  Nitrogen vacancy (NV-) color centers in diamond are a prime candidate for use
in quantum information devices, owing to their spin-1 ground state,
straightforward optical initialization and readout, and long intrinsic
coherence times in a room-temperature solid. While the 13C nuclear spin is
often a dominant source of magnetic noise, we observe transitions between
electron-nuclear hyperfine states of NV- centers in 99% 13C diamond that are
robust to decoherence. At magnetic field strengths ranging from 550 - 900 G,
these transitions are observable by optically detected magnetic resonance
(ODMR), and exhibit linewidths narrowed by factors as high as ~130 at room
temperature over typical electron-type transitions observed from this spin
system. We anticipate the use of these decoherence-protected transitions, in
combination with dynamical decoupling methods, for storage of quantum
information.
