous magnetic field b. F
a
is infinitely close to the maximum value of classical communication 2/3 with increasing b. While increasing the uniform field B can not do this, F
a
are always inferior to 2/3 for enough larger B. 相似文献
12.
Using the effective-field theory based on the Glauber-type stochastic dynamics (DEFT), we investigate dynamic phase transitions and dynamic phase diagrams of the Blume–Emery–Griffiths model under an oscillating magnetic field. We presented the dynamic phase diagrams in (T/J, h0/J), (D/J, T/J) and (K/J, T/J) planes, where T, h0, D, K and z are the temperature, magnetic field amplitude, crystal–field interaction, biquadratic interaction and the coordination number. The dynamic phase diagrams exhibit several ordered phases, coexistence phase regions and special critical points, as well as re-entrant behavior depending on interaction parameters. We also compare and discuss the results with the results of the same system within the mean-field theory based on the Glauber-type stochastic dynamics and find that some of the dynamic first-order phase lines and special dynamic critical points disappeared in the DEFT calculation. 相似文献
13.
D. C. Li Z. L. Cao 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,50(2):207-214
We investigate the entanglement in a two-qubit Heisenberg XYZ
system with different Dzyaloshinskii-Moriya (DM) interaction and
inhomogeneous magnetic field. It is found that the control
parameters (Dx, Bx and bx) are remarkably different
with the common control parameters (Dz, Bz and bz)
in the entanglement and the critical temperature, and these
x-component parameters can increase the entanglement and the
critical temperature more efficiently. Furthermore, we show the
properties of these x-component parameters for the control of
entanglement. In the ground state, increasing Dx (spin-orbit
coupling parameter) can decrease the critical value bxc and
increase the entanglement in the revival region, and adjusting
some parameters (increasing bx and J, decreasing Bx
and Δ) can decrease the critical value Dxc to enlarge
the revival region. In the thermal state, increasing Dx can
increase the revival region and the entanglement in the revival
region (for T or bx), and enhance the critical value
Bxc to make the region of high entanglement larger. Also, the
entanglement and the revival region will increase with the
decrease of Bx (uniform magnetic field). In addition, small
bx (nonuniform magnetic field) has some similar properties to
Dx, and with the increase of bx the entanglement also
has a revival phenomenon, so that the entanglement can exist at
higher temperature for larger bx. 相似文献
14.
J. Chatterjee M. Mitra A.N. Das 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,18(4):573-578
A two-site double exchange model with a single polaron is studied using a perturbation expansion based on the modified Lang-Firsov
transformation. The antiferromagnetic to ferromagnetic transition and the crossover from small to large polaron are investigated
for different values of the antiferromagnetic interaction (J) between the core spins and the hopping (t) of the itinerant electron. Effect of the external magnetic field on the small to large polaron crossover and on the polaronic
kinetic energy are studied. When the magnetic transition and the small to large polaron crossover coincide for some suitable
range of J/t, the magnetic field has very pronounced effect on the dynamics of polarons.
Received 1 June 2000 相似文献
15.
Entanglement teleportation via two spins coupled to each other by one axis twisting spin squeezing interaction is investigated. We mainly concentrate on the properties of the channel entanglement, the output entanglement and the teleportation fidelity. It shows that the output entanglement increases linearly with increasing the value of the input entanglement. With the increasing of T, the teleportated entanglement increases sharply from zero to a maximum value and then decreases slowly to zero when the temperature is improved to one threshold value of T c , and the threshold value of T c increases with the increasing of the input entanglement. When enlarging the external magnetic, F a firstly decreases quickly to a minimum value as the critical magnetic field Ω c is reached, then it increases abruptly to a maximum value and finally it will be a certain value. Besides, the critical external magnetic Ω c increases when μ is larger. For Ω<Ω c the value of the average fidelity increases with the increasing of μ, but for Ω>Ω c the value of it decreases from a maximum value. The influence of T on the average fidelity is similar with μ. 相似文献
16.
X. W. Zhang J. B. Xia 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,58(3):263-268
The electronic structure, spin splitting energies, and g factors of
paramagnetic In1-xMnxAs nanowires under magnetic and electric
fields are investigated theoretically including the sp-d exchange
interaction between the carriers and the magnetic ion. We find that the
effective g factor changes dramatically with the magnetic field. The spin
splitting due to the sp-d exchange interaction counteracts the
Zeeman spin splitting. The effective g factor can be tuned to zero by the
external magnetic field. There is also spin splitting under an electric
field due to the Rashba spin-orbit coupling which is a relativistic effect.
The spin-degenerated bands split at nonzero kz (kz is the wave
vector in the wire direction), and the spin-splitting bands cross at
kz = 0, whose kz-positive part and negative part are symmetrical. A
proper magnetic field makes the kz-positive part and negative part of
the bands asymmetrical, and the bands cross at nonzero kz. In the
absence of magnetic field, the electron Rashba coefficient increases almost
linearly with the electric field, while the hole Rashba coefficient
increases at first and then decreases as the electric field increases. The
hole Rashba coefficient can be tuned to zero by the electric field. 相似文献
17.
K. Maruyama 《Optics and Spectroscopy》2010,108(2):301-304
We present a simple protocol to purify bipartite entanglement in spin-1/2 particles by utilising only natural spin-spin interactions,
i.e., those that can commonly be realised in realistic physical systems, and S
z
-measurements on single spins. Even the standard isotropic Heisenberg interaction is shown to be sufficient to purify mixed
state entanglement if there are at least three pairs of spins. This approach could be useful for quantum information processing
in solid-state-based systems. 相似文献
18.
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 |J
1| and |J
2|, and it showed a symmetry with respect to the point of J
1 = 0 and J
2 = 0. In addition to the above features, there is evidence that the critical temperature is independent of the length of the
chain. 相似文献
19.
A. V. Bondarev V. V. Ozherelyev I. L. Bataronov Yu. V. Barmin 《Bulletin of the Russian Academy of Sciences: Physics》2011,75(10):1352-1356
On the basis of Heisenberg model, the magnetic properties of amorphous terbium were studied by the Monte Carlo method. The
temperature dependences of spontaneous magnetization and magnetic susceptibility were plotted as functions of the fraction
of the constant of anisotropy to the exchange constant D/J
0. The behavior of magnetization in an external magnetic field was studied, and the dependence of a coercive field and residual
magnetization on the value D/J
0 was found. The relaxation of magnetization was investigated after the external magnetic field was switched off. 相似文献
20.
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