Experimental witnessing of the quantum channel capacity in the presence of correlated noise

TL;DR

This paper experimentally demonstrates a method to estimate lower bounds of quantum channel capacity in two-photon systems with correlated noise, highlighting the importance of correlations for enhanced quantum communication.

Contribution

It introduces an experimental approach to detect quantum capacity bounds considering correlated noise, and compares correlated versus uncorrelated channels to show the benefits of correlations.

Findings

Correlated noise affects quantum channel capacity.

Properly accounting for correlations improves capacity estimates.

The method is efficient with polarization-encoded photons.

Abstract

We present an experimental method to detect lower bounds to the quantum capacity of two-qubit communication channels. We consider an implementation with polarisation degrees of freedom of two photons and report on the efficiency of such a method in the presence of correlated noise for varying values of the correlation strength. The procedure is based on the generation of separable states of two qubits and local measurements at the output. We also compare the performance of the correlated two-qubit channel with the single-qubit channels corresponding to the partial trace on each of the subsystems, thus showing the beneficial effect of properly taking into account correlations to achieve a larger quantum capacity.