  We show an experimental procedure to certify the classical capacity for noisy
qubit channels. The method makes use of a fixed bipartite entangled state,
where the system qubit is sent to the channel input and the set of local
measurements $\sigma_{x}\otimes\sigma_{x}$, $\sigma_{y}\otimes\sigma_{y}$ and
$\sigma_{z}\otimes\sigma_{z}$ is performed at the channel output and the
ancilla qubit, thus without resorting to full quantum process tomography. The
witness to the classical capacity is then achieved by reconstructing sets of
conditional probabilities, noise deconvolution, and classical optimization of
the pertaining mutual information. The performance of the method to provide
lower bounds to the classical capacity is tested by a two-photon polarization
entangled state in Pauli channels and amplitude damping channels. The measured
lower bounds to the channels are in high agreement with the simulated data,
which take into account both the experimental entanglement fidelity $F=0.979\pm
0.011$ of the input state and the systematic experimental imperfections.
