David J. Ibberson^1,2, Theodor Lundberg³, James A. Haigh², Louis Hutin⁴, Benoit Bertrand⁴, Sylvain Barraud⁴, Chang-Min Lee⁵, Jason Robinson⁵, Maud Vinet⁴, M. Fernando Gonzalez-Zalba², Lisa A. Ibberson²

¹Quantum Engineering Technology Labs, University of Bristol, Tyndall Avenue, Bristol BS8 1FD, UK
²Hitachi Cambridge Laboratory, J.J. Thomson Avenue, Cambridge CB
³ 0HE, UK 3Cavendish Laboratory, University of Cambridge, J.J. Thomson Avenue, Cambridge CB3 0HE, UK
⁴CEA/LETI-MINATEC, CEA-Grenoble, 38000 Grenoble, France ⁵Department of Materials Science & Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge, CB3 0FS

Silicon spin qubits are attractive candidates for solid state quantum computing applications, due to their long coherence times and compatibility with large scale manufacturing. Viable quantum computer implementations require scalable readout that is much faster than the qubit coherence time in order to implement error correction protocols. Gate based readout is a compact option which is capable of high fidelity measurements in short integration times. Here, we report a large dispersive interaction between the charge state of a double quantum dot in a silicon CMOS nanowire transistor and microwave photons in a lumped-element resonator formed by the co-integration of a superconducting inductor. We enhance the coupling by exploiting the large interdot lever arm of our asymmetric split-gate device, α=0.72, and achieve a coupling rate of g0/2π = 180 MHz. In the dispersive regime, the large coupling strength results in a frequency shift of the order of the resonator linewidth, the condition for maximum state visibility. We use this to demonstrate rapid gate-based readout of the charge state, with an SNR of 3.3 in 50 ns. We present preliminary frequency multiplexing results to demonstrate the scalability of our approach.