Using a spin-triplet encoding to enhance shuttling fidelities in Si/SiGe quantum wells

TL;DR

The paper proposes a valley-singlet two-electron qubit encoding in Si/SiGe quantum wells that improves shuttling fidelity by being immune to Landau-Zener leakage, especially at small valley splittings.

Contribution

It introduces an unconventional two-electron qubit encoding based on valley-singlet states that enhances shuttling fidelities without fine-tuning.

Findings

Shuttling fidelity improves at small valley splittings.

High fidelities are achievable without special procedures.

The encoding is largely immune to Landau-Zener leakage.

Abstract

Spatial variations of the valley splitting in a quantum well present a key challenge for conveyor-mode shuttling of electron spins in Si/SiGe, giving rise to Landau-Zener-like excitations that cause leakage outside the qubit subspace. Here, we propose an unconventional two-electron qubit encoding, based on valley-singlet states, that is largely immune to Landau-Zener leakage processes. In contrast to single-electron spins, the shuttling fidelity actually improves for small valley splittings, in this case. We show that high fidelities can be achieved without applying any special procedures, such as fine-tuning of the shuttling path.