Dispersively Probed Microwave Spectroscopy of a Silicon Hole Double Quantum Dot

Owing to ever increasing gate fidelities and to a potential transferability to industrial CMOS technology, silicon spin qubits have become a compelling option in the strive for quantum computation. In a scalable architecture, each spin qubit will have to be finely tuned and its operating conditions accurately determined. In view of this, spectroscopic tools compatible with a scalable device layout are of primary importance. Here we report a two-tone spectroscopy technique providing access to the spin-dependent energy-level spectrum of a hole double quantum dot defined in a split-gate silicon device. A first gigahertz-frequency tone drives electric dipole spin resonance enabled by the valence-band spin-orbit coupling. A second lower-frequency tone (approximately 500MHz) allows for dispersive readout via rf-gate reflectometry. We compare the measured dispersive response to the linear response calculated in an extended Jaynes-Cummings model and we obtain characteristic parameters such as g factors and tunnel and spin-orbit couplings for both even and odd occupation.

Read more in Ezzouch et al. PhysRevApplied 16 034031 (2022)

Magnetic field resilient high kinetic inductance superconducting niobium nitride coplanar waveguide resonators

High quality superconducting microwave resonators are at the heart of circuit quantum electrodynamics experiments. Here, we report on simple to fabricate coplanar waveguide resonators fabricated from a thin film of NbN. Using the large kinetic inductance of NbN, we achieve characteristic impedances of up to 4 kOhm. These large impedances, paired with the excellent magnetic field resilience (see figure), makes these resonators perfectly suited for cQED experiments requiring magnetic fields such as spin qubits.

Read more in Yu et al. APL 118 054001 (2021)