Optimizing RF Reflectometry for Charge Sensing on Si:P Dopant-based Devices

RF Reflectometry has been applied extensively in the field of spin qubits with the advantage of smaller device footprint, remote sensing, and higher bandwidth. By measuring device impedance, reflectometry signal responds to both conductance and capacitance changes quickly and thus is ideal for charge sensing.

In this talk we discuss constraints on achieving high bandwidth and high sensitivity RF measurement such as coupling constant, circuit Q factor and impedance matching. Thermal constraints put a cap on the maximum RF input power that can be applied before increasing the electron temperature on the device. We evaluate SNR and the minimum impedance contrast that can be differentiated at a given noise level and measurement bandwidth under such constraints. We demonstrate improved SNR of single-shot readout using an STM patterned SET and improved charge sensing on a quantum dot array by having better impedance matching and higher Q factor. We extract and compare spin-filling sequence for two quantum dot arrays with different lattice constant. Our results also provide insights for future device design.