  A scheme is proposed to generate an entangled state between two (Lambda-type)
four-level atoms that interact effectively by means of a detuned optical cavity
and a laser beam that acts perpendicularly to the cavity axis. It is shown how
the degree of entanglement for two atoms passing through the cavity can be
controlled by manipulating their velocity and the (initial) distance between
the atoms. In addition, three realistic schemes are suggested to implement the
two-qubit gates within the framework of the suggested atom-cavity-laser setup,
namely, the i-swap gate, controlled-Z gate and the controlled-NOT gate. For all
these schemes, we analyze and discuss the atomic velocities and inter-atomic
distances for which these gates are realized most reliably.
