Reflectometry of charge transitions in a silicon quadruple dot*

Silicon is considered a promising candidate for realizing large qubit processors [1], making quantum dots in silicon nanowire transistors, fabricated in industrial cleanrooms on 300-mm wafers, particularly attractive [2]. We perform gate-based reflectometry measurements of various charge states in a foundry-fabricated two-dimensional quadruple quantum dot. From a wiring perspective, the low number of control channels (one gate-electrode per dot and global top and back gates) is desirable, provided that tunnel couplings are adjustable to allow controlled single-electron movements [3] and single-shot reflectometry readout.
Using native and virtual gate voltages, we demonstrate charge sensing and dispersive read-out down to the last electron in each dot, and show an adjustability of interdot tunneling rates using the top gate. We support our findings with k x p modeling and simulations based on a constant interaction model, and experimentally demonstrate single-shot detection of interdot charge transitions with unity signal-to-noise ratios at bandwidths exceeding 1 MHz.
[1] Vandersypen et al., npj Quant.Inf. 3, 34 (2017)
[2] Maurand et al., Nat.Comm. 7, 13575 (2016)
[3] Ansaloni et al., arXiv:2004.00894 (2020)