Quantum state readout is a key requirement for a successful qubit platform. In this work, we demonstrate a high-fidelity quantum state readout of a V2 center nuclear spin based on a repetitive readout technique. We demonstrate up to 99.5% readout fidelity and 99% for state preparation. Using this efficient readout, we initialize the nuclear spin by measurement and demonstrate its Rabi and Ramsey nutation. Finally, we use the nuclear spin as a long-lived memory for quantum sensing application of a weakly coupled diatomic nuclear-spin bath.
Funding Agencies|European Commission through the QuantERA project InQuRe [731473, 101017733]; German ministry of education and research for the project InQuRe (BMBF) [16KIS1639K]; European Commission for the Quantum Technology Flagship project QIA [101080128, 101102140]; German ministry of education and research for the project QR.X (BMBF) [16KISQ013]; Baden-Wrttemberg Stiftung for the project SPOC; project Spinning (BMBF) [13N16219]; German Research Foundation (DFG) [GRK2642]; Swedish Research Council under VR [2020-05444]; Knut and Alice Wallenberg Foundation [KAW 2018.0071]