Understanding the limits to the spin-coherence of the nitrogen-vacancy (NV) center in diamond is vital to realizing the full potential of this quantum system. We show that relaxation on the ∣ms=−1⟩↔∣ms=+1⟩ transition occurs approximately twice as fast as relaxation on the ∣ms=0⟩↔∣ms=±1⟩ transitions under ambient conditions in native NVs in high-purity bulk diamond. The rates we observe are independent of NV concentration over four orders of magnitude, indicating they are limited by spin-phonon interactions. We find that the maximum theoretically achievable coherence time for an NV at 295 K is limited to 6.8(2) ms. Finally, we present a theoretical analysis of our results that suggests Orbach-like relaxation from quasilocalized phonons or contributions due to higher-order terms in the spin-phonon Hamiltonian are the dominant mechanism behind ∣ms=−1⟩↔∣ms=+1⟩ relaxation, motivating future measurements of the temperature dependence of this relaxation rate.
@article{arxiv.2007.11529,
title = {State-dependent phonon-limited spin relaxation of nitrogen-vacancy centers},
author = {M. C. Cambria and A. Gardill and Y. Li and A. Norambuena and J. R. Maze and S. Kolkowitz},
journal= {arXiv preprint arXiv:2007.11529},
year = {2021}
}