We report the use of dispersive gate sensing (DGS) as a means of probing the charge environment of heterostructure-based qubit devices. The DGS technique, which detects small shifts in the quantum capacitance associated with single-electron tunnel events, is shown to be sensitive to pockets of charge in the potential-landscape likely under, and surrounding, the surface gates that define qubits and their readout sensors. Configuring a quantum point contact (QPC) as a localized emitter, we show how these charge pockets are activated by the relaxation of electrons tunneling through a barrier. The presence of charge pockets creates uncontrolled offsets in gate-bias and their thermal activation by on-chip tunnel currents suggests further sources of charge-noise that lead to decoherence in semiconductor qubits.
@article{arxiv.1706.09626,
title = {Gate-Sensing Charge Pockets in the Semiconductor Qubit Environment},
author = {X. G. Croot and S. J. Pauka and H. Lu and A. C. Gossard and J. D. Watson and G. C. Gardner and S. Fallahi and M. J. Manfra and D. J. Reilly},
journal= {arXiv preprint arXiv:1706.09626},
year = {2019}
}