Sensitive Radio-Frequency Measurements of a Quantum Dot by Tuning to Perfect Impedance Matching

N. Ares (1) , F. j. Schupp (1) , A. Mavalankar (1) , G. Rogers (1) , J. Griffiths , G. a. c. Jones , I. Farrer , D. a. Ritchie , C. g. Smith , A. Cottet (2) , G. a. d. Briggs (1) , E. a. Laird (1)

1 Department of Materials
2 LPA - Laboratoire Pierre Aigrain

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.

Domaines: Physique [physics]

N. Ares, F. j. Schupp, A. Mavalankar, G. Rogers, J. Griffiths, et al.. Sensitive Radio-Frequency Measurements of a Quantum Dot by Tuning to Perfect Impedance Matching. Physical Review Applied, 2016, 5 (3), pp.034011. ⟨10.1103/PhysRevApplied.5.034011⟩. ⟨hal-01304877⟩