  The field of quantum communications promises the faithful distribution of
quantum information, quantum entanglement, and absolutely secret keys. However,
the highest rates of these tasks are fundamentally limited by the transmission
distances. Quantum repeaters are necessary to overcome the repeaterless bound
which sets the fundamental rate-distance limit of any repeaterless quantum
communication protocol. The ultimate end-to-end rates of quantum repeater
networks are known to be achievable by an optimal entanglement-distillation
protocol followed by quantum teleportation. In this thesis, we give physical
repeater designs for this achievability. We also propose practical repeater
designs with near-term potential for real-world practical applications.
