The observation of quantum interference of the emission from two separate nitrogen vacancy (NV) centers in diamond were reported. Taking advantage of optically induced spin polarization in combination with polarization filtering, a single transition within the zero-phonon line of the non-esonantly excited NV centers was isolated. The time-resolved two-photon interference contrast of this filtered emission reaches 66%. Furthermore, quantum interference from dissimilar NV centers tuned into resonance through the dc Stark effect was observed. These results pave the way towards measurement-based entanglement between remote NV centers and the realization of quantum networks with solid-state spins.

Two-Photon Quantum Interference from Separate Nitrogen Vacancy Centers in Diamond. H.Bernien, L.Childress, L.Robledo, M.Markham, D.Twitchen, R.Hanson: Physical Review Letters, 2012, 108[4], 043604