Long distance quantum implementations would strongly benefit from the use of photons as carriers of information. In both free-space connections, as well as fibre-based networks, the use of light within telecommunication bands will have various advantages. As exemplary in glass fibres, the backbone of our communication infrastructures, the use of quantum light in the so-called telecom O- (centred around 1310 nm) and C-band (centred around 1550 nm) would have the advantages of experiencing minimal photon wavepacket dispersion and absorption. Semiconductor quantum dots are considered as very appealing sources of quantum light, in particular the systems based on the GaAs material platform. We will discuss the techniques that can be employed to realize In(Ga)As/GaAs quantum dots emitting in the telecom O- and C-bands [1]. Furthermore, we will discuss advanced fabrication techniques [2] and optical resonators that can be employed to enhance the source brightness and performances, even operating at liquid nitrogen temperature [3]. Finally, In(Ga)As QDs emitting in the telecom C-band will be integrated into circular Bragg grating cavities. Thanks to Purcell enhancement, a fibre-coupled single-photon count rate of 13.9 MHz is observed (excitation rep. rate of 228 MHz, first-lens collection efficiency ~17%), with a multi-photon contribution as low as g(2)(0) = 0.0052. Operation up to 40K will be discussed [4]. [1] S. L. Portalupi, et al., Semicond. Sci. Technol. 34, 053001 (2019) [2] M. Sartison, et al., Appl. Phys. Lett. 113, 032103 (2018) [3] S. Kolatschek, et al., Nano Lett. 21, 7740 (2021) [4] C. Nawrath, et al., ArXiv 2207.12898 (2022).

Simone Luca Portalupi received his Ph.D. in physics from the University of Pavia, Italy in 2012, working on silicon photonics and spectroscopy of nanostructures and fabrication of photonic crystal cavities (last topic in St. Andrews, UK). As post-doctoral fellow (CNRS in Paris, France), he researched on semiconductor quantum dots (III–V platform), cavity quantum electrodynamics, and deterministic nanofabrication techniques. Currently, he is group leader of the quantum optics group at the IHFG,University of Stuttgart, Germany. His research focuses on quantum optics with semiconductor quantum dots, integrated quantum photonics, hybrid quantum systems, long-distance quantum communication and implementation of advanced nanofabrication techniques.