Exchange interaction in gate-defined quantum dots beyond the Hubbard model

TL;DR

This paper provides a detailed measurement and modeling of exchange interactions in GaAs quantum dots, extending the Hubbard model to better understand spin qubit operations.

Contribution

It introduces an extended Hubbard model including excited states to accurately describe exchange interactions beyond traditional models.

Findings

Measured exchange coupling over three orders of magnitude.

Full configuration interaction simulations match experimental data.

Extended Hubbard model improves fit range and physical understanding.

Abstract

A quantitative description of the exchange interaction in quantum dots is relevant for modeling gate operations of spin qubits. By measuring the amplitude and frequency of exchange-driven qubit state oscillations, we measure the detuning dependence of the exchange coupling in a GaAs double quantum dot over three orders of magnitude. Both 1D and 3D full configuration interaction simulations can replicate the observed behavior. Extending a Hubbard model by including excited states increases the range of detuning where it provides a good fit, thus elucidating the underlying physics.