A cavity-QED scheme for cluster-state quantum computing using crossed atomic beams

A quantum computer is a hypothetical device in which elements of quantum mechanics are used to introduce a degree of parallelism into computations, which could significantly improve on the computational speed of a classical computer at certain tasks. The ideas of cluster state quantum computing (introduced by Raussendorf and Briegel) extend quantum computing to systems that are capable of performing quantum gates, but are intrinsically one-way in their operation. Using the techniques of cluster state quantum computing, we show how a scalable quantum computer could potentially be constructed using microwave cavity quantum electrodynamics (QED). In a departure from the traditional understanding of a computer as a fixed array of computational elements, we show that cluster state quantum computing is actually well suited to atomic beam experiments and that an atomic beam quantum computer could be constructed using elements of microwave cavity QED. While existing experimental parameters do not meet current thresholds for fault-tolerant computing, improvements in both the experiments and in the understanding of fault-tolerance are expected to change this situation.