用神经张量网络模型高效求解任意自旋体系基态,支持上千量子比特。
Hamilton-Zero: A Neural Tensor-Network Foundation Model for Ground States of Arbitrary Quadratic Qubit Hamiltonians

- 将量子基态问题转化为在群流形上的变分优化,避免直接处理希尔伯特空间。
- 在64量子比特上训练,微调后可在8100量子比特系统上准确预测基态能量。
- 适用于大规模多体量子系统研究,尤其适合需要快速泛化的新哈密顿量设计。
实现有用量子优势的关键在于计算经典方法无法模拟的哈密顿系统基态。本文提出一种基础模型,仅需约0.5亿可调参数,通过大语言模型与深度强化学习技术训练,有效覆盖任意通用哈密顿量集合。我们将自旋-1/2体系基态学习建模为在$ m{SU}(2)^N$上的中心奇标量函数流形变分优化,以流形函数替代希尔伯特空间振幅,哈密顿量作用由李导数表示,通过自定义自动微分实现。基于彼得-外尔定理证明该变分原理保持自旋-1/2子空间基态上界,并通过不可行性定理说明纯态基础量子神经网络的局限性。模型在包含数十万种不同哈密顿量的预训练数据集上训练,涵盖连接拓扑、系统规模、相互作用类型与强度的多样性。采用新型$ m{SU}(2)$复制交换朗之万采样器和分片自然梯度优化,扩展了克罗内克分解近似曲率(KFAC)优化器,在系统规模达64量子比特时完成训练。在保留泛化数据集上微调至1024量子比特,评估结果覆盖高达8100量子比特的系统。
原文摘要 · Abstract (English)
A central promise of useful quantum advantage is the ability to compute ground states of Hamiltonian systems beyond the reach of classical simulation methods. Here we demonstrate that this problem can be effectively amortized across an arbitrary and universal set of Hamiltonians by a foundation model with $\sim0.5$B variational parameters, trained with contemporary techniques from large language models and deep reinforcement learning. To do this, we formulate $\text{spin-}1/2$ quantum ground-state learning as manifold variational optimisation over centrally odd scalar functions on $\mathrm{SU}(2)^N$. This replaces explicit Hilbert-space vector amplitudes with manifold functions on which the Hamiltonian acts through Lie derivatives, evaluated by custom automatic differentiation primitives. We prove that the resulting variational principle on this manifold preserves the $\text{spin-}1/2$ sector's ground-state upper bound using the Peter-Weyl theorem and justify the choice of such a representation with a no-go theorem for pure state foundation NQS. We then pre-train our foundation model on a dataset of hundreds of thousands of different Hamiltonian systems, varying the connection topology, system size, interaction types and strengths, bringing together a century of many-body literature. Using a novel $\mathrm{SU}(2)$ replica-exchange Langevin sampler and sharded natural-gradient optimisation, we train our model with our own extension of the Kronecker-Factored Approximate Curvature (KFAC) optimiser on system sizes up to 64 qubits. On a held-out generalisation dataset, we fine-tune our model on system sizes of up to 1024 qubits, and evaluate on systems up to 8100 qubits.
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