  A scheme for preparation of coherent superposition of Fock states of
electromagnetic field is constructed. The superposition state is created inside
the cavity via a strong interaction of a four-level atom with quantum field of
the cavity and classic laser fields. We demonstrate the possibility to create
desired arbitrary superposition of the cavity Fock states just by changing the
relative delay of the fields. Then, as another application of our model, we
study a means of creating entanglement of neutral four-level atoms using
different sequences of interactions with the cavity and laser fields.
