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Paper Abstract and Keywords
Presentation 2012-04-27 10:35
Reconstructing Strings from Substrings with Quantum Queries
Richard Cleve (Univ. of Waterloo), Kazuo Iwama (Kyoto Univ.), Francois Le Gall (Univ. of Tokyo), Harumichi Nishimura (Nagoya Univ.), Seiichiro Tani (NTT), Junichi Teruyama (Kyoto Univ.), Shigeru Yamashita (Ritsumeikan Univ.) COMP2012-2
Abstract (in Japanese) (See Japanese page) 
(in English) This paper investigates the number of quantum queries made
to solve the problem of reconstructing an unknown string from its
substrings in a certain query model. More concretely, the goal of the problem is
to identify an unknown string $S$ by making queries of the following
form: ``Is $s$ a substring of $S$?'', where $s$ is a query string over the given alphabet.
The number of queries required to identify the string $S$ is the query complexity of this problem.

First we show a quantum algorithm that exactly identifies the string $S$
with at most $\frac{3}{4}N + o(N)$ queries, where $N$ is the length of $S$.
This contrasts sharply with the classical query complexity~$N$.
Our algorithm uses Skiena and Sundaram's classical algorithm
and the Grover search as subroutines.
To make them effectively work, we develop another subroutine
that finds a string appearing only once in $S$, which may have an
independent interest. We also prove that any bounded-error quantum algorithm
needs $\Omega(\frac{N}{\log^2{N}})$ queries.
For this, we introduce another query model and obtain a lower bound
for this model with the adversary method, from which bound
we get the desired lower bound in the original query model.
Keyword (in Japanese) (See Japanese page) 
(in English) quantum computing / string algorithms / query complexity / lower bounds / / / /  
Reference Info. IEICE Tech. Rep., vol. 112, no. 21, COMP2012-2, pp. 7-14, April 2012.
Paper # COMP2012-2 
Date of Issue 2012-04-20 (COMP) 
ISSN Print edition: ISSN 0913-5685    Online edition: ISSN 2432-6380
Copyright
and
reproduction
All rights are reserved and no part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopy, recording, or any information storage and retrieval system, without permission in writing from the publisher. Notwithstanding, instructors are permitted to photocopy isolated articles for noncommercial classroom use without fee. (License No.: 10GA0019/12GB0052/13GB0056/17GB0034/18GB0034)
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Conference Information
Committee COMP  
Conference Date 2012-04-27 - 2012-04-27 
Place (in Japanese) (See Japanese page) 
Place (in English) Osaka Prefecture University 
Topics (in Japanese) (See Japanese page) 
Topics (in English)  
Paper Information
Registration To COMP 
Conference Code 2012-04-COMP 
Language English 
Title (in Japanese) (See Japanese page) 
Sub Title (in Japanese) (See Japanese page) 
Title (in English) Reconstructing Strings from Substrings with Quantum Queries 
Sub Title (in English)  
Keyword(1) quantum computing  
Keyword(2) string algorithms  
Keyword(3) query complexity  
Keyword(4) lower bounds  
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1st Author's Name Richard Cleve  
1st Author's Affiliation University of Waterloo (Univ. of Waterloo)
2nd Author's Name Kazuo Iwama  
2nd Author's Affiliation Kyoto University (Kyoto Univ.)
3rd Author's Name Francois Le Gall  
3rd Author's Affiliation The University of Tokyo (Univ. of Tokyo)
4th Author's Name Harumichi Nishimura  
4th Author's Affiliation Nagoya University (Nagoya Univ.)
5th Author's Name Seiichiro Tani  
5th Author's Affiliation NTT Communication Science Laboratories (NTT)
6th Author's Name Junichi Teruyama  
6th Author's Affiliation Kyoto University (Kyoto Univ.)
7th Author's Name Shigeru Yamashita  
7th Author's Affiliation Ritsumeikan University (Ritsumeikan Univ.)
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Speaker Author-6 
Date Time 2012-04-27 10:35:00 
Presentation Time 35 minutes 
Registration for COMP 
Paper # COMP2012-2 
Volume (vol) vol.112 
Number (no) no.21 
Page pp.7-14 
#Pages
Date of Issue 2012-04-20 (COMP) 


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