自动搜索高效量子神经网络架构,兼顾准确率与硬件限制。
QNAS: A Neural Architecture Search Framework for Accurate and Efficient Quantum Neural Networks
- 用多目标优化统一评估准确率、运行时长和电路切割开销。
- 在MNIST等数据集上实现97.16%准确率,仅用8量子比特。
- 发现角度编码和稀疏纠缠结构更适合图像数据,适合实际量子硬件部署。
设计既准确又可在当前无纠错量子硬件(NISQ)上部署的量子神经网络(QNN)极具挑战性。手工设计的变分电路需权衡表达能力、可训练性和资源消耗,且受限于量子比特数量常需电路切割。现有量子架构搜索方法主要优化准确率,对量子资源使用仅启发式控制,并忽略电路切割带来的指数级开销。本文提出QNAS,一个融合硬件感知评估、多目标优化与切割开销感知的神经架构搜索框架,用于混合量子经典神经网络(HQNN)。QNAS训练共享参数的SuperCircuit,并采用NSGA-II联合优化三个目标:(i) 验证误差,(ii) 运行时成本代理(衡量墙钟评估时间),(iii) 在目标量子比特预算下的子电路数量估计。通过少量训练轮次评估候选架构,成功发现清晰的帕累托前沿,揭示准确率、效率与切割开销间的权衡。在MNIST、Fashion-MNIST和Iris基准测试中,嵌入类型与CNOT模式选择显著影响性能:角度编码与稀疏纠缠模式在图像数据上表现更优,幅度编码则在表格式数据(Iris)上占优。在MNIST上最优架构达97.16%测试准确率,仅需8量子比特、2层电路;Fashion-MNIST上达87.38%,仅5量子比特、2层;Iris上达100%验证准确率,仅4量子比特、2层。QNAS在搜索过程中自动揭示这些设计洞见,指导实践者构建兼顾准确率、资源效率与实际可部署性的架构。
原文摘要 · Abstract (English)
Designing quantum neural networks (QNNs) that are both accurate and deployable on NISQ hardware is challenging. Handcrafted ansatze must balance expressivity, trainability, and resource use, while limited qubits often necessitate circuit cutting. Existing quantum architecture search methods primarily optimize accuracy while only heuristically controlling quantum and mostly ignore the exponential overhead of circuit cutting. We introduce QNAS, a neural architecture search framework that unifies hardware aware evaluation, multi objective optimization, and cutting overhead awareness for hybrid quantum classical neural networks (HQNNs). QNAS trains a shared parameter SuperCircuit and uses NSGA-II to optimize three objectives jointly: (i) validation error, (ii) a runtime cost proxy measuring wall clock evaluation time, and (iii) the estimated number of subcircuits under a target qubit budget. QNAS evaluates candidate HQNNs under a few epochs of training and discovers clear Pareto fronts that reveal tradeoffs between accuracy, efficiency, and cutting overhead. Across MNIST, Fashion-MNIST, and Iris benchmarks, we observe that embedding type and CNOT mode selection significantly impact both accuracy and efficiency, with angle-y embedding and sparse entangling patterns outperforming other configurations on image datasets, and amplitude embedding excelling on tabular data (Iris). On MNIST, the best architecture achieves 97.16% test accuracy with a compact 8 qubit, 2 layer circuit; on the more challenging Fashion-MNIST, 87.38% with a 5 qubit, 2 layer circuit; and on Iris, 100% validation accuracy with a 4 qubit, 2 layer circuit. QNAS surfaces these design insights automatically during search, guiding practitioners toward architectures that balance accuracy, resource efficiency, and practical deployability on current hardware.
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