Quadratic Sums-of-Powers for Fixed-Parameter Tractable Quantum-Circuit Simulation

Fuente: arXiv
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Autori principali: de Colnet, Alexis, Geerts, Floris, Hai, Rihan, Laarman, Alfons, Lee, Joon Hyung, Pérez, Guillermo A.
Natura: Preprint
Pubblicazione: 2026
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author de Colnet, Alexis
Geerts, Floris
Hai, Rihan
Laarman, Alfons
Lee, Joon Hyung
Pérez, Guillermo A.
author_facet de Colnet, Alexis
Geerts, Floris
Hai, Rihan
Laarman, Alfons
Lee, Joon Hyung
Pérez, Guillermo A.
contents Strongly simulating a quantum circuit, that is, computing an output amplitude, amounts to summing the circuit's Feynman paths, a weighted count over assignments to the Boolean ``path'' variables. The circuit's gates induce correlations among these variables, forming a graph whose structure determines the hardness of the simulation task. This sum-of-powers viewpoint underlies recent simulators built on knowledge-representation tools from artificial intelligence, namely binary decision diagrams and weighted model counting. We show that the structural quantity most accurately governing the difficulty is the rank-width of the path-variable graph, and we give an algorithm that evaluates the amplitude in time that is exponential only in this rank-width and polynomial in the circuit size. Rank-width can be far smaller than the widths that control competing methods: as corollaries, our algorithm reproduces a recent decision-diagram simulation breakthrough as a special case and matches the Markov--Shi tensor-network contraction bound. To complement this, we exhibit circuit families on which our algorithm provably beats both competing methods. The new method applies to every circuit built from Hadamard and diagonal gates, in particular to circuits over Clifford+T. In practical terms, general-purpose decision-diagram and model-counting tools can serve as the workhorse, with our specialized algorithm dispatched to exploit a small rank-width of the associated graph when it is present.
format Preprint
id arxiv_https___arxiv_org_abs_2605_29944
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Quadratic Sums-of-Powers for Fixed-Parameter Tractable Quantum-Circuit Simulation
de Colnet, Alexis
Geerts, Floris
Hai, Rihan
Laarman, Alfons
Lee, Joon Hyung
Pérez, Guillermo A.
Quantum Physics
Data Structures and Algorithms
Logic in Computer Science
Strongly simulating a quantum circuit, that is, computing an output amplitude, amounts to summing the circuit's Feynman paths, a weighted count over assignments to the Boolean ``path'' variables. The circuit's gates induce correlations among these variables, forming a graph whose structure determines the hardness of the simulation task. This sum-of-powers viewpoint underlies recent simulators built on knowledge-representation tools from artificial intelligence, namely binary decision diagrams and weighted model counting. We show that the structural quantity most accurately governing the difficulty is the rank-width of the path-variable graph, and we give an algorithm that evaluates the amplitude in time that is exponential only in this rank-width and polynomial in the circuit size. Rank-width can be far smaller than the widths that control competing methods: as corollaries, our algorithm reproduces a recent decision-diagram simulation breakthrough as a special case and matches the Markov--Shi tensor-network contraction bound. To complement this, we exhibit circuit families on which our algorithm provably beats both competing methods. The new method applies to every circuit built from Hadamard and diagonal gates, in particular to circuits over Clifford+T. In practical terms, general-purpose decision-diagram and model-counting tools can serve as the workhorse, with our specialized algorithm dispatched to exploit a small rank-width of the associated graph when it is present.
title Quadratic Sums-of-Powers for Fixed-Parameter Tractable Quantum-Circuit Simulation
topic Quantum Physics
Data Structures and Algorithms
Logic in Computer Science
url https://arxiv.org/abs/2605.29944