With the miniaturization of electronic devices, the semiconductor industry has to deal with complex technical barriers and is forced to introduce novel and innovative concepts. LONGSPIN is exactly in line with this new paradigm as it diverts CMOS technology to explore a new path for quantum information processing with spin quantum bits (qubits). Concretely the project developed ultra-fast and ultra-coherent spin-orbit qubits based on silicon CMOS nanowire transistors. While spins are excellent qubits, their long-range coupling remains a challenge to tackle towards complex quantum computing architectures. LONGSPIN started to take up this challenge with the vision to use microwave photons as quantum mediators between spin-orbit qubits. To the end, LONGSPIN used a unique approach leveraging a standard silicon-on-insulator CMOS process for the implementation of the qubits co-integrated with microwave resonators made from disordered superconductor. With these new chips combining two worlds of the solid-states physics i.e. semiconductor quantum dot device and microwave quantum electrodynamics, LONGSPIN realized and studied the quantum coupling between CMOS spin qubits and microwave photons.
At the end of this five yearlong research project, a CMOS quantum toolkit with optimized designs and materials for fast and coherent qubits is available with a profound understanding of the physical limitations to coherence and qubit gate fidelity of hole spin in silicon. Moreover, LONGSPIN results open the path towards spin circuit electrodynamics coupling silicon hole spin qubits to microwave photons promising new capabilities for quantum information processing ranging from spin qubit readout to long distance spin-spin entanglement.
