Ares, N and Schupp, F J and Mavalankar, A and Rogers, G and Griffiths, J P and Jones, G A C and Farrer, I and Ritchie, D. A. and Smith, C G and Cottet, A and Briggs, G A D and Laird, E A (2016) Sensitive Radio-Frequency Measurements of a Quantum Dot by Tuning to Perfect Impedance Matching. Physical Review Applied, 5. ISSN 2331-7019
Full text not available from this repository.Abstract
Electrical readout of spin qubits requires fast and sensitive measurements, which are hindered by poor impedance matching to the device. We demonstrate perfect impedance matching in a radio-frequency readout circuit, using voltage-tunable varactors to cancel out parasitic capacitances. An optimized capacitance sensitivity of 1.6 aF/√Hz is achieved at a maximum source-drain bias of 170−μV root-mean-square and with a bandwidth of 18 MHz. Coulomb blockade in a quantum-dot is measured in both conductance and capacitance, 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.