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

Abstract

A crucial requirement for quantum computing, in particular for scalable quantum computing and error correction, is a 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 GaAs and Si/SiGe asymmetric sensing dots (ASDs) specifically designed to provide a significantly improved response compared to conventional charge sensing dots. Our ASD design features a strongly decoupled drain reservoir from the sensor dot, which mitigates negative feedback effects found in conventional sensors. This results in a boosted output swing of $3\,\text{mV}$, which exceeds the response in the conventional regime of our device by more than ten times. The enhanced output signal paves the way for employing very low-power readout amplifiers in close proximity to the qubit.