Majorana box qubits

TL;DR

This paper proposes a new architecture for Majorana-based qubits that leverages topological protection and non-local properties without requiring braiding, enabling universal quantum computation with existing techniques.

Contribution

It introduces a novel Majorana qubit design using a wire network that avoids braiding, facilitating practical implementation of topologically protected quantum gates.

Findings

Design of a Majorana qubit using three wires and Coulomb blockade

Implementation of measurement-based Clifford gates

Feasibility of proof-of-principle demonstration with current technology

Abstract

Quantum information protected by the topology of the storage medium is expected to exhibit long coherence times. Another feature are topologically protected gates generated through braiding of Majorana bound states. However, braiding requires structures with branched topological segments which have inherent difficulties in the semiconductor-superconductor heterostructures now believed to host Majorana bound states. In this paper, we construct quantum bits taking advantage of the topological protection and non-local properties of Majorana bound states in a network of parallel wires, but without relying on braiding for quantum gates. 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.