The unpolarized spin environment surrounding a central spin qubit is typically considered as an incoherent source of dephasing, however, precise characterization and control of the spin bath can yield a resource for storing and sensing with quantum states. In this work, we use nitrogen-vacancy (NV) centers in diamond to measure the coherence of optically-dark paramagnetic nitrogen defects (P1 centers) and detect coherent interactions between the P1 centers and a local bath of 13C nuclear spins. The dipolar coupling between the P1 centers and 13C nuclear spins is identified by signature periodic collapses and revivals in the P1 spin coherence signal. We then demonstrate, using a range of dynamical decoupling protocols, that the probing NV centers and the P1 spins are coupled to independent ensembles of 13C nuclear spins. Our work illustrates how the optically-dark P1 spins, despite being unpolarized, can be used to extract information from their local environment and offers new insight into the interactions within a many-body system.
@article{arxiv.2311.18181,
title = {Observing coherence in an incoherent paramagnetic nitrogen spin bath},
author = {R. M. Goldblatt and A. M. Martin and A. A. Wood},
journal= {arXiv preprint arXiv:2311.18181},
year = {2023}
}