Measuring the complex admittance of a carbon nanotube double quantum dot

TL;DR

This paper demonstrates how radio-frequency reflectometry can measure the complex admittance of a carbon nanotube double quantum dot, advancing non-invasive charge and spin state detection techniques.

Contribution

It provides the first detailed measurement of complex admittance in a tunable carbon nanotube double quantum dot using rf reflectometry, aligning with theoretical models.

Findings

Measured complex admittance as a function of single-electron energies

Good agreement with incoherent limit theoretical model

Progress towards non-invasive quantum state readout

Abstract

We investigate radio-frequency (rf) reflectometry in a tunable carbon nanotube double quantum dot coupled to a resonant circuit. By measuring the in-phase and quadrature components of the reflected rf signal, we are able to determine the complex admittance of the double quantum dot as a function of the energies of the single-electron states. The measurements are found to be in good agreement with a theoretical model of the device in the incoherent limit. Besides being of fundamental interest, our results present an important step forward towards non-invasive charge and spin state readout in carbon nanotube quantum dots.