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arXiv · 2404.01369

Cluster state as a non-invertible symmetry protected topological phase

Sahand Seifnashri·Shu-Heng Shao
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Abstract

We show that the standard 1+1d $\mathbb{Z}_2\times \mathbb{Z}_2$ cluster model has a non-invertible global symmetry, described by the fusion category Rep(D$_8$). Therefore, the cluster state is not only a $\mathbb{Z}_2\times \mathbb{Z}_2$ symmetry protected topological (SPT) phase, but also a non-invertible SPT phase. We further find two new commuting Pauli Hamiltonians for the other two Rep(D$_8$) SPT phases on a tensor product Hilbert space of qubits, matching the classification in field theory and mathematics. We identify the edge modes and the local projective algebras at the interfaces between these non-invertible SPT phases. Finally, we show that there does not exist a symmetric entangler that maps between these distinct SPT states.

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Sahand Seifnashri, Shu-Heng Shao. 2024-04-01. Cluster state as a non-invertible symmetry protected topological phase. https://doi.org/10.1103/physrevlett.133.116601

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