Dephasing of Si singlet-triplet qubits due to charge and spin defects

TL;DR

This paper develops a theoretical framework to analyze how charge and spin defects cause dephasing in silicon singlet-triplet qubits, aiding experimental identification of the most harmful defects.

Contribution

It introduces a model linking defect properties to dephasing rates, integrating industrial defect knowledge to improve qubit coherence analysis.

Findings

Charge fluctuators cause more dephasing than spin fluctuators.

Dephasing rates relate to measurable defect parameters.

Framework aids experimental defect identification.

Abstract

We study the effect of charge and spin noise on singlet-triplet qubits in Si quantum dots. We set up a theoretical framework aimed at enabling experiment to efficiently identify the most deleterious defects, and complement it with the knowledge of defects gained in decades of industrial and academic work. We relate the dephasing rates $\Gamma_\phi$ due to various classes of defects to experimentally measurable parameters such as charge dipole moment, spin dipole moment and fluctuator switching times. We find that charge fluctuators are more efficient in causing dephasing than spin fluctuators.