Entanglement assisted quantum communication protocols

by Amelie Piveteau (Stockholm University)

Thursday 19 Mar 2026, 10:00 → 13:00 Europe/Stockholm

FB55 (AlbaNova Main Building)

Abstract
Quantum entanglement plays a central role in many quantum communication protocols. It allows distant particles to
share correlations beyond the limits of classical interactions. Entanglement is essential for superdense coding, quantum
teleportation, and secure cryptographic key distribution in quantum communication. It is also a pillar for developing
quantum networks, where the management and distribution of entanglement are crucial for connecting distant nodes.
Although perfect entanglement is a sought-after ideal, experimental imperatives, including entanglement distribution over
long distances, often limit the quality of entangled states. An important question is whether weaker entanglement still
offers advantages.
First, we study more general tasks than dense coding to show that simpler measurements, combined with entanglement,
allow advantageous and sometimes even optimal qubit communication protocols to be obtained. We also demonstrate that
simple measurements can generate quantum correlations that cannot be modelled by two classical communication bits and
can constitute an optimal protocol with quantum resources.
We implement a novel Bell-type inequality tailored for certifying full network non-locality (FNN) to develop
certification methods guaranteeing security on an entanglement-based network. Our experiment uses two pairs of polarised
entangled photons in a network configuration with three nodes, briefly referred to as a bilocal network scenario.
Finally, we show that weakly entangled states can improve communication over a qubit channel using only separate
(local) measurements on isotropic non-steerable two-qubit states, without interference, of individual photons, across two
communication tasks: secret sharing and its stochastic variant.