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Continuous-time quantum walks provide a natural framework to tackle the fundamental problem of finding a node among a set of marked nodes in a graph, known as spatial search. Whether spatial search by continuous-time quantum walk provides a…

Quantum Physics · Physics 2022-10-24 Simon Apers , Shantanav Chakraborty , Leonardo Novo , Jérémie Roland

The problem of finding a marked node in a graph can be solved by the spatial search algorithm based on continuous-time quantum walks (CTQW). However, this algorithm is known to run in optimal time only for a handful of graphs. In this work,…

Quantum Physics · Physics 2016-03-23 Shantanav Chakraborty , Leonardo Novo , Andris Ambainis , Yasser Omar

We present a novel methodological framework for quantum spatial search, generalising the Childs & Goldstone ($\mathcal{CG}$) algorithm via alternating applications of marked-vertex phase shifts and continuous-time quantum walks. We…

Quantum Physics · Physics 2021-09-30 S. Marsh , J. B. Wang

The quantum-walk-based spatial search problem aims to find a marked vertex using a quantum walk on a graph with marked vertices. We describe a framework for determining the computational complexity of spatial search by continuous-time…

Quantum Physics · Physics 2024-12-25 Pedro H. G. Lugão , Renato Portugal , Mohamed Sabri , Hajime Tanaka

Chakraborty and Leonardo have shown that a spatial search by quantum walk is optimal for almost all graphs. However, we observed that on some graphs, certain states cannot be searched optimally. We present a method for constructing an…

Quantum Physics · Physics 2018-04-10 Xi Li , Hanwu Chen , Yue Ruan , Mengke Xu , Jianing Tang , Zhihao Liu

To investigate the performance of quantum information tasks on networks whose topology changes in time, we study the spatial search algorithm by continuous time quantum walk to find a marked node on a random temporal network. We consider a…

Quantum Physics · Physics 2017-11-30 Shantanav Chakraborty , Leonardo Novo , Serena Di Giorgio , Yasser Omar

We address quantum spatial search on graphs and its implementation by continuous-time quantum walks in the presence of dynamical noise. In particular, we focus on search on the complete graph and on the star graph of order $N$, proving that…

Quantum Physics · Physics 2018-11-29 Marco Cattaneo , Matteo A. C. Rossi , Matteo G. A. Paris , Sabrina Maniscalco

The quantum walk dynamics obey the laws of quantum mechanics with an extra locality constraint, which demands that the evolution operator is local in the sense that the walker must visit the neighboring locations before endeavoring to…

Quantum Physics · Physics 2023-05-23 Caue F. T. Silva , Daniel Posner , Renato Portugal

Spatial search on graphs is one of the most important algorithmic applications of quantum walks. To show that a quantum-walk-based search is more efficient than a random-walk-based search is a difficult problem, which has been addressed in…

Combinatorics · Mathematics 2022-02-01 Hajime Tanaka , Mohamed Sabri , Renato Portugal

Spatial search is an important problem in quantum computation, which aims to find a marked vertex on a graph. We propose a novel approach for designing deterministic quantum search algorithms on a variety of graphs via alternating quantum…

Quantum Physics · Physics 2023-08-25 Qingwen Wang , Ying Jiang , Shiguang Feng , Lvzhou Li

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

In quantum computing, the quantum walk search algorithm is designed for locating fixed marked nodes within a graph. However, when multiple marked nodes exist, the conventional search algorithm lacks the capacity to simultaneously amplify…

Quantum Physics · Physics 2024-02-06 Himanshu Sahu , Kallol Sen

In this paper, we study Grover's search algorithm focusing on continuous-time quantum walk on graphs. We propose an alternative optimization approach to Grover's algorithm on graphs that can be summarized as follows: instead of finding…

Mathematical Physics · Physics 2022-07-06 Gamal Mograby , Radhakrishnan Balu , Kasso A. Okoudjou , Alexander Teplyaev

This work examines the time complexity of quantum search algorithms on combinatorial $t$-designs with multiple marked elements using the continuous-time quantum walk. Through a detailed exploration of $t$-designs and their incidence…

Quantum Physics · Physics 2025-04-08 Pedro H. G. Lugão , Renato Portugal

Kronecker graphs, obtained by repeatedly performing the Kronecker product of the adjacency matrix of an "initiator" graph with itself, have risen in popularity in network science due to their ability to generate complex networks with…

Quantum Physics · Physics 2018-08-01 Thomas G. Wong , Konstantin Wünscher , Joshua Lockhart , Simone Severini

In this work, we consider the spatial search for a general marked state on graphs by continuous time quantum walks. As a simplest case, we compute the amplitude expression of the search for the multi-vertex uniform superposition state on…

Mathematical Physics · Physics 2018-04-10 Xi Li , Hanwu Chen , Yue Ruan , Zhihao Liu , Mengke Xu , Jianing Tan

Quantum walks provide a natural framework to approach graph problems with quantum computers, exhibiting speedups over their classical counterparts for tasks such as the search for marked nodes or the prediction of missing links.…

Quantum Physics · Physics 2023-06-27 Duarte Magano , João Moutinho , Bruno Coutinho

We study spatial search with continuous-time quantum walks on real-world complex networks. We use smaller replicas of the Internet network obtained with a recent geometric renormalization method introduced by Garc\'ia-P\'erez et al., Nat.…

Quantum Physics · Physics 2022-12-19 Joonas Malmi , Matteo A. C. Rossi , Guillermo García-Pérez , Sabrina Maniscalco

The Maximum Matching problem has a quantum query complexity lower bound of $\Omega(n^{3/2})$ for graphs on $n$ vertices represented by an adjacency matrix. The current best quantum algorithm has the query complexity $O(n^{7/4})$, which is…

Quantum Physics · Physics 2025-10-31 Alcides Gomes Andrade Júnior , Akira Matsubayashi

Quantum computing promises to improve the information processing power to levels unreachable by classical computation. Quantum walks are heading the development of quantum algorithms for searching information on graphs more efficiently than…

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