543 research outputs found
Strong correlations in quantum vortex nucleation of ultracold atomic gases
We review some recent developments in the theory of rotating atomic gases.
These studies have thrown light on the process of nucleation of vortices in
regimes where mean-field methods are inadequate. In our review we shall
describe and compare quantum vortex nucleation of a dilute ultracold bosonic
gas trapped in three different configurations: a one-dimensional ring lattice,
a one-dimensional ring superlattice and a two-dimensional asymmetric harmonic
trap. In all of them there is a critical rotation frequency, at which the
particles in the ground state exhibit strong quantum correlations. However, the
entanglement properties vary significantly from case to case. We explain these
differences by characterizing the intermediate states that participate in the
vortex nucleation process. Finally, we show that noise correlations are
sensitive to these differences. These new studies have, therefore, shown how
novel quantum states may be produced and probed in future experiments with
rotating neutral atom systems.Comment: 17 pages, 5 figure
A generalized phase space approach for solving quantum spin dynamics
Numerical techniques to efficiently model out-of-equilibrium dynamics in
interacting quantum many-body systems are key for advancing our capability to
harness and understand complex quantum matter. Here we propose a new numerical
approach which we refer to as GDTWA. It is based on a discrete semi-classical
phase-space sampling and allows to investigate quantum dynamics in lattice spin
systems with arbitrary . We show that the GDTWA can accurately
simulate dynamics of large ensembles in arbitrary dimensions. We apply it for
spin-models with dipolar long-range interactions, a scenario arising in
recent experiments with magnetic atoms. We show that the method can capture
beyond mean-field effects, not only at short times, but it also correctly
reproduces long time quantum-thermalization dynamics. We benchmark the method
with exact diagonalization in small systems, with perturbation theory for short
times, and with analytical predictions made for closed system which feature
quantum-thermalization at long times. By computing the Renyi entropy, currently
an experimentally accessible quantifier of entanglement, we reveal that large
systems can feature larger entanglement than corresponding systems.
Our analyses demonstrate that the GDTWA can be a powerful tool for modeling
complex spin dynamics in regimes where other state-of-the art numerical methods
fail
Many-Body Quantum Spin Dynamics with Monte Carlo Trajectories on a Discrete Phase Space
Interacting spin systems are of fundamental relevance in different areas of
physics, as well as in quantum information science, and biology. These spin
models represent the simplest, yet not fully understood, manifestation of
quantum many-body systems. An important outstanding problem is the efficient
numerical computation of dynamics in large spin systems. Here we propose a new
semiclassical method to study many-body spin dynamics in generic spin lattice
models. The method is based on a discrete Monte Carlo sampling in phase-space
in the framework of the so-called truncated Wigner approximation. Comparisons
with analytical and numerically exact calculations demonstrate the power of the
technique. They show that it correctly reproduces the dynamics of one- and
two-point correlations and spin squeezing at short times, thus capturing
entanglement. Our results open the possibility to study the quantum dynamics
accessible to recent experiments in regimes where other numerical methods are
inapplicable.Comment: 8 pages, 6 figure
Bragg spectroscopy of trapped one dimensional strongly interacting bosons in optical lattices: Probing the cake-structure
We study Bragg spectroscopy of strongly interacting one dimensional bosons
loaded in an optical lattice plus an additional parabolic potential. We
calculate the dynamic structure factor by using Monte Carlo simulations for the
Bose-Hubbard Hamiltonian, exact diagonalizations and the results of a recently
introduced effective fermionization (EF) model. We find that, due to the
system's inhomogeneity, the excitation spectrum exhibits a multi-branched
structure, whose origin is related to the presence of superfluid regions with
different densities in the atomic distribution. We thus suggest that Bragg
spectroscopy in the linear regime can be used as an experimental tool to unveil
the shell structure of alternating Mott insulator and superfluid phases
characteristic of trapped bosons.Comment: 7 pages, 4 figure
Probing the Kondo Lattice Model with Alkaline Earth Atoms
We study transport properties of alkaline-earth atoms governed by the Kondo
Lattice Hamiltonian plus a harmonic confining potential, and suggest simple
dynamical probes of several different regimes of the phase diagram that can be
implemented with current experimental techniques. In particular, we show how
Kondo physics at strong coupling, low density, and in the heavy fermion phase
is manifest in the dipole oscillations of the conduction band upon displacement
of the trap center.Comment: 5 pages, 4 figure
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