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arXiv 2004.08949cs.CGcs.CCcs.DSquant-ph
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计算几何问题的量子算法

Quantum algorithms for computational geometry problems

Andris Ambainis, Nikita Larka

摘要:

本文研究了计算几何中的量子算法,如三线上点问题。在这个问题中,我们给出一组直线,要求我们找到至少位于其中$3$上的一个点。三线上点和许多其他计算几何问题都是已知的3和-难问题。也就是说,解决这些问题通常需要时间$Ω(n^{2-o(1)})$,除非有更快的算法用于众所周知的3SUM问题(其中我们给出了一组$n$整数的$S$,并且必须确定是否存在$a, b, c \in S$,使得$a + b + c = 0$)。在量子上,利用Grover的量子搜索算法,可以在时间$O(n \log n)$上求解3SUM。这就引出了一个问题:对于$c<2$,我们能否在$O(n^c)$时间上量子地解决三线上点问题和其他3和-困难问题?我们肯定地回答这个问题,通过构建一个量子算法,解决点3线在时间$O(n^{1 + o(1)})$。该算法结合了振幅放大的递归使用和几何思想。我们表明,同样的想法给$O(n^{1 + o(1)})$时间算法的许多3SUM-困难的几何问题。

英文摘要:

We study quantum algorithms for problems in computational geometry, such as POINT-ON-3-LINES problem. In this problem, we are given a set of lines and we are asked to find a point that lies on at least $3$ of these lines. POINT-ON-3-LINES and many other computational geometry problems are known to be 3SUM-HARD. That is, solving them classically requires time $Ω(n^{2-o(1)})$, unless there is faster algorithm for the well known 3SUM problem (in which we are given a set $S$ of $n$ integers and have to determine if there are $a, b, c \in S$ such that $a + b + c = 0$). Quantumly, 3SUM can be solved in time $O(n \log n)$ using Grover's quantum search algorithm. This leads to a question: can we solve POINT-ON-3-LINES and other 3SUM-HARD problems in $O(n^c)$ time quantumly, for $c<2$? We answer this question affirmatively, by constructing a quantum algorithm that solves POINT-ON-3-LINES in time $O(n^{1 + o(1)})$. The algorithm combines recursive use of amplitude amplification with geometrical ideas. We show that the same ideas give $O(n^{1 + o(1)})$ time algorithm for many 3SUM-HARD geometrical problems.

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