Quantum computing through electron propagation in the edge states of quantum spin Hall systems

TL;DR

This paper proposes a method for quantum computing using electron wave propagation in quantum spin Hall systems, enabling all-electrical control of universal quantum gates with high fidelity.

Contribution

It introduces a novel approach to implement universal quantum gates via edge state electron propagation and Coulomb interactions in QSH systems, advancing scalable quantum computing.

Findings

High-fidelity single-qubit gates achieved

Two-qubit controlled phase gate demonstrated

All-electrical control of quantum gates possible

Abstract

We propose to implement quantum computing based on electronic spin qubits by controlling the propagation of the electron wave packets through the helical edge states of quantum spin Hall systems (QSHs). Specfically, two non-commutative single-qubit gates, which rotate a qubit around z and y axes, can be realized by utilizing gate voltages either on a single QSH edge channel or on a quantum point contact structure. The more challenging two-qubit controlled phase gate can be implemented through the on-demand capacitive Coulomb interaction between two adjacent edge channels from two parallel QSHs. As a result, a universal set of quantum gates can be achieved in an all-electrical way. The fidelity and purity of the two-qubit gate are calculated with both time delay and finite width of the wave packets taken into consideration, which can reach high values with the existing high-quality single electron source.