Cross-material operating windows of electric-field programmable Rashba qubits for frequency allocation and leakage control

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 ( Δ q ), isolation energy ( Δ ᵢₛₒ ), 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 ( Δ ᵥ , 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 Δ ᵥ 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.