Universal Quantum Computation with Hybrid Spin-Majorana Qubits

TL;DR

This paper proposes a theoretical framework for universal quantum computation using hybrid spin-Majorana qubits, introducing new gate operations and scalable network architectures that do not require braiding or projective measurements.

Contribution

It introduces a set of universal quantum gates for hybrid spin-Majorana qubits and scalable network designs that simplify quantum computation protocols.

Findings

Hybrid CNOT gate enabled by spin-Majorana exchange interaction.

Scalable network architecture for neighboring qubits without braiding.

Universal gate set including phase, SWAP, and hybrid SWAP gates.

Abstract

We theoretically propose a set of universal quantum gates acting on a hybrid qubit formed by coupling a quantum dot spin qubit and Majorana fermion qubit. First, we consider a quantum dot tunnel-coupled to two topological superconductors. The effective spin-Majorana exchange facilitates a hybrid CNOT gate for which either qubit can be the control or target. The second setup is a modular scalable network of topological superconductors and quantum dots. As a result of the exchange interaction between adjacent spin qubits, a CNOT gate is implemented that acts on neighboring Majorana qubits, and eliminates the necessity of inter-qubit braiding. In both setups the spin-Majorana exchange interaction allows for a phase gate, acting on either the spin or the Majorana qubit, and for a SWAP or hybrid SWAP gate which is sufficient for universal quantum computation without projective measurements.