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.     

Continuous variable entanglement measurement without phase-locking

In this work, we propose a new simple entanglement measurement scheme, which can be utilized to take a measurement for the bright EPR beams generated by a nondegenerate optical parametric amplifier. Owing to the output signal and idler modes being frequency degenerate and in phase, one need not take a measurement for the signal and idler modes, respectively. By virtue of a quarter-wave plate and a half-wave plate, and then inserting a polarizing beam splitter, one can realize the measurements of the correlated phase quadratures and anti-correlated amplitude quadratures, simultaneously. Therefore, phase-locking and local oscillators are avoided.     

Effective preparation of the N-dimension spin Greenberger–Horne–Zeilinger state with quantum dots embedded in microcavities

We propose a scheme for preparation of the N-dimension spin Greenberger–Horne–Zeilinger state by exploiting quantum dots (QDs) embedded in microcavities. Numerically analysed results show that with the spin-selective photon reflection from the cavity, we can complete the scheme assisted by one polarized photon with high fidelity and 100% successful probability in principle. Furthermore, the set-up is just composed of simple linear optical elements, delay lines and conventional photon detectors, which are feasible with existing experimental technology. Moreover, QDs have numerous admirable features in weak-coupling regime, which are practicable in realistic cavity quantum electrodynamics system shown by previous numerical simulations and experiments. Therefore, our scheme might be realized in near future.     

棉精梳机胶辊的应用与维护

为稳定并提高棉精梳半成品纺纱质量,介绍棉精梳机用牵伸胶辊、分离胶辊及导向胶辊的性能特点,分析胶辊制作、磨砺、表面处理方法及保养维护、周期管理和日常管理注意事项,提出棉精梳工序温湿度控制和减少胶辊缠花的措施。指出:应根据原料特性和纺纱品种合理选择胶辊型号和硬度,保持绒辊清洁、温湿度合理,使胶辊运行状态良好以减少胶辊缠花;要严格按照棉精梳机胶辊的技术要求,强化胶辊的维护管理,对提高半成品纺纱质量和减少后工序断头作用重大;分析生产过程中出现问题的原因,充分发挥胶辊在棉精梳工序的功能,以稳定并提高棉精梳半成品纺纱质量。     

纠缠相干态的制备

提出了一个利用单一的二能级原子和处于相干态的腔模来制备Bell型和簇型纠缠相干态的方案。并对这两种纠缠相干态进行了讨论。让一个单一的二能级原子和两个Remsey zones以及两个处于相干态的腔模相互作用,并通过原子测量,就可以在分离的腔中实现Bell型纠缠相干态的制备。通过增加Remsey zones 和腔模就可以制备簇型纠缠相干态。原子和每个腔模的相互作用时间均为 ,其中 是原子和腔的有效耦合常数。最后讨论了方案的实验上的可行性。     

腔耦合双J-C模型中原子纠缠的猝灭和猝生

研究了腔间有耦合的双J-C模型中原子纠缠的动力学, 分析了腔间耦合系数A和原子的初态对原子纠缠的猝灭(ESD)和猝生(ESB)的影响. 通过对原子间共生纠缠度的数值分析发现, 当原子初态为第一类类Bell态时, 不会出现ESD和ESB, 腔间的耦合可使原子的纠缠加大, 并能使初态为分离态的原子产生纠缠. 当原子初态为第二类类Bell态时, A的大小可改变出现ESD与ESB的时间间隔, 或决定是否出现ESD, 但腔间的耦合不能使初态不纠缠的原子产生纠缠.     

在非均匀磁场中 Dzialoshinskii-Moriya相互作用对伊辛链热纠缠的影响

采用Negativity理论研究了具有Dzyaloshinskii -Moriya (DM)相互作用的伊辛模型在非均匀磁场中的纠缠特性。结果发现,DM相互作用的存在明显的增强两量子比特间的热纠缠并且能够把纠缠增加到一个最大值0.5;而外磁场具有减小热纠缠的作用。温度的高低也直接影响热纠缠。另外,讨论了磁场的非均匀性对伊辛链热纠缠的影响,在一定程度上,非均匀磁场对热纠缠的影响类似于匀强磁场。研究表明：可以通过调节DM相互作用强度、外磁场大小和温度高低来控制热纠缠。