A defect in diamond with long spin relaxation times at room temperature

Spin defects in diamond are promising platforms for quantum sensing and quantum information processing. However, very few solid-state defects show spin properties comparable to nitrogen vacancy centers in diamond, especially at elevated temperatures. Here, we characterize the WAR5 defect ^[1] using pulsed electron spin resonance and observe long spin relaxation (T₁) and coherence (T₂) times. The T₁ is 14.38 min at 4 K and 0.97 ms at room temperature. The T₂ is observed to be 245 μs at 4 K, which we determine to be limited by P1 centers in the sample. Using dynamical decoupling, we extend T₂ to 6.49 ms. Furthermore, we demonstrate wavelength-dependent optical spin polarization in the blue region of the visible spectrum and point out potential zero-phonon line candidates in photoluminescence. Based on electronic structure calculations and the growth chemistry of the diamond, we assign the defect as the neutral oxygen vacancy center.

[1] B. L. Cann, Ph.D. thesis, University of Warwick (2009).