Harnessing multi-partite entanglement in quantum networks

The field of quantum communication concerns the distribution of quantum information in networks, encoded into quantum states of matter. By leveraging properties of quantum information that are unique to quantum physics, it can develop advanced network communication methods that overcome the limitations of classical physics. Quantum cryptography, a closely related field, details the use of quantum information for secure communication, in particular through quantum key distribution, which promises unconditionally secure communication. Entanglement --- a quintessential property of quantum states for which there exists no classical counterpart --- is a ubiquitous resource fundamental to this field. It manifests as correlations between two or more quantum systems (`bi-partite' and `multi-partite' entanglement, respectively) that cannot be explained by classical physics. This thesis presents my two main research contributions. First, it provides a theoretical study of multi-partite entanglement, presenting analytical tools to evaluate and compare its myriad different forms, additionally studying the potential equivalence between these forms. Second, it presents the utilization of multi-partite entanglement in cryptographic tasks, specifically focusing on anonymous conference key agreement (ACKA). ACKA protocols allow any number of nodes in a network to secretly communicate, while keeping their identities private. The research presented in this thesis demonstrates that multi-partite entanglement can enhance communication protocols compared to traditional bi-partite approaches, contributing to the ongoing development of quantum communication technologies and the emerging vision of a global quantum internet.