Bounds on quantum conference key agreement in pair-entangled networks

TL;DR

This paper establishes upper bounds on the maximum achievable conference key in quantum networks with bipartite entanglement, showing these bounds are tight in certain cases and identifying optimal key distillation strategies.

Contribution

It derives network-dependent upper bounds on distillable conference keys and proves their tightness for specific network configurations, highlighting optimal strategies.

Findings

Upper bounds depend on network topology and entanglement degree.

Tightness of bounds proven for specific network cases.

Pairwise key distillation followed by merging is optimal in some scenarios.

Abstract

We investigate the task of conference key agreement in near-term quantum networks, where the nodes are connected by sources of bipartite entangled states, under the class of local operations not requiring quantum memory. We derive upper bounds on the distillable conference key depending on the network topology and degree of entanglement of the sources, and prove tightness of these bounds for some particular cases. In these cases, we show that pairwise bipartite key distillation followed by merging the bipartite keys into the conference key is optimal.