Charge noise suppression in capacitively coupled singlet-triplet spin qubits under magnetic field

TL;DR

This paper theoretically identifies nearly sweet spots in coupled singlet-triplet spin qubits under magnetic fields, enabling high-fidelity two-qubit gates by suppressing charge noise using optimized ramping sequences.

Contribution

It reveals the existence of nearly sweet spots in coupled singlet-triplet qubits under magnetic fields and proposes ramping protocols to maximize gate fidelity.

Findings

Nearly sweet spots appear with strong magnetic fields.

Ramping sequences improve gate fidelity under noise.

High-fidelity two-qubit gates are achievable in these systems.

Abstract

Charge noise is the main hurdle preventing high-fidelity operation, in particular that of two-qubit gates, of semiconductor-quantum-dot-based spin qubits. While certain sweet spots where charge noise is substantially suppressed have been demonstrated in several types of spin qubits, the existence of one for coupled singlet-triplet qubits is unclear. We theoretically demonstrate, using full configuration-interaction calculations, that a range of nearly sweet spots appear in the coupled singlet-triplet qubit system when a strong enough magnetic field is applied externally. We further demonstrate that ramping to and from the judiciously chosen nearly sweet spot using sequences based on the shortcut to adiabaticity offers maximal gate fidelities under charge noise and phonon-induced decoherence. These results should facilitate realization of high-fidelity two-qubit gates in singlet-triplet qubit systems.