2015/10/31 by N. Ares, F. J. Schupp, A. Mavalankar +9 · 1 citation
Physics and Astronomy · #cond-mat.mes-hall
paper · pdf · doi:10.1103/physrevapplied.5.034011
published as Phys. Rev. Applied 5, 034011 (2016)
arxiv created 2015/11/30 · arxiv updated 2016/03/28
Electrical readout of spin qubits requires fast and sensitive measurements, but these are hindered by poor impedance matching to the device. We demonstrate perfect impedance matching in a radio-frequency readout circuit, realized by incorporating voltage-tunable varactors to cancel out parasitic capacitances. In the optimized setup, a capacitance sensitivity of 1.6~aF/√(Hz) is achieved at a maximum source-drain bias of 170~μV root-mean-square and with bandwidth above 15~MHz. Coulomb blockade is measured via both conductance and capacitance in a quantum dot, and the two contributions are found to be proportional, as expected from a quasistatic tunneling model. We benchmark our results against the requirements for single-shot qubit readout using quantum capacitance, a goal that has so far been elusive.