The superactivation of quantum capacity is an effect that some quantum channels present such that is two of those channels with zero capacity are combined, a non-zero channel capacity can be achieved for the combined channel. This is obviously an effect that can only happen in the quantum world, as it is known that in classical communications two zero-capacity channels give a zero-capacity channel when combined.
This is one of the most surprising and weird effects known from quantum information theory, and so I am wondering if someone can give reference about an experimental realization of such effect.