Coherent Control of a Long-Lived Nuclear Memory Spin in a Germanium-Vacancy Multi-Qubit Node
Nick Grimm, Katharina Senkalla, Philipp J. Vetter, Jurek Frey, Prithvi Gundlapalli, Tommaso Calarco, Genko T. Genov, Matthias M. Müller, Fedor Jelezko · Physical Review Letters · 2025
The ability to process and store information on surrounding nuclear spins is a major requirement for group-IV color center-based repeater nodes. We demonstrate coherent control of a ^{13}C nuclear spin strongly coupled to a negatively charged germanium-vacancy center in diamond with coherence times beyond 2.5 s at mK temperatures, which is the longest reported for group-IV defects. Detailed analysis allows us to model the system's dynamics, extract the coupling parameters, and characterize noise. We estimate an achievable memory time of 18.1 s with heating limitations considered, paving the way to successful applications as a quantum repeater node.