Supervision : Eleni DIAMANTI

Design and implementation of protocols for quantum photonic networks

The thesis is situated in the field of quantum information and in particular quantum communication networks. The goal of such networks is to provide fundamentally new technology by enabling quantum communication between distant parties, eventually leading to a Quantum Internet. Such networks allow the transmission of quantum bits (qubits) over long distances in order to solve tasks that are provably impossible for any classical communication network. Possibly the most well-known protocol is quantum key distribution, which enables secure communication; but, quantum communication is also known to offer significant advantages for many other tasks. Moreover, the ability to generate entanglement between distant sites provides scientists with a unique new platform for fundamental studies of nature. Photonic resources will be at the heart of the quantum network infrastructure as they provide the optimal means for communication between the network nodes. In this thesis, we will develop a photonic experimental platform tailored to the implementation of quantum communication protocols, with the goal of demonstrating a quantum advantage in security in a network environment. Our basic resource will be entangled photon generation and distribution between two or more parties. This will be used for the implementation of tasks such as verified anonymous quantum message transmission and authenticated quantum teleportation, which are prominent cases of useful protocols where a quantum advantage can be rigorously shown as our group has proven previously. To address the stringent constraints imposed by the theoretical analysis of these protocols to show such an advantage, the experiments performed in the thesis will test new techniques for improving the efficiency and the quality of the generated quantum states and of the single-photon detection process relying on superconducting nanowire devices. They will aim at surpassing the state of the art both for our experimental resources and for the demonstrated applications. We expect that the outcome of this thesis will provide photonic devices and systems readily useful as building blocks in quantum networks with a demonstrated operation and successful performance for well-defined tasks in this context