  We propose and analyze a scheme for "on demand" creation of coherent
superposition of meta-stable states in a tripod-structured atom using
frequency-chirped laser pulses. Negligible excitation of the atoms during the
creation of the superposition states is a priority in our consideration. The
underlying physics of the scheme is explained using the formalism of adiabatic
states. By numerically solving master equation for the density matrix operator,
we analyze the influence of the spontaneous decay and transverse relaxation on
the efficiency of the creation of superposition states. We show that the
proposed scheme is robust against small-to-medium variations of the parameters
of the laser pulses. We provide a detailed analysis of the effect of the
inhomogeneous (Doppler-) broadening on the efficiency of the coherence creation
and show that the proposed scheme may be equally efficient in both
homogeneously and Doppler-broadened media.
