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arXiv · 1510.06944

Sensitive radio-frequency measurements of a quantum dot by tuning to perfect impedance matching

N. Ares·F. J. Schupp·A. Mavalankar·G. Rogers·J. Griffiths·G. A. C. Jones·I. Farrer·D. A. Ritchie·C. G. Smith·A. Cottet·G. A. D. Briggs·E. A. Laird
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Abstract

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 $1.6~\mathrm{aF}/\sqrt{\mathrm{Hz}}$ is achieved at a maximum source-drain bias of $170~μ$V 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.

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N. Ares, F. J. Schupp, A. Mavalankar, G. Rogers, J. Griffiths, G. A. C. Jones, I. Farrer, D. A. Ritchie, C. G. Smith, A. Cottet, G. A. D. Briggs, E. A. Laird. 2015-11-30. Sensitive radio-frequency measurements of a quantum dot by tuning to perfect impedance matching. https://doi.org/10.1103/physrevapplied.5.034011

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