Homological origin of transversal implementability of logical diagonal gates in quantum CSS codes

Fuente: arXiv
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Main Author: Haruna, Junichi
Format: Preprint
Published: 2026
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author Haruna, Junichi
author_facet Haruna, Junichi
contents Transversal Pauli $Z$ rotations provide a natural route to fault-tolerant logical diagonal gates in quantum CSS codes, but their capability is inherently constrained. We develop a homological framework that organizes transversal diagonal gates in terms of their logical action and physical implementation, revealing two layers of structure that govern their behavior. At a fixed level, we establish that their logical action admits a classification in terms of homological data of the underlying chain complex, extending the standard description of logical operators. We then formulate the refinement to finer angles as a lifting problem and derive two Bockstein-type obstruction maps, whose vanishing is a necessary and sufficient condition for the existence of a transversal logical diagonal gate at the next level. Within this framework, known algebraic conditions such as divisibility and triorthogonality are reinterpreted as necessary conditions for the existence of transversal logical diagonal gates with uniform rotation angles. Our results identify homological obstructions governing transversal implementability and provide a conceptual foundation for a formal theory of transversal structures in quantum error correction.
format Preprint
id arxiv_https___arxiv_org_abs_2602_14499
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Homological origin of transversal implementability of logical diagonal gates in quantum CSS codes
Haruna, Junichi
Quantum Physics
Strongly Correlated Electrons
High Energy Physics - Theory
Mathematical Physics
Transversal Pauli $Z$ rotations provide a natural route to fault-tolerant logical diagonal gates in quantum CSS codes, but their capability is inherently constrained. We develop a homological framework that organizes transversal diagonal gates in terms of their logical action and physical implementation, revealing two layers of structure that govern their behavior. At a fixed level, we establish that their logical action admits a classification in terms of homological data of the underlying chain complex, extending the standard description of logical operators. We then formulate the refinement to finer angles as a lifting problem and derive two Bockstein-type obstruction maps, whose vanishing is a necessary and sufficient condition for the existence of a transversal logical diagonal gate at the next level. Within this framework, known algebraic conditions such as divisibility and triorthogonality are reinterpreted as necessary conditions for the existence of transversal logical diagonal gates with uniform rotation angles. Our results identify homological obstructions governing transversal implementability and provide a conceptual foundation for a formal theory of transversal structures in quantum error correction.
title Homological origin of transversal implementability of logical diagonal gates in quantum CSS codes
topic Quantum Physics
Strongly Correlated Electrons
High Energy Physics - Theory
Mathematical Physics
url https://arxiv.org/abs/2602.14499