  Two dimensional materials are becoming increasingly popular as a platform for
studies of quantum phenomena and for the production of prototype quantum
technologies. Quantum emitters in 2D materials can host two level systems that
can act as qubits for quantum information processing. Here, we characterize the
behavior of position-controlled quantum emitters in hexagonal boron nitride at
cryogenic temperatures. Over two dozen sites, we observe an ultra-narrow
distribution of the zero phonon line at ~436 nm, together with strong linearly
polarized emission. We employ resonant excitation to characterize the emission
lineshape and find spectral diffusion and phonon broadening contribute to
linewidths in the range 1-2 GHz. Rabi oscillations are observed at a range of
resonant excitation powers, and under 1 ${\mu}$W excitation a coherent
superposition is maintained up to 0.90 ns. Our results are promising for future
employment of quantum emitters in hBN for scalable quantum technologies.
