Omnidirectional shuttling to avoid valley excitations in Si/SiGe quantum wells

TL;DR

This paper investigates methods to prevent valley excitations during electron shuttling in Si/SiGe quantum wells, proposing a 2D shuttler for improved fidelity and a modular architecture for scalable quantum computing.

Contribution

It introduces a 2D omnidirectional shuttling scheme to avoid valley excitations, enhancing fidelity in quantum dot qubit transport.

Findings

2D shuttler outperforms multichannel scheme in fidelity

Simulations show high-fidelity electron shuttling achievable

Proposes a modular qubit architecture with all-to-all connectivity

Abstract

Conveyor-mode shuttling is a key approach for implementing intermediate-range coupling between electron-spin qubits in quantum dots. Initial implementations are encouraging; however, long shuttling trajectories are guaranteed to encounter regions of low conduction-band valley energy splittings, due to the presence of random-alloy disorder in Si/SiGe quantum wells. Here, we theoretically explore two schemes for avoiding valley-state excitations at these valley-splitting minima, by allowing the electrons to detour around them. A multichannel shuttling scheme allows electrons to tunnel between parallel channels, while a two-dimensional (2D) shuttler provides full omnidirectional control. Using simulations, we estimate shuttling fidelities in these two schemes, obtaining a clear preference for the 2D shuttler. Based on such encouraging results, we propose a modular qubit architecture based on 2D shuttling, which enables all-to-all connectivity within qubit plaquettes and high-fidelity communication between different plaquettes.