Readout Sweet Spots for Spin Qubits with Strong Spin-Orbit Interaction
Domonkos Svastits (Budapest University of Technology and Economics)
Bence Hetényi (IBM Research)
Gábor Széchenyi (Eötvös Loránd University)
James Wootton (Moth Quantum AG, Arlesheim, IBM Research)
Daniel Loss (University of Basel)
Stefano Bosco (TU Delft - QCD/Bosco Group, Kavli institute of nanoscience Delft, TU Delft - QuTech Advanced Research Centre)
András Pályi (Budapest University of Technology and Economics, HUN-REN, Quantum Technology, Budapest)
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Abstract
Qubit readout schemes often deviate from ideal projective measurements, introducing critical issues that limit quantum computing performance. In this Letter, we model charge-sensing-based readout for semiconductor spin qubits in double quantum dots, and identify key error mechanisms caused by the backaction of the charge sensor. We quantify how the charge noise of the sensor, residual tunneling, and g-tensor modulation degrade readout fidelity, induce a mixed postmeasurement state, and cause leakage from the computational subspace. For state-of-the-art systems with strong spin-orbit interaction and electrically tunable g tensors, we identify a readout sweet spot, that is, a special device configuration where readout is closest to projective. Our framework provides a foundation for developing effective readout error mitigation strategies, with broad applications for optimizing readout performance for a variety of charge-sensing techniques, advancing quantum protocols, and improving adaptive circuits for error correction.
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