Spin shuttling in a silicon double quantum dot

TL;DR

This paper models and analyzes the coherent spin shuttling process in a silicon double quantum dot, considering spin-orbit and magnetic effects, and demonstrates low infidelity achievable through optimized protocols.

Contribution

It provides a theoretical framework for spin transport in silicon quantum dots, including effects of spin-orbit interaction and magnetic field inhomogeneity, with numerical and analytical analysis.

Findings

Achieves spin infidelity as low as 0.002 with optimal parameters.

Identifies the role of avoided crossings and interference in spin shuttling.

Demonstrates feasibility of fast, coherent spin transport in silicon DQDs.

Abstract

The transport of quantum information between different nodes of a quantum device is among the challenging functionalities of a quantum processor. In the context of spin qubits, this requirement can be met by coherent electron spin shuttling between semiconductor quantum dots. Here we theoretically study a minimal version of spin shuttling between two quantum dots. To this end, we analyze the dynamics of an electron during a detuning sweep in a silicon double quantum dot (DQD) occupied by one electron. Possibilities and limitations of spin transport are investigated. Spin-orbit interaction and the Zeeman effect in an inhomogeneous magnetic field play an important role for spin shuttling and are included in our model. Interactions that couple the position, spin and valley degrees of freedom open a number of avoided crossings in the spectrum allowing for diabatic transitions and interfering paths. The outcomes of single and repeated spin shuttling protocols are explored by means of numerical simulations and an approximate analytical model based on the solution of the Landau--Zener problem. We find that a spin infidelity as low as $1-F_s\lesssim 0.002$ with a relatively fast level velocity of $\alpha = 600\, {\mu}$eV/ns is feasible for optimal choices of parameters or by making use of constructive interference.