Near-Unity Charge Readout in a Nonlinear Resonator without Matching

In this paper, we present a nonlinear resonator performing the readout of a charge-sensing quantum dot. We show that by driving the resonator in the nonlinear regime, we achieve a near-unity signal. This despite not satisfying the impedance matching requirements necessary for such large signals in the linear regime. Our experiments, supported by numerical calculations, demonstrate that the signal increase stems from the sensor dissipation shifting the onset of the nonlinear resonator response. By lifting the matching requirement, we increase the bandwidth limit of resonator readout-based charge detection by an order of magnitude, opening up the avenue to ultra-fast charge detectors.