共查询到20条相似文献，搜索用时 250 毫秒
1.
量子存储可以将光的量子态存储于原子系综的自旋波激发态中,是量子中继器的关键部件。由于退相干机制的存在,使得已实现的量子存储的寿命都非常短,只有10微秒左右,这极大地限制了量子中继器在远距离量子通信中的实际应用。通常认为,短的存储寿命是由存储量子态的自旋波在梯度磁场下退相干所造成的。通过对量子存储退相干机制的详细研究, 相似文献
2.
量子特性在信息领域中有着独特的功能，在提高运算速度、确保信息安全、增大信息容量和提高检测精度等方面可能突破现有经典信息系统的极限。我们以液态NMR技术实现量子信息处理中的应用主题开展研究，所取得的成果包括：1）利用NMR实验实现了两个无直接耦合自旋之间的量子密集编码和三个量子位之间的量子密集编码过程。实验结果表明：量子密集编码只需传送N-1个量子位便可以传递N个经典位的信息。2）利用NMR实验实现了三种多量子算法；提出了一种实现n阶耦合变换的理论方法，根据这种方法可实现任意量子位的Deutsch-Jozsa算法。3）提出了一种基于量子克隆的量子编码和纠错方案。该方案一方面说明了量子克隆与量子纠错存在一定程度上的联系，另一方面也反映出一些量子克隆过程本身具有一定的抗消相干的能力。4）提出用二维NMR中的多量子相干实现无消相干子空间（DFS），并在实验上验证了该DFS的避错能力。本方法有效地利用了甲基中三个磁等价的氢核，把原本需要四个化学位移各不相同的核自旋构造的二逻辑位的DFS变成了只需两个化学位移各不相同的核自旋体系构造的二逻辑位的DFS，虽然用的核自旋数“更少”，却能避免更多的错误算符。用多量子相干作为量子计算中的量子位，是一种全新的概念，可以充分利用磁等价的原子核自旋来构造多个量子位，从而扩展了可利用的量子位的数目。 相似文献
3.
4.
研究了处于W类态的三纠缠原子与相干态光场相互作用过程中光场的量子特性;运用数值方法,讨论了三纠缠原子初始状态和相干态光场的强弱对系统光场压缩和二阶相干特性的影响。提出了一个基于腔QED技术的制备三原子最大W态的一般方案。通过讨论表明三个原子不论是被同时注入腔中还是在不同的时刻被注入腔中我们都能得到三原子最大W态。该方案可以在当前的技术范围内实现并且可以推广到制备n个原子的W态。 相似文献
5.
《科学中国人》2018,(10)
正大规模硅基集成高维光量子芯片实现北京大学"极端光学创新研究团队"王剑威、龚旗煌教授等与布里斯托尔大学物理系量子光学中心等单位合作,利用大规模集成硅基纳米光量子芯片技术,实现对高维度光量子纠缠体系的高精度和普适化量子调控和量子测量,研究论文发表于Science。实现功能强大的量子信息处理芯片是当前量子科技革命的关键。研究团队实现了一种新型的多路径加载高维量子态方式,即每个光子以量子叠加态的形式同时存在于多条光波导路径,从而实现了一个高达15×15的高维量子纠缠系统。通过可控地激发16个参量四波混频单光子源阵列,可以制备具有任意复系数的高维度量子纠缠态。 相似文献
6.
7.
8.
为提高量子网络通信的抗干扰能力和安全性,避免光纤双折射效应引起的光子偏振态的随机改变而产生的噪声影响,改进了量子密钥分配方案,新的方案可生成双光子纠缠态密钥,并可在验证过程中进行概率检验,从而控制信息传输,新方案可抵抗光纤传输中集体偏振噪声和偏振损失的影响,在同样抗噪特性下通信效率得到很大的提升。最后分析了新方案的信道、解码器的实现方法,说明了改进后方案于现有技术条件下具有可行性。 相似文献
9.
10.
白春礼副院长当选亚太材料学会副主席6月2日,在俄罗斯新西伯利亚举行的亚太材料学会全体大会上,中国科学院副院长、我国扫描隧道显微学领域的开拓者白春礼院士当选该学会副主席。中国科技大学在量子通信实验领域取得重要进展该校量子物理与量子信息院重点实验室成功实现了量子纠缠态浓缩和量子中继器,研究成果“量子纠缠态浓缩及量子中继器的实验实现”刊登在5月23日Phys.Rev.Lett.上。5月22日Nature以封面文章形式发表了潘建伟博士等“任意纠缠态纯化的实验研究”论文,这是该实验研究中的一项突破性进展。大连化学物理研究所在分子反应动… 相似文献
11.
Multivariable uniform finite-time output feedback reentry attitude control for RLV with mismatched disturbance 总被引：1，自引：0，他引：1
Bailing Tian Hanchen Lu Zongyu Zuo Qun Zong 《Journal of The Franklin Institute》2018,355(8):3470-3487
A continuous multivariable uniform finite-time output feedback reentry attitude control scheme is developed for Reusable Launch Vehicle (RLV) with both matched and mismatched disturbances. A novel finite-time controller is derived using the bi-limit homogeneous technique, which ensures that the attitude tracking can be achieved in a uniformly bounded convergence time from any initial states. A multivariable uniform finite-time observer is designed based on an arbitrary order robust sliding mode differentiator to estimate the unknown states and the external disturbances, simultaneously. Then, an output feedback control scheme is established through the combination of the developed controller and the observer. A rigorous proof of the uniform finite-time stability of the closed-loop system is presented using Lyapunov and homogeneous techniques. Finally, numerical simulation is provided to demonstrate the efficiency of the proposed scheme. 相似文献
12.
Farid Tajaddodianfar 《Journal of The Franklin Institute》2018,355(14):6435-6453
This paper proposes anti-oscillation and chaos control scheme for the fractional-order brushless DC motor system wherein there exist unknown dynamics, immeasurable states and chaotic oscillation. Aimed at immeasurable states, the high-gain observers with fast convergence are presented to obtain the information of system states. To compensate uncertainties existing in the dynamic system, a finite-time echo state network with a weight is proposed to approximate uncertain dynamics while its weight is tuned by a fractional-order adaptive law online. Meanwhile a fractional-order filter is introduced to deal with the repeated derivative of the backstepping. Based on the fractional-order Lyapunov stability criterion, the anti-oscillation and chaos control scheme integrated with a high-gain observer, an echo state network and a filter are proposed by using recursive steps of backstepping. The proposed scheme guarantees the boundedness of all signals of the closed-loop system in the sense of global asymptotic stability, and also suppresses chaotic oscillation. Finally, the effectiveness of our scheme is demonstrated by simulation results. 相似文献
13.
《Journal of The Franklin Institute》2021,358(15):7309-7332
The current paper addresses the fuzzy adaptive tracking control via output feedback for single-input single-output (SISO) nonlinear systems in strict-feedback form. Under the situation of system states being unavailable, the system output is used to set up the state observer to estimate the real system states. Furthermore, the estimation states are employed to design controller. During the control design process, fuzzy logic systems (FLSs) are used to model the unknown nonlinearities. A novel observer-based finite-time tracking control scheme is proposed via fuzzy adaptive backstepping and barrier Lyapunov function approach. The suggested fuzzy adaptive output feedback controller can force the output tracking error to meet the pre-specified accuracy in a fixed time. Meanwhile, all the closed-loop variables are bounded. Compared to some existing finite-time output feedback control schemes, the developed control strategy guarantees that the settling time and the error accuracy are independent of the uncertainties and can be specified by the designer. At last, the effectiveness and feasibility of the proposed control scheme are demonstrated by two simulation examples. 相似文献
14.
In this paper, two output feedback controllers are proposed for motion control of double-rod electro-hydraulic servo actuators with matched and mismatched disturbances rejection. All of them employ an linear extended state observer (LESO) to achieve real-time estimates of the unmeasured system states and matched disturbance, and a nonlinear disturbance observer (NDO) to estimate the largely unknown mismatched disturbance at the same time. Thus, the disturbances are compensated via their online estimates in a feedforward way when implementing the resulting control algorithms, respectively. Furthermore, a continuously differentiable friction model is employed to compensate the majority of nonlinear friction existing in the system and reduce the burden of the NDO. Specially, one of the proposed control schemes utilizes model-based compensation terms depending on the desired trajectory to be tracked instead of the estimated system states. By doing this, online computation burden can be reduced. The stability of the whole closed-loop system under each control scheme is guaranteed by theoretical analysis. Moreover, the applicability of each control scheme are validated by experiments in different working conditions. 相似文献
15.
《Journal of The Franklin Institute》2022,359(5):2030-2057
The comprehensive effect of external disturbance, measurement delay, unmeasurable states and input saturation makes the difficulties and challenges for a HAGC system. In this paper, an adaptive fuzzy output feedback control scheme is designed for a HAGC system under the simultaneous consideration of those factors. At the first place, by state transformation technique, the dynamic model of a HAGC system is simply expressed as a strict feedback form, where measurement delay is converted into input delay. Then, an auxiliary system is employed to compensate for the effect of input delay. Furthermore, an asymmetric barrier Lyapunov function (BLF) is constructed to ensure the output error constraint requirement of thickness error and the fuzzy observer is established to solve unmeasurable states, unknown nonlinear functions at the same time. With the aid of backstepping method, adaptive fuzzy controller is developed to assure that the closed-loop system is semi-globally boundedness and the output error of thickness error doesn’t violate its constraint. At the end, compared simulations are carried out to verify the efficiency of the proposed control scheme. 相似文献
16.
A discrete-time output feedback quasi-sliding mode control scheme is proposed to realize the problem of robust tracking and model following for a class of uncertain linear systems in which states are unavailable and estimated states are not required. The proposed scheme guarantees the stability of the closed-loop system and achieves a very small ultimate boundedness of the tracking error in the presence of matched uncertain parameters and external slow disturbances. This scheme ensures the robustness to matched parametric uncertainties and disturbances. Since the proposed controller is designed without any switching element, the chattering phenomenon is eliminated. Furthermore, the knowledge of upper bound of uncertainties is not required. Simulation results demonstrate the effectiveness of the proposed scheme. 相似文献
17.
This paper investigates the adaptive fuzzy output feedback fault-tolerant tracking control problem for a class of switched uncertain nonlinear systems with unknown sensor faults. In this paper, since the sensor may suffer from an unknown constant loss scaling failure, only actual output can be used for feedback design. A failure factor is employed to represent the loss of effectiveness faults. Then, an adaptive estimation coefficient is introduced to estimate the failure factor, and a state observer based on the actual output is constructed to estimate the system states. Fuzzy logic systems are used to approximate the unknown nonlinear functions. Based on the Lyapunov function method and the backstepping technique, the proposed control scheme with average dwell time constraints can guarantee that all states of the closed-loop system are bounded and the tracking error can converge to a small neighborhood of zero. Finally, two simulation examples are given to illustrate the effectiveness of the proposed scheme. 相似文献
18.
Meibao Yao Xueming Xiao Yang Tian Hutao Cui 《Journal of The Franklin Institute》2021,358(10):5386-5407
This paper proposes a novel fast terminal sliding mode (FTSM) control scheme, which accelerates convergence of the controlled system both in its approaching and after reaching the sliding manifold. The novelty lies in the design of time-varying sliding surface without a priori knowledge of the initial system states, so achieving insensitivity to the uncertainty of the initial states. Based on this, we design a corresponding FTSM control strategy, where the singularity problem of conventional terminal sliding mode (TSM) control systems is overcome by restricting the TSM surfaces to non-singular areas. We prove stability and finite-time convergence of the system with the proposed controller. Furthermore, we extend the proposed FTSM control scheme to high-order systems and discuss its application in practical systems. Preliminary simulation results and comparative studies demonstrate the validity of the proposed FTSM control scheme with the designed sliding surface. 相似文献
19.
《Journal of The Franklin Institute》2023,360(9):6296-6320
The objective of this article is to present an adaptive neural inverse optimal consensus tracking control for nonlinear multi-agent systems (MASs) with unmeasurable states. In the control process, firstly, to approximate the unknown state, a new observer is created which includes the outputs of other agents and their estimated information. The neural network is used to reckon the uncertain nonlinear dynamic systems. Based on a new inverse optimal method and the construction of tuning functions, an adaptive neural inverse optimal consensus tracking controller is proposed, which does not depend on the auxiliary system, thus greatly reducing the computational load. The developed scheme not only insures that all signals of the system are cooperatively semiglobally uniformly ultimately bounded (CSUUB), but also realizes optimal control of all signals. Eventually, two simulations provide the effectiveness of the proposed scheme. 相似文献
20.
《Journal of The Franklin Institute》2022,359(7):2932-2948
In this paper, an adaptive neural control scheme is proposed for a class of unknown nonlinear systems with unknown sensor hysteresis. The radial basis function neural networks are employed to approximate the unknown nonlinearities and the backstepping technique is implemented to construct controllers. The difficulty of the control design lies in that the genuine states of the system are not available for feedback, which is caused by sensor hysteresis. The proposed control scheme eventually ensures the practical finite-time stability of the closed-loop system, which is proved by the Lyapunov theory. A numerical simulation example is included to verify the effectiveness of the developed approach. 相似文献