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Quantum random walk finds application in efficient quantum algorithms as well as in quantum network theory. Here we study the mixing time of a discrete quantum walk over a square lattice in presence percolation and decoherence. We consider…

Quantum Physics · Physics 2018-09-12 Arkaprabha Ghosal , Prasenjit Deb

Continuous-time quantum walks (CTQW) have shown the capability to perform efficiently the spatial search of a marked site on many kinds of graphs. However, most of such graphs are hard to realize in an experimental setting. Here we study…

Quantum Physics · Physics 2021-12-08 C. Benedetti , D. Tamascelli , M. G. A. Paris , A. Crespi

Random Search is one of the most widely-used method for Hyperparameter Optimization, and is critical to the success of deep learning models. Despite its astonishing performance, little non-heuristic theory has been developed to describe the…

Machine Learning · Computer Science 2024-02-13 Chuying Han , Yasong Feng , Tianyu Wang

We provide numerical evidence that the nonlinear searching algorithm introduced by Wong and Meyer \cite{meyer2013nonlinear}, rephrased in terms of quantum walks with effective nonlinear phase, can be extended to the finite 2-dimensional…

Quantum Physics · Physics 2020-11-16 Basile Herzog , Giuseppe Di Molfetta

We identify a key difference between quantum search by discrete- and continuous-time quantum walks: a discrete-time walk typically performs one walk step per oracle query, whereas a continuous-time walk can effectively perform multiple walk…

Quantum Physics · Physics 2015-08-24 Thomas G. Wong , Andris Ambainis

While most theoretical run time analyses of discrete randomized search heuristics focused on finite search spaces, we consider the search space $\mathbb{Z}^n$. This is a further generalization of the search space of multi-valued decision…

Neural and Evolutionary Computing · Computer Science 2023-10-10 Jonathan Gadea Harder , Timo Kötzing , Xiaoyue Li , Aishwarya Radhakrishnan

We investigate a quantum spatial search problem on fractal lattices, such as Sierpinski carpets and Menger sponges. In earlier numerical studies of the Sierpinski gasket, the Sierpinski tetrahedron, and the Sierpinski carpet, conjectures…

Quantum Physics · Physics 2020-02-19 Rei Sato , Tetsuro Nikuni , Shohei Watabe

A quantum search algorithm based on the partial adiabatic evolution\cite{Tulsi2009} is provided. We calculate its time complexity by studying the Hamiltonian in a two-dimensional Hilbert space. It is found that the algorithm improves the…

Data Structures and Algorithms · Computer Science 2015-05-19 Ying-Yu Zhang , Song-Feng Lu

We study variable time search, a form of quantum search where queries to different items take different time. Our first result is a new quantum algorithm that performs variable time search with complexity $O(\sqrt{T}\log n)$ where…

Quantum Physics · Physics 2023-08-04 Andris Ambainis , Martins Kokainis , Jevgēnijs Vihrovs

Quantum walks have been useful for designing quantum algorithms that outperform their classical versions for a variety of search problems. Most of the papers, however, consider a search space containing a single marked element only. We show…

Quantum Physics · Physics 2017-10-12 Nikolajs Nahimovs , Raqueline A. M. Santos

Variational quantum algorithms have become the de facto model for current quantum computations. A prominent example of such algorithms -- the quantum approximate optimization algorithm (QAOA) -- was originally designed for combinatorial…

Quantum Physics · Physics 2024-07-16 Ernesto Campos , Daniil Rabinovich , Alexey Uvarov

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

Quantum search is among the most important algorithms in quantum computing. At its core is quantum amplitude amplification, a technique that achieves a quadratic speedup over classical search by combining two global reflections: the oracle,…

Quantum Physics · Physics 2026-05-05 John Burke , Ciaran McGoldrick

Shenvi, Kempe and Whaley's quantum random-walk search (SKW) algorithm [Phys. Rev. A 67, 052307 (2003)] is known to require $O(\sqrt N)$ number of oracle queries to find the marked element, where $N$ is the size of the search space. The…

Quantum Physics · Physics 2009-03-20 V. Potocek , A. Gabris , T. Kiss , I. Jex

Many search-based quantum algorithms that achieve a theoretical speedup are not practically relevant since they require extraordinarily long coherence times, or lack the parallelizability of their classical counterparts.This raises the…

Quantum Physics · Physics 2024-04-24 Vahideh Eshaghian , Sören Wilkening , Johan Åberg , David Gross

Quantum computation using continuous-time evolution under a natural hardware Hamiltonian is a promising near- and mid-term direction toward powerful quantum computing hardware. We investigate the performance of continuous-time quantum walks…

Quantum Physics · Physics 2019-12-24 Adam Callison , Nicholas Chancellor , Florian Mintert , Viv Kendon

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

Anytime heuristic search algorithms try to find a (potentially suboptimal) solution as quickly as possible and then work to find better and better solutions until an optimal solution is obtained or time is exhausted. The most widely-known…

Artificial Intelligence · Computer Science 2023-12-21 Sofia Lemons , Wheeler Ruml , Robert C. Holte , Carlos Linares López

Inspired by a class of algorithms proposed by Farhi et al. (arXiv:1411.4028), namely the quantum approximate optimization algorithm (QAOA), we present a circuit-based quantum algorithm to search for a needle in a haystack, obtaining the…

Quantum Physics · Physics 2017-06-21 Zhang Jiang , Eleanor G. Rieffel , Zhihui Wang

Ordered search is the task of finding an item in an ordered list using comparison queries. The best exact classical algorithm for this fundamental problem uses $\lceil \log_{2}{n}\rceil$ queries for a list of length $n$. Quantum computers…

Quantum Physics · Physics 2025-08-01 Joseph Carolan , Andrew M. Childs , Matt Kovacs-Deak , Luke Schaeffer