We study decoherence of a single nitrogen-vacancy (NV) center induced by the ${}^{13}\mathrm{C}$ nuclear spin bath of diamond. By comparing Hahn-Echo experiments on single and double-quantum transitions of the NV triplet ground state we demonstrate that this bath can be tuned into two different regimes. At low magnetic fields, the nuclei behave as a quantum bath which causes decoherence by entangling with the NV central spin. At high magnetic fields, the bath behaves as a source of classical magnetic field noise, which creates decoherence by imprinting a random phase on the NV central spin.

• Received 27 July 2011

DOI:https://doi.org/10.1103/PhysRevLett.108.200402