• Oct 09 2013

    Stellenbosch Node Seminar: Mauritz van den Worm (NITheP, Stellenbosch)

    NITheP cordially invites you to a seminar by:

    Mauritz van den Worm (NITheP, Stellenbosch)

    Date: Wednesday 09 October 2013
    Time: 14:00
    Venue: NITheP Stellenbosch Node, Seminar Room

    TITLE: Supersonic Spreading of Correlations in Long-Range Quantum Lattice Models

    ABSTRACT: For a large class of initial conditions, exact analytic results are obtained for correlation functions in arbitrary lattice dimension in the presence of long-range interactions decaying asymptotically as a power law. These exact results are used to study the non-equilibrium dynamics of correlations in quantum lattice models.
    For exponents larger than the lattice dimensionality, a Lieb-Robinson-type bound effectively restricts the spreading of correlations to the interior of a causal region, but allows supersonic (faster than linear) propagation. We show here that this decay is not only sufficient but also necessary. Using tools of quantum metrology, for any exponents smaller than the lattice dimension, we construct Hamiltonians giving rise to quantum channels with capacities not restricted to any causal region. An analytical analysis of long-range Ising models illustrates the disappearance of the causal region and the creation of correlations becoming distance-independent. Numerical results for the XXZ spin chain reveal the presence of a sound cone for large exponents, and supersonic propagation for small ones. In all models we analyzed the fast spreading of correlations follows a power law, but not the exponential increase of the long-range Lieb-Robinson bound. Time permitting, we touch on how the analytic results can be used to study multipartite entanglement of long-range interacting quantum lattice models.

    Navrae/Enquiries: Rene Kotze
    Tel: 021 808 2653

    2013 10 09 Mauritz Vd Worm Seminar