Si hole qubits in a cQED architecture*

With the recent development of spin-orbit qubit based on holes in silicon and in germanium, it is nowadays conceivable to use a microwave photon as a « quantum bus » for long distance spin-orbit qubits interaction. The strong spin/photon coupling has been achieved using an engineered spin-orbit interaction with electron spins in silicon and long-range microwave mediated interactions have also been demonstrated recently. Our goal here is to use the intrinsic spin-orbit term in the valence band of silicon to achieve this coherent spin/photon coupling.

Here we present our co-integration project: a CMOS silicon spin qubit embedded in a high-impedance NbN superconducting microwave resonator. We demonstrated high quality factors coplanar waveguide resonators from a 10nm NbN film on silicon oxide. From a kinetic inductance of 192pH/sq, we fabricated high-impedance resonators up to 4.1kΩ with Qi>1e4 in the single photon regime but also in magnetic fields for the many photons regime. We then co-integrated these resonators on an industrially processed wafer with p-type CMOS silicon transistors. We performed charge and spin readout experiments in the cQED architecture which paves the way to the long-range coupling of Si hole spin qubits.