We present measurements of the capacitive coupling energy and the inter-dot capacitances in a linear quadruple quantum dot array in undoped Si/SiGe. With the device tuned to a regime of strong (>1 GHz) intra-double dot tunnel coupling, as is typical for double dot qubits, we measure a capacitive coupling energy of 20.9±0.3 GHz. In this regime, we demonstrate a fitting procedure to extract all the parameters in the 4D Hamiltonian for two capacitively coupled charge qubits from a 2D slice through the quadruple dot charge stability diagram. We also investigate the tunability of the capacitive coupling energy, using inter-dot barrier gate voltages to tune the inter- and intra-double dot capacitances, and change the capacitive coupling energy of the double dots over a range of 15-32 GHz. We provide a model for the capacitive coupling energy based on the electrostatics of a network of charge nodes joined by capacitors, which shows how the coupling energy should depend on inter-double dot and intra-double dot capacitances in the network, and find that the expected trends agree well with the measurements of coupling energy.
Cite
@article{arxiv.1907.08216,
title = {Measurements of capacitive coupling within a quadruple quantum dot array},
author = {Samuel F. Neyens and E. R. MacQuarrie and J. P. Dodson and J. Corrigan and Nathan Holman and Brandur Thorgrimsson and M. Palma and Thomas McJunkin and L. F. Edge and Mark Friesen and S. N. Coppersmith and M. A. Eriksson},
journal= {arXiv preprint arXiv:1907.08216},
year = {2020}
}