Secure quantum dialogue based on single-photon

In this paper a quantum dialogue scheme is proposed by using N batches of single photons. The same secret message is encoded on each batch of single photons by the sender with two different unitary operations, and then the N batches of single photons are sent to the receiver. After eavesdropping check, the message is encoded on the one remaining batch by the receiver. It is shown that the intercept-and-resend attack and coupling auxiliary modes attack can be resisted more efficiently, because the photons are sent only once in our quantum dialogue scheme.     

Scheme for generating a cluster-type entangled squeezed vacuum state via cavity QED

A scheme is proposed to generate an N-qubit cluster-type entangled squeezed vacuum state （CTESVS） based on the two-photon interaction between a two-level atomand the cavity fields with the cavity QED system. The CTESVS in N separate cavities can be effectively obtained after performing a simple one-qubit measurement on the atom. The influence of cavity decay on the CTESVS is also discussed.     

Measurement-induced disturbance and nonequilibrium thermal entanglement in a qutritben qubit mixed spin XXZ model

We investigate the dynamics of nonequilibrium thermal quantum correlation of a qutrit-qubit mixed spin system coupled to two bosonic reservoirs at different temperatures using measurement-induced disturbance. The effects of initial states of the spins and temperatures of the reservoirs on measurement-induced disturbance and entanglement are discussed. The results demonstrate that measurement-induced disturbance is more robust than entanglement against the influence of both these factors and there is no sudden death phenomenon for measurement-induced disturbance. The dependences of steady-state measurement-induced disturbance and entanglement on coupling constant and anisotropy parameter are also studied. Steady-state entanglement vanishes for a ferromagnetic qutrit-qubit model, while steady-state measurement-induced disturbance exists for both the antiferromagnetic and ferromagnetic cases. Appropriately modulating the coupling constant and anisotropy parameter can strengthen quantum correlation.     

利用三粒子部分纠缠GHZ 态和二粒子纠缠态概率隐形传送任意二粒子态

我们提出了利用三粒子非最大纠缠GHZ态和二粒子非最大纠缠态从一个发送者概率隐形传送任意未知二粒子态至两个接收者中的一个的方案。发送者进行两次Bell-state 测量，接收者以另一个可能的接收者进行的Hadamard操作和投影测量的结果为条件引入两个适当的幺正变换就可以概率隐形传送任意未知二粒子态。     

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.     

Change-over switch for quantum states transfer with topological channels in a circuit-QED lattice

We propose schemes to realize robust quantum states transfer between distant resonators using the topological edge states of a one-dimensional circuit quantum electrodynamics(QED)lattice.Analyses show that the distribution of edge states can be regulated accordingly with the on-site defects added on the resonators.And we can achieve different types of quantum state transfer without adjusting the number of lattices.Numerical simulations demonstrate that the on-site defects can be used as a change-over switch for high-fidelity single-qubit and two-qubit quantum states transfer.This work provides a viable prospect for flexible quantum state transfer in solid-state topological quantum system.     

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.     

Deterministic implementations of fermionic quantum SWAP and Fredkin gates for spin qubits based on charge detection

We propose a scheme to implement fermionic quantum SWAP and Fredkin gates for spin qubits with the aid of charge detection. The scheme is deterministic without the need of qubit–qubit interaction, and the proposed setups consist of simple polarizing beam splitters, single-spin rotations, and charge detectors. Compared with linear optics quantum computation, this charge-measurement-based qubit scheme greatly enhances the success probability for im- plementing quantum SWAP and Fredkin gates and greatly simplifies the experimental realization of scalable quantum computers with noninteracting electrons.     

Nonlocal quantum cloning via quantum dots trapped in distant cavities

A scheme for implementing nonlocal quantum cloning via quantum dots trapped in cavities is proposed.By modulating the parameters of the system,the optimal 1 → 2 universal quantum cloning machine,1 → 2 phase-covariant cloning machine,and 1 → 3 economical phase-covariant cloning machine are constructed.The present scheme,which is attainable with current technology,saves two qubits compared with previous cloning machines.     

广义路代数与点Hopf代数

Most of pointed Hopf algebras of dimension p^m with large coradtical are shown to be generalized path algebras. By the theory of generalized path algebras, the representations, homological dimensions and radicals of these Hopf algebras are obtained. The relations between the radicals of path algebras and connectivity of directed graphs are given.