arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2007.08285cs.DSquant-ph
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带割查询的图问题的量子算法

Quantum algorithms for graph problems with cut queries

Troy Lee, Miklos Santha, Shengyu Zhang

摘要:

设$G$是一个有$m$边的$n$ -顶点图.当询问顶点的子集$S$时,对$G$的切割查询返回在$S$中恰好有一个端点的$G$的边的数目。我们表明,有一个有界错误的量子算法,确定所有连接组件的$G$后,$O(\log(n)^6)$许多削减查询。与此相反,它遵循从结果的通信复杂性,任何随机化算法,即使只是决定图是否连接或不必须至少$Ω(n/\log(n))$许多切割查询。我们进一步表明,与$O(\log(n)^8)$许多切割查询的量子算法可以以高概率输出生成森林的$G$。在证明这些结果的过程中,我们设计了量子算法,用于使用切割查询来学习图。我们表明,量子算法可以学习一个最大程度的图$d$后$O(d \log(n)^2)$许多切割查询,并可以学习一个一般的图与$O(\sqrt{m} \log(n)^{3/2})$许多切割查询。这两个上界是紧到多对数因子,并比较$Ω(dn)$和$Ω(m/\log(n))$的切割查询的随机算法所需的数量上的下界相同的问题,分别。我们的结果中的关键成分是Bernstein-Vazirani算法,近似计数与“或查询”,并学习稀疏向量的内积在压缩感知。

英文摘要:

Let $G$ be an $n$-vertex graph with $m$ edges. When asked a subset $S$ of vertices, a cut query on $G$ returns the number of edges of $G$ that have exactly one endpoint in $S$. We show that there is a bounded-error quantum algorithm that determines all connected components of $G$ after making $O(\log(n)^6)$ many cut queries. In contrast, it follows from results in communication complexity that any randomized algorithm even just to decide whether the graph is connected or not must make at least $Ω(n/\log(n))$ many cut queries. We further show that with $O(\log(n)^8)$ many cut queries a quantum algorithm can with high probability output a spanning forest for $G$. En route to proving these results, we design quantum algorithms for learning a graph using cut queries. We show that a quantum algorithm can learn a graph with maximum degree $d$ after $O(d \log(n)^2)$ many cut queries, and can learn a general graph with $O(\sqrt{m} \log(n)^{3/2})$ many cut queries. These two upper bounds are tight up to the poly-logarithmic factors, and compare to $Ω(dn)$ and $Ω(m/\log(n))$ lower bounds on the number of cut queries needed by a randomized algorithm for the same problems, respectively. The key ingredients in our results are the Bernstein-Vazirani algorithm, approximate counting with "OR queries", and learning sparse vectors from inner products as in compressed sensing.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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