Electric-Field Programmable Rashba Qubits: Cross-Material Operating Windows for Frequency Allocation and Leakage Control

Abstract This work presents a cross-material, design-oriented framework for electrically tunable spin–orbit qubits, focusing on realistic operating windows for four key semiconductor platforms: GaAs, InAs, InSb, and SiGe. Building on validated two-band models, we introduce a unified set of energy-based figures of merit— qubit gap (Δq), isolation energy (Δᵢₛₒ), and anharmonicity (A)—to assess qubit performance and leakage suppression within experimentally achievable magnetic fields (GaAs/SiGe below 2~T; InAs/InSb up to 5~T). The framework reveals explicit trade-offs between controllability and fidelity by mapping the combined effects of Rashba (α) and Dresselhaus (β) spin–orbit couplings, vertical electric field F, and valley splitting parameters (Δᵥ, tᵥ). Results highlight that InAs offers strong intrinsic tunability with minimal leakage, while GaAs requires careful co-tuning of α and β, and SiGe performance depends critically on maximizing Δᵥ and minimizing tᵥ. These findings provide practical guidelines for material selection and device optimization, bridging theoretical modeling with experimental implementation for next-generation semiconductor qubits.