Classical capacity of a noiseless quantum channel assisted by noisy entanglement

We derive the general formula for the capacity of a noiseless quantum channel assisted by an arbitrary amount of noisy entanglement. In the capacity formula, the role of mutual information is played by the ratio of the quantum mutual information and the von Neumann entropy of the sender’s part of the noisy entanglement. A consequence of our results is that bound entangled states cannot increase the capacity of a noiseless quantum channel.