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arXiv 2507.10285quant-ph
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从线性微分方程到幺正算子:一种具有近最优量子算法的动量匹配扩张框架

From Linear Differential Equations to Unitaries: A Moment-Matching Dilation Framework with Near-Optimal Quantum Algorithms

The Pennsylvania State University(宾夕法尼亚州立大学)

Xiantao Li

AI总结:

本文提出了一种动量匹配扩张框架,将非幺正线性流转化为幺正演化,实现近最优量子算法。

摘要:

量子动力学模拟的加速通常需要幺正时间演化,而现实中物理模型中遇到的大型ODE/PDE系统通常是非幺正的。我们提出了一种通用动量满足的扩张,将任意线性、非厄米特流\dot x = Lx(其中L=-iH+K)嵌入到一个扩展的希尔伯特空间中的严格幺正演化中:$$ ( (l| \otimes I ) \mathcal T e^{-i \int ( I_A\otimes H +i F\otimes K) dt} ( |r) \otimes I ) = \mathcal T e^{\int L dt}, $$ 提供三元组(F, (l|, |r))满足在辅助空间中的紧动量恒等式(l| F^{k}|r)=1对于所有k≥0。这个代数条件恢复了Schrödingerization [Phys. Rev. Lett. 133, 230602 (2024)] 和线性-组合-哈密顿量(LCHS)方案 [Phys. Rev. Lett. 131, 150603 (2023)],同时揭示了由微分、积分、伪微分和差分生成器构建的整个新的扩张家族。每个家族都带有连续调节参数,并且在保持动量不变的相似变换下闭合,从而产生了一个庞大的设计空间,允许量子扩张与特定应用、算法和硬件共同优化。作为具体演示,我们证明了在有限区间内简单的有限差分扩张在 oracle 复杂度上达到近最优。Maxwell粘弹性波传播的数值实验证实了该方法的准确性和鲁棒性。

英文摘要:

Quantum speed-ups for dynamical simulation usually demand unitary time-evolution, whereas the large ODE/PDE systems encountered in realistic physical models are generically non-unitary. We present a universal moment-fulfilling dilation that embeds any linear, non-Hermitian flow $\dot x = L x$ with $L=-iH+K$ into a strictly unitary evolution on an enlarged Hilbert space: \[ ( (l| \otimes I ) \mathcal T e^{-i \int ( I_A\otimes H +i F\otimes K) dt} ( |r) \otimes I ) = \mathcal T e^{\int L dt}, \] provided the triple $( F, (l|, |r) )$ satisfies the compact moment identities $(l| F^{k}|r) =1$ for all $k\ge 0$ in the ancilla space. This algebraic criterion recovers both \emph{Schrödingerization} [Phys. Rev. Lett. 133, 230602 (2024)] and the linear-combination-of-Hamiltonians (LCHS) scheme [Phys. Rev. Lett. 131, 150603 (2023)], while also unveiling whole families of new dilations built from differential, integral, pseudo-differential, and difference generators. Each family comes with a continuous tuning parameter \emph{and} is closed under similarity transformations that leave the moments invariant, giving rise to an overwhelming landscape of design space that allows quantum dilations to be co-optimized for specific applications, algorithms, and hardware. As concrete demonstrations, we prove that a simple finite-difference dilation in a finite interval attains near-optimal oracle complexity. Numerical experiments on Maxwell viscoelastic wave propagation confirm the accuracy and robustness of the approach.

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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