Noise Robustness of Quantum Relaxation for Combinatorial Optimization

Relaxation is a common way for dealing with combinatorial optimization problems. Quantum random-access optimization (QRAO) is a quantum-relaxation-based optimizer that uses fewer qubits than the number of bits in the original problem by encoding multiple variables per qubit using quantum random-acce...

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Main Authors: Kentaro Tamura, Yohichi Suzuki, Rudy Raymond, C. Hiroshi Watanabe, Yuki Sato, Ruho Kondo, Michihiko Sugawara, Naoki Yamamoto
Format: Article
Language:English
Published: IEEE 2024-01-01
Series:IEEE Transactions on Quantum Engineering
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Online Access:https://ieeexplore.ieee.org/document/10623712/
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author Kentaro Tamura
Yohichi Suzuki
Rudy Raymond
C. Hiroshi Watanabe
Yuki Sato
Ruho Kondo
Michihiko Sugawara
Naoki Yamamoto
author_facet Kentaro Tamura
Yohichi Suzuki
Rudy Raymond
C. Hiroshi Watanabe
Yuki Sato
Ruho Kondo
Michihiko Sugawara
Naoki Yamamoto
author_sort Kentaro Tamura
collection DOAJ
description Relaxation is a common way for dealing with combinatorial optimization problems. Quantum random-access optimization (QRAO) is a quantum-relaxation-based optimizer that uses fewer qubits than the number of bits in the original problem by encoding multiple variables per qubit using quantum random-access code (QRAC). Reducing the number of qubits will alleviate physical noise (typically, decoherence), and as a result, the quality of the binary solution of QRAO may be robust against noise, which is, however, unknown. In this article, we numerically demonstrate that the mean approximation ratio of the (3, 1)-QRAC Hamiltonian, i.e., the Hamiltonian utilizing the encoding of three bits into one qubit by QRAC, is less affected by noise compared with the conventional Ising Hamiltonian used in the quantum annealer and the quantum approximate optimization algorithm. Based on this observation, we discuss a plausible mechanism behind the robustness of QRAO under depolarizing noise. Finally, we assess the number of shots required to estimate the values of binary variables correctly under depolarizing noise and show that the (3, 1)-QRAC Hamiltonian requires less shots to achieve the same accuracy compared with the Ising Hamiltonian.
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institution Kabale University
issn 2689-1808
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publishDate 2024-01-01
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series IEEE Transactions on Quantum Engineering
spelling doaj-art-4e63221b41b5428298061138ca3f623e2025-01-28T00:02:21ZengIEEEIEEE Transactions on Quantum Engineering2689-18082024-01-0151910.1109/TQE.2024.343913510623712Noise Robustness of Quantum Relaxation for Combinatorial OptimizationKentaro Tamura0https://orcid.org/0009-0001-6971-6109Yohichi Suzuki1Rudy Raymond2https://orcid.org/0000-0003-1005-6705C. Hiroshi Watanabe3Yuki Sato4https://orcid.org/0000-0003-2069-0355Ruho Kondo5Michihiko Sugawara6https://orcid.org/0000-0003-0484-9899Naoki Yamamoto7https://orcid.org/0000-0002-8497-4608Department of Applied Physics and Physico-Informatics, Keio University, Yokohama, JapanQuantum Computing Center, Keio University, Yokohama, JapanQuantum Computing Center, Keio University, Yokohama, JapanQuantum Computing Center, Keio University, Yokohama, JapanQuantum Computing Center, Keio University, Yokohama, JapanQuantum Computing Center, Keio University, Yokohama, JapanQuantum Computing Center, Keio University, Yokohama, JapanDepartment of Applied Physics and Physico-Informatics, Keio University, Yokohama, JapanRelaxation is a common way for dealing with combinatorial optimization problems. Quantum random-access optimization (QRAO) is a quantum-relaxation-based optimizer that uses fewer qubits than the number of bits in the original problem by encoding multiple variables per qubit using quantum random-access code (QRAC). Reducing the number of qubits will alleviate physical noise (typically, decoherence), and as a result, the quality of the binary solution of QRAO may be robust against noise, which is, however, unknown. In this article, we numerically demonstrate that the mean approximation ratio of the (3, 1)-QRAC Hamiltonian, i.e., the Hamiltonian utilizing the encoding of three bits into one qubit by QRAC, is less affected by noise compared with the conventional Ising Hamiltonian used in the quantum annealer and the quantum approximate optimization algorithm. Based on this observation, we discuss a plausible mechanism behind the robustness of QRAO under depolarizing noise. Finally, we assess the number of shots required to estimate the values of binary variables correctly under depolarizing noise and show that the (3, 1)-QRAC Hamiltonian requires less shots to achieve the same accuracy compared with the Ising Hamiltonian.https://ieeexplore.ieee.org/document/10623712/Combinatorial optimizationdepolarizing noisequantum random-access code (QRAC)quantum relaxation
spellingShingle Kentaro Tamura
Yohichi Suzuki
Rudy Raymond
C. Hiroshi Watanabe
Yuki Sato
Ruho Kondo
Michihiko Sugawara
Naoki Yamamoto
Noise Robustness of Quantum Relaxation for Combinatorial Optimization
IEEE Transactions on Quantum Engineering
Combinatorial optimization
depolarizing noise
quantum random-access code (QRAC)
quantum relaxation
title Noise Robustness of Quantum Relaxation for Combinatorial Optimization
title_full Noise Robustness of Quantum Relaxation for Combinatorial Optimization
title_fullStr Noise Robustness of Quantum Relaxation for Combinatorial Optimization
title_full_unstemmed Noise Robustness of Quantum Relaxation for Combinatorial Optimization
title_short Noise Robustness of Quantum Relaxation for Combinatorial Optimization
title_sort noise robustness of quantum relaxation for combinatorial optimization
topic Combinatorial optimization
depolarizing noise
quantum random-access code (QRAC)
quantum relaxation
url https://ieeexplore.ieee.org/document/10623712/
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