At the beginning of my third year at ESPCI Paris, I did a 6-month engineering internship in Japan at the telecommunication company Nippon Telegraph and Telecom (NTT), one of the few companies with a research laboratory specialized in fundamental physics: the Basic Research Laboratories.

The goal of NTT is to realize photonic circuits, where photons replace electrons, making circuits less sensitive to the heat released by usual electronic processors, and allowing a higher data transfer rate. I discovered there the field of quantum nanophotonics by working on the generation of polarization-entangled pairs of photons on a silicon photonic circuit.

By using two silicon with waveguide photon pair sources, connected by an ultra-small silicon wire polarization rotator, we generated Bell-type polarization-entangled photon pairs with high fidelity.

In this project, we showed the quality of the produced entanglement, still cited as one of the best sources of entangled photon pairs in semiconductors. This work was an important contribution for the fabrication of a commercial, telecom-compatible quantum source.

Published in the journal Scientific Reports of the Nature group, this work has been very well received in scientific journals, as these topics are at the heart of the concerns the photonic telecommunications community but also are of interest to fundamental physicists. This paper also received the NTT BRL Director Best Paper Award in early 2013, showing the importance of this work for the company and the real technological potential of those quantum states.