We discuss the estimation of channel parameters for a noisy quantum channel - the so-called Pauli channel - using finite resources. It turns out that prior entanglement considerably enhances the fidelity of the estimation when we compare it to an estimation scheme based on separable quantum states.
@article{arxiv.quant-ph/0103160,
title = {Enhanced Estimation of a Noisy Quantum Channel Using Entanglement},
author = {Dietmar G. Fischer and Holger Mack and Markus A. Cirone and Matthias Freyberger},
journal= {arXiv preprint arXiv:quant-ph/0103160},
year = {2009}
}