  Single color centers in solid have emerged as promising physical platforms
for quantum information science. Creating these centers with excellent quantum
properties is a key foundation for further technological developments. In
particular, the microscopic understanding of the spin bath environments is the
key to engineer color centers for quantum control. In this work, we propose and
demonstrate a distinct high-temperature annealing (HTA) approach for creating
high-quality nitrogen vacancy (NV) centers in implantation-free diamonds.
Simultaneously using the created NV centers as probes for their local
environment we verify that no damage was microscopically induced by the HTA.
Nearly all single NV centers created in ultra-low-nitrogen-concentration
membranes possess stable and Fourier-transform-limited optical spectra.
Furthermore, HTA strongly reduces noise sources naturally grown in ensemble
samples, and leads to more than three-fold improvements of decoherence time and
sensitivity. We also verify that the vacancy activation and defect reformation,
especially H3 and P1 centers, can explain the reconfiguration between spin
baths and color centers. This novel approach will become a powerful tool in
vacancy-based quantum technology.
