License: Creative Commons Attribution 4.0 International license (CC BY 4.0)
When quoting this document, please refer to the following
DOI: 10.4230/LIPIcs.CPM.2023.9
URN: urn:nbn:de:0030-drops-179637
URL: http://dagstuhl.sunsite.rwth-aachen.de/volltexte/2023/17963/
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Equi, Massimo ; Meijer-van de Griend, Arianne ; Mäkinen, Veli

From Bit-Parallelism to Quantum String Matching for Labelled Graphs

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LIPIcs-CPM-2023-9.pdf (1 MB)

Abstract

Many problems that can be solved in quadratic time have bit-parallel speed-ups with factor w, where w is the computer word size. A classic example is computing the edit distance of two strings of length n, which can be solved in O(n²/w) time. In a reasonable classical model of computation, one can assume w = Θ(log n), and obtaining significantly better speed-ups is unlikely in the light of conditional lower bounds obtained for such problems.
In this paper, we study the connection of bit-parallelism to quantum computation, aiming to see if a bit-parallel algorithm could be converted to a quantum algorithm with better than logarithmic speed-up. We focus on string matching in labeled graphs, the problem of finding an exact occurrence of a string as the label of a path in a graph. This problem admits a quadratic conditional lower bound under a very restricted class of graphs (Equi et al. ICALP 2019), stating that no algorithm in the classical model of computation can solve the problem in time O(|P||E|^(1-ε)) or O(|P|^(1-ε)|E|). We show that a simple bit-parallel algorithm on such restricted family of graphs (level DAGs) can indeed be converted into a realistic quantum algorithm that attains subquadratic time complexity O(|E|√|P|).

BibTeX - Entry

@InProceedings{equi_et_al:LIPIcs.CPM.2023.9,
  author =	{Equi, Massimo and Meijer-van de Griend, Arianne and M\"{a}kinen, Veli},
  title =	{{From Bit-Parallelism to Quantum String Matching for Labelled Graphs}},
  booktitle =	{34th Annual Symposium on Combinatorial Pattern Matching (CPM 2023)},
  pages =	{9:1--9:20},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-276-1},
  ISSN =	{1868-8969},
  year =	{2023},
  volume =	{259},
  editor =	{Bulteau, Laurent and Lipt\'{a}k, Zsuzsanna},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/opus/volltexte/2023/17963},
  URN =		{urn:nbn:de:0030-drops-179637},
  doi =		{10.4230/LIPIcs.CPM.2023.9},
  annote =	{Keywords: Bit-parallelism, quantum computation, string matching, level DAGs}
}

Keywords: Bit-parallelism, quantum computation, string matching, level DAGs
Collection: 34th Annual Symposium on Combinatorial Pattern Matching (CPM 2023)
Issue Date: 2023
Date of publication: 21.06.2023

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