  Defects in wide-bandgap semiconductors are promising qubit candidates for
quantum communication and computation. Epitaxially grown II-VI semiconductors
are particularly promising host materials due to their direct bandgap and
potential for isotopic purification to a spin-zero nuclear background. Here, we
show a new type of single photon emitter with potential electron spin qubit
based on Cl impurities in ZnSe. We utilize a quantum well to increase the
binding energies of donor emission and confirm single photon emission with
short radiative lifetimes of 192 ps. Furthermore, we verify that the ground
state of the Cl donor complex contains a single electron by observing
two-electron satellite emission, leaving the electron in higher orbital states.
We also characterize the Zeeman splitting of the exciton transition by
performing polarization-resolved magnetic spectroscopy on single emitters. Our
results suggest single Cl impurities are suitable as single photon source with
potential photonic interface.
