Transversal non-Clifford gates on almost-good quantum LDPC and quantum locally testable codes

Fuente: arXiv
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Autori principali: Li, Yiming, Li, Zimu, Liu, Zi-Wen
Natura: Preprint
Pubblicazione: 2026
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author Li, Yiming
Li, Zimu
Liu, Zi-Wen
author_facet Li, Yiming
Li, Zimu
Liu, Zi-Wen
contents We exhibit nontrivial transversal logical multi-controlled-$Z$ gates on $[\![N,Θ(N),\tildeΘ(N)]\!]$ quantum low-density parity-check codes and $[\![N,Θ(N),\tildeΘ(N)]\!]$ quantum locally testable codes with soundness $\tildeΘ(1)$, combining nearly optimal code parameters with fault-tolerant non-Clifford gates for the first time. Remarkably, our proofs are almost entirely algebraic-topological, showing that such presumably intricate logical gates naturally arise as a fundamental topological phenomenon. We develop a general framework for constructing a rich new family of homological invariant forms which we call ''cupcap gates'' that induce transversal logical multi-controlled-$Z$ and, building on insights from [Li et al., arXiv:2603.25831], covering space methods to certify their nontriviality. The claimed almost-good code results follow immediately as examples.
format Preprint
id arxiv_https___arxiv_org_abs_2604_01874
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Transversal non-Clifford gates on almost-good quantum LDPC and quantum locally testable codes
Li, Yiming
Li, Zimu
Liu, Zi-Wen
Quantum Physics
Information Theory
Mathematical Physics
We exhibit nontrivial transversal logical multi-controlled-$Z$ gates on $[\![N,Θ(N),\tildeΘ(N)]\!]$ quantum low-density parity-check codes and $[\![N,Θ(N),\tildeΘ(N)]\!]$ quantum locally testable codes with soundness $\tildeΘ(1)$, combining nearly optimal code parameters with fault-tolerant non-Clifford gates for the first time. Remarkably, our proofs are almost entirely algebraic-topological, showing that such presumably intricate logical gates naturally arise as a fundamental topological phenomenon. We develop a general framework for constructing a rich new family of homological invariant forms which we call ''cupcap gates'' that induce transversal logical multi-controlled-$Z$ and, building on insights from [Li et al., arXiv:2603.25831], covering space methods to certify their nontriviality. The claimed almost-good code results follow immediately as examples.
title Transversal non-Clifford gates on almost-good quantum LDPC and quantum locally testable codes
topic Quantum Physics
Information Theory
Mathematical Physics
url https://arxiv.org/abs/2604.01874