Non-Classical States of Light for Device-Independent Quantum Key Distribution

Communication stands as one of the most precious faces of human interaction, forming the bedrock upon which relationships, knowledge exchange and, societal progress are established. However, certain communication contexts demand confidentiality and, in this context, cryptographics protocols become a must. In these protocols, the communicating parties encrypt, transmit and decrypt their messages using specific algorithms to ensure information remains confidential from an eavesdropper. For the encryption, the use of a key becomes crucial, that is, a secret method used by the communicating parties to encode and decode their message. Quantum key distribution leverages the principles of quantum mechanics to create keys that are provably secure. However, cobventional quantum key distribution relies on assumptions about the devices used by the communicating parties to generate the key. To address this vulnerability, device independent quantum key distribution emerges as a critical approach, though its implementation demands stringent practical requirements. In this chapter, we study how through the use of non-classical states of light, one can relax this requirements, and investigate whether the use of high-dimensional systems could be useful in this regard.