Robust coherent spin centers from stable azafullerene radicals entrapped in cycloparaphenylene rings.

Molecular entities with robust spin-1/2 are natural two-level quantum systems for realizing qubits and are key ingredients of emerging quantum technologies such as quantum computing. Here we show that robust and abundant spin-1/2 species can be created in the solid state from spin-active azafullerene CN cages supramolecularly hosted in crystals of [10]cycloparaphenylene ([10]CPP) nanohoops. This is achieved a two-stage thermally-assisted homolysis of the parent diamagnetic [10]CPP⊃(CN)⊂[10]CPP supramolecular complex. Upon cooling, the otherwise unstable CN˙ radical is remarkably persistent with a measured radical lifetime of several years. Additionally, pulsed electron paramagnetic resonance measurements show long coherence times, fulfilling a basic condition for any qubit manipulation, and observed Rabi oscillations demonstrate single qubit operation. These findings together with rapid recent advances on the synthesis of carbon nanohoops offer the potential to fabricate tailored cycloparaphenylene networks hosting CN˙ centers, providing a promising platform for building complex qubit circuits.