Deutsch-Jozsa problem (DJn\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$DJ_{n}$$\end{document}) showed for the first time that quantum computation can achieve exponential advantages over classical computers, which encouraged and laid the foundation for further research on quantum algorithms. A generalization of Deutsch-Jozsa problem (DJnk\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$DJ<^>{k}_{n}$$\end{document}, proposed by Phys Rev A 97:062331, 2018) maintains the exponential advantage when the parameter k is a constant. However, these achieved exponential advantages are just in the case that all outputs are required to be accurate. In contrast, this paper studies classical randomizeddecisiontree complexities of DJn\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$DJ_{n}$$\end{document} and DJnk\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$DJ<^>{k}_{n}$$\end{document}. It is proved that the first complexity R2(DJn)<= 3\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$R_complexity(DJ_{n})\le 3$$\end{document} in all cases and the second complexity R2(DJnk)\documentclass[12pt]{
The problem Local Search, which finds a local minimum of a black-box function on a given graph, is of both practical and theoretical importance to combinatorial optimization, complexity theory, and many other areas in...
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The problem Local Search, which finds a local minimum of a black-box function on a given graph, is of both practical and theoretical importance to combinatorial optimization, complexity theory, and many other areas in theoretical computer science. In this paper, we study the problem in both the randomized and the quantum query models and give new lower and upper bound techniques in both models. The lower bound technique works for any graph that contains a product graph as a subgraph. Applying it to the Boolean hypercube {0, 1}(n) and the constant-dimensional grids [n](d), two particular product graphs that recently drew much attention, we get the following tight results: RLS({0, 1}(n)) = Theta(2(n)/(2)n(1/2)), QLS({0, 1}(n)) = Theta(2(n/3)n(1/6)), RLS([n](d)) = Theta(n(d/2)) for d >= 4, QLS([n](d)) = Theta(n(d/3)) for d >= 6. Here RLS(G) and QLS(G) are the randomized and quantum query complexities of Local Search on G, respectively. These improve the previous results by Aaronson [in Proceedings of the Thirty-Sixth Annual ACM Symposium on Theory of Computing, 2004, pp. 465-474], Ambainis (unpublished), and Santha and Szegedy [in Proceedings of the Thirty-Sixth Annual ACM Symposium on Theory of Computing, 2004, pp. 494-501]. Our new algorithms work well when the underlying graph expands slowly. As an application to [n](2), a new quantum algorithm using O(root n(log log n)(1.5)) queries is given. This improves the previously best known upper bound of O(n(2/3)) (see Aaronson [in Proceedings of the Thirty-Sixth Annual ACM Symposium on Theory of Computing, 2004, pp. 465-474]), and implies that Local Search on grids exhibits different properties in low dimensions.
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