{"@context":"https:\/\/schema.org\/","@type":"ScholarlyArticle","@id":"#article8964","name":"Quantum Communication Complexity of Distributed Set Joins","abstract":"Computing set joins of two inputs is a common task in database theory. Recently, Van Gucht, Williams, Woodruff and Zhang [PODS 2015] considered the complexity of such problems in the natural model of (classical) two-party communication complexity and obtained tight bounds for the complexity of several important distributed set joins.\r\n\r\nIn this paper we initiate the study of the quantum communication complexity of distributed set joins. We design a quantum protocol for distributed Boolean matrix multiplication, which corresponds to computing the composition join of two databases, showing that the product of two n times n Boolean matrices, each owned by one of two respective parties, can be computed with widetilde-O(sqrt{n} ell^{3\/4}) qubits of communication, where ell denotes the number of non-zero entries of the product. Since Van Gucht et al. showed that the classical communication complexity of this problem is widetilde-Theta(n sqrt{ell}), our quantum algorithm outperforms classical protocols whenever the output matrix is sparse. We also show a quantum lower bound and a matching classical upper bound on the communication complexity of distributed matrix multiplication over F_2. \r\n\r\nBesides their applications to database theory, the communication complexity of set joins is interesting due to its connections to direct product theorems in communication complexity. In this work we also introduce a notion of all-pairs product theorem, and relate this notion to standard direct product theorems in communication complexity.","keywords":["quantum communication complexity","distributed quantum computing","database joins"],"author":[{"@type":"Person","name":"Jeffery, Stacey","givenName":"Stacey","familyName":"Jeffery"},{"@type":"Person","name":"Le Gall, Fran\u00e7ois","givenName":"Fran\u00e7ois","familyName":"Le Gall"}],"position":54,"pageStart":"54:1","pageEnd":"54:13","dateCreated":"2016-08-19","datePublished":"2016-08-19","isAccessibleForFree":true,"license":"https:\/\/creativecommons.org\/licenses\/by\/3.0\/legalcode","copyrightHolder":[{"@type":"Person","name":"Jeffery, Stacey","givenName":"Stacey","familyName":"Jeffery"},{"@type":"Person","name":"Le Gall, Fran\u00e7ois","givenName":"Fran\u00e7ois","familyName":"Le Gall"}],"copyrightYear":"2016","accessMode":"textual","accessModeSufficient":"textual","creativeWorkStatus":"Published","inLanguage":"en-US","sameAs":"https:\/\/doi.org\/10.4230\/LIPIcs.MFCS.2016.54","publisher":"Schloss Dagstuhl \u2013 Leibniz-Zentrum f\u00fcr Informatik","citation":["http:\/\/dx.doi.org\/10.1137\/05063235X","https:\/\/cs.uwaterloo.ca\/~watrous\/CS766\/"],"isPartOf":{"@type":"PublicationVolume","@id":"#volume6261","volumeNumber":58,"name":"41st International Symposium on Mathematical Foundations of Computer Science (MFCS 2016)","dateCreated":"2016-08-19","datePublished":"2016-08-19","editor":[{"@type":"Person","name":"Faliszewski, Piotr","givenName":"Piotr","familyName":"Faliszewski"},{"@type":"Person","name":"Muscholl, Anca","givenName":"Anca","familyName":"Muscholl"},{"@type":"Person","name":"Niedermeier, Rolf","givenName":"Rolf","familyName":"Niedermeier"}],"isAccessibleForFree":true,"publisher":"Schloss Dagstuhl \u2013 Leibniz-Zentrum f\u00fcr Informatik","hasPart":"#article8964","isPartOf":{"@type":"Periodical","@id":"#series116","name":"Leibniz International Proceedings in Informatics","issn":"1868-8969","isAccessibleForFree":true,"publisher":"Schloss Dagstuhl \u2013 Leibniz-Zentrum f\u00fcr Informatik","hasPart":"#volume6261"}}}