High-fidelity single-spin shuttling in silicon

TL;DR

This paper demonstrates high-fidelity, rapid electron shuttling in silicon quantum dots, crucial for scalable quantum computing, with a new traveling wave method that preserves spin coherence over extended distances.

Contribution

It introduces a traveling wave potential technique for electron transport in silicon, achieving 99.5% fidelity over 10 μm in under 200 ns, surpassing previous methods.

Findings

Traveling wave method improves spin coherence during shuttling.

Achieved 99.5% fidelity in electron transport over 10 μm.

Transport time under 200 ns for large-scale quantum processing.

Abstract

The computational power and fault-tolerance of future large-scale quantum processors derive in large part from the connectivity between the qubits. One approach to increase connectivity is to engineer qubit-qubit interactions at a distance. Alternatively, the connectivity can be increased by physically displacing the qubits. This has been explored in trapped-ion experiments and using neutral atoms trapped with optical tweezers. For semiconductor spin qubits, several studies have investigated spin coherent shuttling of individual electrons, but high-fidelity transport over extended distances remains to be demonstrated. Here we report shuttling of an electron inside an isotopically purified Si/SiGe heterostructure using electric gate potentials. First, we form static quantum dots, and study how spin coherence decays as we repeatedly move a single electron between up to five dots. Next, we create a traveling wave potential to transport an electron in a moving quantum dot. This second method shows substantially better spin coherence than the first. It allows us to displace an electron over an effective distance of 10 $\mu$m in under 200 ns with an average fidelity of 99.5%. These results will guide future efforts to realize large-scale semiconductor quantum processors, making use of electron shuttling both within and between qubit arrays.