The decoherence of quantum entanglement and teleportation in Bell-diagonal states

We study the dynamics of entanglement and teleportation in Bell-diagonal states. Using the concepts of concurrence and fidelity, the analytical expressions of the entanglement, the output entanglement and the average fidelity with decoherence are obtained for this model. We discover a class of initial states in which the output entanglement and the average fidelity are destroyed by decoherence. The quality of teleportation depends on the system parameters and time.     

不确定度漫议——一个数据处理结果引发的讨论

分析了不确定度教学的难点,指出加强不确定度教学的重要性及其实施策略。给出了便于在物理实验教学中应用的不确定度评定的一种简化模式。     

不同方向Dzyaloshinskii-Moriya相互作用和磁场对自旋系统纠缠和保真度退相干的影响

通过求解系统的Milburn方程,研究了包含Dzyaloshinskii-Moriya相互作用的自旋链系统中纠缠和保真度的动力学演化特性,讨论了不同方向Dzyaloshinskii-Moriya相互作用、不同方向均匀和非均匀磁场、不同初始态对纠缠以及保真度退相干的影响.研究发现,非均匀磁场的引入能够抑制纠缠退相干的发生,初始态的选择对系统纠缠状态的影响很大,可以通过调制Dzyaloshinskii-Moriya相互作用的方向来获得所需纠缠和较高的保真度.研究还发现,退相干条件下,无论是均匀还是非均匀磁场对于保真度的提高并不明显.纠缠和保真度随初始态角度的变化具有周期性,可以根据需要来选取不同系统中的最优初始态.     

Li掺杂熔融织构YBCO晶体的面内磁阻

在0～9T范围内测量了磁场平行于P轴时Li掺杂熔融织构YBCO样品面内电阻的温度关系．我们用A～H模型拟合实验数据．结果表明，以R／Rn=20％作为高阻区和低阻区的分界线，R～T曲线可分别用R=Rn{I0[CH^-p（1-t）^q]}^-2来描述，其中Rn是正常态的电阻Rn=-5．36＋0．145T．p=0．78，1．88和q=1．5,3．5分别是高阻区和低阻区的拟合参数．     

熔融织构Y0.8Ca0.2Ba2Cu3Oy的电子比热

采用热驰豫方法在0到9T范围内测量了熔融织构Y0.8Ca0.2Ba2Cu3O y的比热.零场下,2～180K的比热结果可以用Einstein模型来描述.通过4-Einstein峰拟合声子谱的方法,我们分别处理了不同磁场下超导转变附近的比热,获得了晶格比热和不同磁场下的电子比热,并将实验结果与London模型的计算结果进行对比,发现London模型能够很好地模拟出我们的实验结果.     

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.     

Entanglement in a two-qubit Heisenberg XXZ chain with different Dzyaloshinskii-Moriya couplings and an inhomogeneous magnetic field

Ground state entanglement and thermal entanglement of a two-qubit Heisenberg XXZ chain in the presence of the different Dzyaloshinski-Moriya interaction and inhomogeneous magnetic field are investigated.By the concept of concurrence,we find that the inhomogeneity of the magnetic field may make entanglement last for a long time and the critical temperature is dependent on Jz and b.The entanglement can be increased by increasing the temperature in some cases.We also find that the x-component parameter Dx has a higher critical temperature and more entanglement for a certain condition than the z-component parameter Dz.     

Li掺杂熔融织构YBCO晶体的面内磁阻

在0～9T范围内测量了磁场平行于c-轴时Li掺杂熔融织构YBCO样品面内电阻的温度关系.我们用A～H模型拟合实验数据.结果表明,以R/Rn=20%作为高阻区和低阻区的分界线,R～T曲线可分别用R=Rn{I0[CH-p(1-t)q]}-2来描述,其中Rn是正常态的电阻Rn=-5.36 0.145T.p=0.78,1.88 和q=1.5, 3.5分别是高阻区和低阻区的拟合参数.     

熔融织构YBa2Cu2.99Li0.01Oy的交流磁化性质

在不同直流磁场、交流磁场和频率下测量了熔融织构YBa2Cu2.99Li0.01Oy样品交流磁化率的温度关系.基于非线性磁通耗散理论,研究了交流场的大小和频率对χ″的峰值温度Tp的影响,获得了磁通有效钉扎势与温度、直流场和电流密度的关系,U(J, Hdc, T)(J-(Hdc-0.75(1-T2/Tc2)3/2,其中μ约为0.13与理论预期的μ=1/7相一致,表明该样品中可能存在涡旋玻璃相变.     

Effects of inhomogeneous magnetic fields and different Dzyaloshinskii-Moriya interaction on entanglement and teleportation in a two-qubit Heisenberg XY Z chain

In this paper we calculate the thermal entanglement and teleportation in a two-qubit Heisenberg XYZ chain with the different Dzyaloshinskii-Moriya interaction and inhomogeneous magnetic fields. The analytical expressions of the concurrence and the average fidelity are obtained for this model. We have shown that the quantum phase transition occurs in the system and the quantum phase transition point depends on the inhomogeneity of magnetic fields. We compare the x-component Dzyaloshinskii-Moriya interaction with the z-component Dzyaloshinskii-Moriya interaction on the effects of quantum teleportation. It is found that we can take Dzyaloshinskii-Moriya interaction as one of the effective control parameters for the teleportation manipulation.