论文标题

法律:环顾四周和温暖启动的自然梯度下降量子量子神经网络

LAWS: Look Around and Warm-Start Natural Gradient Descent for Quantum Neural Networks

论文作者

Tao, Zeyi, Wu, Jindi, Xia, Qi, Li, Qun

论文摘要

由于其在嘈杂的中间尺度量子计算机(NISQ)中的表现,变异量子算法(VQA)最近受到了研究界的极大关注。但是,具有随机初始初始化参数的参数化量子电路(PQC)以贫瘠的高原(BP)为特征的VQA,其中梯度在Qubits的数量中呈指数级消失。在本文中,我们首先回顾了从经典的一阶优化的角度来看,它是VQA中最流行的算法之一。然后,我们提出了一个\下划线{l} ook \下划线{a}圆形\下划线{w} arm- \下划线{s} tart qng qng(law)算法来减轻广泛的现有BP问题。法律是利用模型参数初始化和QNG快速收敛的组合优化策略。法律反复重新定制了下一个迭代参数更新的参数搜索空间。通过对接近电流最佳的梯度进行采样,可以仔细选择重新定义的参数搜索空间。此外,我们提出了一个统一的框架(WS-SGD),用于将参数初始化技术集成到优化器中。我们为基于polyak-lojasiewicz(PL)条件的凸面和非凸目标函数提供了提议的框架的收敛证明。我们的实验结果表明,所提出的算法可以减轻BP,并且在量子分类问题中具有更好的概括能力。

Variational quantum algorithms (VQAs) have recently received significant attention from the research community due to their promising performance in Noisy Intermediate-Scale Quantum computers (NISQ). However, VQAs run on parameterized quantum circuits (PQC) with randomly initialized parameters are characterized by barren plateaus (BP) where the gradient vanishes exponentially in the number of qubits. In this paper, we first review quantum natural gradient (QNG), which is one of the most popular algorithms used in VQA, from the classical first-order optimization point of view. Then, we proposed a \underline{L}ook \underline{A}round \underline{W}arm-\underline{S}tart QNG (LAWS) algorithm to mitigate the widespread existing BP issues. LAWS is a combinatorial optimization strategy taking advantage of model parameter initialization and fast convergence of QNG. LAWS repeatedly reinitializes parameter search space for the next iteration parameter update. The reinitialized parameter search space is carefully chosen by sampling the gradient close to the current optimal. Moreover, we present a unified framework (WS-SGD) for integrating parameter initialization techniques into the optimizer. We provide the convergence proof of the proposed framework for both convex and non-convex objective functions based on Polyak-Lojasiewicz (PL) condition. Our experiment results show that the proposed algorithm could mitigate the BP and have better generalization ability in quantum classification problems.

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