Identity Test of Single <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msup><mml:mrow><mml:mi>NV</mml:mi></mml:mrow><mml:mrow><mml:mo>?</mml:mo></mml:mrow></mml:msup></mml:mrow></mml:math> Centers in Diamond at Hz-Precision Level

Atomic-like defects in solids are not considered to be identical owing the imperfections of host lattice. Here, we found that even under ambient conditions, negatively charged nitrogen-vacancy (NV$^-$) centers diamond could still manifest at Hz-precision level, corresponding a 10$^{-7}$-level relative precision, while lattice strain can destroy identity by tens Hz. All parameters involved NV$^-$-$^{14}$N Hamiltonian determined formulating six nuclear frequencies 10-mHz-level precision and measuring them Hz-level precision. The most precisely measured parameter, $^{14}$N quadrupole coupling $P$, is given -4945754.9(8) Hz, whose improved nearly four orders magnitude compared with previous measurements. We offer an approach for performing measurements deepening our understandings NV as well other solid-state defects. Besides, these high-precision results imply potential application robust integrated atomic-like clock based on ensemble centers.