Highly Coherent Nitrogen‐Vacancy Centers in Diamond via Rational High‐Pressure and High‐Temperature Synthesis and Treatment

Abstract The high‐pressure and high‐temperature (HPHT) diamonds with well‐controlled defects and low stress offer an ideal host substrate for the fields of quantum information science; however, fabrication of quantum‐grade HPHT diamonds remains a pressing challenge. Here, a major advance in generating highly coherent nitrogen‐vacancy (NV) centers, a promising spin defect in diamonds, via tailored HPHT synthesis and postgrown annealing treatment is reported. The resulting well‐dispersed single NV − centers in type‐IIa diamonds exhibit long spin coherence times comparable to that of the reported chemical vapor deposition diamonds. Moreover, high‐density NV − ensembles in 〈100〉‐grown type‐Ib diamonds with superb zero‐phonon lines considerably sharper than those of native NV − centers in as‐grown diamonds, together with low splitting of resonances are produced. These findings demonstrate a superior synthesis and optimization protocol for creating high‐quality NV − centers avoiding lattice damage in diamond to meet the stringent requirements for a wide range of emerging quantum technologies.