Probing the limits of gate-based charge sensing

TitleProbing the limits of gate-based charge sensing
Publication TypeJournal Article
Year of Publication2015
AuthorsGonzalez-Zalba M.F, Barraud S., Ferguson A.J, Betz A.C
JournalNature Communications
Date Published01/2015

Quantum computation requires a qubit-specific measurement capability to readout the final state of individual qubits. Promising solid-state architectures use external readout electrometers but these can be replaced by a more compact readout element, an in situ gate sensor. Gate-sensing couples the qubit to a resonant circuit via a gate and probes the qubit’s radiofrequency polarizability. Here we investigate the ultimate performance of such a resonant readout scheme and the noise sources that limit its operation. We find a charge sensitivity of 37 μe Hz−1/2, the best value reported for this technique, using the example of a gate sensor strongly coupled to a double quantum dot at the corner states of a ​silicon nanowire transistor. We discuss the experimental factors limiting gate detection and highlight ways to optimize its sensitivity. In total, resonant gate-based readout has advantages over external electrometers both in terms of reduction of circuit elements as well as absolute charge sensitivity.