Limitations of the g-tensor formalism of semiconductor spin qubits

György, Zoltán and Pályi, András and Széchenyi, Gábor (2025) Limitations of the g-tensor formalism of semiconductor spin qubits. PHYSICAL REVIEW B (112). No.-045428. ISSN 2469-9950

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Abstract

The g-tensor formalism is a powerful method for describing the electrical driving of semiconductor spin qubits. However, up to now, this technique has only been applied to the simplest qubit dynamics, resonant monochromatic driving by a single gate. Here, we study the description of (i) monochromatic driving using two driving gates and bichromatic driving via (ii) one or (iii) two gates. Assuming a general Hamiltonian with qubit states well separated from excited orbital states, we find that when (i) two driving gates are used for monochromatic driving or (ii) a single one for bichromatic, the g-tensor formalism successfully captures the leading-order dynamics. We express the Rabi frequency and the Bloch-Siegert shift using the g-tensor and its first and second derivatives with respect to the gate voltage. However, when (iii) bichromatic driving is realized using two distinct driving gates, we see a breakdown of g-tensor formalism: The Rabi frequency cannot be expressed using the g-tensor and its derivatives. We find that beyond the g-tensor and its derivatives, three additional parameters are needed to capture the dynamics. We demonstrate our general results by assuming an electron (hole) confined in a circular quantum dot, subjected to Rashba spin-orbit interaction.

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