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We provide an expression for the measure of coherence of quantum pure states, which is obtained by quantifying the deviation or distance between the measured state and the maximally coherent states in the same Hilbert space. We classify quantum pure states in a Hilbert space according to their coherence and prove that the variance measure of coherence is proper for all quantum pure states. We demonstrate that the variance measure of coherence is simpler and easier to obtain than the l1-norm of coherence and the relative entropy of coherence.
相似文献2.
Guang-Yong Zhou Lin-Jian Huang Jun-Ya Pan Li-Yun Hu Jie-Hui Huang 《Frontiers of Physics》2018,13(4):130701
Resource theory is applied to quantify the quantum correlation of a bipartite state and a computable measure is proposed. Since this measure is based on quantum coherence, we present another possible physical meaning for quantum correlation, i.e., the minimum quantum coherence achieved under local unitary transformations. This measure satisfies the basic requirements for quantifying quantum correlation and coincides with concurrence for pure states. Since no optimization is involved in the final definition, this measure is easy to compute irrespective of the Hilbert space dimension of the bipartite state. 相似文献
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量子化的Dicke模型在非旋波近似条件下表现为量子混沌动力学特征.利用单粒子一阶时间关联函数,通过数值计算详细考察了Dicke模型中单粒子相干动力学特性.结果表明:当初始相干态处在混沌区域时,一阶时间关联函数曲线衰减较快,而当初始相干态处在规则区域时,一阶时间关联函数曲线衰减较慢,单粒子相干动力学对初态具有较强的敏感性,经典混沌抑制量子相干.考察单粒子相干动力学在相空间的平均演化性质,得到一种较好的量子经典对应关系.最后研究了相空间单粒子相干的整体动力学性质,更好地揭示了相空间的混沌和规则结构. 相似文献
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We study the skew information-based coherence of quantum states and derive explicit formulas for Werner states and isotropic states in a set of autotensors of mutually unbiased bases (MUBs). We also give surfaces of skew information-based coherence for Bell-diagonal states and a special class of X states in both computational basis and in MUBs. Moreover, we depict the surfaces of the skew information-based coherence for Bell-diagonal states under various types of local nondissipative quantum channels. The results show similar as well as different features compared with relative entropy of coherence and l1 norm of coherence. 相似文献
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量子相干性是量子信息处理的基本要素,在量子计算中扮演着重要的角色.为了便于讨论量子相干性在量子计算中的作用,本文从离散Wigner函数角度对量子相干性进行了探讨.首先对奇素数维量子系统的离散Wigner函数进行了分析,分离出表征相干性的部分,提出了一种可能的基于离散Wigner函数的量子相干性度量方法,并对其进行了量子相干性度量规范的分析;同时也比较了该度量与l_1范数相干性度量之间的关系.重要的是,这种度量方法能够明确给出量子相干性程度与衡量量子态量子计算加速能力的负性和之间不等式关系,由此可以解析地解释量子相干性仅是量子计算加速的必要条件. 相似文献
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几类相干态的量子保真度 总被引:1,自引:1,他引:0
在坐标表象下,研究了几类相干态的量子保真度,对于相干态,我们给出了量子保真度的解析表达式,考查了谐振子特征长度 ,平移距离 对保真度的影响;对于相干态 与 的叠加态,考查了初态量子干涉对量子保真度的影响,结论表明:量子保真度呈周期性;与相干态的量子保真度比较而言,当谐振子处于第二类相干态时,量子干涉能抑制量子态失真,当谐振子处于第三类相干态时,量子干涉能抑制量子态失真,也可能加大量子态失真. 相似文献
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In this paper, we analyze the evolution of quantum coherence in a two-qubit system going through the amplitude damping channel. After they have gone through this channel many times, we analyze the systems with respect to the coherence of their output states. When only one subsystem goes through the channel, frozen coherence occurs if and only if this subsystem is incoherent and an auxiliary condition is satisfied for the other subsystem. When two subsystems go through this quantum channel, quantum coherence can be frozen if and only if the two subsystems are both incoherent. We also investigate the evolution of coherence for maximally incoherent-coherent states and derive an equation for the output states after one or two subsystems have gone through the amplitude damping channel. 相似文献
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Coherence is a key resource in quantum information science.Exactly understanding and controlling the variation of coherence are vital for implementation in realistic quantum systems.Using P-representation of density matrix,we obtain the analytical solution of the master equation for the classical states in the non-Markovian process and investigate the coherent dynamics of Gaussian states.It is found that quantum coherence can be preserved in such a process if the coupling strength between system and environment exceeds a threshold value.We also discuss the characteristic function of the Gaussian states in the non-Markovian process,which provides an inevitable bridge for the control and operation of quantum coherence. 相似文献
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纠缠交换,即纠缠态的量子离物传送,是实现远程量子通讯及量子信息网络的必要手段之一 . 要完成纠缠交换实验,首先必须具有两组相互独立的纠缠源. 对于连续变量系统,两独立 的纠缠源为具有经典相干但量子起伏互不关联的两组EPR纠缠态光场. 利用自行研制的瓦级 连续双波长输出Nd3+: YAP/KTP稳频激光器为抽运源,抽运两台结 构完全相同的非简 并光学参量放大器,获得了具有经典相干性的两组独立的EPR纠缠光束. 讨论了两组具有经 典相干性的EPR光束产生的实验方法,及不完善模匹配效率对关联测量的影响.
关键词:
EPR纠缠态光场
经典相干
非简并光学参量放大器 相似文献
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E.B. Karlsson 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,22(3):393-400
The coherence in quantum superposition states of protons (and chemically similar particles, the positive muons) has been studied
in some condensed matter environments. It is shown that if the proton systems and the experimental techniques used to study
them are carefully selected, it is possible to observe quantum delocalization states of single particles and to understand
the mechanisms for their loss of coherence. Quantum correlated two- and multiparticle states of protons lose coherence very
fast when coupled to condensed matter environments, but new sub-femtosecond techniques have made them accessible to experimental
studies. The degree of decoherence can be measured as function of time and the decoherence mechanisms can, at least in certain
cases, be identified. Although less clean than in corresponding studies of quantum optical systems, these studies can be seen
as a first step towards understanding the conditions for preservation of quantum correlation and entanglement in massive systems.
Some consequences and some suggestions for future work are discussed.
Received 28 August 2002 Published online 7 January 2003 相似文献
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《中国光学快报(英文版)》2017,(5)
We show how to optimally protect quantum states and freeze coherence under incoherent channels using a quantum weak measurement and quantum measurement reversal. In particular, we present explicit formulas for the conditions for freezing quantum coherence in a given quantum state. 相似文献
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We study the decoherence rate for estimating the time at which the coherence instability of a quantum pure state is onset. We analyze the coherence stability of pure states of a three-level quantum system under the effect of a bosonic reservoir and driven by two Raman classical fields. By assuming the boson systems to be in thermal states we find for a symmetric V-system a set of three states free from decoherence and, for a symmetric cascade-system, a two-dimensional subspace whose states are stable against the considered decoherence mechanism. 相似文献
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Wen-Jian Yu Yong-Bo Wei Hai Li Lin Li Jian Zou Bin Shao 《International Journal of Theoretical Physics》2016,55(11):4785-4797
We investigate the quantum speed limit (QSL) time of an electronic spin coupled to a bath of nuclear spins. We consider three types of initial states with different correlations between the system and bath, i.e., quantum correlation, classical correlation, and no any correlation. Interestingly, we show that the QSL times of the central spin for these three types of initial correlations are identical when the couplings are homogeneous. However, it is remarkable different for inhomogenous couplings. The QSL time of the central spin is sensitive to the initial states, the average coupling strength, the distribution of the couplings between the system and bath and the number of the nuclear spins in the bath. Furthermore, we find that the coherence in the initial state has significant influences on the QSL time of the system, and can lead to the increase of QSL time for homogeneous couplings. 相似文献
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Lian-Wu Yang 《中国物理 B》2021,30(12):120304-120304
Quantum coherence and discord are two kinds of manifestations of nonclassicality. By calculating the coherence and discord in the specific bipartite quantum systems, we show quantitative connections between the coherence and the discord in the bipartite quantum systems created from local systems with the help of incoherent operations. We show that the coherence bounds the dynamical discord, and under particular conditions of the initial quantum states, the coherence of single systems is equal to the dynamical discord. We extend these results to the multipartite quantum systems. 相似文献
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Chuu CS Strassel T Zhao B Koch M Chen YA Chen S Yuan ZS Schmiedmayer J Pan JW 《Physical review letters》2008,101(12):120501
We report the experimental demonstration of quantum memory for collective atomic states in a far-detuned optical dipole trap. Generation of the collective atomic state is heralded by the detection of a Raman scattered photon and accompanied by storage in the ensemble of atoms. The optical dipole trap provides confinement for the atoms during the quantum storage while retaining the atomic coherence. We probe the quantum storage by cross correlation of the photon pair arising from the Raman scattering and the retrieval of the atomic state stored in the memory. Nonclassical correlations are observed for storage times up to 60 mus. 相似文献
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Qing-Yun Zhou 《中国物理 B》2023,32(1):10304-010304
Entanglement and coherence are two important resources in quantum information theory. A question naturally arises: Is there some connection between them? We prove that the entanglement of formation and the first-order coherence of two-qubit states satisfy an inequality relation. Two-qubit pure state reaches the upper bound of this inequality. A large number of randomly generated states are used to intuitively verify the complementarity between the entanglement of formation and the first-order coherence. We give the maximum accessible coherence of two-qubit states. Our research results will provide a reliable theoretical basis for conversion of the two quantum resources. 相似文献
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Zhiming Huang Haozhen Situ Cai Zhang 《International Journal of Theoretical Physics》2017,56(7):2178-2191
We study quantum coherence and quantum correlation for detecting quantum phase transition (QPT) by means of quantum renormalization group (QRG) in various spin chain models with Dzyaloshinskii-Moriya (DM) interaction, including XXZ model with DM interaction, Ising model with DM interaction and XY model with DM interaction. It is found that through enough QRG iterations, l 1 norm quantum coherence and one-norm geometric quantum discord can effectively characterize QPT. We also discuss the effect of DM interaction and anisotropy on quantum coherence and quantum correlation. 相似文献
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Jin-Hua Zhang Fu-Lin Zhang Zhi-Xi Wang Hui Yang Shao-Ming Fei 《Entropy (Basel, Switzerland)》2022,24(1)
We investigate the discrimination of pure-mixed (quantum filtering) and mixed-mixed states and compare their optimal success probability with the one for discriminating other pairs of pure states superposed by the vectors included in the mixed states. We prove that under the equal-fidelity condition, the pure-pure state discrimination scheme is superior to the pure-mixed (mixed-mixed) one. With respect to quantum filtering, the coherence exists only in one pure state and is detrimental to the state discrimination for lower dimensional systems; while it is the opposite for the mixed-mixed case with symmetrically distributed coherence. Making an extension to infinite-dimensional systems, we find that the coherence which is detrimental to state discrimination may become helpful and vice versa. 相似文献