Readout sweet spots for spin qubits with strong spin-orbit interaction

TL;DR

This paper models charge-sensing readout for semiconductor spin qubits with strong spin-orbit interaction, identifying a device configuration that optimizes fidelity by minimizing back-action and noise effects.

Contribution

It introduces a framework to identify readout sweet spots in spin qubits with strong spin-orbit coupling, enhancing measurement fidelity and error mitigation strategies.

Findings

Identifies a readout sweet spot with near-projective measurement fidelity.

Quantifies how charge noise and residual tunneling degrade readout quality.

Provides a foundation for optimizing charge-sensing readout techniques.

Abstract

Qubit readout schemes often deviate from ideal projective measurements, introducing critical issues that limit quantum computing performance. In this work, we model charge-sensing-based readout for semiconductor spin qubits in double quantum dots, and identify key error mechanisms caused by the back-action 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 post-measurement 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.