用隐变量控制量子电路,高效生成复杂量子态分布。
Latent-Conditioned Parameterized Quantum Circuits as Universal Approximators for Distributions over Quantum States

- 用神经网络将隐变量映射为量子电路参数,实现量子态分布生成。
- 在1-瓦瑟斯坦距离下可逼近任意量子态概率分布,且优化更稳定。
- 适合需要生成多量子态的化学模拟与量子机器学习任务。
量子模拟、量子化学和量子机器学习等应用常需生成代表系统异质性的量子态集合,逐个准备代价高昂。本文提出隐变量条件化的参数化量子电路(LPQC),通过经典神经网络将先验分布采样的隐变量映射为量子电路参数。证明了LPQC在1-瓦瑟斯坦距离下对密度算符的概率测度具有通用逼近能力,扩展了经典通用逼近定理至量子分布场景。引入多模态隐变量先验与专家混合电路结构,实验表明该参数化缓解了优化中的荒原梯度问题,提供部分严格保证。数值实验验证其在合成多簇混合态及基于QM9的三维分子结构集合上的有效性,性能优于近期量子生成基线,达到经典神经网络基准水平,且输出维度仅随量子比特数线性增长,而非指数增长。借助隐空间的经典表达能力,LPQC为量子生成建模提供了可计算路径。
原文摘要 · Abstract (English)
Many applications in quantum simulation, quantum chemistry, and quantum machine learning require not a single quantum state but an ensemble of states characterizing the heterogeneity of a target system. Preparing such ensembles state-by-state is prohibitive in both variational and fault-tolerant settings, thereby motivating a generative modeling approach. We introduce latent-conditioned parameterized quantum circuits (LPQCs), a hybrid quantum-classical framework in which classical neural networks map a latent variable sampled from a prior distribution to the parameters of a parameterized quantum circuit. We prove that LPQCs are universal approximators for probability measures over density operators in the 1-Wasserstein distance, extending classical universal approximation theorems to the quantum-distribution setting. We additionally introduce a multimodal latent prior and a mixture-of-experts circuit architecture, and show empirically that the latent-conditioned parameterization alleviates the barren plateau problem during optimization, a behavior for which we provide rigorous partial guarantees. Numerical experiments validate the framework on a synthetic multi-cluster ensemble of mixed quantum states and on a QM9-derived ensemble of 3-D molecular structures. In these tasks, LPQC outperforms recent quantum generative baselines and matches the generation quality of a classical neural-network baseline, while requiring an output dimension that grows only linearly with the number of qubits rather than exponentially. By leveraging classical expressivity in the latent space, LPQCs offer a tractable route to quantum generative modeling.
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