Impact of Alloy Disorder on Resonant Exchange Operation in Triple-Quantum-Dot Qubits

Triple quantum dot (TQD) exchange-only qubits are a promising platform for quantum computing because they utilize the fast, tunable and electrically controllable exchange interaction.  Long-distance coupling, via superconducting cavities, is possible in the resonant exchange (RX) regime where a non-vanishing transverse dipole moment can couple TQD spins to photons [1].  However, RX operation is challenging since this regime exists at narrow operating points in bias space, making it sensitive to disorder sources, such as the alloy disorder unavoidable in Si/SiGe quantum dots.  Alloy disorder is known to significantly impact single-electron properties like valley splitting.  In this talk, we study the effects of alloy disorder on multi-electron properties like exchange using a device simulator based on the full configuration interaction (FCI) method [2].  We show that FCI wavefunctions are critical for predicting RX regimes and spin-photon coupling rates compared to wavefunctions from simpler models and quantify the impact of levels of random alloy disorder on variability in device performance.

[1] J. M. Taylor et al., Phys. Rev. Lett. 111, 050502 (2013)

[2] C. Anderson et al., AIP Adv., 12, 065123 (2022)