Tolerant-gate implementation for the trapped-ion quantum-information processor

A sequence of five laser pulses is presented, implementing a controlled-NOT gate in a linear arrangement of trapped ions. This gate works if the quantum number of the collective vibration (phonon bus) is zero or one. We interpret this property as tolerance against errors caused by imperfect ground-state preparation. The periodicity of two Rabi frequencies is used in order to obtain this property. The gate implementation is designed in a way which does not correspond to the well-known phase-gate construction.