Southwest Quantum Information and Technology

Multipartite entanglement and secret key distribution in quantum networks

Presenting Author: Eneet Kaur, Louisiana State University
Contributing Author(s): Masahiro Takeoka, Mark M. Wilde, Wojciech Roga

Distribution and distillation of entanglement over a quantum network is an important task in quantum information theory. A fundamental question is to determine the ultimate performance of entanglement distribution over a given network. Although this question has been extensively explored for bipartite entanglement scenarios, less is known about multipartite entanglement distribution. Here we establish the fundamental limit on distributing multipartite entanglement, in the form of GHZ states, over a quantum network. In particular, we determine the multipartite entanglement/secret key distribution capacity of a quantum network in which the nodes are connected by lossy bosonic quantum channels, which corresponds to a practical quantum network consisting of optical links. Our result is also applicable to the distribution of multipartite secret keys, known as a common key in the quantum network scenario. These results set benchmarks for designing a network topology, as well as for network quantum repeaters for efficient GHZ state/common key distribution. Our result follows from an upper bound on distillable GHZ entanglement introduced here, called the "recursive-cut-and-merge" bound and which constitutes major progress on a longstanding fundamental problem in multipartite entanglement theory. This bound allows us to determine the exact distillable GHZ entanglement for a class of states consisting of products of bipartite pure states.

(Session 9b : Sunday from 4:45pm - 5:15pm)