共查询到20条相似文献,搜索用时 109 毫秒
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核磁共振系统是实现量子计算的有效物理体系之一.但是随着量子位数的不断增加,运用核磁共振技术实现计算任务存在明显的局限性,原因之一是量子计算的初始态-赝纯态,随着量子位数的增加,信号指数性的衰减,量子位数越多制备赝纯态所需的脉冲序列越复杂,越不容易实现,不利于量子位数的扩展;另外,由于核磁共振中制备的赝纯态实际上也是一种混合态,用于实现量子信息任务时存在一定的争议.该文介绍的利用仲氢诱导极化技术(PHIP)制备出的实验初态,能够解决初态处于混合态的问题,并且信号强度显著增强,作者利用此态实现了 ALTADENA 条件下的两量子位的 Deutsch-Jozsa 量子算法和 PASADENA 条件下的三量子位的Deutsch-Like 量子算法. 相似文献
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利用两对二粒子非最大纠缠态概率隐形传送任意三粒子纠缠W态 总被引:2,自引:0,他引:2
提出一种仅利用两对二粒子非最大纠缠态作为量子信道传送任意三粒子纠缠W态的方案,与以往的方法相比,本方案不仅节约了纠缠资源(以往的量子信道三对EPR或者三粒子纠缠态),而且由于作为量子信道的二粒子纠缠态要比任何别的三粒子纠缠态在实验上更容易制备,因而本方案在量子信息理论与实验的发展中都具有参考价值. 相似文献
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该文提出一个能使多量子跃迁、卫星跃迁魔角旋转及其变种方法的灵敏度明显增强的方法.在通常多量子激发或卫星跃迁激发脉冲之前施加一个预备脉冲,对初始态优化从而使循环延迟时间显著减小.利用几个代表性核种(23Na,11B和87Rb)在两个不同磁场下演示了这一方法.该方法可在低至4.7 T的磁场及6 kHz的转速下在任何常规固体核磁共振实验中实现,无需附加硬件或软件.此外,尽管完整的理论解说将另行发表,文中给出具体的实验步骤,使该方法可由用户灵活订制实验,针对每个样品优化实验参数. 相似文献
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量子Fisher信息(QFI)是量子度量学中的一个重要物理量,可给出预估参数精度的最优值.本文研究如何引入弱测量和测量反转操作,来提高有限温环境下以Greenberger-Horne-Zeilinger态作为量子通道的隐形传态过程中的QFI.依据隐形传态过程中量子比特的传输情形,考虑了三种不同方案相应的QFI.首先,通过构造每种量子隐形传态方案的量子线路图,分析了QFI与推广振幅衰减噪声参数的变化关系.随后对各种方案中的受噪声粒子施加弱测量和测量反转操作,并对相应的部分测量参数进行优化,着重探讨了施加最优部分测量操作后QFI的改进量.结果表明,经过优化后的部分测量操作能有效提高有限温环境下量子隐形传态过程输出态的QFI;而且量子系统所处的环境温度越低,QFI的提高效果可越显著. 相似文献
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设计了一组新的量子远程态制备步骤,在发送方对手中的粒子完成测量后,接收方采用该步骤可以有效降低远程态制备的经典通信消耗-给出一种利用部分纠缠的三粒子Greenberger-Horne-Zeilinger(GHZ)态和部分纠缠的二粒子态作信道,远程制备一个三粒子GHZ态的方案,以此方案为例具体说明上述方法的运用步骤并给出了该方法的适用范围-结果表明,运用该方法后只需消耗1bit经典信息即可远程制备一个三粒子GHZ态-
关键词:
远程态制备
经典通信消耗
三粒子Greenberger-Horne-Zeilinger态
量子信道 相似文献
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量子相干性作为量子力学一个最显著的特征,被认为是量子信息过程中很重要的一种量子资源.单模压缩态和双模压缩态(Einstein-Podolsky-Rosen纠缠态)均具有量子相干性,在制备和传输过程中的量子相干性对于实际应用具有重要意义.利用平衡零拍探测重构量子态的协方差矩阵,本文定量分析了量子态制备过程中的不完美以及信道传输损耗对单模和双模压缩态量子相干性的影响.实验证明量子态的压缩和纠缠特性及量子相干性对损耗均是鲁棒的.特别地,压缩和纠缠特性会随着量子态制备过程中热光子数的增大而减小,直至消失,而当压缩和纠缠均已消失时,量子相干性依然存在.实验结果为压缩态、纠缠态光场的量子相干性作为量子资源在量子信息过程中的应用提供了参考. 相似文献
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Yun-Hai Zhang Shi-Min Xu Xing-Lei Xu Hong-Qi Li 《International Journal of Theoretical Physics》2009,48(5):1300-1311
Some unitary operators are derived using quantum state by depending on the technique of integration within an ordered product
of operators, for example parity operator, displacement operator, squeezed operator, etc. The characteristics of these operators
are analyzed. Their unitary transformations play an essential role in some transformations. As applications, the dynamic problems
of the double momentum coupling harmonic oscillators are solved exactly. 相似文献
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多光子非线性过程中的振幅平方压缩 总被引:4,自引:0,他引:4
本文研究了多光子非线性光学过程中的振幅平方压缩,证明了K光子么正算符Sk(z)(K>2)对非真空相干态的作用在—级近似下会产生振幅平方压缩.以及Sk(z)(K>2,K≠4)对真空态的作用不会产生振幅平方压缩.发现4个光子么正算符S4(z)对真空态的作用可以产生振幅平方压缩,这表明振幅平方压缩是一种独立于二阶压缩、反聚束以及亚泊松统计分布的新的光场非经典效应. 相似文献
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《中国物理 B》2019,(8)
Based on the Weyl expansion representation of Wigner operator and its invariant property under similar transformation, we derived the relationship between input state and output state after a unitary transformation including Wigner function and density operator. It is shown that they can be related by a transformation matrix corresponding to the unitary evolution. In addition, for any density operator going through a dissipative channel, the evolution formula of the Wigner function is also derived. As applications, we considered further the two-mode squeezed vacuum as inputs, and obtained the resulted Wigner function and density operator within normal ordering form. Our method is clear and concise, and can be easily extended to deal with other problems involved in quantum metrology, steering, and quantum information with continuous variable. 相似文献
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Quantum gates are unitary operators and pure states are denoted by unit vectors in state spaces. A quantum gate (i.e., unitary operator) maps convex combinations of vectors in the closed unit ball of the state space to themselves. On the contrary, whether or not some kinds of convex combinations preserving maps on the closed unit ball of the state space are unitary. In the paper, we devote to giving an answer to the inverse problem.
相似文献15.
Mostafazadeh A 《Physical review letters》2007,99(13):130502
A non-Hermitian operator with a real spectrum and a complete set of eigenvectors may serve as the Hamiltonian operator for a unitary quantum system provided that one makes an appropriate choice for the defining the inner product of physical Hilbert state. We study the consequences of such a choice for the representation of states in terms of projection operators and the geometry of the state space. This allows for a careful treatment of the quantum Brachistochrone problem and shows that it is indeed impossible to achieve faster unitary evolutions using PT-symmetric or other non-Hermitian Hamiltonians than those given by Hermitian Hamiltonians. 相似文献
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SUN Changyou 《Chinese Journal of Lasers》1996,5(2):129-136
TheSqueezingOperatorandtheSqueezedStatesof"Superspace"¥SUNChangyou(DepartmentofPhysics,HeiheTecher'sCollege,Heihe164300)MAAiq... 相似文献
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利用简洁的幺正变换得到双模压缩算符在纠缠态中表示,使用同样的方法可得到双模压缩算符在坐标和动量本征态中的表示。 相似文献
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分析量子条件振幅算子的性质,该算子起一个类似于在经典信息理论中的条件概率的作用.论证表示一个量子双组元系统的条件算子的频谱在局域幺正变换下是不变的,并且表明它的不可分性.证明一个可分态的条件振幅算子不能有一个超过1的本征值.得出一个在von Neumann条件熵的非负性基础上的相关的可分性条件.
关键词:
条件概率
条件振幅算子
von Neumann条件熵
可分性条件 相似文献
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This paper establishes dynamical localization properties of certain families of unitary random operators on the d-dimensional lattice in various regimes. These operators are generalizations of one-dimensional physical models of quantum
transport and draw their name from the analogy with the discrete Anderson model of solid state physics. They consist in a
product of a deterministic unitary operator and a random unitary operator. The deterministic operator has a band structure,
is absolutely continuous and plays the role of the discrete Laplacian. The random operator is diagonal with elements given
by i.i.d. random phases distributed according to some absolutely continuous measure and plays the role of the random potential.
In dimension one, these operators belong to the family of CMV-matrices in the theory of orthogonal polynomials on the unit
circle. We implement the method of Aizenman-Molchanov to prove exponential decay of the fractional moments of the Green function
for the unitary Anderson model in the following three regimes: In any dimension, throughout the spectrum at large disorder
and near the band edges at arbitrary disorder and, in dimension one, throughout the spectrum at arbitrary disorder. We also
prove that exponential decay of fractional moments of the Green function implies dynamical localization, which in turn implies
spectral localization. These results complete the analogy with the self-adjoint case where dynamical localization is known
to be true in the same three regimes. 相似文献
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Hui-Zhi Xia Chao Li Qing Yang Ming Yang Zhuo-Liang Cao 《Brazilian Journal of Physics》2012,42(3-4):167-171
The operator entanglement of two-qubit joint unitary operations is revisited. The Schmidt number, an important attribute of a two-qubit unitary operation, may have connection with the entanglement measure of the unitary operator. We find that the entanglement measure of a two-qubit unitary operators is classified by the Schmidt number of the unitary operators. We also discuss the exact relation between the operator entanglement and the parameters of the unitary operator. 相似文献