Transversal Clifford-Hierarchy Gates via Non-Abelian Surface Codes

Fuente: arXiv
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Autores principales: Warman, Alison, Schafer-Nameki, Sakura
Formato: Preprint
Publicado: 2025
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author Warman, Alison
Schafer-Nameki, Sakura
author_facet Warman, Alison
Schafer-Nameki, Sakura
contents We present an entirely 2D transversal realization of phase gates at any level of the Clifford hierarchy, and beyond, using non-Abelian surface codes. Our construction encodes a logical qubit in the quantum double $D(G)$ of a non-Abelian group $G$ on a triangular spatial patch. The logical gate is implemented transversally by stacking on the spatial region a symmetry-protected topological (SPT) phase specified by a group 2-cocycle. The Bravyi--König theorem limits the unitary gates implementable by constant-depth quantum circuits on Pauli stabilizer codes in $D$ dimensions to the $D$-th level of the Clifford hierarchy. We bypass this limitation, by constructing transversal unitary gates at arbitrary levels of the Clifford hierarchy purely in 2D, without sacrificing locality or fault tolerance, at the cost of using the quantum double of a non-Abelian group $G$. Specifically, for $G = D_{4N}$, the dihedral group of order $8N$, we realize the phase gate $T^{1/N} = \mathrm{diag}(1, e^{iπ/(4N)})$ in the logical $\overline{Z}$ basis. In this context we propose a non-abelian stabilizer group formalism, which we work out for dihedral groups. For $8N = 2^n$, the logical gate lies at the $n$-th level of the Clifford hierarchy and, importantly, has a qubit-only realization: we show that it can be constructed in terms of Clifford-hierarchy stabilizers for a code with $n$ physical qubits on each edge of the lattice. We also discuss code-switching to the $\mathbb{Z}_2 \times \mathbb{Z}_2$ and $\mathbb{Z}_2$ surface-codes, which can be utilized for the quantum error correction in this setup.
format Preprint
id arxiv_https___arxiv_org_abs_2512_13777
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Transversal Clifford-Hierarchy Gates via Non-Abelian Surface Codes
Warman, Alison
Schafer-Nameki, Sakura
Quantum Physics
Strongly Correlated Electrons
High Energy Physics - Theory
Mathematical Physics
We present an entirely 2D transversal realization of phase gates at any level of the Clifford hierarchy, and beyond, using non-Abelian surface codes. Our construction encodes a logical qubit in the quantum double $D(G)$ of a non-Abelian group $G$ on a triangular spatial patch. The logical gate is implemented transversally by stacking on the spatial region a symmetry-protected topological (SPT) phase specified by a group 2-cocycle. The Bravyi--König theorem limits the unitary gates implementable by constant-depth quantum circuits on Pauli stabilizer codes in $D$ dimensions to the $D$-th level of the Clifford hierarchy. We bypass this limitation, by constructing transversal unitary gates at arbitrary levels of the Clifford hierarchy purely in 2D, without sacrificing locality or fault tolerance, at the cost of using the quantum double of a non-Abelian group $G$. Specifically, for $G = D_{4N}$, the dihedral group of order $8N$, we realize the phase gate $T^{1/N} = \mathrm{diag}(1, e^{iπ/(4N)})$ in the logical $\overline{Z}$ basis. In this context we propose a non-abelian stabilizer group formalism, which we work out for dihedral groups. For $8N = 2^n$, the logical gate lies at the $n$-th level of the Clifford hierarchy and, importantly, has a qubit-only realization: we show that it can be constructed in terms of Clifford-hierarchy stabilizers for a code with $n$ physical qubits on each edge of the lattice. We also discuss code-switching to the $\mathbb{Z}_2 \times \mathbb{Z}_2$ and $\mathbb{Z}_2$ surface-codes, which can be utilized for the quantum error correction in this setup.
title Transversal Clifford-Hierarchy Gates via Non-Abelian Surface Codes
topic Quantum Physics
Strongly Correlated Electrons
High Energy Physics - Theory
Mathematical Physics
url https://arxiv.org/abs/2512.13777