On the Improvement of Gate Fidelity in Spin Qubits With Two-Level Fluctuators at Higher Temperatures

The importance of the role of two-level fluctuators (TLFs) in causing qubit frequency (fq) shifts has been highlighted in previous studies to improve the gate fidelity in silicon spin qubits at higher temperatures. In this study, we employed a simulation technique to investigate the origin of the temperature dependence of fq shifts in silicon spin qubits. Among the various possible microscopic origins, we focused on the charge noise, which is attributed to the TLFs at the semiconductor/oxide interface, for which the experimental features of the fq shift have been theoretically reproduced in previous studies. We analyze the TLF characteristics required to improve the gate fidelity by simulating the effect of charge noise, considering the spatial and energetic distributions, as well as characteristic parameters.We observed that the exponential distribution of the activation energies was preferable for reproducing the fq shift and fidelity improvement. Moreover, in terms of parameter selection, a short transition time and a steep temperature transition can improve fidelity during higher-temperature operations. Based on these findings, we discussed the origin of TLFs and observed that electronic transitions are more likely to produce TLFs than transitions involving atomic displacement.