Abstract

The field of quantum communication in general, and quantum key distribution in particular, has seen a remarkable development in recent years. Nowadays, national and international quantum communication networks are built, partly involving satellites, and even commercial QKD devices are available. Achieving these technological milestones requires overcoming numerous challenges, from the development of mathematical security proofs to the fabrication of quantum sources and detectors, the installation of fibre networks, and even launching satellites into orbit. However, despite these significant technological achievements, fundamental theoretical questions remain. To truly guarantee security against an all-powerful adversary, as quantum cryptography promises, we must address deeper theoretical issues. In this talk, I will begin by providing an overview of the current challenges in QKD . I will then delve into a key foundational question underlying the security of all QKD protocols: Where is information localised in spacetime?