Germanium Vacancy in Diamond Quantum Memory Exceeding 20 ms

Negatively charged group-IV defects in diamond show great potential as quantum network nodes due to their efficient spin-photon interface. However, reaching sufficiently long coherence times remains a challenge. In this work, we demonstrate coherent control of germanium vacancy center (GeV) at millikelvin temperatures and extend its coherence time by several orders of magnitude to more than 20 ms. We model the magnetic and amplitude noise as an Ornstein-Uhlenbeck process, reproducing the experimental results well. The utilized method paves the way to optimized coherence times of group-IV defects in various experimental conditions and their successful applications in quantum technologies.Received 27 July 2023Accepted 29 November 2023DOI:https://doi.org/10.1103/PhysRevLett.132.026901© 2024 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasColor centersQuantum coherence & coherence measuresQuantum communication, protocols & technologyQuantum measurementsQuantum memoriesVacanciesTechniquesCoherent controlQuantum Information, Science & TechnologyAtomic, Molecular & Optical