Tripartite states Bell-nonlocality sudden death in a quantum-critical environment

We demonstrate that multipartite Bell-inequalities violations can be fully destroyed in finite time in three-qubit states under a quantum-critical environment, which is an Ising model in a transverse field. We use the Mermin--Ardehali--Belinksii--Klyshko (MABK) inequality to detect the degree of nonlocality as measured by the extent of their violations. The effects of system-environment couplings, the size of degrees of freedom of environment and the strength of transverse field on the Bell-inequality violations are given for two different initial states, namely, the W class and GHZ class states. The results indicate that the Bell-inequality violations of the tripartite states will be completely destroyed by the decoherence under certain conditions.     

Tripartite states Bell-nonlocality sudden death in an antiferromagnetic environment

By using spin wave approximation, we show that the tripartite Bell-inequality violations can be fully destroyed in finite time in an antiferrromagnetic environment under an external magnetic field. Furthermore, the class of decoherence-free states have been found out for our model.     

Disentanglement of Three-qubit States Coupled to an <Emphasis Type="Italic">XY</Emphasis> Spin Chain with Multisite Interaction

The entanglement dynamics of three-qubit states coupled to a general XY spin-chain with a three-site interaction environment is investigated. By using negativity as entanglement measure, we find that the entanglement evolution depends on not only the system-environment couplings but also the strength of three-site interaction. In the strong-coupling region, the three-site interaction can remarkably enhance the decay of the entanglement of three-qubit states. However, in the weak-coupling region, the process of disentanglement depends on the strength of the three-site interaction.     

Local basis-dependent noise-induced Bell-nonlocality sudden death in tripartite systems

We demonstrate that multipartite Bell-inequality violations can be fully destroyed in finite time in three-qubit systems subject only to the mechanism of local external asymptotic dephasing noise. This broadens the study of local-noise-induced sudden death of nonlocal behavior, extending it beyond the realm of bipartite systems, to which it had previously been restricted.     

Effects of photon addition on the quantum nonlocality of squeezed entangled-coherent states

Effects of photon addition on the quantum nonlocality of squeezed entangled coherent states for Bell-inequality tests are studied theoretically. By utilizing the method of photon-parity measurement, it is found that photon addition can always increase the degrees of Bell violations within a certain parameter range. A possible scheme for generating photon-added squeezed entangled coherent states is proposed.     

Effects of photon addition on quantum nonlocality of squeezed entangled coherent states

Effects of photon addition on quantum nonlocality of squeezed entangled coherent states for Bell-inequality tests are studied theoretically. By utilizing the method of photon-parity measurement, it is found that photon addition can always increase the degrees of Bell violations within a certain parameter range. A possible scheme for generating photon-added squeezed entangled coherent states is proposed.     

Dense Coding in a Three-Qubit Heisenberg XXZ Spin Chain with Three-Site Interactions

This paper investigates the quantum dense coding of a three-qubit XXZ Heisenberg spin chain at thermal equilibrium, with three-site interactions in the presence of an external magnetic field. We analyze the effects of various system parameters on the dense coding in multiple cases with different types of three-site interactions. The results show that the most ideal case for dense coding is the model including both types of three-site interactions, with the imposed condition of XZX + YZY type of three-site interaction is larger than the XZY − YZX type of three-site interaction. The inclusion of the z direction coupling parameter J_Z, and external magnetic parameter B are found to be effective for optimizing the dense coding capacity, while the temperature T is turned out to be destructive. Moreover, the ferromagnet (FM) is shown to be more ideal for quantum dense coding than the antiferromagnet (AFM). For FM, by comparing the two types of three-site interactions (XZY − YZX and XZX + YZY), the appropriate model for valid dense coding is suggested and their dominant regions are clarified.

     

费米环境中两个三能级原子系统的纠缠演化

利用负性纠缠度(negativity)研究了两个三能级原子系统在费米环境中的纠缠演化问题-结果表明,两个三能级原子系统的纠缠演化不仅依赖于系统和环境的相互作用强度,而且还依赖于系统所处的具体量子态-通过例子发现,系统和环境相互作用强度越大,纠缠衰减越快;对于纯态,仅当时间趋于无穷时纠缠才被完全破坏;对于混态,则在有限的时间内纠缠即被彻底破坏-通过一般的分析找到了一类免退相干的量子子空间-在这些子空间中,量子态不受环境的影响,故其纠缠不变-研究有助于理解费米环境造成的退相干对玻色系统纠缠的影响- 关键词： 费米环境 纠缠演化 两个三能级原子     

Entanglement dynamics of three-qubit coupled to an XY spin chain at finite temperature with three-site interaction

The entanglement dynamics of three-qubit states under an XY spin chain at finite temperature with three-site interaction is investigated. It is shown that the three-site interaction does not affect the behavior of quantum phase transition (QPT) induced by the external magnetic field and does not induce new critical regions in the XY model. In addition, concerned with the effect of the three-site interaction on the entanglement evolution, we find the three-site interaction can not only enhance but also suppress the decay of the entanglement between the three-qubit system, which depends on the initial states of the system and the parameters related with the environmental spin chain.     

Energy levels of 1s~2n d(n≤9)states for lithium-like ions

The full-core plus correlation method with multi-configuration interaction wave functions is extended to the calculation of the non-relativistic energies of 1s²nd (n ≤ 9) states for the lithium isoelectronic sequence from Z = 11 to 20. Relativistic and mass-polarization effects on the energy are calculated as the first-order perturbation correction. The quantum-electrodynamics correction is also included. The fine structure splittings are determined from the expectation values of spin—orbit and spin—other-orbit interaction operators in the Pauli—Breit approximation. Combining the term energies of lowly excited states obtained with the quantum defects calculated by the single channel quantum defect theory, each of which is a smooth function of energy and approximated by a weakly varying function of energy, the ion potentials of highly excited states (n ≤ 6) are obtained with the semi-empirical iteration method. The results are compared with experimental data in the literature and found to be closely consistent with the regularity.     

Cyclic period-3 window in antiferromagnetic potts and Ising models on recursive lattices

The magnetic properties of the antiferromagnetic Potts model with two-site interaction and the antiferromagnetic Ising model with three-site interaction on recursive lattices have been studied. A cyclic period-3 window has been revealed by the recurrence relation method in the antiferromagnetic Q-state Potts model on the Bethe lattice (at Q < 2) and in the antiferromagnetic Ising model with three-site interaction on the Husimi cactus. The Lyapunov exponents have been calculated, modulated phases and a chaotic regime in the cyclic period-3 window have been found for one-dimensional rational mappings determined the properties of these systems.     

A new application of the Gürsey and Radicati mass formula

We study the spin- and flavour-dependent SU(6) violations in the baryon spectrum by means of a Gürsey-Radicati mass formula. The average energy of each SU(6) multiplet is described using the SU(6)-invariant interaction given by a hypercentral potential containing a linear and a hyper-Coulomb term. We show that the nonstrange- and strange-baryon masses are, in general, fairly well reproduced and moreover that the Gürsey-Radicati formula holds in a satisfactory way also for the excited states up to 2 GeV.     

Loschmidt echo of a central spin coupled to an XY spin chain: Role of three-site interaction

Effects of two types of three-site interaction, i.e., XZX+YZY and XZY−YZX, on Loschmidt Echo (LE) of a central spin coupled to an XY spin chain are studied. The dynamical evolution behaviors of the LE are investigated analytically and numerically. The XZX+YZY type of three-site interaction (α₁) can shift the critical points of the magnetic field λ. At the critical points |λ−α₁|=1, the decay of the LE is enhanced. The role of the XZY−YZX type of three-site interaction (α₂) depends on its strength. In some specific intervals, α₂ can remarkably delay the decay of the LE.     

Shell model study of 52V and 52Cr and gamma decay of isobaric analogue states in 52Cr

The spectrum of ⁵²V is studied with the Kuo-Brown (KB) renormalized interaction and with Vervier's interactions. Wave functions of isobaric analogue states (IAS) in ⁵²Cr are generated from ⁵²V wave functions. Wave functions of low-lying levels of ⁵²Cr are obtained by a shell model calculation with the KB interaction and with the phenomenological effective interaction of Lips and McEllistrem. Electromagnetic decay of IAS to low-lying states via the isovector part of the transition operator is considered. Transition rates are first calculated by assuming that the final state configurations do have the proper isospin. A projection operator is defined in isospace to construct basis states having the proper isospin, starting with excited configurations of ⁵²Cr which do not have well-defined isospin. Two methods — diagonalization after projection and projection after diagonalization — are developed in which the definite isospin of basis states can be handled.     

Quantum communication in spin chains with three-site and Dzyaloshinsky–Moriya interactions

We investigate an arbitrary single-qubit state transfer through spin chains with three-site and Dzyaloshinsky–Moriya interactions as well as the quantum discord transfer through double independent spin chains. It is shown that both the three-site and Dzyaloshinsky–Moriya interactions can improve the transfer quality in some cases and the influence of a combination of the three-site and Dzyaloshinsky–Moriya interactions is not simply a linear addition of each contribution. We also find that the three-site coupling may enhance the maximum discord more obviously while the Dzyaloshinsky–Moriya coupling may accelerate the maximum discord more effectively. Furthermore, we show that the quantum discord can always be transferred while the quantum entanglement has a threshold of minimum entanglement to be transferred and may experience entanglement sudden birth and death or even never receive any entanglement for some initial states.     

Green’s function method in the problem of complex configurations in fermi systems with pairing

The Green’s function method is used to derive general equations for describing effects of pairing in Fermi systems where there are two types of interaction, two-particle and quasiparticle-phonon interaction. These equations generalize Bardeen-Cooper-Schrieffertheory to the case of complex configurations involving “strong” phonons. In the approximation of weak coupling to phonons, realistic equations that make it possible to describe excited states of nonmagic even-even nuclei with allowance for a single-particle continuum and complex configurations of the two quasiparticles ? phonon type are formulated for the first time. These equations are solved for an isovector E 1 resonance in the stable isotope ¹²⁰ Sn and in the unstable isotopes ^104,132Sn. It is shown that complex configurations must be taken into account in order to describe E1 excitations—in particular, in a broad energy region around the nucleon binding energy.

     

Tensor Network States and Geometry

Tensor network states are used to approximate ground states of local Hamiltonians on a lattice in D spatial dimensions. Different types of tensor network states can be seen to generate different geometries. Matrix product states (MPS) in D=1 dimensions, as well as projected entangled pair states (PEPS) in D>1 dimensions, reproduce the D-dimensional physical geometry of the lattice model; in contrast, the multi-scale entanglement renormalization ansatz (MERA) generates a (D+1)-dimensional holographic geometry. Here we focus on homogeneous tensor networks, where all the tensors in the network are copies of the same tensor, and argue that certain structural properties of the resulting many-body states are preconditioned by the geometry of the tensor network and are therefore largely independent of the choice of variational parameters. Indeed, the asymptotic decay of correlations in homogeneous MPS and MERA for D=1 systems is seen to be determined by the structure of geodesics in the physical and holographic geometries, respectively; whereas the asymptotic scaling of entanglement entropy is seen to always obey a simple boundary law—that is, again in the relevant geometry. This geometrical interpretation offers a simple and unifying framework to understand the structural properties of, and helps clarify the relation between, different tensor network states. In addition, it has recently motivated the branching MERA, a generalization of the MERA capable of reproducing violations of the entropic boundary law in D>1 dimensions.     

Transfer of nonclassical properties from a microscopic superposition to macroscopic thermal states in the high temperature limit

We present several examples where prominent quantum properties are transferred from a microscopic superposition to thermal states at high temperatures. Our work is motivated by an analogy of Schr?dinger's cat paradox, where the state corresponding to the virtual cat is a mixed thermal state with a large average photon number. Remarkably, quantum entanglement can be produced between thermal states with nearly the maximum Bell-inequality violation even when the temperatures of both modes approach infinity.     

Diffusive Hydrodynamic Limits for Systems of Interacting Diffusions with Finite Range Random Interaction

We consider a system of interacting diffusive particles with finite range random interaction. The variables can be interpreted as charges at sites indexed by a periodic multidimensional lattice. The equilibrium states of the system are canonical Gibbs measures with finite range random interaction. Under the diffusive scaling of lattice spacing and time, we derive a deterministic nonlinear diffusion equation for the time evolution of the macroscopic charge density. This limit is almost sure with respect to the random environment. Received: 3 October 1996 / Accepted: 13 February 1997     

Bi2Te3-xSex(x≤3)同晶化合物电子结构的第一性原理研究

本文采用基于密度泛函理论的第一性原理全势能线性缀加平面波方法(FLAPW),分析了Bi₂Te_3-xSe_x体系中各原子自旋轨道耦合(SOI)的p_1/2修正对体系性质的影响,并对Bi₂Te_3-xSe_x(x≤3)同晶化合物的电子特性进行系统的理论研究,首次计算出Bi₂S 关键词： 2Te_3-xSe_x(x≤3)同晶化合物')" href="#">Bi₂Te_3-xSe_x(x≤3)同晶化合物 第一性原理 电子结构 自旋轨道耦合