title: Destroying a topological quantum bit by condensing Ising vortices.
abstract: The imminent realization of topologically protected qubits in fabricated systems will provide not only an elementary implementation of fault-tolerant quantum computing architecture, but also an experimental vehicle for the general study of topological order. The simplest topological qubit harbours what is known as a Z2 liquid phase, which encodes information via a degeneracy depending on the system's topology. Elementary excitations of the phase are fractionally charged objects called spinons, or Ising flux vortices called visons. At zero temperature, a Z2 liquid is stable under deformations of the Hamiltonian until spinon or vison condensation induces a quantum-phase transition destroying the topological order. Here we use quantum Monte Carlo to study a vison-induced transition from a Z2 liquid to a valence-bond solid in a quantum dimer model on the kagome lattice. Our results indicate that this critical point is beyond the description of the standard Landau paradigm.
authors.affiliation: Department of Physics and Astronomy, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1.
authors.forename: Zhihao
authors.initials: Z
authors.lastname: Hao
authors.affiliation: 1] Department of Physics and Astronomy, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1 [2] Department of Physics, Arnold Sommerfeld Center for Theoretical Physics and Center for NanoScience, University of Munich, Theresienstrasse 37, 80333 Munich, Germany.
authors.forename: Stephen
authors.initials: S
authors.lastname: Inglis
authors.affiliation: 1] Department of Physics and Astronomy, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1 [2] Perimeter Institute for Theoretical Physics, Waterloo, Ontario, Canada N2L 2Y5.
authors.forename: Roger
authors.initials: R
authors.lastname: Melko