Bound Information: The Classical Analog to Bound Quantum Entanglemen

It was recently pointed out that there is a close connection between information-theoretic key agreement and quantum entanglement purification. This suggests that the concept of bound entanglement (entanglement which cannot be purified) has a classical counterpart: bound information, which cannot be used to generate a secret key by any protocol. We analyse a probability distribution which results when a specific bound entangled quantum state is measured. We show strong evidence for the fact that the corresponding mutual information is indeed bound. The probable existence of such information stands in contrast to previous beliefs in classical information theory.