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Condensed Matter > Strongly Correlated Electrons
Title: A Noisy Approach to Intrinsically Mixed-State Topological Order
(Submitted on 20 Mar 2024 (v1), last revised 22 Mar 2024 (this version, v2))
Abstract: We propose a general framework for studying two-dimensional (2D) topologically ordered states subject to local correlated errors and show that the resulting mixed-state can display intrinsically mixed-state topological order (imTO) -- topological order which is not expected to occur in the ground state of 2D local gapped Hamiltonians. Specifically, we show that decoherence, previously interpreted as anyon condensation in a doubled Hilbert space, is more naturally phrased as, and provides a physical mechanism for, "gauging out" anyons in the original Hilbert space. We find that gauging out anyons generically results in imTO, with the decohered mixed-state strongly symmetric under certain anomalous 1-form symmetries. This framework lays bare a striking connection between the decohered density matrix and topological subsystem codes, which can appear as anomalous surface states of 3D topological orders. Through a series of examples, we show that the decohered state can display a classical memory, encode logical qubits (i.e., exhibit a quantum memory), and even host chiral or non-modular topological order. We argue that the decohered states represent genuine mixed-state quantum phases of matter and that a partial classification of imTO is given in terms of braided fusion categories.
Submission history
From: Abhinav Prem [view email][v1] Wed, 20 Mar 2024 18:00:01 GMT (361kb,D)
[v2] Fri, 22 Mar 2024 02:16:28 GMT (365kb,D)
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