Efficient Circuit Implementations of Continuous-Time Quantum Walks for Quantum Search

Quantum walks are a powerful framework for simulating complex quantum systems and designing quantum algorithms, particularly for spatial search on graphs, where the goal is to find a marked vertex efficiently. In this work, we present efficient quantum circuits that implement the evolution operator...

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Main Authors: Renato Portugal, Jalil Khatibi Moqadam
Format: Article
Language:English
Published: MDPI AG 2025-04-01
Series:Entropy
Subjects:
Online Access:https://www.mdpi.com/1099-4300/27/5/454
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author Renato Portugal
Jalil Khatibi Moqadam
author_facet Renato Portugal
Jalil Khatibi Moqadam
author_sort Renato Portugal
collection DOAJ
description Quantum walks are a powerful framework for simulating complex quantum systems and designing quantum algorithms, particularly for spatial search on graphs, where the goal is to find a marked vertex efficiently. In this work, we present efficient quantum circuits that implement the evolution operator of continuous-time quantum-walk-based search algorithms for three graph families: complete graphs, complete bipartite graphs, and hypercubes. For complete and complete bipartite graphs, our circuits exactly implement the evolution operator. For hypercubes, we propose an approximate implementation that closely matches the exact evolution operator as the number of vertices increases. Our Qiskit simulations demonstrate that even for low-dimensional hypercubes, the algorithm effectively identifies the marked vertex. Furthermore, the approximate implementation developed for hypercubes can be extended to a broad class of graphs, enabling efficient quantum search in scenarios where exact implementations are impractical.
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series Entropy
spelling doaj-art-3a8b29ea847640468e6dd9f8e2c6bba92025-08-20T02:33:54ZengMDPI AGEntropy1099-43002025-04-0127545410.3390/e27050454Efficient Circuit Implementations of Continuous-Time Quantum Walks for Quantum SearchRenato Portugal0Jalil Khatibi Moqadam1National Laboratory of Scientific Computing (LNCC), Av. Getulio Vargas 333, Petrópolis 25651-075, BrazilNational Laboratory of Scientific Computing (LNCC), Av. Getulio Vargas 333, Petrópolis 25651-075, BrazilQuantum walks are a powerful framework for simulating complex quantum systems and designing quantum algorithms, particularly for spatial search on graphs, where the goal is to find a marked vertex efficiently. In this work, we present efficient quantum circuits that implement the evolution operator of continuous-time quantum-walk-based search algorithms for three graph families: complete graphs, complete bipartite graphs, and hypercubes. For complete and complete bipartite graphs, our circuits exactly implement the evolution operator. For hypercubes, we propose an approximate implementation that closely matches the exact evolution operator as the number of vertices increases. Our Qiskit simulations demonstrate that even for low-dimensional hypercubes, the algorithm effectively identifies the marked vertex. Furthermore, the approximate implementation developed for hypercubes can be extended to a broad class of graphs, enabling efficient quantum search in scenarios where exact implementations are impractical.https://www.mdpi.com/1099-4300/27/5/454quantum computerquantum walkspatial search algorithmcomplete graphbipartite graphhypercube
spellingShingle Renato Portugal
Jalil Khatibi Moqadam
Efficient Circuit Implementations of Continuous-Time Quantum Walks for Quantum Search
Entropy
quantum computer
quantum walk
spatial search algorithm
complete graph
bipartite graph
hypercube
title Efficient Circuit Implementations of Continuous-Time Quantum Walks for Quantum Search
title_full Efficient Circuit Implementations of Continuous-Time Quantum Walks for Quantum Search
title_fullStr Efficient Circuit Implementations of Continuous-Time Quantum Walks for Quantum Search
title_full_unstemmed Efficient Circuit Implementations of Continuous-Time Quantum Walks for Quantum Search
title_short Efficient Circuit Implementations of Continuous-Time Quantum Walks for Quantum Search
title_sort efficient circuit implementations of continuous time quantum walks for quantum search
topic quantum computer
quantum walk
spatial search algorithm
complete graph
bipartite graph
hypercube
url https://www.mdpi.com/1099-4300/27/5/454
work_keys_str_mv AT renatoportugal efficientcircuitimplementationsofcontinuoustimequantumwalksforquantumsearch
AT jalilkhatibimoqadam efficientcircuitimplementationsofcontinuoustimequantumwalksforquantumsearch