Sensing dot with high output swing for scalable baseband readout of spin qubits

A crucial requirement for quantum computing---in particular, for scalable quantum computing and error correction---is fast and high-fidelity qubit readout. For semiconductor-based qubits, one limiting factor for local low-power signal amplification is the output swing of the charge sensor. We demonstrate $\mathrm{Ga}\mathrm{As}$ and Si asymmetric sensing dots (ASDs) specifically designed to provide a significantly larger response compared to conventional charge-sensing dots. Our ASD design features a drain reservoir strongly decoupled from the sensor dot, which mitigates negative feedback effects found in conventional sensors. This results in a boosted output swing of $3\phantom{\rule{0.2em}{0ex}}\mathrm{mV}$, which exceeds the response in the conventional regime of our device by more than a factor of 10. The enhanced output signal paves the way for employing very low-power readout amplifiers in close proximity to the qubit.