Optimal estimation of entanglement and discord in two-qubit states

TL;DR

This paper demonstrates experimental methods to optimally estimate entanglement and quantum discord in two-qubit states, achieving the highest possible precision for quantum resource characterization.

Contribution

It introduces and tests optimal estimation techniques for entanglement and discord, advancing quantum resource measurement tools.

Findings

Optimal estimators reach quantum mechanical precision bounds.

Techniques are effective across a range of two-qubit states.

Results improve reliability of quantum resource quantification.

Abstract

Recently, the fast development of quantum technologies led to the need for tools allowing the characterization of quantum resources. In particular, the ability to estimate non-classical aspects, e.g. entanglement and quantum discord, in two-qubit systems, is relevant to optimise the performance of quantum information processes. Here we present an experiment in which the amount of entanglement and discord are measured exploiting different estimators. Among them, some will prove to be optimal, i.e., able to reach the ultimate precision bound allowed by quantum mechanics. These estimation techniques have been tested with a specific family of states ranging from nearly pure Bell states to completely mixed states. This work represents a significant step in the development of reliable metrological tools for quantum technologies.