  We show how realistic cavity-assisted interaction between neutral atoms and
coherent optical pulses, and measurement techniques, combined with optical
transportation of atoms, allow for a universal set of quantum gates acting on
decoherence-free subspace (DFS) in deterministic way. The logical qubits are
immunized to the dominant source of decoherece--dephasing; while, the
influences of additional errors are shown by numerical simulations. We analyze
the performance and stability of all required operations and emphasize that all
techniques we use are feasible with current experimental technology.
