提出首个量子稀疏恢复算法,实现高效量子态重构。
Quantum Sparse Recovery and Quantum Orthogonal Matching Pursuit
- 设计量子正交匹配追踪算法,结合量子内积估计与误差重置机制。
- 在非正交字典下,多项式时间内恢复稀疏态的精确支持集。
- 适用于量子层析、信号处理,可突破经典下限并加速经典算法。
我们研究非正交、过完备字典中的量子稀疏恢复问题:给定对量子态和向量字典的相干访问,目标是以最少向量数在ℓ₂误差范围内重构该状态。首先证明该问题为NP难,排除了通用高效精确算法的可能性。为此,我们提出量子正交匹配追踪(QOMP),首个类比经典OMP的量子算法。QOMP结合量子内积估计、最大值查找及块编码投影子程序,并采用误差重置设计,避免迭代间误差累积。在标准互不相干性和良好条件稀疏性假设下,QOMP可多项式时间恢复K-稀疏态的精确支持集。作为应用,我们给出首个基于非正交字典的稀疏量子层析框架,在ℓ₂范数下实现查询复杂度˜O(√N/ε),仅需估计K个系数而非全部N个振幅。特别地,对于纯态层析,当字典向量数m=O(N)且稀疏度K=˜O(1)时,可在良条件子字典上绕过经典密集正交字典下的˜Ω(N/ε)下限,不矛盾地利用稀疏性与非正交性。除层析外,我们在QRAM模型中分析QOMP,获得对经典OMP的多项式加速;并提供一种量子算法以在O(m/ε)查询内估计包含m个向量的字典的互不相干性,优于确定性及量子启发的经典方法。
原文摘要 · Abstract (English)
We study quantum sparse recovery in non-orthogonal, overcomplete dictionaries: given coherent quantum access to a state and a dictionary of vectors, the goal is to reconstruct the state up to $\ell_2$ error using as few vectors as possible. We first show that the general recovery problem is NP-hard, ruling out efficient exact algorithms in full generality. To overcome this, we introduce Quantum Orthogonal Matching Pursuit (QOMP), the first quantum analogue of the classical OMP greedy algorithm. QOMP combines quantum subroutines for inner product estimation, maximum finding, and block-encoded projections with an error-resetting design that avoids iteration-to-iteration error accumulation. Under standard mutual incoherence and well-conditioned sparsity assumptions, QOMP provably recovers the exact support of a $K$-sparse state in polynomial time. As an application, we give the first framework for sparse quantum tomography with non-orthogonal dictionaries in $\ell_2$ norm, achieving query complexity $\widetilde{O}(\sqrt{N}/ε)$ in favorable regimes and reducing tomography to estimating only $K$ coefficients instead of $N$ amplitudes. In particular, for pure-state tomography with $m=O(N)$ dictionary vectors and sparsity $K=\widetilde{O}(1)$ on a well-conditioned subdictionary, this circumvents the $\widetildeΩ(N/ε)$ lower bound that holds in the dense, orthonormal-dictionary setting, without contradiction, by leveraging sparsity together with non-orthogonality. Beyond tomography, we analyze QOMP in the QRAM model, where it yields polynomial speedups over classical OMP implementations, and provide a quantum algorithm to estimate the mutual incoherence of a dictionary of $m$ vectors in $O(m/ε)$ queries, improving over both deterministic and quantum-inspired classical methods.
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