  We report the experimental demonstration of a controlled-NOT (CNOT) quantum
logic gate between motional and internal state qubits of a single ion where, as
opposed to previously demonstrated gates, the conditional dynamics depends on
the extent of the ion's wave-packet. Advantages of this CNOT gate over one
demonstrated previously are its immunity from Stark shifts due to off-resonant
couplings and the fact that an auxiliary internal level is not required. We
characterize the gate logic through measurements of the post-gate ion state
populations for both logic basis and superposition input states, and we
demonstrate the gate coherence via an interferometric measurement.
