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We compare discrete-time quantum walks on graphs to their natural classical equivalents, which we argue are lifted Markov chains, that is, classical Markov chains with added memory. We show that these can simulate quantum walks, allowing us…

Quantum Physics · Physics 2018-09-26 Simon Apers , Alain Sarlette , Francesco Ticozzi

We describe a general method to obtain quantum speedups of classical algorithms which are based on the technique of backtracking, a standard approach for solving constraint satisfaction problems (CSPs). Backtracking algorithms explore a…

Quantum Physics · Physics 2016-01-05 Ashley Montanaro

Quantum walks provide a powerful framework for achieving algorithmic speedup in quantum computing. This paper presents a quantum search algorithm for 2-tessellable graphs, a generalization of bipartite graphs, achieving a quadratic speedup…

Quantum Physics · Physics 2025-04-18 Gustavo Alves Bezerra , Andris Ambainis , Renato Portugal

Quantum walks (QW) are of crucial importance in the development of quantum information processing algorithms. Recently, several quantum algorithms have been proposed to implement network analysis, in particular to rank the centrality of…

Quantum Physics · Physics 2021-01-04 Tong Wu , J. A. Izaac , Zi-Xi Li , Kai Wang , Zhao-Zhong Chen , Shining Zhu , J. B. Wang , Xiao-Song Ma

A recent paper on quantum walks by Childs et al. [STOC'03] provides an example of a black-box problem for which there is a quantum algorithm with exponential speedup over the best classical randomized algorithm for the problem, but where…

Quantum Physics · Physics 2007-05-23 Stephen A. Fenner , Yong Zhang

Rydberg atoms provide a highly promising platform for quantum computation, leveraging their strong tunable interactions to encode and manipulate information in the electronic states of individual atoms. Key advantages of Rydberg atoms…

Quantum Physics · Physics 2025-07-29 Gabriel Almeida , Raul Santos , Lara Janiurek , Yasser Omar

Many interesting computational problems can be reformulated in terms of decision trees. A natural classical algorithm is to then run a random walk on the tree, starting at the root, to see if the tree contains a node n levels from the root.…

Quantum Physics · Physics 2009-10-30 Edward Farhi , Sam Gutmann

We construct a quantum random walk algorithm, based on the Dirac operator instead of the Laplacian. The algorithm explores multiple evolutionary branches by superposition of states, and does not require the coin toss instruction of…

Quantum Physics · Physics 2007-05-23 Apoorva Patel , K. S. Raghunathan , Pranaw Rungta

Quantum walk has emerged as an essential tool for searching marked vertices on various graphs. Recent advances in the discrete-time quantum walk search algorithm have enabled it to effectively handle multiple marked vertices, expanding its…

Quantum Physics · Physics 2025-10-07 Pulak Ranjan Giri , Rei Sato , Kazuhiro Saito

There are few known exponential speedups for quantum algorithms and these tend to fall into even fewer families. One speedup that has mostly resisted generalization is the use of quantum walks to traverse the welded-tree graph, due to…

Quantum Physics · Physics 2026-01-21 Shankar Balasubramanian , Tongyang Li , Aram Harrow

Many quantum algorithms make use of oracles which evaluate classical functions on a superposition of inputs. In order to facilitate implementation, testing, and resource estimation of such algorithms, we present quantum circuits for…

Quantum Physics · Physics 2018-06-01 Thomas Häner , Martin Roetteler , Krysta M. Svore

Up to now, relatively few exponential quantum speed-ups have been achieved. Out of them, the welded tree problem (Childs, Cleve, Deotto, Farhi, Gutmann, and Spielman'2003) is one of the unusual examples, as the exponential speed-up is…

Quantum Physics · Physics 2024-05-01 Aleksandrs Belovs

We explore the use of machine-learning techniques to detect quantum speedup in random walks on graphs. Specifically, we investigate the performance of three different neural-network architectures (variations on fully connected and…

Quantum Physics · Physics 2023-09-06 Hanna Linn , Yu Zheng , Anton Frisk Kockum

Quantum walks have been shown to be fruitful tools in analysing the dynamic properties of quantum systems. This article proposes to use quantum walks as an approach to Quantum Neural Networks (QNNs). QNNs replace binary McCulloch-Pitts…

Quantum Physics · Physics 2014-04-02 Maria Schuld , Ilya Sinayskiy , Francesco Petruccione

Demonstrating quantum advantage has been a pressing challenge in the field. Most claimed quantum speedups rely on a subroutine in which classical information can be accessed in a coherent quantum manner, which imposes a crucial constraint…

Quantum Physics · Physics 2025-11-04 Nhat A. Nghiem

Quantum walks have been employed widely to develop new tools for quantum information processing recently. A natural quantum walk dynamics of interacting particles can be used to implement efficiently the universal quantum computation. In…

Quantum Physics · Physics 2016-10-04 Alexey A. Melnikov , Leonid E. Fedichkin

The task of finding an entry in an unsorted list of $N$ elements famously takes $O(N)$ queries to an oracle for a classical computer and $O(\sqrt{N})$ queries for a quantum computer using Grover's algorithm. Reformulated as a spatial search…

Quantum Physics · Physics 2022-01-04 Thomas G. Wong

We study quantum algorithms for spatial search on finite dimensional grids. Patel et al. and Falk have proposed algorithms based on a quantum walk without a coin, with different operators applied at even and odd steps. Until now, such…

Quantum Physics · Physics 2015-10-14 Andris Ambainis , Renato Portugal , Nikolay Nahimov

Quantum walks on graphs have shown prioritized benefits and applications in wide areas. In some scenarios, however, it may be more natural and accurate to mandate high-order relationships for hypergraphs, due to the density of information…

Quantum Physics · Physics 2017-09-26 Ying Liu , Jiabin Yuan , Bojia Duan , Dan Li

Continuous-time quantum walks have proven to be an extremely useful framework for the design of several quantum algorithms. Often, the running time of quantum algorithms in this framework is characterized by the quantum hitting time: the…

Quantum Physics · Physics 2021-10-13 Yosi Atia , Shantanav Chakraborty