title: Universal fault-tolerant quantum computation on decoherence-free subspaces
abstract: A general scheme to perform universal, fault-tolerant quantum computation within decoherence-free subspaces (DFSs) is presented. At most two-qubit interactions are required, and the system remains within the DFS throughout the entire implementation of a quantum gate. We show explicitly how to perform universal computation on clusters of the four-qubit DFS encoding one logical qubit each under spatially symmetric (collective) decoherence. Our results have immediate relevance to quantum computer implementations in which quantum logic is implemented through exchange interactions, such as the recently proposed spin-spin coupled quantum dot arrays and donor-atom arrays.
authors.affiliation: Department of Chemistry, University of California, Berkeley, California 94720 and Physics Department, University of California, Berkeley, California 94720, USA.
authors.initials: D
authors.lastname: Bacon
authors.initials: J
authors.lastname: Kempe
authors.initials: DA
authors.lastname: Lidar
authors.initials: KB
authors.lastname: Whaley