Tunneling Statistics and Spin Readout of Few-donor Quantum Dots in Silicon

The long electron spin coherence and relaxation times achievable in donor-based quantum dots in silicon provide a promising route towards scalable solid-state quantum computation. High-fidelity single-shot spin readout and initialization are essential for implementing fault-tolerant quantum algorithms. However, unwanted dynamic interactions between the quantum dot electron and its environment and charge sensor can significantly limit the spin readout fidelity. Here we present our recent spin readout and initialization measurements in few-donor cluster quantum dots using STM-patterned single-electron transistor charge sensors in the strong response regime. Using spectroscopic measurements of single-electron loading/unloading rates and analysis of spin-selective tunneling statistics, we investigate the charge and spin dynamics between the few-donor quantum dot and charge sensor where spin-to-charge conversion and random telegraph switching occur. We discuss the impact of charge noise and the charge sensor's density of states fluctuations on the spin-state readout and initialization, as well as perspectives on device design, fabrication, and measurement conditions to optimize spin-readout fidelity for robust single electron spin qubit manipulation.