  The Rydberg blockade mechanism has shown noteworthy promise for scalable
quantum computation with neutral atoms. Both qubit states and gate-mediating
Rydberg state belong to the same optically-trapped atom. The trapping fields,
while being essential, induce detrimental decoherence. Here we theoretically
demonstrate that this Stark-induced decoherence may be completely removed using
powerful concepts of "magic" optical traps. We analyze "magic" trapping of a
prototype three-level system: a Rydberg state along with two qubit states:
hyperfine states attached to a J=1/2 ground state. Our numerical results show
that, while such a "magic" trap for alkali metals would require prohibitively
large magnetic fields, the group IIIB metals such as Al are suitable
candidates.
