Daniel Lidar at MSRI - Universal Fault Tolerant Quantum Computation On Decoherence-Free Subspaces

<BODY> MSRI Streaming Video Series <BR> Daniel Lidar - Universal Fault Tolerant Quantum Computation On Decoherence-Free Subspaces <BR> Decoherence-free subspaces (DFSs) are "quiet corners" of the Hilbert space of a quantum system coupled to a bath. We recently developed a general scheme to perform universal quantum computation fault-tolerantly on DFSs. This scheme has the new and important 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. This result will be presented and it will be shown 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). These results have immediate relevance to a number of proposed quantum computer implementations, in particular those in which the internal system Hamiltonian is of the Heisenberg type, such as spin-spin coupled quantum dots. </BODY>