10,646 research outputs found
Quantum magnetism with ultracold molecules
This article gives an introduction to the realization of effective quantum
magnetism with ultracold molecules in an optical lattice, reviews experimental
and theoretical progress, and highlights future opportunities opened up by
ongoing experiments. Ultracold molecules offer capabilities that are otherwise
difficult or impossible to achieve in other effective spin systems, such as
long-ranged spin-spin interactions with controllable degrees of spatial and
spin anisotropy and favorable energy scales. Realizing quantum magnetism with
ultracold molecules provides access to rich many-body behaviors, including many
exotic phases of matter and interesting excitations and dynamics.
Far-from-equilibrium dynamics plays a key role in our exposition, just as it
did in recent ultracold molecule experiments realizing effective quantum
magnetism. In particular, we show that dynamical probes allow the observation
of correlated many-body spin physics, even in polar molecule gases that are not
quantum degenerate. After describing how quantum magnetism arises in ultracold
molecules and discussing recent observations of quantum magnetism with polar
molecules, we survey prospects for the future, ranging from immediate goals to
long-term visions.Comment: 21 pages, 6 figures, 1 table. Review articl
Advanced flight deck/crew station simulator functional requirements
This report documents a study of flight deck/crew system research facility requirements for investigating issues involved with developing systems, and procedures for interfacing transport aircraft with air traffic control systems planned for 1985 to 2000. Crew system needs of NASA, the U.S. Air Force, and industry were investigated and reported. A matrix of these is included, as are recommended functional requirements and design criteria for simulation facilities in which to conduct this research. Methods of exploiting the commonality and similarity in facilities are identified, and plans for exploiting this in order to reduce implementation costs and allow efficient transfer of experiments from one facility to another are presented
Nonequilibrium dynamics of spin-boson models from phase space methods
An accurate description of the nonequilibrium dynamics of systems with
coupled spin and bosonic degrees of freedom remains theoretically challenging,
especially for large system sizes and in higher than one dimension. Phase space
methods such as the Truncated Wigner Approximation (TWA) have the advantage of
being easily scalable and applicable to arbitrary dimensions. In this work we
adapt the TWA to generic spin-boson models by making use of recently developed
algorithms for discrete phase spaces [Schachenmayer, PRX 5, 011022 (2015)].
Furthermore we go beyond the standard TWA approximation by applying a scheme
based on the Bogoliubov-Born-Green-Kirkwood-Yvon (BBGKY) hierarchy of equations
[Pucci, PRB 93, 174302 (2016)] to our coupled spin-boson model. This allows in
principle to study how systematically adding higher order corrections improves
the convergence of the method. To test various levels of approximation we study
an exactly solvable spin-boson model which is particularly relevant for
trapped-ion arrays. Using TWA and its BBGKY extension we accurately reproduce
the time evolution of a number of one- and two-point correlation functions in
several dimensions and for arbitrary number of bosonic modes.Comment: 10+5 pages, 5 figure
Emergent Time Scale in Entangled Quantum Dynamics of Ultracold Molecules in Optical Lattices
We derive a novel lattice Hamiltonian, the \emph{Molecular Hubbard
Hamiltonian} (MHH), which describes the essential many body physics of
closed-shell ultracold heteronuclear molecules in their absolute ground state
in a quasi-one-dimensional optical lattice. The MHH is explicitly
time-dependent, making a dynamic generalization of the concept of quantum phase
transitions necessary. Using the Time-Evolving Block Decimation (TEBD)
algorithm to study entangled dynamics, we demonstrate that, in the case of hard
core bosonic molecules at half filling, the MHH exhibits an emergent time scale
over which spatial entanglement grows, crystalline order appears, and
oscillations between rotational states self-damp into an asymptotic
superposition. We show that this time scale is a non-monotonic function of the
physical parameters describing the lattice. We also point out that experimental
mapping of the static phase boundaries of the MHH can be used to measure the
molecular polarizability tensor.Comment: 31 pages, 13 figure
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