Noise-Protected Gate for Six-Electron Double-Dot Qubits

TL;DR

This paper demonstrates that six-electron double quantum dot qubits can achieve high-fidelity phase gates by exploiting orbital symmetry to protect against charge noise, especially with rapid switching between charge stability regions.

Contribution

It introduces a noise-protected gate scheme for six-electron double-dot qubits utilizing orbital symmetry and rapid switching to enhance charge noise immunity.

Findings

Fidelities close to one predicted with subnanosecond switching.

Symmetry of orbitals in the second energy shell reduces charge noise sensitivity.

Rapid switching between charge stability regions optimizes gate performance.

Abstract

Singlet-triplet spin qubits in six-electron double quantum dots, in moderate magnetic fields, can show superior immunity to charge noise. This immunity results from the symmetry of orbitals in the second energy shell of circular quantum dots: singlet and triplet states in this shell have identical charge distributions. Our phase-gate simulations, which include $1/f$ charge noise from fluctuating traps, show that this symmetry is most effectively exploited if the gate operation switches rapidly between sweet spots deep in the (3,3) and (4,2) charge stability regions; fidelities very close to one are predicted if subnanosecond switching can be performed.