Chromium single-photon emitters in diamond fabricated by ion implantation

Controlled fabrication and identification of bright single-photon emitters is at the heart of quantum optics. Here we demonstrate controlled engineering of a chromium bright single-photon source in bulk diamond by ion implantation. The Cr center has fully polarized emission with a zero-phonon line centered at 749 nm, full width at half maximum of 4 nm, an extremely short lifetime of ~1 ns, and a count rate of 0.5×10⁶ counts/s. By combining the polarization measurements and the vibronic spectra, a model of the center has been proposed consisting of one interstitial chromium atom with a transition dipole along one of the $⟨100⟩$ directions.