  Point-defects in wide bandgap semiconductors are promising candidates for
future applications that necessitate quantum light sources. Recently,
defect-based single photon sources have been observed in ZnO that are very
bright and remain photoactive from 4.5 K to room temperature. Despite several
investigations, the structure and electronic states of these emitters remain
unknown. In this work, we establish a procedure to distinguish a Z dipole from
an XY dipole when studying quantum emitters that are randomly oriented. Our
cryogenic and room temperature polarization measurements collectively establish
that these unidentified ZnO quantum emitters have a Z dipole. We show that the
associated absorption and emission dipoles are parallel within experimental
uncertainty for all 32 individuals studied. Additionally, we apply group theory
and find that assuming the defect symmetry belongs to a point-group relevant to
the ZnO wurtzite lattice, the ground and excited states are orbital singlets.
These results are a significant step in identifying the structure and
electronic states of defect-based single photon sources in ZnO.
