Quantum systems on non-k-hyperfinite complexes: A generalization of classical statistical mechanics on expander graphs

Michael H. Freedman, Matthew B. Hastings

Research output: Contribution to journalArticlepeer-review

Abstract

We construct families of cell complexes that generalize expander graphs. These families are called non-k-hyperfinite, generalizing the idea of a non-hyperfinite (NH) family of graphs. Roughly speaking, such a complex has the property that one cannot remove a small fraction of points and be left with an object that looks k - 1-dimensional at large scales. We then consider certain quantum systems on these complexes. A future goal is to construct a family of Hamiltonians such that every low energy state has topological order as part of an attempt to prove the quantum PCP conjecture. This goal is approached by constructing a toric code Hamiltonian with the property that every low energy state without vertex defects has topological order, a property that would not hold for any local system in any lattice Zd or indeed on any 1-hyperfinite complex. Further, such NH complexes find application in quantum coding theory. The hypergraph product codes[1] of Tillich and Zémor are generalized using NH complexes.

Original languageEnglish
Pages (from-to)144-180
Number of pages37
JournalQuantum Information and Computation
Volume14
Issue number1-2
StatePublished - 1 Jan 2014
Externally publishedYes

ASJC Scopus subject areas

  • Theoretical Computer Science
  • Statistical and Nonlinear Physics
  • Nuclear and High Energy Physics
  • Mathematical Physics
  • General Physics and Astronomy
  • Computational Theory and Mathematics

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