Radio-Frequency Capacitive Gate-Based Sensing

Developing fast, accurate, and scalable techniques for quantum-state readout is an active area in semiconductor-based quantum computing. Here, we present results on dispersive sensing of silicon corner state quantum dots coupled to lumped-element electrical resonators via the gate. The gate capacitance of the quantum device is placed in parallel with a superconducting spiral inductor resulting in resonators with loaded $Q$ factors in the 400-800 range. We utilize resonators operating at 330 and 616 MHz, and achieve charge sensitivities of 7.7 and 1.3 $\mu$e $\sqrt Hz$, respectively. We perform a parametric study of the resonator to reveal its optimal operation points and perform a circuit analysis to determine the best resonator design. The results place gate-based sensing on a par with the best reported radio-frequency single-electron transistor sensitivities while providing a fast and compact method for quantum-state readout.