Suppressing Si Valley Excitation and Valley-Induced Spin Dephasing for Long-Distance Shuttling

TL;DR

This paper introduces a scalable protocol to suppress errors in electron spin shuttling within silicon quantum dots, enhancing fidelity and speed by modeling valley dynamics and optimizing velocity profiles.

Contribution

The work develops a novel error suppression protocol that maps valley dynamics to a Landau-Zener problem and optimizes shuttling velocity to improve quantum transport fidelity.

Findings

Protocol reliably returns valley state to ground state

Error suppression is minimal in time and complexity

Maximum shuttling velocities are much higher than current speeds

Abstract

We present a scalable protocol for suppressing errors during electron spin shuttling in silicon quantum dots. The approach maps the valley Hamiltonian to a Landau-Zener problem to model the nonadiabatic dynamics in regions of small valley splitting. An optimization refines the shuttling velocity profile over a single small segment of the shuttling path. The protocol reliably returns the valley state to the ground state at the end of the shuttle, disentangling the spin and valley degrees of freedom, after which a single virtual $z$-rotation on the spin compensates its evolution during the shuttle. The time cost and complexity of the error suppression is minimal and independent of the distance over which the spin is shuttled, and the maximum velocities imposed by valley physics are found to be orders of magnitude larger than current experimentally achievable shuttling speeds. This protocol offers a chip-scale solution for high-fidelity quantum transport in silicon spin-based quantum computing devices.