"Electronic spins are usually detected by their interaction with electromagnetic fields at microwave frequencies. Since this interaction is very weak, only large ensembles of spins can be detected. In circuit quantum electrodynamics (cQED) on the other hand, artificial superconducting atoms are made to interact strongly with microwave fields at the single photon level, and quantum-limited detection of few-photon microwave signals has been developed.The goal of this project is to apply the concepts and techniques of cQED to the detection and manipulation of electronic and nuclear spins, in order to reach a novel regime in which a single electronic spin strongly interacts with single microwave photons. This will lead to1) A considerable enhancement of the sensitivity of spin detection by microwave methods. We plan to detect resonantly single electronic spins in a few milliseconds. This could enable A) to perform electron spin resonance spectroscopy on few-molecule samples B) to measure the magnetization of various nano-objects at millikelvin temperatures, using the spin as a magnetic sensor with nanoscale resolution.2) Applications in quantum information science. Strong interaction with microwave fields at the quantum level will enable the generation of entangled states of distant individual electronic and nuclear spins, using superconducting qubits, resonators and microwave photons, as “quantum data buses” mediating the entanglement. Since spins can have coherence times in the seconds range, this could pave the way towards a scalable implementation of quantum information processing protocols.These ideas will be primarily implemented with NV centers in diamond, which are electronic spins with properties suitable for the project."