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Universal Fault-Tolerant Computation on Decoherence-Free Subspaces

Dave Bacon·Julia Kempe·Daniel A. Lidar·K. B. Whaley
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Abstract

A general scheme to perform universal quantum computation within decoherence-free subspaces (DFSs) of a system's Hilbert space is presented. This scheme leads to the first fault-tolerant realization of universal quantum computation on DFSs with the properties that (i) only one- and two-qubit interactions are required, and (ii) 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 "collective decoherence" (qubit-permutation-invariant system-bath coupling). Our results have immediate relevance to a number of solid-state quantum computer implementations, in particular those in which quantum logic is implemented through exchange interactions, such as the recently proposed spin-spin coupled GaAs quantum dot arrays and the Si:$^{31}$P nuclear spin arrays.

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Dave Bacon, Julia Kempe, Daniel A. Lidar, K. B. Whaley. 2000-06-29. Universal Fault-Tolerant Computation on Decoherence-Free Subspaces. https://doi.org/10.1103/physrevlett.85.1758

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