Fig. 1.

Device layout and circuitry for qubit dispersive sensing and manipulation. a False-color transmission electron micrograph of a double-gate Si device. The 11-nm-thick, 35-nm-wide Si nanowire (light blue) connects p-type, boron-doped source-drain contacts (dark blue) and lies on a 140-nm-thick SiO₂ buffer layer (pink). The two 35-nm-wide gates (grey) are spaced by 35 nm. Si₃N₄ spacers (cyan) prevent dopant implantation in the Si channel. At 20 mK, proper gate voltages induce the accumulation of two hole quantum dots: one can be used as a spin qubit, the other as a helper dot for qubit readout. One gate is connected to a lumped-element resonator excited at frequency f_R for dispersive readout. A ultra-high frequency digital lock-in demodulates the reflected signal after a directional coupler, separating the incoming and outgoing waves, and a low-noise amplifier at 4 K. The other gate applies square pulses and GHz radiation to drive controlled coherent rotations of the hole spin qubit. At the bottom, DQD energy diagram with E_v as valence band edge and E_F as Fermi energy. b Phase response (ϕ) and attenuation (A) of the resonator at base temperature. c Scanning electron micrograph of the device