Chinese Physics B

Yu, Xin; Ren, Zhi-Gang; Xu, Chao

doi: 10.1088/1674-1056/23/4/040201pmid: N/A

In this paper, we consider a numerical approximation for the boundary optimal control problem with the control constraint governed by a heat equation defined in a variable domain. For this variable domain problem, the boundary of the domain is moving and the shape of the boundary is defined by a known time-dependent function. By making use of the Galerkin finite element method, we first project the original optimal control problem into a semi-discrete optimal control problem governed by a system of ordinary differential equations. Then, based on the aforementioned semi-discrete problem, we apply the control parameterization method to obtain an optimal parameter selection problem governed by a lumped parameter system, which can be solved as a nonlinear optimization problem by a Sequential Quadratic Programming (SQP) algorithm. The numerical simulation is given to illustrate the effectiveness of our numerical approximation for the variable domain problem with the finite element method and the control parameterization method.

Zhou, Xian-Chun; Shi, Lan-Fang; Mo, Jia-Qi

doi: 10.1088/1674-1056/23/4/040202pmid: N/A

A time delay model of a two-layer barotropic ocean with Rayleigh dissipation is built. Using the improved perturbation method, an analytic asymptotic solution of a better approximate degree is obtained in the mid-latitude wind field, and the physical meaning of the corresponding solution is also discussed.

Ge, Hong-Xia; Cheng, Rong-Jun

doi: 10.1088/1674-1056/23/4/040203pmid: N/A

Fractional diffusion equations have been the focus of modeling problems in hydrology, biology, viscoelasticity, physics, engineering, and other areas of applications. In this paper, a meshfree method based on the moving Kriging interpolation is developed for a two-dimensional time-fractional diffusion equation. The shape function and its derivatives are obtained by the moving Kriging interpolation technique. For possessing the Kronecker delta property, this technique is very efficient in imposing the essential boundary conditions. The governing time-fractional diffusion equations are transformed into a standard weak formulation by the Galerkin method. It is then discretized into a meshfree system of time-dependent equations, which are solved by the standard central difference method. Numerical examples illustrating the applicability and effectiveness of the proposed method are presented and discussed in detail.

Wen, Jing-Ji; Kyu-Hwang, Yeon; Wang, Hong-Fu; Zhang, Shou

doi: 10.1088/1674-1056/23/4/040301pmid: N/A

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 atom and 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.

Xie, Dong; Wang, An-Min

doi: 10.1088/1674-1056/23/4/040302pmid: N/A

We study the nonlocal non-Markovian effects through local interactions between two subsystems and the corresponding two environments. It has been found that the initial correlations between two environments can turn a Markovian to a non-Markovian regime with extra control on the local interaction time. We further research the nonlocal non-Markovian effects from two situations: without extra control, the nonlocal non-Markovian effects only appear under the condition that two local dynamics are non-Markoviannon-Markovian (both of the two local dynamics are non-Markovian) or Markoviannon-Markovian, but not under the condition of MarkovianMarkovian; with extra control, the nonlocal non-Markovian effects can occur under the condition of MarkovianMarkovian. It shows that the function of correlations between two environments has an upper bound, which makes a flow of information from the environment back to the global system beginning finitely earlier than that back to one of the two local systems, not infinitely. Then, we proposed two special ways to distribute classical correlations between two environments without initial correlations. Finally, from numerical solutions in the spin star configuration, we found that the self-correlation (internal correlation) of each environment promotes the nonlocal non-Markovian effects.

Shen, Li-Tuo; Chen, Rong-Xin; Wu, Huai-Zhi; Yang, Zhen-Biao

doi: 10.1088/1674-1056/23/4/040303pmid: N/A

We propose a scheme to prepare the steady-state entanglement for two atoms, which are held in separate cavities that are coupled through a short optical fiber or optical resonator. The entangled steady-state with a high fidelity can be achieved even with a low cooperativity parameter, by making use of the driving laser fields. Such a cooling mechanism is based on a resonant laser pump of the unwanted ground states to the excited states, which finally decay to the desired steady-state.

Cao, Cong; Liu, Gang; Zhang, Ru; Wang, Chuan

doi: 10.1088/1674-1056/23/4/040304pmid: N/A

Implementation of a nonlocal multi-qubit conditional phase gate is an essential requirement in some quantum information processing (QIP) tasks. Recently, a novel solid-state cavity quantum electrodynamics (QED) system, in which the nitrogenvacancy (NV) center in diamond is coupled to a microtoroidal resonator (MTR), has been proposed as a potential system for hybrid quantum information and computing. By virtue of such systems, we present a scheme to realize a nonlocal N-qubit conditional phase gate directly. Our scheme employs a cavity inputoutput process and single-photon interference, without the use of any auxiliary entanglement pair or classical communication. Considering the currently available technologies, our scheme might be quite useful among different nodes in quantum networks for large-scaled QIP.

Meng, Xiang-Jia; Feng, Hai-Ran; Zheng, Yu-Jun

doi: 10.1088/1674-1056/23/4/040305pmid: N/A

In this work, we propose an algebraic recursion method to study the dynamical evolution of the two-site BoseHubbard model. We analyze its properties from the viewpoints of single partite purity, energy, and trace distance, in which the model is considered as a typical bipartite system. The analytical expressions for the quantities are derived. We show that the purity can well reflect the transition between different regimes for the system. In addition, we demonstrate that the transition from the delocalization regime to the self-trapping regime with the ratio η increasing not only happens for an initially local state but also for any initial states. Furthermore, we confirm that the dynamics of the system presents a periodicity for η = 0 and the period is tc = /2J when the initial state is symmetric.

Meng, Shao-Ying; Chen, Xi-Hao; Wu, Wei; Fu, Li-Bin

doi: 10.1088/1674-1056/23/4/040306pmid: N/A

In the present paper, we investigate the instability, adiabaticity, and controlling effects of external fields for a dark state in a homonuclear atomtetramer conversion that is implemented by a generalized stimulated Raman adiabatic passage. We analytically obtain the regions for the appearance of dynamical instability and study the adiabatic evolution by a newly defined adiabatic fidelity. Moreover, the effects of the external field parameters and the spontaneous emissions on the conversion efficiency are also investigated.

Ji, Ying-Hua; Hu, Ju-Ju

doi: 10.1088/1674-1056/23/4/040307pmid: N/A

We demonstrate the controllable generation of multi-photon Fock states in circuit quantum electrodynamics (circuit QED). The external bias flux regulated by a counter can effectively adjust the bias time on each superconducting flux qubit so that each flux qubit can pass in turn through the circuit cavity and thereby avoid the effect of decoherence. We further investigate the quantum correlation dynamics of coupling superconducting qubits in a Fock state. The results reveal that the lower the photon number of the light field in the number state, the stronger the interaction between qubits is, then the more beneficial to maintaining entanglement between qubits it will be.