Projet de recherche doctoral numero :4770


Date depot: 1 janvier 1900
Titre: Beyond-QKD continuous-variable quantum cryptographic protocols
Directrice de thèse: Eleni DIAMANTI (LIP6)
Domaine scientifique: Sciences et technologies de l'information et de la communication
Thématique CNRS : Non defini

Resumé: A central application of quantum information science is quantum key distribution (QKD), which allows two parties to share a secret key that can be subsequently used for message exchange, even in the presence of eavesdroppers with unlimited power. This is impossible by classical means. Continuous-variable (CV) QKD, where the key information is encoded on the quadratures of the electromagnetic field, is particularly appealing from a practical point of view in that it only requires off-the-shelf telecom components as we have shown in fibre-optic long-distance experiments in our laboratory [Nature Photon. 7, 378 (2013)]. There is however a wealth of two-party cryptographic protocols beyond QKD. Prominent examples include coin flipping, bit commitment, and oblivious transfer, which have numerous applications in communication networks, as well as quantum money. Some promising studies in the discrete-variable regime, i.e., using single-photon encoding and detection techniques, have been performed recently, including in our group; see [Nature Commun. 5, 3717 (2014)] for quantum coin flipping and [quant-ph arXiv:1705.01428] for quantum money. In this doctoral project, we propose to study such quantum cryptographic protocols in the continuous-variable framework, based on security proof techniques employed in CV-QKD. A difficulty found in some of these primitives is that they cannot be achieved perfectly even with quantum resources. This can be the case, however, if we make reasonable assumptions about the technology available to an adversary, for instance, assuming that their quantum memories are necessarily noisy. These primitives can then be proven to be secure in the so-called “noisy storage model”. This opens the way to a large variety of protocols and implementations, and it becomes interesting to investigate whether continuous-variable protocols can lead to easier implementations, at the price of a more involved security analysis, as is the case for QKD. First steps in this direction have in fact been taken [quant-ph arXiv: 1509.09123] while it is in general possible to recover information theoretic security if imperfect protocols can be accepted.

Doctorant.e: Ghorai Shouvik