Time-delayed quantum interference and single-photon echo in coherent three-level systems

A new version of time-delayed quantum interference of photons is proposed, which may be manifested in the emergence of a single-photon echo signal in coherent three-level macroscopic media. Nonclassical properties of this type of interference, reflected in peculiarities of the interaction between the field and the medium, are analysed along with the properties of the emitted echo signal.