Stephan Plugge, Asbjørn Rasmussen, Reinhold Egger, Karsten Flensberg

Published:

Quantum information protected by the topology of the storage medium is
expected to exhibit long coherence times. Another attractive feature are
topologically protected gates generated through braiding of Majorana bound
states. However, braiding requires branched structures which have inherent
difficulties in the semiconductor-superconductor heterostructures now believed
to host Majorana bound states. Here, we construct quantum bits taking advantage
of the topological protection and non-local properties of Majorana bound states
in a network of parallel wires. The elementary unit is made from three
topological wires, two wires coupled by a trivial superconductor and the third
acting as an interference arm. Coulomb blockade of the combined wires spawns a
fractionalized spin, non-locally addressable by quantum dots used for
single-qubit readout, initialization, and manipulation. We describe how the
same tools allow for measurement-based implementation of the Clifford gates, in
total making the architecture universal. Proof-of-principle demonstration of
topologically protected qubits using existing techniques is therefore within
reach.