Ergotropic interpretation of entanglement entropy

Entanglement entropy is one of the most prominent measures in quantum physics. We show that it has an interesting ergotropic interpretation in terms of unitarily extracted work. It determines how much energy one can extract from a source of pure unknown states by applying unitary operations when only local measurements can be performed to characterize this source. Additionally, entanglement entropy sets a limit on the minimal temperature to which these partially characterized states can be cooled down, by using only unitary operations.