Succinct QUBO formulations for permutation problems by sorting networks

Fuente: arXiv
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Auteurs principaux: Friedl, Katalin, Gegő, Levente, Kabódi, László, Nemkin, Viktória
Format: Preprint
Publié: 2026
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author Friedl, Katalin
Gegő, Levente
Kabódi, László
Nemkin, Viktória
author_facet Friedl, Katalin
Gegő, Levente
Kabódi, László
Nemkin, Viktória
contents Quadratic Unconstrained Binary Optimization (QUBO) is a standard NP-hard optimization problem. Recently, it has gained renewed interest through quantum computing, as QUBOs directly reduce to the Ising model, on which quantum annealing devices are based. We introduce a QUBO formulation for permutations using compare-exchange networks, with only $O(n \log^2 n)$ binary variables. This is a substantial improvement over the standard permutation matrix encoding, which requires $n^2$ variables and has a much denser interaction graph. A central feature of our approach is uniformity: each permutation corresponds to a unique variable assignment, enabling unbiased sampling. Our construction also allows additional constraints, including fixed points and parity. Moreover, it provides a representation of permutations that supports the operations multiplication and inversion, and also makes it possible to check the order of a permutation. This can be used to uniformly generate permutations of a given order or, for example, permutations that commute with a specified permutation. To our knowledge, this is the first result linking oblivious compare-exchange networks with QUBO encodings. While similar functionality can be achieved using permutation matrices, our method yields QUBOs that are both smaller and sparser. We expect this method to be practically useful in areas where unbiased sampling of constrained permutations is important, including cryptography and combinatorial design.
format Preprint
id arxiv_https___arxiv_org_abs_2603_07579
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Succinct QUBO formulations for permutation problems by sorting networks
Friedl, Katalin
Gegő, Levente
Kabódi, László
Nemkin, Viktória
Quantum Physics
Data Structures and Algorithms
90C20, 05A05, 81P68
G.1.6; G.2.1; F.1.2
Quadratic Unconstrained Binary Optimization (QUBO) is a standard NP-hard optimization problem. Recently, it has gained renewed interest through quantum computing, as QUBOs directly reduce to the Ising model, on which quantum annealing devices are based. We introduce a QUBO formulation for permutations using compare-exchange networks, with only $O(n \log^2 n)$ binary variables. This is a substantial improvement over the standard permutation matrix encoding, which requires $n^2$ variables and has a much denser interaction graph. A central feature of our approach is uniformity: each permutation corresponds to a unique variable assignment, enabling unbiased sampling. Our construction also allows additional constraints, including fixed points and parity. Moreover, it provides a representation of permutations that supports the operations multiplication and inversion, and also makes it possible to check the order of a permutation. This can be used to uniformly generate permutations of a given order or, for example, permutations that commute with a specified permutation. To our knowledge, this is the first result linking oblivious compare-exchange networks with QUBO encodings. While similar functionality can be achieved using permutation matrices, our method yields QUBOs that are both smaller and sparser. We expect this method to be practically useful in areas where unbiased sampling of constrained permutations is important, including cryptography and combinatorial design.
title Succinct QUBO formulations for permutation problems by sorting networks
topic Quantum Physics
Data Structures and Algorithms
90C20, 05A05, 81P68
G.1.6; G.2.1; F.1.2
url https://arxiv.org/abs/2603.07579