Inverted Singlet-Triplet Qubit Coded on a Two-Electron Double Quantum Dot

TL;DR

This paper introduces the inverted singlet-triplet qubit (ISTQ), a new qubit encoding using two quantum dots of different sizes and magnetic fields, enabling universal control with spin-orbit interactions.

Contribution

The paper proposes the concept of the inverted STQ, utilizing size and magnetic field asymmetry in double quantum dots for qubit encoding and control.

Findings

ISTQ can be realized in GaAs and InAs DQDs.

Spin-orbit interactions enable universal qubit control.

Operation is feasible under realistic noise conditions.

Abstract

The $s_z=0$ 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 $s_z=0$ subspace. Spin-orbit interactions act nontrivially on the $s_z=0$ 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.