Variability of electron and hole spin qubits due to interface roughness and charge traps

TL;DR

This paper models how interface roughness and charge traps affect the variability of electron and hole spin qubits in semiconductor devices, highlighting charge traps as a major limiting factor for qubit consistency.

Contribution

It provides a detailed analysis of disorder effects on spin qubit properties, emphasizing the dominant role of charge traps over interface roughness.

Findings

Charge traps cause greater variability in Rabi frequencies than interface roughness.

Charge traps can scatter Rabi frequencies over an order of magnitude.

Implications for qubit design and material selection are discussed.

Abstract

Semiconductor spin qubits may show significant device-to-device variability in the presence of spin-orbit coupling mechanisms. Interface roughness, charge traps, layout or process inhomogeneities indeed shape the real space wave functions, hence the spin properties. It is, therefore, important to understand how reproducible the qubits can be, in order to assess strategies to cope with variability, and to set constraints on the quality of materials and fabrication. Here we model the variability of single qubit properties (Larmor and Rabi frequencies) due to disorder at the Si/SiO$_2$ interface (roughness, charge traps) in metal-oxide-semiconductor devices. We consider both electron qubits (with synthetic spin-orbit coupling fields created by micro-magnets) and hole qubits (with intrinsic spin-orbit coupling). We show that charge traps are much more limiting than interface roughness, and can scatter Rabi frequencies over one order of magnitude. We discuss the implications for the design of spin qubits and for the choice of materials.