Characterization of individual charge fluctuators in Si/SiGe quantum dots - Part I

Electron spins in silicon quantum dots are a promising quantum computing platform due to their long coherence times, scalability, and compatibility with advanced semiconductor technology. Even though single- and two-qubit gates with fidelities above 99% have been achieved in Si quantum dots, charge noise in the semiconductor environment still hinders gate fidelities, and key questions like what fluctuators cause charge noise, where they are in the device, and how they are thermalized, remain unanswered. Here, we probe individual two-level fluctuators (TLFs) in Si/SiGe quantum dots via simple quantum-dot transport measurements. Using the Allan variance, we determine the switching times of individual TLFs. We find that the TLF switching rates depend sensitively on gate voltages. Furthermore, our findings suggest that the TLFs we observe are likely not described by a model involving isolated dipole fluctuators coupled to a phonon bath.