Today, optical quantum technologies are limited both by the low efficiency of heralded single-photon sources and by the probabilistic operation of two-photon gates. Deterministic sources and gates can in principle be obtained making use of the single-photon sensitivity of an atomic transition. In this context, artificial atoms in the form of semiconductor quantum dots have emerged as a promising system to boost optical quantum technologies, offering the potential of integration and scalability. However, this requires an ideal atom-photon interface, where the quantum dot interacts with only a single mode of the optical field and is isolated from any source of decoherence.
In this seminar, I will present our progress along this research line. I will explain how near optimal atom-photon interfaces are obtained by positioning a semiconductor quantum dot in a microcavity . The quantum dot is shown to interact with a single mode of the optical field and is largely protected from all sources of decoherence, including phonons [2,3]. These technological developments have allowed the fabrication of bright solid-state sources of single-photon with single photon purity and indistinguishability exceeding 99%. The brightness of the sources exceeds by a factor 20 the one of currently used sources . We have also made progresses toward the development of deterministic two-photon gates, with devices performing as nonlinear switches at the single-photon level, converting a coherent pulse into a highly non-classical light wave-packet .
 A. Nowak et al., Nature Communications 5, 3240 (2014)
 V. Giesz et al., Nature Communications 7, 11986 (2016)
 N. Somaschi, et al. Nature Photonics 10, 340 (2016).
 T. Grange et al., Physical Review Letters 118, 253602 (2017)
 L. De Santis et al, Nature Nanotechnology 12, 663–667 (2017)
A coffee break will be served at 11h00. The seminar will be given in English.