The sz=0 spin configuration of two electrons confined at a double quantum dot (DQD) encodes the singlet-triplet qubit (STQ). We introduce the inverted STQ (ISTQ) that emerges from the setup of two quantum dots (QDs) differing significantly in size and out-of-plane magnetic fields. The strongly confined QD has a two-electron singlet ground state, but the weakly confined QD has a two-electron triplet ground state in the sz=0 subspace. Spin-orbit interactions act nontrivially on the sz=0 subspace and provide universal control of the ISTQ together with electrostatic manipulations of the charge configuration. GaAs and InAs DQDs can be operated as ISTQs under realistic noise conditions.
@article{arxiv.1408.1010,
title = {Inverted Singlet-Triplet Qubit Coded on a Two-Electron Double Quantum Dot},
author = {Sebastian Mehl and David P. DiVincenzo},
journal= {arXiv preprint arXiv:1408.1010},
year = {2014}
}