Wigner molecules and hybrid qubits

TL;DR

This paper uses full configuration-interaction calculations to accurately predict spectra of three-electron hybrid qubits in GaAs quantum dots, revealing the crucial role of Wigner molecules in their behavior, which previous models could not capture.

Contribution

It demonstrates that FCI calculations can predict hybrid qubit spectra and highlight the importance of Wigner molecules, surpassing traditional independent-particle or Hubbard models.

Findings

Spectroscopic patterns are linked to Wigner molecule formation.

Excellent agreement with recent experimental data.

Method applicable to Si/SiGe hybrid qubits.

Abstract

It is demonstrated that exact diagonalization of the microscopic many-body Hamiltonian via systematic full configuration-interaction (FCI) calculations is able to predict the spectra as a function of detuning of three-electron hybrid qubits based on GaAs asymmetric double quantum dots. It is further shown that, as a result of strong inter-electron correlations, these spectroscopic patterns, including avoided crossings between states associated with different electron occupancies of the left and right wells, are inextricably related to the formation of Wigner molecules. These physical entities cannot be captured by the previously employed independent-particle or Hubbard-type theoretical modeling of the hybrid qubit. We report remarkable agreement with recent experimental results. Moreover, the present FCI methodology for multi-well quantum dots can be straightforwardly extended to treat Si/SiGe hybrid qubits, where the central role of Wigner molecules was recently experimentally confirmed as well.