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Measurement-based quantum computation in an optical setup shows great promise towards the implementation oflarge-scale quantum computation. The difficulty of measurement-based quantum computation lies in the preparation ofcluster state. In this paper, we propose the method of generating the large-scale cluster state, which is a platform formeasurement-based quantum computation. In order to achieve more complex quantum circuits, the preparation protocolof N-photon cluster state will be proposed as a generalization of the preparation of four- and five-photon cluster states.Furthermore, our proposal is experimentally feasible. 相似文献
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We study the spin squeezing property of weighted graph states,which can be used to improve sensitivity in interferometry.We study the time evolution of spin squeezing under local decoherence acting independently on each qubit.Based on the analysis,the spin squeezing of the weighted graph states is somehow robust in the presence of decoherence and the decoherence limit in the improvement of the interferometric sensitivity is still achievable.Furthermore,one can obtain the optimal improvement of sensitivity by tuning the weighted of each edges of the weighted graph state. 相似文献
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Irreversibility of a quantum walk induced by controllable decoherence employing random unitary operations 下载免费PDF全文
Quantum walk is different from random walk in reversibility and interference. Observation of the reduced re- versibility in a realistic quantum walk is of scientific interest in understanding the unique quantum behavior. We propose an idea to experimentally investigate the decoherence-induced irreversibility of quantum walks with trapped ions in phase space via the average fidelity decay. By introducing two controllable decoherence sources, i.e., the phase damping channel (i.e., dephasing) and the high temperature amplitude reservoir (i.e., dissipation), in the intervals between the steps of quantum walk, we find that the high temperature amplitude reservoir shows more detrimental effects than the phase damping channel on quantum walks. Our study also shows that the average fidelity decay works better than the position variance for characterizing the transition from quantum walks to random walk. Experimental feasibility to monitor the irreversibility is justified using currently available techniques. 相似文献
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This article aims to provide a review on quantum walks. Starting form a basic idea of discrete-time quantum walks, we will review the impact of disorder and decoherence on the properties of quantum walks. The evolution of the standard quantum walks is deterministic and disorder introduces randomness to the whole system and change interference pattern leading to the localization effect. Whereas, decoherence plays the role of transmitting quantum walks to classical random walks. 相似文献
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利用循环伏安法对我们新设计合成的两种二茂铁甲基二氧大环多胺化合物——1-二茂铁甲基-1,4,8,11-四氮杂环十三烷-5,7-二酮(简称FcCH2L1)和1-二茂铁甲基-1,4,7,11,14-五氮杂环十六烷-3,15-二酮(简称FcCH2L2)——的电化学性质进行了研究,包括酸碱度的影响以及它们对Zn2+,Ca2+,Cd2+,Cu2+,Ni2+,Co2+等金属离子的电化学响应情况.在乙醇和水的混合溶剂体系中化合物FcCH2L1对Ni2+具有选择性络合,而化合物FcCH2L2对高氧化态的Ni3+有稳定作用 相似文献
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We experimentally investigate the impact of static disorder and dynamic disorder on the non-unitary dynamics of parity-time(PT)-symmetric quantum walks.Via temporally alternating photon losses in an interferometric network,we realize the passive PT-symmetric quantum dynamics for single photons.Controllable coin operations allow us to simulate different environmental influences,which result in three different behaviors of quantum walkers:a standard ballistic spread,a diffusive behavior,and a localization,respectively,in a PT-symmetric quantum walk architecture. 相似文献
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激光窃听技术通常不直接照射被窃听目标, 且由于玻璃散射的原因, 利用现有的拦截式激光预警技术无法获取其窃听源方位等信息, 针对该问题, 提出利用CCD相机结合滤光片的方案对窗户进行凝视成像的反激光窃听预警系统, 同时, 构建了窃听激光源、被照射玻璃上的散射激光光斑以及反激光窃听系统之间的空间几何模型, 结合边缘检测等图像特征提取算法以及最小二乘图像拟合算法对散射激光光斑轮廓进行拟合, 推导出窃听激光光源来袭方位的数学模型。实验结果表明:所搭建的激光窃听预警系统不但可以检测到照射到玻璃上的窃听光斑, 且可以有效地追溯到该激光束的方位角和俯仰角信息, 定位精度≤ 4°, 从而达到了对窃听源定位的目的, 有助于推动现有激光预警技术的进一步发展, 且在国防安全等领域发挥积极作用。 相似文献
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为了使腔体在复杂电磁环境下处于谐振状态,保持超导腔加速电压的幅度相位稳定,研发了一种应用于自激锁相模式的腔体新型调谐算法。利用正交电压Q值控制调谐器调谐,从而消除了输入和输出间的相位误差,给出了理论推导过程与该算法的可靠性分析。该算法已应用于中国科学院近代物理研究所ADS项目超导加速器中,简化了传统控制模式中的信号采样数量,提高了系统控制精度与抗干扰能力,使腔体克服了在调谐过程中由于功率上冲引起的氦压波动。保证了超导腔在工作状态下,频率稳定在162.5 MHz,频率误差小于17 Hz。For the purposes of keeping the resonant cavity steady in a complex electromagnetic environment and maintaining stable amplitude and phase, a new tuning algorithm for superconducting RF cavity operated in self-excited phase-locked mode has been developed. The quadrature voltage was employed to control the tuner under the phase-locked condition, so as to eliminate phase measurement between the input and the output. This paper demonstrates the principle of this "Minimum Q" tuning algorithm and presents an analysis of the stability of the system. The algorithm is applied to the superconducting accelerator of the Institute of Modern Physics' ADS project. The "Minimum Q" tuning algorithmnot only simplifies the number of signal sampling but also improves the control accuracy and anti-interference ability of the system, while enables the cavity to overcome the helium pressure fluctuation which caused by power overshoot. It ensures that the frequency of the superconducting cavity is stable at 162.5 MHz, and the frequency error is less than 17 Hz. 相似文献