We present a detailed, realistic analysis of the implementation of a proposalfor a quantum phase gate based on atomic vibrational states, specializing it toneutral rubidium atoms on atom chips. We show how to create a double--wellpotential with static currents on the atom chips, using for all relevantparameters values that are achieved with present technology. The potentialbarrier between the two wells can be modified by varying the currents in orderto realize a quantum phase gate for qubit states encoded in the atomic externaldegree of freedom. The gate performance is analyzed through numericalsimulations; the operation time is ~10 ms with a performance fidelity above99.9%. For storage of the state between the operations the qubit state can betransferred efficiently via Raman transitions to two hyperfine states, whereits decoherence is strongly inhibited. In addition we discuss the limitsimposed by the proximity of the surface to the gate fidelity.
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