Probing the limits of gate-based charge sensing

• Published in: Nature communications 2015-01, Vol.6 (1), p.6084-6084, Article 6084
• Main Authors: Gonzalez-Zalba, M. F., Barraud, S., Ferguson, A. J., Betz, A. C.
• Format: Article
• Language: English
• Subjects: 639/766/119/1000/1016; 639/766/119/1000/1017; 639/925/927/511; 639/925/930/1032; Humanities and Social Sciences; multidisciplinary; Science; Science (multidisciplinary)
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/ncomms7084

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. Reading out the state of quantum bits is an essential requirement that any quantum computer implementation must satisfy. Gonzalez-Zalba et al . now show that in situ resonant gate-based detection can be a more sensitive approach than external electrometers while reducing the qubit architecture’s complexity.