Coupling single spins to superconducting circuits

Coupling single spins to superconducting circuits represents a powerful route toward scalable hybrid quantum technologies. At the intersection of quantum information processing, nanoscale sensing, and condensed matter physics, this emerging research direction aims to unite the best qualities of two very different quantum systems. Spins—whether associated with electrons, nuclei, or defects—are among the most coherent quantum systems known, with coherence times that can exceed seconds. However, their weak interaction with electromagnetic fields makes them notoriously difficult to control and read out individually. Superconducting circuits, on the other hand, offer exceptional control, scalability, and strong coupling to electromagnetic fields, but they tend to suffer from shorter coherence times. Bridging these two platforms can yield hybrid quantum systems that harness the best of both worlds: the long-lived quantum memory of spins and the fast, flexible control of superconducting devices. An additional key motivation for integrating single spins with superconducting circuits is the ability to perform spectroscopy at the nanoscale, enabling the investigation of quantum systems with unprecedented spatial and energy resolution. Spins, due to their sensitivity to magnetic and electric fields, serve as exquisite local probes of their environment. This synergy not only offers powerful tools for probing quantum phenomena at the nanoscale but also opens the possibility of hybrid quantum processors combining long-lived spin states with fast superconducting-circuit control.