The entanglement of microwave photons and spin qubits in silicon represents an important step forwards for quantum information processing using semiconductor quantum dots. Such hybrid spin circuit quantum electrodynamics experiments have been achieved by delocalizing spins in a double quantum dot with spin–orbit interactions to produce a flopping-mode spin qubit with a substantial electric dipole moment. Unfortunately, demonstrations of these qubits have not shown the coherence properties necessary for them to be used as practical single qubits. Here we present a flopping-mode hole-spin qubit in a silicon nanowire coupled to a high-impedance niobium nitride microwave read-out resonator. We report Rabi frequencies exceeding 100 MHz with coherence times in the microsecond range, resulting in a single-gate quality factor of 380. This establishes the speed and reliability of flopping-mode spin qubits. Moreover, using the large frequency tunability of the qubit, we find that radiative decay is the main relaxation channel in our experiment and argue that photon shot noise is the main source of dephasing. These results indicate that optimized microwave engineering can unlock the potential of flopping-mode spin qubits in hybrid circuit quantum electrodynamics architectures and offer a scalable and robust platform for fast and coherent spin qubits with strong coupling to microwave photons.

Hybrid superconductor-semiconductor structures attract increasing attention owing to a variety of potential applications in quantum computing devices. They can serve the realization of topological superconducting systems as well as gate-tunable superconducting quantum bits. Here, we combine a SiGe/Ge/SiGe quantum-well heterostructure hosting high-mobility two-dimensional holes and aluminum superconducting leads to realize prototypical hybrid devices, such as Josephson field-effect transistors (JoFETs) and superconducting quantum interference devices (SQUIDs). We observe gate-controlled supercurrent transport with Ge channels as long as one micrometer and estimate the induced superconducting gap from tunnel spectroscopy measurements. Transmission electron microscopy reveals the diffusion of Ge into the Al contacts, whereas no Al is detected in the Ge channel.