Sub 10 μeHz^-1/2 Gate-based Sensing

Semiconductor-based quantum computing architectures require sensitive electrometers to readout the state of the qubits. This requires high-precision external electrometers. A compact alternative, in-situ gate based dispersive readout has been proposed to facilitate scalability. However, single-shot dispersive readout of an electron spin state, which is a crucial requirement for error correction protocols, has not been performed yet. In order to facilitate time-resolved gate-based reflectometry, improvements in the sensitivity of this technique need to be achieved. Large coupling of the quantum system to a high-Q resonator is hence desired. Here, we present results on gate-based sensing of a silicon corner state quantum dot with a large gate-coupling α = 0.89. The quantum device is connected via the gate to a lumped-element resonator with a high loaded Q factor ~ 400. We find a charge sensitivity of 7.7 μeHz^-1/2, an improvement by a factor of ~ 5 with respect to the best value reported for this technique. Additionally, we perform a circuit analysis to determine the optimal resonator design. Overall, our results place the sensitivity of gate-based sensing at par with the best semiconductor-based radio frequency single-electron transistors.