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arXiv 2409.04550quant-phcond-mat.mes-hall
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在量子计算机上求解自由费米问题

Solving Free Fermion Problems on a Quantum Computer

QuTech, TU Delft(代尔夫特理工大学 QuTech);Delft Institute of Applied Mathematics, TU Delft(代尔夫特理工大学应用数学研究所);Department of Physics, ETH Zürich(苏黎世联邦理工学院物理系);QuSoft and CWI(QuSoft 和荷兰国家数学与计算机科学中心)

Maarten Stroeks, Daan Lenterman, Barbara Terhal, Yaroslav Herasymenko

AI总结:

本文提出了一种在量子计算机上以显著降低计算成本求解自由费米问题的算法,通过将相关矩阵和格林函数编码为单位ary,实现指数级内存和运行时间的改进。

摘要:

模拟非相互作用费米系统是计算许多体物理中的常见任务。在没有平移对称性的情况下,用N个模式建模自由费米子通常需要多项式N的计算资源。虽然通常适度,但当考虑大型系统时,这些成本可能变得非常昂贵。我们提出了几个可以由量子算法以显著降低的计算成本解决的自由费米问题。内存成本提高了指数级,为poly log(N)。与目前已知的最佳经典算法相比,运行时间的改进要么是指数级,要么是显著的多项式级,这取决于问题的几何结构。自由费米子动力学的模拟属于BQP-hard复杂性类别。这表明(在标准假设下),我们的算法在任何经典算法中至少对于某些几何结构提供了指数级加速。我们算法中的关键技术是将相关矩阵和格林函数等对象编码为单位ary。我们展示了如何在紧束缚哈密顿量的动力学和热力学状态的背景下,高效地将此类单位ary实现为量子电路。离散无序和非均匀晶格以及大非晶格图的特殊情况被详细展示。最后,我们证明我们的模拟算法可以推广到其他有前景的目标,包括自由玻色子系统。

英文摘要:

Simulating noninteracting fermion systems is a common task in computational many-body physics. In absence of translational symmetries, modeling free fermions on $N$ modes usually requires poly$(N)$ computational resources. While often moderate, these costs can be prohibitive in practice when large systems are considered. We present several free-fermion problems that can be solved by a quantum algorithm with substantially reduced computational costs. The memory costs are exponentially improved, poly log$(N)$. The runtime improvement, compared to the best known classical algorithms, is either exponential or significantly polynomial, depending on the geometry of the problem. The simulation of free-fermion dynamics belongs to the BQP-hard complexity class. This implies (under standard assumptions) that our algorithm yields an exponential speedup for any classical algorithm at least for some geometries. The key technique in our algorithm is the block-encoding of objects such as correlation matrices and Green's functions into a unitary. We demonstrate how such unitaries can be efficiently realized as quantum circuits, in the context of dynamics and thermal states of tight-binding Hamiltonians. The special cases of disordered and inhomogeneous lattices, as well as large non-lattice graphs, are presented in detail. Finally, we show that our simulation algorithm generalizes to other promising targets, including free boson systems.

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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