Adiabatic paths of Hamiltonians, symmetries of topological order, and automorphism codes

Mar 21, 2022
36 pages
Published in:
  • Phys.Rev.B 106 (2022) 8, 085122
  • Published: Aug 15, 2022
e-Print:
DOI:

Citations per year

20222023202420251730212
Abstract: (APS)
The recent “honeycomb code” is a fault-tolerant quantum memory defined by a sequence of checks, which implements a nontrivial automorphism of the toric code. We argue that a general framework to understand this code is to consider continuous adiabatic paths of gapped Hamiltonians and we give a conjectured description of the fundamental group and second and third homotopy groups of this space in two spatial dimensions. A single cycle of such a path can implement some automorphism of the topological order of that Hamiltonian. We construct such paths for arbitrary automorphisms of two-dimensional doubled topological order. Then, realizing this in the case of the toric code, we turn this path back into a sequence of checks, constructing an automorphism code closely related to the honeycomb code.
Note:
  • 36 pages, 10 figures; v2: additional references and minor revisions
  • phase: topological
  • symmetry: topological
  • dimension: 2
  • Hamiltonian
  • adiabatic
  • homotopy