In this talk, possible pathways to fault-tolerant large-scale quantum information processors based on trapped ions are presented. The envisioned machines incorporate millions of qubits, feature operation errors on physical qubits of order 10-4 and memory coherence times on the order of hours. Qubit connectivity with sufficiently low crosstalk is achieved by moving ions around in a large array of traps and executing operations on small groups of ions that are sufficiently isolated from all other qubits and the environment1. Fault-tolerant execution of complex algorithms is facilitated by extensive use of ""helper qubits"" that serve to cool the motion, initialize internal states, and read out error syndromes without compromising computational qubits in the algorithm substantially.

While building a machine of this scale is currently out of reach, present efforts can inform this vision and the performance of many necessary components can be demonstrated in separate proof-of-principle experiments in dedicated, smaller scale setups. Relevant experiments in the Ion Storage Group at NIST and in other laboratories will be discussed.