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Stability of the bulk gap for frustration-free topologically ordered quantum lattice systems (2102.07209v3)
Published 14 Feb 2021 in math-ph, cond-mat.str-el, math.MP, and quant-ph
Abstract: We prove that uniformly small short-range perturbations do not close the bulk gap above the ground state of frustration-free quantum spin systems that satisfy a standard local topological quantum order condition. In contrast with earlier results, we do not require a positive lower bound for finite-system Hamiltonians uniform in the system size. To obtain this result, we adapt the Bravyi-Hastings-Michalakis strategy to the GNS representation of the infinite-system ground state.