Given its potential for integration and scalability, silicon is likely to be a key platform for large-scale quantum technologies. Individual artificial atoms, formed by impurities, have emerged as a promising solution for silicon-based integrated quantum circuits. However, single qubits featuring an optical interface, which is needed for long-distance information exchanges, have never been studied for quantum technology applications.
In the first part of the talk, I will introduce light-emitting centers that were initially found after the irradiation of silicon. A center known as the G-center, composed of two carbon atoms bound to the same silicon atom, has been extensively studied in the ’60s due to its relatively high brightness . We performed time, and temperature-dependent photoluminescence measurements of an ensemble of color centers in annealed-heavily carbon implanted commercial silicon followed by proton irradiation. We revealed the fast recombination dynamics of the exited state  and a slower decay time due to the presence of an excited metastable state potentially originating from a triplet spin state.
In the second part, I will report the isolation of single optically active point defects from low fluence carbon implanted silicon. These artificial atoms exhibit a bright, linearly polarized single-photon emission with a quantum efficiency of the order of unity . This single-photon emission occurs at telecom wavelengths suitable for long-distance propagation in optical fibers. We also report the detection of individual emitters in silicon belonging to seven different families of optically active point defects .
Our results show that silicon can accommodate single isolated optical point defects despite a small bandgap (1.1 eV). This discovery paves the way for quantum optical networks and quantum photonic chips using fully integrated all-silicon devices.
 L. W. Song, et al., Phys. Rev. B 42, 5765
 C. Beaufils, W. Redjem et al. Phys. Rev. B 97, 035303
 Redjem, W., Durand, A., Herzig, T., et al. Single artificial atoms in silicon emitting at telecom wavelengths. Nat Electron 3, 738–743 (2020)
 A. Durand, Y. Baron, W. Redjem, et al. Rev. Lett. 126, 083602
Dr. Walid Redjem completed his master’s degree in quantum devices from Ecole normale Superieure and the University of Paris Diderot in 2016. He then joined the University of Montpellier in France as a Ph.D. student, working on silicon-integrated quantum light sources. He discovered single artificial atoms in silicon that emit single photons in the telecommunication wavelengths. He is currently a postdoctoral fellow in Boubacar Kante’s group at the University of California, Berkeley, in the EECS department. He is developing new types of classical and quantum light sources based on topological photonics. He is the co-inventor of the scalable open-Dirac surface-emitting laser.