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arXiv · 2605.11016

Counting anticommuting Pauli pairs in linear time

Hyunho Cha·Jungwoo Lee
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Abstract

Many quantum computing workflows manipulate long lists of Pauli strings. A basic classical subroutine involves taking $m$ Pauli strings on $n$ qubits, each of weight bounded by a constant, to determine if they are pairwise commuting, identify any counterexamples, or calculate the exact number of anticommuting unordered pairs. The standard general-purpose route represents Pauli strings in binary symplectic form and checks pairs in $O(m^2)$ time. Here, we provide an $O(m)$ algorithm for the bounded locality regime. It maintains counts of all labeled subpatterns of previously inserted strings and answers each new string query by a subset zeta identity. Our algorithm is particularly useful for processing large collections of Pauli strings within the bounded locality regime.

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Hyunho Cha, Jungwoo Lee. 2026-05-10. Counting anticommuting Pauli pairs in linear time. https://arxiv.org/abs/2605.11016

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