Topological materials and topological quantum computing

Abstract

A paradigm to build a quantum computer based on topological invariants is highlighted. The identities in the ensemble of knots, links and braids originally discovered in relation to topological quantum field theory are generalized to define Artin braid group—the mathematical basis of topological quantum computation (TQC). Vector spaces of TQC correspond to associated strings of particle interactions and TQC operates its calculations on braided strings of special physical qvasiparticles—anyons with non-Abelian statistics. The physical platform of TQC is to use the topological quantum numbers of small groups of anyons as qubits and to perform operations on these qubits by exchanging the anyons, both within the groups that form the qubits and, for multi-qubit gates, between groups. By braiding two or more anyons, they acquire up a topological phase or Berry phase similar to that found in the Aharonov-Bohm effect. Topological matter such as fractional quantum Hall systems and novel discovered topological insulators open the way to form system of anyons—Majorana fermions— with the unique property of encoding and processing quantum information in a naturally fault-tolerant way. In the topological insulators due to its fundamental attribute of topological surface state occurrence the bound Majorana fermions are generated at its heterocontact with superconductors.One of the key operations of TQC—braiding of non-Abelian anyons— it is illustrated how can be implemented in one-dimensional topological isolator wire networks.