Spin qubits in germanium are a promising contender for scalable quantum computers. Reading out of the spin and charge configuration of quantum dots formed in Ge/Si core/shell nanowires is typically performed by measuring the current through the nanowire. Here, we demonstrate a more versatile approach on investigating the charge configuration of these quantum dots. We employ a high-impedance, magnetic-field resilient superconducting resonator based on NbTiN and couple it to a double quantum dot in a Ge/Si nanowire. This allows us to dispersively detect charging effects, even in the regime where the nanowire is fully pinched off and no direct current is present. Furthermore, by increasing the electro-chemical potential far beyond the nanowire pinch-off, we observe indications for depleting the last hole in the quantum dot by using the second quantum dot as a charge sensor. This work opens the door for dispersive readout and future spin-photon coupling in this system.
@article{arxiv.2211.00763,
title = {Charge-sensing of a Ge/Si core/shell nanowire double quantum dot using a high-impedance superconducting resonator},
author = {J. H. Ungerer and P. Chevalier Kwon and T. Patlatiuk and J. Ridderbos and A. Kononov and D. Sarmah and E. P. A. M. Bakkers and D. Zumbühl and C. Schönenberger},
journal= {arXiv preprint arXiv:2211.00763},
year = {2023}
}