# Large dispersive interaction between a CMOS double quantum dot and microwave photons

David J. Ibberson, Theodor Lundberg, James A. Haigh, Louis Hutin, Benoit Bertrand, Sylvain Barraud, Chang-Min Lee, Nadia A. Stelmashenko, Jason W. A. Robinson, Maud Vinet, M. Fernando Gonzalez-Zalba, Lisa A. Ibberson

Research output: Contribution to journalArticle (Academic Journal)peer-review

## Abstract

We report a large coupling rate, $g_0/(2\pi)=183$ MHz, between the charge state of a double quantum dot in a CMOS split-gate silicon nanowire transistor and microwave photons in a lumped-element resonator formed by hybrid integration with a superconducting inductor. We enhance the coupling by exploiting the large interdot lever arm of an asymmetric split-gate device, $\alpha=0.72$, and by inductively coupling to the resonator to increase its impedance, $Z_\text{r}=560$ $\Omega$. In the dispersive regime, the large coupling strength at the DQD hybridisation point produces a frequency shift comparable to the resonator linewidth, the optimal setting for maximum state visibility. We exploit this regime to demonstrate rapid gate-based readout of the charge degree of freedom, with an SNR of 3.3 in 50 ns. In the resonant regime, the fast charge decoherence rate precludes reaching the strong coupling regime, but we show a clear route to spin-photon circuit quantum electrodynamics using hybrid CMOS systems.
Original language English 020315 PRX Quantum 2 https://doi.org/10.1103/PRXQuantum.2.020315 Published - 5 May 2021

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