Description
Date depot: 1 octobre 2020
Titre: Continuous-variable quantum key distribution through atmospheric turbulence
Directrice de thèse:
Eleni DIAMANTI (LIP6)
Encadrant :
Jean-Marc CONAN (ONERA)
Encadrante :
Caroline LIM (ONERA)
Domaine scientifique: Sciences et technologies de l'information et de la communication
Thématique CNRS : Non defini
Resumé:
In the context of the future space-ground optical links and telecommunication networks, the issue of securing the transmission channel using quantum resources is currently under intense investigation around the world because of the promise it holds for security levels impossible to reach solely by classical means. Quantum key distribution (QKD) enables two parties to share a secret key used to encrypt and decrypt the exchanged messages with information-theoretic (unconditional) security. Among prevalent QKD technologies, continuous-variable quantum key distribution (CV-QKD) systems offer the major advantage of being compatible with standard telecommunication technologies, which could greatly facilitate and limit the cost of their deployment. Since the demonstration by the LIP6 team that such systems could be suitable for long-distance fibered communication on the ground, this technology has been the subject of intense developments worldwide.
In this PhD thesis, our main goal is to demonstrate the feasibility of CV-QKD between a Low Earth Orbit (LEO) satellite and the ground, considering the particularities of a turbulent transmission channel and solutions based on adaptive optics (AO). Estimating the impact of the coupled flux fluctuations on the key generation rate is essential and constitutes a major goal of the thesis. A first part of this work consists in a theoretical and modelling study. The aim is to develop a numerical tool enabling to relate directly the coupled flux statistics to the secret key generation rate. The PhD student will benefit both from the expertise of LIP6 in quantum information and cryptography and from the expertise of ONERA in wave front sensing and correction. Besides the LEO-to-ground scenario, different configurations of optical links may be considered: geostationary satellite-to-ground transmission, and free-space urban CV-QKD, for example between a building and a drone. Comparisons with discrete-variable (DV) QKD protocols will also be performed. The second part of the thesis will then be dedicated to the design and implementation of a first in-lab experimental demonstration. This would constitute a world first proof of concept and pave the way towards the development of space-based CV-QKD systems.
Doctorant.e: Marulanda Acosta Valentina