求解作业车间调度问题的全局邻域搜索方法

采用传统的关键邻域搜索方法求解作业车间调度问题时,往往容易陷入局部极值而且难以跳出.为此,提出了一种具有动态调整能力的全局邻域交换策略,该策略有可能产生大量的不可行调度,需要一种筛选方法加以过滤.证明了一个新的邻域交换性质,利用该性质可以对所得调度方案作可行性约束判定,从而有效地过滤掉不可行调度.在此基础上,提出了一种求解作业车间调度问题的算法.最后,取不同规模的Benchmark问题算例对该算法进行测试,结果表明,无论从解的质量还是计算时间都取得了较好的效果.     

Dynamics of pairwise entanglement in the four-qubit Heisenberg XX spin chain

We discuss the dynamic evolution of pairwise entanglement in a four-qubit Heisenberg XX spin chain with the periodic boundary condition and the external magnetic field considered. The results show that the so-called entanglement sudden death (ESD) effect can be weakened when introducing the periodic boundary condition and the magnetic impurity. In addition, we also find that the ESD affects the dynamic evolution of entanglement between weakly interacting alternate qubits stronger than that for strongly interacting nearest qubits.     

Entanglement generated in a nanomechanical oscillator system

We consider a Fabry–Perot cavity with one fixed mirror and a movable perfectly reflecting mirror. Applying a linearised fluctuation analysis, we derive the quantum fluctuations and correlation matrix between the cavity and nanomechanical oscillator. We investigate the continuous-variable (CV) entanglement and squeezing between the cavity and nanomechanical oscillator. It is found that high intensity of entanglement and squeezing between the cavity and nanomechanical oscillator can be achieved.     

Controlling tripartite entanglement among optical cavities by reservoir engineering

We study how to control the dynamics of tripartite entanglement among optical cavities using non-Markovian baths. In particular, we demonstrate how the reservoir engineering through the utilization of non-Markovian baths with different types of Lorentzian and ohmic spectral densities can lead to an entanglement survival for longer times and in some cases considerable regain of seemingly lost entanglement. Both of these behaviours indicate a better sustainability of entanglement (in time) compared to the usual Markovian bath situations which assumes a flat spectrum of the bath around the system resonant frequency. Our scheme shows these effects in the context of optical cavities starting off in a maximally entangled W and Greenberger–Horne–Zeilinger tripartite states. In Lorentzian cases, we find that the far detuned double Lorentzian baths with small coupling strengths and for ohmic-type baths super-ohmic environments with smaller cutoff frequencies are the best candidates for preserving entanglement among cavities for significant amount of time. A non-Markovian quantum jump approach is employed to understand the entanglement dynamics in these cases, especially to recognize the collapse and revival of the entanglement in both W and GHZ states.     

Noisy parametric amplifiers in non-equilibrium thermo field dynamics

Single-mode and two-mode parametric amplifiers under the influence of Markovian environments are studied by means of non-equilibrium thermo field dynamics. In the presence of both parametric coupling and system–environment interaction, the dissipative Heisenberg equations of motion are solved for the optical modes of interest. By making use of the solutions, it is examined whether the noisy parametric amplifiers can exhibit the non-classical properties. Furthermore, it is shown that the two-mode parametric amplifier is equivalent to the two single-mode parametric amplifiers with subsequent beam splitting, even if they are influenced by the environments.     

A model for non-local bonding in bipartite systems

We hypothesize a non-local model for two-component quantum systems based on a non-linear but non-perturbatively solvable operator equation. The equation introduces a meta-structure, which conforms with quantum mechanics but constrains the range of admissible states of the system. According to the proposed model the composite system as a whole may bind into a non-local molecule with an energy gap different than that of free components.     

Time evolution,squeezing and entanglement for an optical frequency up-conversion with a driving term

By using the Lewis–Riesenfeld quantum invariant theory, an explicit analytical solution for the time evolution operator of the frequency up-conversion system with a driving term is obtained. It is then used to investigate mainly the influence of the driving term, frequency detuning, and the initial states on the quantum statistical properties of the output-coupled fields. It is found that the time evolution for the general up-conversion system can efficiently convert a low-frequency squeezed light into a high-frequency squeezed light, in the case of zero-detuning, but the squeezed effect of the output fields is independent of the driving term. It is also shown that there is an entanglement between the signal and idler output photons for the general up-conversion system.