Geometric global quantum discord of two-qubit states

We consider the geometric global quantum discord(GGQD) of two-qubit systems. By analyzing the symmetry of geometric global quantum discord we give an approach for deriving analytical formulae of the extremum problem which lies at the core of computing the GGQD for arbitrary two-qubit states. Furthermore, formulae of GGQD of arbitrary two-qubit states and some concrete examples are presented.     

Relative entropy of entanglement of two-qubit ’X’ states

Two closest single-qubit states could be diagonalised by the same unitary matrix,which helps to find the relative entropy of entanglement of a two-qubit ’X’ state.We formulate two binary equations for the relative entropy of entanglement and the corresponding closest separable state of a given two-qubit ’X’ state.This approach can be applied to get the relative entropy of entanglement of many widely-discussed two-qubit states,such as pure states,Werner states,and so on.     

Simple experimental scheme of teleporting a two-qubit state via linear optical elements

We propose a simple experimental scheme in which an unknown two-qubit state is faithfully and deterministically teleported from Alice to Bob. The scheme is constructed with four photons from parametric down conversion, linear optical elements, and conventional photon detectors, all of which are available in current technology. It is shown that the probability of successful teleportation ideally reaches 100% based on single-photon two-qubit-assisted Bell-state measurement, which can distinguish all four Bell-states simultaneously via conventional photon detectors. By generalizing the scheme, the teleportation of an unknown multi-qubit system can also be realized.     

Entanglement capacity of two-qubit unitary operator for rank two mixed states

The entanglement capacity of two-qubit unitary operator acting on rank two mixed states in concurrence is discussed. The condition of perfect entangler is the same as that acting on pure states and the entanglement capacity is the mixing parameter v1. For non-perfect entangler, the upper and lower bound of the entanglement capacity are given.     

Fast and Robust Nondestructive Parity Meter for Cat-State Qubits via Reverse Engineering and Optimal Control

In this paper, a protocol for nondestructive parity meter (NPM) of two cat-state qubits is proposed. The physical model contains two cavities and an auxiliary qubit. For each cavity, the quantum information is encoded on the odd and even cat state, forming a cat-state qubit. By adjusting the strength of the driving field on the auxiliary qubit, an effective Hamiltonian for cavity-selective transition is derived. Moreover, reverse engineering based on the effective Hamiltonian is applied to find the evolution path, and the systematic-error-sensitivity nullification method is used to select proper parameters of the evolution path. In this way, robust control fields are designed to combat the influence of the systematic errors. Furthermore, the effects of random noise and decoherence on the fidelity of the protocol are considered. Numerical simulations show that the protocol is insensitive to the experimental imperfection, including systematic errors, random noise and decoherence. Therefore, the protocol is expected to expand the vision of realizing NPM.     

Controlled quantum state transfer via parity measurement

In this work, a scheme for controlled quantum state transfer is proposed using parity measurement in a cavity-waveguide system. As two special cases, two schemes of controlled quantum state transfer for one qubit and two qubits are investigated in detail. An important advantage is that controlled quantum state transfer can be completed by single-qubit rotations and the measurement of parity. Therefore, the present scheme might be realized in the scope of current experimental technology.     

Unnatural parity resonance states in positron-excited hydrogen scattering

<正>The coupled-channels optical method for positron scattering has been applied to investigate resonance states with unnatural parities in a positron-excited hydrogen system.The positronium formation channels and continuum channel are included via a complex equivalent local potential.Resonance states with angular momenta L = 1 to L = 2 and parities（—1）^L+1 are calculated.Resonance energies and widths are reported and compared with other theoretical calculations.We found that the opening positronium formation channels play an important role in forming nondipole Feshbach resonances.     

基于光谱椭偏仪的纳米光栅无损检测

本文制备了硅基和光刻胶两种材料的纳米光栅,利用自研制的新型广义椭偏仪对该纳米结构的光栅进行了测量,随后利用建立的拟合模型对其测量数据进行了拟合,结果证明了运用该仪器进行纳米光栅结构无损检测的可行性,在入射角60°,方位角75°的测量条件下,纳米结构关键尺寸、侧壁角等三维形貌参数的测量精度最大可达99.97%,最大误差小于1%,该技术对于无损检测有着一定的推动意义. 关键词： 纳米压印 光栅 无损检测 拟合     

Remote preparation of an entangled two-qubit state with three parties

We present a scheme for probabilistic remote preparation of an entangled two-qubit state with three parties from a sender to either of two receivers. The quantum channel is composed of a paxtially entangled two-qubit state and a partially entangled three-qubit state. We calculate the successful total probabilities of the scheme in general and particular cases, respectively. We also calculate total classical communication cost in a general case and two particular cases, respectively.     

Direct measurement of two-qubit phononic entangled states via optomechanical interactions

We propose schemes of direct concurrence measurement for two-qubit phononic states from quantized mechanical vibration. By combining the Mach-Zehnder interferometer with the optomechanical cross-Kerr nonlinear effect, direct concurrence measurement schemes for two-qubit phononic entangled states are achieved with the help of photon detection with respect to the output of the interferometer. For different types of entangled states, diversified quantum devices and operations are designed accordingly. The final analysis shows reasonable performance under the current parameter conditions. Our schemes may be useful for potential phonon-based quantum computation and information in the future.     

Remote preparation of an entangled two-qubit state with three parties

We present a scheme for probabilistic remote preparation of an entangled two-qubit state with three parties from a sender to either of two receivers. The quantum channel is composed of a partially entangled two-qubit state and a partially entangled three-qubit state. We calculate the successful total probabilities of the scheme in general and particular cases, respectively. We also calculate total classical communication cost in a general case and two particular cases, respectively.     

基于法拉第旋转构造光子Bell态分析器和GHZ态分析器

基于偏振光被囚禁原子光腔反射后所获得的法拉第旋转构造了光子Bell态分析器和GHZ态分析器,并能实现非破坏地识别所有的光子Bell态和GHZ态.该方案不需要腔场的强耦合条件,在低品质光腔中也能实现,从而大大降低了实验难度.     

Complete four-photon cluster-state analyzer based on cross-Kerr nonlinearity

We propose a method to construct an optical cluster-state analyzer based on cross-Kerr nonlinearity combined with linear optics elements. In the scheme, we employ two four-qubit parity gates and the controlled phase gate （CPG） from only the cross-Kerr nonlinearity and show that all the orthogonal four-qubit cluster states can be completely identified. The scheme is significant for the large-scale quantum communication and quantum information processing networks. In addition, the scheme is feasible and deterministic under current experimental conditions.     

Collective bands of the positive parity states inf 7/2 shell nuclei

Collective bands of the positive parity states in odd-A f _7/2 shell nuclei are described in the framework of deformed Hartree-Fock theory by projecting states from lowest energy intrinsic states with (d ₃ ^2/−1 f ₇ ^2/n+1 ) one hole configurations. In the calculation empirical (d _3/2 −f _7/2)² effective matrix elements have been used to test the tacit assumptions of the Bansal and French model.     

Teleportation via thermally entangled states of a two-qubit Heisenberg XXZ chain

We investigate quantum teleportation as a tool to study the thermally entangled state of a twoqubit Heisenberg XXZ chain.Our work is mainly to investigate the characteristics of a Heisenberg XXZ chain and get some analytical results of the fully entangled fraction.We also consider the entanglement teleportation via a two-qubit Heisenberg XXZ chain.     

Teleportation via thermally entangled states of a two-qubit Heisenberg XXZ chain

We investigate quantum teleportation as a tool to study the thermally entangled state of a two-qubit Heisenberg XXZ chain. Our work is mainly to investigate the characteristics of a Heisenberg XXZ chain and get some analytical results of the fully entangled fraction. We also consider the entanglement teleportation via a two-qubit Heisenberg XXZ chain.     

一种基于快中子的化学战剂无损检测技术

为了检测标识不清的弹体内的装药成分是否含有化学战剂,建立了一套基于伴随粒子技术的快中子化学战剂无损检测系统。系统的主要部分包括D-T中子源、粒子探测器、探测器及其屏蔽体以及相应的电子学处理系统等。利用该系统对沙林、VX、芥子气和亚当氏剂四种具有代表性的化学战剂进行测量,获得了四种化学战剂的14 MeV中子诱发的特征谱。谱分析的结果表明,除了As元素外,P,F,S,Cl元素的特征峰清晰可见,说明采用这种方法可以实现化学战剂的无损检测。     

Analysis of polarization state in quantum key distribution via single-photon two-qubit states

An improved quantum key distribution scheme via single-photon two-qubit states is proposed. The input–output model of the polarization state is established. And the influence of the interferometers to the polarization state is analyzed. Quantum bit error rate of polarization coding caused by birefringent and coordinate system difference between incident light and the fast and slow axes in fiber interferometer is simulated. Furthermore, maintaining conditions of polarization state are given on this basis.     

通过大失谐的双光子Jaynes-Cummings模的时间演化和对腔场的探测生成原子纠缠态

提出了通过大失谐的双光子ＪａｙｎｅｓＣｕｍｍｉｎｇｓ模的时间演化和对腔场的探测生成原子纠缠态的方法     

Quantifying entanglement of two-qubit Werner states

In this article, we introduce a framework for entanglement quantification of photon pairs represented by two-qubit Werner states. The measurement scheme is based on the symmetric informationally complete POVM. To make the framework realistic, we impose the Poisson noise on the measured two-photon coincidences. For various settings, numerical simulations were performed to evaluate the efficiency of the framework.