title: From Majorana fermions to topological order.
abstract: We consider a system consisting of a 2D network of links between Majorana fermions on superconducting islands. We show that the fermionic Hamiltonian modeling this system is topologically ordered in a region of parameter space: we show that Kitaev's toric code emerges in fourth-order perturbation theory. By using a Jordan-Wigner transformation we can map the model onto a family of signed 2D Ising models in a transverse field where the signs, ferromagnetic or antiferromagnetic, are determined by additional gauge bits. Our mapping allows an understanding of the nonperturbative regime and the phase transition to a nontopological phase. We discuss the physics behind a possible implementation of this model and argue how it can be used for topological quantum computation by adiabatic changes in the Hamiltonian.
authors.affiliation: Institute for Quantum Information, RWTH Aachen University, 52056 Aachen, Germany.
authors.forename: Barbara M
authors.initials: BM
authors.lastname: Terhal
authors.forename: Fabian
authors.initials: F
authors.lastname: Hassler
authors.forename: David P
authors.initials: DP
authors.lastname: DiVincenzo