Realization of decoherence-induced averaged symmetry-protected topological phases on quantum processors

Abstract:Symmetry-protected topological (SPT) phases are conventionally formulated for pure states protected by exact symmetries. In open quantum systems, however, decoherence generates mixed-state ensembles in which average symmetry can instead emerge only after averaging over microscopic trajectories. In this work, we realize decoherence-induced averaged SPT (ASPT) order on programmable quantum processors. Starting from a one-dimensional cluster SPT, we engineer sublattice-selective Pauli-$Z$ dephasing through ancilla-assisted quantum circuits. We observe the resulting symmetry conversion through the decay of the symmetry charge. Moreover, a two-replica Renyi-2 string correlator measured through destructive SWAP readout remains nontrivial, revealing the ASPT structure encoded at the density-matrix level. We further show that the engineered dephasing redistributes spectral weight among reduced-stabilizer sectors while preserving the characteristic twofold pairing of the half-chain entanglement spectrum. These results establish a gate-based route to engineering and probing ASPT order and demonstrate structured decoherence as a programmable resource for realizing mixed-state topological quantum matter.

arXiv:2609.07831 [quant-ph]

(or arXiv:2609.07831v1 [quant-ph] for this version)

https://doi.org/10.48550/arXiv.2609.07831 Focus to learn more arXiv-issued DOI via DataCite (pending registration)

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