91 research outputs found
Floquet approach to lattice gauge theories with ultracold atoms in optical lattices
Quantum simulation has the potential to investigate gauge theories in
strongly-interacting regimes, which are up to now inaccessible through
conventional numerical techniques. Here, we take a first step in this direction
by implementing a Floquet-based method for studying lattice
gauge theories using two-component ultracold atoms in a double-well potential.
For resonant periodic driving at the on-site interaction strength and an
appropriate choice of the modulation parameters, the effective Floquet
Hamiltonian exhibits symmetry. We study the dynamics of the
system for different initial states and critically contrast the observed
evolution with a theoretical analysis of the full time-dependent Hamiltonian of
the periodically-driven lattice model. We reveal challenges that arise due to
symmetry-breaking terms and outline potential pathways to overcome these
limitations. Our results provide important insights for future studies of
lattice gauge theories based on Floquet techniques
Rapid Prototyping of Topology Control Algorithms by Graph Transformation
Topology control algorithms are used to improve the energy efficiency (or other quality parameters) of wireless sensor networks. In this paper, we propose a model-driven rapid prototyping approach for the kTC topology control algorithm to enable the fast implementation and the evaluation of its different variants, and consequently, to accelerate the network quality experimentation cycle. In our approach, wireless sensor networks are described by graph-based models, and three variants of the kTC topology control algorithm are implemented by graph transformation, which are then executed on input network descriptions to derive modified topologies whose quality is then measured in several contexts to be able to assess the achieved network quality improvement
Exploring 4D Quantum Hall Physics with a 2D Topological Charge Pump
The discovery of topological states of matter has profoundly augmented our
understanding of phase transitions in physical systems. Instead of local order
parameters, topological phases are described by global topological invariants
and are therefore robust against perturbations. A prominent example thereof is
the two-dimensional integer quantum Hall effect. It is characterized by the
first Chern number which manifests in the quantized Hall response induced by an
external electric field. Generalizing the quantum Hall effect to
four-dimensional systems leads to the appearance of a novel non-linear Hall
response that is quantized as well, but described by a 4D topological invariant
- the second Chern number. Here, we report on the first observation of a bulk
response with intrinsic 4D topology and the measurement of the associated
second Chern number. By implementing a 2D topological charge pump with
ultracold bosonic atoms in an angled optical superlattice, we realize a
dynamical version of the 4D integer quantum Hall effect. Using a small atom
cloud as a local probe, we fully characterize the non-linear response of the
system by in-situ imaging and site-resolved band mapping. Our findings pave the
way to experimentally probe higher-dimensional quantum Hall systems, where new
topological phases with exotic excitations are predicted
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