Quantum Polymorphisms and the Complexity of Quantum Constraint Satisfaction

Fuente: arXiv
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Main Authors: Ciardo, Lorenzo, Joubert, Gideo, Mottet, Antoine
Format: Preprint
Published: 2025
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author Ciardo, Lorenzo
Joubert, Gideo
Mottet, Antoine
author_facet Ciardo, Lorenzo
Joubert, Gideo
Mottet, Antoine
contents We introduce the concept of quantum polymorphisms to the complexity theory of quantum constraint satisfaction. Via this notion, we build an algebraic framework of reductions between quantum CSPs, and we establish a Galois connection between quantum polymorphism minions and quantum relational constructions. By leveraging a contextuality property of quantum polymorphisms, we fully characterise the existence of commutativity gadgets for relational structures, introduced by Ji as a method for achieving quantum soundness of classical CSP reductions. Prior to our work, only a partial classification was known for a subclass of Boolean languages and for non-Boolean languages meeting specific structural conditions [Culf--Mastel, FOCS'25]. As an application of our framework, we prove that the quantum CSPs parameterised by odd cycles and the quantum CSP expressing quantum satisfiability of Siggers clauses are undecidable.
format Preprint
id arxiv_https___arxiv_org_abs_2511_23445
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Quantum Polymorphisms and the Complexity of Quantum Constraint Satisfaction
Ciardo, Lorenzo
Joubert, Gideo
Mottet, Antoine
Quantum Physics
Computational Complexity
Logic in Computer Science
Combinatorics
81P45, 05C15
We introduce the concept of quantum polymorphisms to the complexity theory of quantum constraint satisfaction. Via this notion, we build an algebraic framework of reductions between quantum CSPs, and we establish a Galois connection between quantum polymorphism minions and quantum relational constructions. By leveraging a contextuality property of quantum polymorphisms, we fully characterise the existence of commutativity gadgets for relational structures, introduced by Ji as a method for achieving quantum soundness of classical CSP reductions. Prior to our work, only a partial classification was known for a subclass of Boolean languages and for non-Boolean languages meeting specific structural conditions [Culf--Mastel, FOCS'25]. As an application of our framework, we prove that the quantum CSPs parameterised by odd cycles and the quantum CSP expressing quantum satisfiability of Siggers clauses are undecidable.
title Quantum Polymorphisms and the Complexity of Quantum Constraint Satisfaction
topic Quantum Physics
Computational Complexity
Logic in Computer Science
Combinatorics
81P45, 05C15
url https://arxiv.org/abs/2511.23445