title: Probing the limits of gate-based charge sensing.
abstract: 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.
authors.affiliation: Hitachi Cambridge Laboratory, J. J. Thomson Avenue, Cambridge CB3 0HE, UK.
authors.forename: M F
authors.initials: MF
authors.lastname: Gonzalez-Zalba
authors.affiliation: CEA, LETI, Minatec Campus, F-38054 Grenoble, France.
authors.forename: S
authors.initials: S
authors.lastname: Barraud
authors.affiliation: Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, UK.
authors.forename: A J
authors.initials: AJ
authors.lastname: Ferguson
authors.affiliation: Hitachi Cambridge Laboratory, J. J. Thomson Avenue, Cambridge CB3 0HE, UK.
authors.forename: A C
authors.initials: AC
authors.lastname: Betz