{"id":435339,"date":"2018-11-06T16:45:31","date_gmt":"2018-11-07T00:45:31","guid":{"rendered":"https:\/\/cm-edgetun.pages.dev\/en-us\/research\/?post_type=msr-research-item&#038;p=435339"},"modified":"2018-11-06T16:45:31","modified_gmt":"2018-11-07T00:45:31","slug":"the-polynomial-method-strikes-back-tight-quantum-query-bounds-via-dual-polynomials-2","status":"publish","type":"msr-research-item","link":"https:\/\/cm-edgetun.pages.dev\/en-us\/research\/publication\/the-polynomial-method-strikes-back-tight-quantum-query-bounds-via-dual-polynomials-2\/","title":{"rendered":"The Polynomial Method Strikes Back: Tight Quantum Query Bounds via Dual Polynomials"},"content":{"rendered":"<p>The approximate degree of a Boolean function f is the least degree of a real polynomial that approximates f pointwise to error at most 1\/3. Approximate degree is known to be a lower bound on quantum query complexity. We resolve or nearly resolve the approximate degree and quantum query complexities of the following basic functions:<\/p>\n<ul>\n<li><span id=\"MathJax-Element-2-Frame\" class=\"MathJax\"><span id=\"MathJax-Span-4\" class=\"math\"><span id=\"MathJax-Span-5\" class=\"mrow\"><span id=\"MathJax-Span-6\" class=\"mi\">k<\/span><\/span><\/span><\/span>-distinctness: For any constant <span id=\"MathJax-Element-3-Frame\" class=\"MathJax\"><span id=\"MathJax-Span-7\" class=\"math\"><span id=\"MathJax-Span-8\" class=\"mrow\"><span id=\"MathJax-Span-9\" class=\"mi\">k<\/span><\/span><\/span><\/span>, the approximate degree and quantum query complexity of <span id=\"MathJax-Element-4-Frame\" class=\"MathJax\"><span id=\"MathJax-Span-10\" class=\"math\"><span id=\"MathJax-Span-11\" class=\"mrow\"><span id=\"MathJax-Span-12\" class=\"mi\">k<\/span><\/span><\/span><\/span>-distinctness is <span id=\"MathJax-Element-5-Frame\" class=\"MathJax\"><span id=\"MathJax-Span-13\" class=\"math\"><span id=\"MathJax-Span-14\" class=\"mrow\"><span id=\"MathJax-Span-15\" class=\"mi\">\u03a9<\/span><span id=\"MathJax-Span-16\" class=\"mo\">(<\/span><span id=\"MathJax-Span-17\" class=\"msubsup\"><span id=\"MathJax-Span-18\" class=\"mi\">n^{<\/span><span id=\"MathJax-Span-19\" class=\"texatom\"><span id=\"MathJax-Span-20\" class=\"mrow\"><span id=\"MathJax-Span-21\" class=\"mn\">3<\/span><span id=\"MathJax-Span-22\" class=\"texatom\"><span id=\"MathJax-Span-23\" class=\"mrow\"><span id=\"MathJax-Span-24\" class=\"mo\">\/<\/span><\/span><\/span><span id=\"MathJax-Span-25\" class=\"mn\">4<\/span><span id=\"MathJax-Span-26\" class=\"mo\">\u2212<\/span><span id=\"MathJax-Span-27\" class=\"mn\">1<\/span><span id=\"MathJax-Span-28\" class=\"texatom\"><span id=\"MathJax-Span-29\" class=\"mrow\"><span id=\"MathJax-Span-30\" class=\"mo\">\/<\/span><\/span><\/span><span id=\"MathJax-Span-31\" class=\"mo\">(<\/span><span id=\"MathJax-Span-32\" class=\"mn\">2<\/span><span id=\"MathJax-Span-33\" class=\"mi\">k<\/span><span id=\"MathJax-Span-34\" class=\"mo\">)}<\/span><\/span><\/span><\/span><span id=\"MathJax-Span-35\" class=\"mo\">)<\/span><\/span><\/span><\/span>. This is nearly tight for large <span id=\"MathJax-Element-6-Frame\" class=\"MathJax\"><span id=\"MathJax-Span-36\" class=\"math\"><span id=\"MathJax-Span-37\" class=\"mrow\"><span id=\"MathJax-Span-38\" class=\"mi\">k<\/span><\/span><\/span><\/span> (Belovs, FOCS 2012).<\/li>\n<li>Image size testing: The approximate degree and quantum query complexity of testing the size of the image of a function <span id=\"MathJax-Element-8-Frame\" class=\"MathJax\"><span id=\"MathJax-Span-42\" class=\"math\"><span id=\"MathJax-Span-43\" class=\"mrow\"><span id=\"MathJax-Span-44\" class=\"mo\">[<\/span><span id=\"MathJax-Span-45\" class=\"mi\">n<\/span><span id=\"MathJax-Span-46\" class=\"mo\">]<\/span><span id=\"MathJax-Span-47\" class=\"mo\">\u2192<\/span><span id=\"MathJax-Span-48\" class=\"mo\">[<\/span><span id=\"MathJax-Span-49\" class=\"mi\">n<\/span><span id=\"MathJax-Span-50\" class=\"mo\">]<\/span><\/span><\/span><\/span> is <span id=\"MathJax-Element-9-Frame\" class=\"MathJax\"><span id=\"MathJax-Span-51\" class=\"math\"><span id=\"MathJax-Span-52\" class=\"mrow\"><span id=\"MathJax-Span-53\" class=\"texatom\"><span id=\"MathJax-Span-54\" class=\"mrow\"><span id=\"MathJax-Span-55\" class=\"munderover\"><span id=\"MathJax-Span-56\" class=\"mi\">\u03a9<\/span><span id=\"MathJax-Span-57\" class=\"mo\">~<\/span><\/span><\/span><\/span><span id=\"MathJax-Span-58\" class=\"mo\">(<\/span><span id=\"MathJax-Span-59\" class=\"msubsup\"><span id=\"MathJax-Span-60\" class=\"mi\">n^{<\/span><span id=\"MathJax-Span-61\" class=\"texatom\"><span id=\"MathJax-Span-62\" class=\"mrow\"><span id=\"MathJax-Span-63\" class=\"mn\">1<\/span><span id=\"MathJax-Span-64\" class=\"texatom\"><span id=\"MathJax-Span-65\" class=\"mrow\"><span id=\"MathJax-Span-66\" class=\"mo\">\/<\/span><\/span><\/span><span id=\"MathJax-Span-67\" class=\"mn\">2}<\/span><\/span><\/span><\/span><span id=\"MathJax-Span-68\" class=\"mo\">)<\/span><\/span><\/span><\/span>. This proves a conjecture of Ambainis et al. (SODA 2016), and it implies the following lower bounds:\n<ul>\n<li><span id=\"MathJax-Element-11-Frame\" class=\"MathJax\"><span id=\"MathJax-Span-72\" class=\"math\"><span id=\"MathJax-Span-73\" class=\"mrow\"><span id=\"MathJax-Span-74\" class=\"mi\">k<\/span><\/span><\/span><\/span>-junta testing: A tight <span id=\"MathJax-Element-12-Frame\" class=\"MathJax\"><span id=\"MathJax-Span-75\" class=\"math\"><span id=\"MathJax-Span-76\" class=\"mrow\"><span id=\"MathJax-Span-77\" class=\"texatom\"><span id=\"MathJax-Span-78\" class=\"mrow\"><span id=\"MathJax-Span-79\" class=\"munderover\"><span id=\"MathJax-Span-80\" class=\"mi\">\u03a9<\/span><span id=\"MathJax-Span-81\" class=\"mo\">~<\/span><\/span><\/span><\/span><span id=\"MathJax-Span-82\" class=\"mo\">(<\/span><span id=\"MathJax-Span-83\" class=\"msubsup\"><span id=\"MathJax-Span-84\" class=\"mi\">k^{<\/span><span id=\"MathJax-Span-85\" class=\"texatom\"><span id=\"MathJax-Span-86\" class=\"mrow\"><span id=\"MathJax-Span-87\" class=\"mn\">1<\/span><span id=\"MathJax-Span-88\" class=\"texatom\"><span id=\"MathJax-Span-89\" class=\"mrow\"><span id=\"MathJax-Span-90\" class=\"mo\">\/<\/span><\/span><\/span><span id=\"MathJax-Span-91\" class=\"mn\">2}<\/span><\/span><\/span><\/span><span id=\"MathJax-Span-92\" class=\"mo\">)<\/span><\/span><\/span><\/span> lower bound, answering the main open question of Ambainis et al. (SODA 2016).<\/li>\n<li>Statistical Distance from Uniform: A tight <span id=\"MathJax-Element-14-Frame\" class=\"MathJax\"><span id=\"MathJax-Span-96\" class=\"math\"><span id=\"MathJax-Span-97\" class=\"mrow\"><span id=\"MathJax-Span-98\" class=\"texatom\"><span id=\"MathJax-Span-99\" class=\"mrow\"><span id=\"MathJax-Span-100\" class=\"munderover\"><span id=\"MathJax-Span-101\" class=\"mi\">\u03a9<\/span><span id=\"MathJax-Span-102\" class=\"mo\">~<\/span><\/span><\/span><\/span><span id=\"MathJax-Span-103\" class=\"mo\">(<\/span><span id=\"MathJax-Span-104\" class=\"msubsup\"><span id=\"MathJax-Span-105\" class=\"mi\">n^{<\/span><span id=\"MathJax-Span-106\" class=\"texatom\"><span id=\"MathJax-Span-107\" class=\"mrow\"><span id=\"MathJax-Span-108\" class=\"mn\">1<\/span><span id=\"MathJax-Span-109\" class=\"texatom\"><span id=\"MathJax-Span-110\" class=\"mrow\"><span id=\"MathJax-Span-111\" class=\"mo\">\/<\/span><\/span><\/span><span id=\"MathJax-Span-112\" class=\"mn\">2}<\/span><\/span><\/span><\/span><span id=\"MathJax-Span-113\" class=\"mo\">)<\/span><\/span><\/span><\/span> lower bound, answering the main question left open by Bravyi et al. (STACS 2010 and IEEE Trans. Inf. Theory 2011).<\/li>\n<li>Shannon entropy: A tight <span id=\"MathJax-Element-16-Frame\" class=\"MathJax\"><span id=\"MathJax-Span-117\" class=\"math\"><span id=\"MathJax-Span-118\" class=\"mrow\"><span id=\"MathJax-Span-119\" class=\"texatom\"><span id=\"MathJax-Span-120\" class=\"mrow\"><span id=\"MathJax-Span-121\" class=\"munderover\"><span id=\"MathJax-Span-122\" class=\"mi\">\u03a9<\/span><span id=\"MathJax-Span-123\" class=\"mo\">~<\/span><\/span><\/span><\/span><span id=\"MathJax-Span-124\" class=\"mo\">(<\/span><span id=\"MathJax-Span-125\" class=\"msubsup\"><span id=\"MathJax-Span-126\" class=\"mi\">n^{<\/span><span id=\"MathJax-Span-127\" class=\"texatom\"><span id=\"MathJax-Span-128\" class=\"mrow\"><span id=\"MathJax-Span-129\" class=\"mn\">1<\/span><span id=\"MathJax-Span-130\" class=\"texatom\"><span id=\"MathJax-Span-131\" class=\"mrow\"><span id=\"MathJax-Span-132\" class=\"mo\">\/<\/span><\/span><\/span><span id=\"MathJax-Span-133\" class=\"mn\">2}<\/span><\/span><\/span><\/span><span id=\"MathJax-Span-134\" class=\"mo\">)<\/span><\/span><\/span><\/span> lower bound, answering a question of Li and Wu (2017).<\/li>\n<\/ul>\n<\/li>\n<li>Surjectivity: The approximate degree of the Surjectivity function is <span id=\"MathJax-Element-18-Frame\" class=\"MathJax\"><span id=\"MathJax-Span-138\" class=\"math\"><span id=\"MathJax-Span-139\" class=\"mrow\"><span id=\"MathJax-Span-140\" class=\"texatom\"><span id=\"MathJax-Span-141\" class=\"mrow\"><span id=\"MathJax-Span-142\" class=\"munderover\"><span id=\"MathJax-Span-143\" class=\"mi\">\u03a9<\/span><span id=\"MathJax-Span-144\" class=\"mo\">~<\/span><\/span><\/span><\/span><span id=\"MathJax-Span-145\" class=\"mo\">(<\/span><span id=\"MathJax-Span-146\" class=\"msubsup\"><span id=\"MathJax-Span-147\" class=\"mi\">n^{<\/span><span id=\"MathJax-Span-148\" class=\"texatom\"><span id=\"MathJax-Span-149\" class=\"mrow\"><span id=\"MathJax-Span-150\" class=\"mn\">3<\/span><span id=\"MathJax-Span-151\" class=\"texatom\"><span id=\"MathJax-Span-152\" class=\"mrow\"><span id=\"MathJax-Span-153\" class=\"mo\">\/<\/span><\/span><\/span><span id=\"MathJax-Span-154\" class=\"mn\">4}<\/span><\/span><\/span><\/span><span id=\"MathJax-Span-155\" class=\"mo\">)<\/span><\/span><\/span><\/span>. The best prior lower bound was <span id=\"MathJax-Element-19-Frame\" class=\"MathJax\"><span id=\"MathJax-Span-156\" class=\"math\"><span id=\"MathJax-Span-157\" class=\"mrow\"><span id=\"MathJax-Span-158\" class=\"mi\">\u03a9<\/span><span id=\"MathJax-Span-159\" class=\"mo\">(<\/span><span id=\"MathJax-Span-160\" class=\"msubsup\"><span id=\"MathJax-Span-161\" class=\"mi\">n^{<\/span><span id=\"MathJax-Span-162\" class=\"texatom\"><span id=\"MathJax-Span-163\" class=\"mrow\"><span id=\"MathJax-Span-164\" class=\"mn\">2<\/span><span id=\"MathJax-Span-165\" class=\"texatom\"><span id=\"MathJax-Span-166\" class=\"mrow\"><span id=\"MathJax-Span-167\" class=\"mo\">\/<\/span><\/span><\/span><span id=\"MathJax-Span-168\" class=\"mn\">3}<\/span><\/span><\/span><\/span><span id=\"MathJax-Span-169\" class=\"mo\">)<\/span><\/span><\/span><\/span>. Our result matches an upper bound of <span id=\"MathJax-Element-20-Frame\" class=\"MathJax\"><span id=\"MathJax-Span-170\" class=\"math\"><span id=\"MathJax-Span-171\" class=\"mrow\"><span id=\"MathJax-Span-172\" class=\"texatom\"><span id=\"MathJax-Span-173\" class=\"mrow\"><span id=\"MathJax-Span-174\" class=\"munderover\"><span id=\"MathJax-Span-175\" class=\"mi\">O<\/span><span id=\"MathJax-Span-176\" class=\"mo\">~<\/span><\/span><\/span><\/span><span id=\"MathJax-Span-177\" class=\"mo\">(<\/span><span id=\"MathJax-Span-178\" class=\"msubsup\"><span id=\"MathJax-Span-179\" class=\"mi\">n^{<\/span><span id=\"MathJax-Span-180\" class=\"texatom\"><span id=\"MathJax-Span-181\" class=\"mrow\"><span id=\"MathJax-Span-182\" class=\"mn\">3<\/span><span id=\"MathJax-Span-183\" class=\"texatom\"><span id=\"MathJax-Span-184\" class=\"mrow\"><span id=\"MathJax-Span-185\" class=\"mo\">\/<\/span><\/span><\/span><span id=\"MathJax-Span-186\" class=\"mn\">4}<\/span><\/span><\/span><\/span><span id=\"MathJax-Span-187\" class=\"mo\">)<\/span><\/span><\/span><\/span> due to Sherstov, which we reprove using different techniques. The quantum query complexity of this function is known to be <span id=\"MathJax-Element-21-Frame\" class=\"MathJax\"><span id=\"MathJax-Span-188\" class=\"math\"><span id=\"MathJax-Span-189\" class=\"mrow\"><span id=\"MathJax-Span-190\" class=\"mi\">\u0398<\/span><span id=\"MathJax-Span-191\" class=\"mo\">(<\/span><span id=\"MathJax-Span-192\" class=\"mi\">n<\/span><span id=\"MathJax-Span-193\" class=\"mo\">)<\/span><\/span><\/span><\/span> (Beame and Machmouchi, QIC 2012 and Sherstov, FOCS 2015).<\/li>\n<\/ul>\n<p>Our upper bound for Surjectivity introduces new techniques for approximating Boolean functions by low-degree polynomials. Our lower bounds are proved by significantly refining techniques recently introduced by Bun and Thaler (FOCS 2017).<\/p>\n","protected":false},"excerpt":{"rendered":"<p>The approximate degree of a Boolean function f is the least degree of a real polynomial that approximates f pointwise to error at most 1\/3. Approximate degree is known to be a lower bound on quantum query complexity. We resolve or nearly resolve the approximate degree and quantum query complexities of the following basic functions: [&hellip;]<\/p>\n","protected":false},"featured_media":0,"template":"","meta":{"msr-url-field":"","msr-podcast-episode":"","msrModifiedDate":"","msrModifiedDateEnabled":false,"ep_exclude_from_search":false,"_classifai_error":"","msr-author-ordering":null,"msr_publishername":"","msr_publisher_other":"","msr_booktitle":"","msr_chapter":"","msr_edition":"","msr_editors":"","msr_how_published":"","msr_isbn":"","msr_issue":"","msr_journal":"arvix.org","msr_number":"","msr_organization":"","msr_pages_string":"","msr_page_range_start":"","msr_page_range_end":"","msr_series":"","msr_volume":"","msr_copyright":"","msr_conference_name":"","msr_doi":"","msr_arxiv_id":"","msr_s2_paper_id":"","msr_mag_id":"","msr_pubmed_id":"","msr_other_authors":"","msr_other_contributors":"","msr_speaker":"","msr_award":"","msr_affiliation":"","msr_institution":"","msr_host":"","msr_version":"","msr_duration":"","msr_original_fields_of_study":"","msr_release_tracker_id":"","msr_s2_match_type":"","msr_citation_count_updated":"","msr_published_date":"2017-10-25","msr_highlight_text":"","msr_notes":"","msr_longbiography":"","msr_publicationurl":"https:\/\/arxiv.org\/abs\/1710.09079","msr_external_url":"","msr_secondary_video_url":"","msr_conference_url":"","msr_journal_url":"","msr_s2_pdf_url":"","msr_year":0,"msr_citation_count":0,"msr_influential_citations":0,"msr_reference_count":0,"msr_s2_match_confidence":0,"msr_microsoftintellectualproperty":true,"msr_s2_open_access":false,"msr_s2_author_ids":[],"msr_pub_ids":[],"msr_hide_image_in_river":0,"footnotes":""},"msr-research-highlight":[],"research-area":[243138],"msr-publication-type":[193715],"msr-publisher":[],"msr-focus-area":[],"msr-locale":[268875],"msr-post-option":[],"msr-field-of-study":[],"msr-conference":[],"msr-journal":[],"msr-impact-theme":[],"msr-pillar":[],"class_list":["post-435339","msr-research-item","type-msr-research-item","status-publish","hentry","msr-research-area-quantum","msr-locale-en_us"],"msr_publishername":"","msr_edition":"","msr_affiliation":"","msr_published_date":"2017-10-25","msr_host":"","msr_duration":"","msr_version":"","msr_speaker":"","msr_other_contributors":"","msr_booktitle":"","msr_pages_string":"","msr_chapter":"","msr_isbn":"","msr_journal":"arvix.org","msr_volume":"","msr_number":"","msr_editors":"","msr_series":"","msr_issue":"","msr_organization":"","msr_how_published":"","msr_notes":"","msr_highlight_text":"","msr_release_tracker_id":"","msr_original_fields_of_study":"","msr_download_urls":"","msr_external_url":"","msr_secondary_video_url":"","msr_longbiography":"","msr_microsoftintellectualproperty":1,"msr_main_download":"","msr_publicationurl":"https:\/\/arxiv.org\/abs\/1710.09079","msr_doi":"","msr_publication_uploader":[{"type":"url","viewUrl":"false","id":"false","title":"https:\/\/arxiv.org\/abs\/1710.09079","label_id":"243109","label":0}],"msr_related_uploader":"","msr_citation_count":0,"msr_citation_count_updated":"","msr_s2_paper_id":"","msr_influential_citations":0,"msr_reference_count":0,"msr_arxiv_id":"","msr_s2_author_ids":[],"msr_s2_open_access":false,"msr_s2_pdf_url":null,"msr_attachments":[{"id":0,"url":"https:\/\/arxiv.org\/abs\/1710.09079"}],"msr-author-ordering":[{"type":"text","value":"Mark 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