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Alleviating the quantum Big-M problem

delete2025-07-26
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OA
AI
E
Edoardo Alessandroni *
S
Sergi Ramos-Calderer
I
Ingo Roth
E
Emiliano Traversi
L
Leandro Aolita
DOI:10.1038/s41534-025-01067-0delete
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Abstract

Abstract

En 中文
A major obstacle for quantum optimizers is the reformulation of constraints as a quadratic unconstrained binary optimization (QUBO). Current QUBO translators exaggerate the weight M of the penalty terms. Classically known as the “Big-M” problem, the issue becomes even more daunting for quantum solvers, since it affects the physical energy scale. We take a systematic, encompassing look at the quantum big-M problem, revealing NP-hardness in finding the optimal M and establishing bounds on the Hamiltonian spectral gap Δ as a function of the weight M, inversely related to the expected run-time of quantum solvers. We propose a practical translation algorithm, based on SDP relaxation, that outperforms previous methods in numerical benchmarks. Our algorithm gives values of Δ orders of magnitude greater, e.g. for portfolio optimization instances. Solving such instances with an adiabatic algorithm on 6-qubits of an IonQ device, we observe significant advantages in time to solution and average solution quality. Our findings are relevant to quantum and quantum-inspired solvers alike.
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Journal

npj Quantum Information cover
npj Quantum Information
IF:
8.3
Papers:
1.4K
Citations:
8.1K

Organization

Q
quantum research centre
Scholars:
4
Papers: 1
Citations: 0
D
Department of Information Systems
Scholars:
74
Papers: 57
Citations: 0