QUROPE Quantum Information Processing and Communication in Europe

We point out a contrasting role the entanglement plays in communication and estimation scenarios.
In the first case it brings noticeable benefits at the measurement stage (output super-additvity),
whereas in the latter it is the entanglement of the input probes that enables significant performance
enhancement (input super-additvity). We identify a weak estimation regime where a strong connection
between concepts crucial to the two fields is demonstrated; the accessible information and the
Holevo quantity on one side and the quantum Fisher information related quantities on the other.
This allows us to shed new light on the problem of super-additivity in communication using the
concepts of quantum estimation theory.