Controling the fluorescence of semiconductor nanocrystals with plamonic structures for the generation of quantum states of light – QDOTICS

QDOTICS aims at the generation of quantum states of light based on original nanocrystals (NCs) coupled to innovative plasmonic structures. First, we will design single photon sources which do not blink. Their performances in terms of collected and detected photons rate (20%), polarization rate (90%) and cycling rate (0.2 GHz) are consistent with a realistic quantum cryptography device. CdSe core NCs surrounded by a thick CdS shell will be used. The thick shell prevents blinking and fluorescence quenching when NCs are coupled to plasmonic structures. In this part, the project relies also on original metallic structures supporting hybrid plasmon modes resulting from the strong coupling of localized and delocalized plasmons.
In the field of quantum optics, the coupling of CdSe/CdS NCs to metallic structures opens the possibility to achieve more complex states of light at the root of many protocols of quantum information. Using hybrid plasmons or plasmon of semi-continuous films, we will look to produce photons whose indistinguishability is sufficient to observe the effect of coalescence. An originality of QDOTICS is to obtain this effect by making time-resolved experiments. Coalescence above 80% is expected.
The last objective is to generate pairs of polarization-entangled photons. NCs are well-known single photon emitters: due to the Auger effect, multiexcitonic states recombine non radiatively and only the last pair decays radiatively resulting in the emission of a single photon. In the case of CdSe/CdS NCs with the thickest shell, a very important delocalization of the charge carriers leads to a strong reduction of Auger processes efficiency. To produce entangled photons, we will design specific DLSPPW (Dielectric-Loaded Surface Plasmon Polariton Waveguide). Our goal is to obtain polarization-entangled photons violating Bell’s inequalities of at least 10%.