Coherent coupling of a superconducting flux qubit to an electron spin ensemble in diamond

Hybrid quantum devices, in which a superconducting qubit is coupled to a dedicated quantum memory based on natural atomic or molecular ensembles, are promising for quantum information processing. However, it has not been clear whether the required strength of coherent quantum coupling could be achieved. Zhu et al. improve the prospects of such technology, demonstrating coherent strong coupling and exchange of a quantum of energy between a superconducting flux qubit and an ensemble of electron spins associated with nitrogen-vacancy defects in diamond.