  We report experimental generation of a noisy entangled four-photon state that
exhibits a separation between the secure key contents and distillable
entanglement, a hallmark feature of the recently established quantum theory of
private states. The privacy analysis, based on the full tomographic
reconstruction of the prepared state, is utilized in a proof-of-principle key
generation. The inferiority of distillation-based strategies to extract the key
is exposed by an implementation of an entanglement distillation protocol for
the produced state.
