  In quantum information processing, quantum cavities play an important role by
providing the mechanisms to transfer information between atom qubits and photon
qubits, or to couple single atoms with the optical modes of the cavity field.
We explore numerically the population transfer in an atom + cavity system by
using the $\pi$-pulse and adiabatic passage methods. While the first method is
very efficient transferring the atomic population for no radiative decay of the
intermediate level, the second method shows very interesting nonadiabatic,
resonance-like properties that can be used to achieve very large transfer
efficiencies without needing very large Rabi frequencies or very long
interaction times. We introduce a simple analytical model to explore the origin
of these properties and describe "qualitatively" the power-law dependence of
the failure probability on the product of the pulse amplitude and the
interaction time. We also examine numerically the transfer of interatomic
coherence in a two-atom + cavity system by using adiabatic methods. For some
specific symmetry conditions, we show that the dynamics of the original system
can be studied as the individual evolution of a symmetric and an antisymmetric
system, interacting separately with the classical field and the cavity mode,
but mutually exchanging the atomic coherence.

Quantum Physics