  Hexagonal boron nitride (hBN) has recently gained attention as a solid state
host of quantum emitters. However, hBN emitters reported to date lack the
properties needed for their deployment in scalable quantum technologies. Here
we employ spectral hole burning spectroscopy and resonant polarization
measurements to observe nearly-coherent hBN quantum emitters, both as singles
and in ensembles, with three discrete polarization axes indicative of a C2v
symmetry defect. Our results constitute an important milestone towards the
implementation of hBN quantum emitters in integrated quantum photonics.
