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arXiv 2005.12934quant-phcond-mat.stat-mechcs.NI
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连续变量随机量子网络中纠缠的形成

Entanglement formation in continuous-variable random quantum networks

Bingzhi Zhang, Quntao Zhuang

摘要:

纠缠态不仅对理解多体系统的基本性质很重要,而且是在实际信息处理任务中实现量子优势的关键资源。虽然以前的纠缠形成和网络的工作集中在离散变量系统,光-作为网络中量子信息的唯一传播载体-是玻色子,因此一般需要连续变量的描述。在这项工作中,我们将研究扩展到连续变量量子网络。通过将任意网络上的系综平均纠缠动力学映射为图上的随机行走过程,我们能够精确地求解纠缠动力学并揭示独特的现象。我们确定压缩作为纠缠产生的来源,它触发了一个抛物光锥纠缠的扩散传播。纠缠分布与随机游走的概率分布直接相关,而加扰时间则由随机游走的混合时间决定。二体纠缠的动力学是由二体纠缠的边界决定的;基于多体纠缠在感知任务中的优势,引入了多体纠缠的操作见证来表征多体纠缠的增长。理论预测和数值验证了纠缠增长中令人惊讶的线性叠加定律,当时空中的挤压器稀疏时,尽管纠缠动力学具有非线性性质。我们也给出了平衡纠缠分布的精确解(Page曲线),包括它的起伏,并发现各种形状依赖于平均压缩密度和强度。

英文摘要:

Entanglement is not only important for understanding the fundamental properties of many-body systems, but also the crucial resource enabling quantum advantages in practical information processing tasks. While previous works on entanglement formation and networking focus on discrete-variable systems, light---as the only travelling carrier of quantum information in a network---is bosonic and thus requires a continuous-variable description in general. In this work, we extend the study to continuous-variable quantum networks. By mapping the ensemble-averaged entanglement dynamics on an arbitrary network to a random-walk process on a graph, we are able to exactly solve the entanglement dynamics and reveal unique phenomena. We identify squeezing as the source of entanglement generation, which triggers a diffusive spread of entanglement with a parabolic light cone. The entanglement distribution is directly connected to the probability distribution of the random walk, while the scrambling time is determined by the mixing time of the random walk. The dynamics of bipartite entanglement is determined by the boundary of the bipartition; An operational witness of multipartite entanglement, based on advantages in sensing tasks, is introduced to characterize the multipartite entanglement growth. A surprising linear superposition law in the entanglement growth is predicted by the theory and numerically verified, when the squeezers are sparse in space-time, despite the nonlinear nature of the entanglement dynamics. We also give exact solution to the equilibrium entanglement distribution (Page curves), including its fluctuations, and found various shapes dependent on the average squeezing density and strength.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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