38 research outputs found
A robust boson dispenser: Quantum state preparation in interacting many-particle systems
We present a technique to control the spatial state of a small cloud of
interacting particles at low temperatures with almost perfect fidelity using
spatial adiabatic passage. To achieve this, the resonant trap energies of the
system are engineered in such a way that a single, well-defined eigenstate
connects the initial and desired states and is isolated from the rest of the
spectrum. We apply this procedure to the task of separating a well-defined
number of particles from an initial cloud and show that it can be implemented
in radio-frequency traps using experimentally realistic parameters.Comment: 10 pages, 9 figure
Coherent transport of holes in microtap arrays
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Twonniers: Interaction-induced effects on Bose-Hubbard parameters
We study the effects of the repulsive on-site interactions on the broadening
of the localized Wannier functions used for calculating the parameters to
describe ultracold atoms in optical lattices. For this, we replace the common
single-particle Wannier functions, which do not contain any information about
the interactions, by two-particle Wannier functions ("Twonniers") obtained from
an exact solution which takes the interactions into account. We then use these
interaction-dependent basis functions to calculate the Bose--Hubbard model
parameters, showing that they are substantially different both at low and high
lattice depths, from the ones calculated using single-particle Wannier
functions. Our results suggest that density effects are not negligible for many
parameter ranges and need to be taken into account in metrology experiments.Comment: 6 pages, 3 figure
Shaken not stirred: Creating exotic angular momentum states by shaking an optical lattice
We propose a method to create higher orbital states of ultracold atoms in the
Mott regime of an optical lattice. This is done by periodically modulating the
position of the trap minima (known as shaking) and controlling the interference
term of the lasers creating the lattice. These methods are combined with
techniques of shortcuts to adiabaticity. As an example of this, we show
specifically how to create an anti-ferromagnetic type ordering of angular
momentum states of atoms. The specific pulse sequences are designed using
Lewis-Riesenfeld invariants and a four-level model for each well. The results
are compared with numerical simulations of the full Schroedinger equation.Comment: 20 pages, 8 figure
Transport of ultracold atoms between concentric traps via spatial adiabatic passage
Spatial adiabatic passage processes for ultracold atoms trapped in
tunnel-coupled cylindrically symmetric concentric potentials are investigated.
Specifically, we discuss the matter-wave analogue of the rapid adiabatic
passage (RAP) technique for a high fidelity and robust loading of a single atom
into a harmonic ring potential from a harmonic trap, and for its transport
between two concentric rings. We also consider a system of three concentric
rings and investigate the transport of a single atom between the innermost and
the outermost rings making use of the matter-wave analogue of the stimulated
Raman adiabatic passage (STIRAP) technique. We describe the RAP-like and
STIRAP-like dynamics by means of a two- and a three-state models, respectively,
obtaining good agreement with the numerical simulations of the corresponding
two-dimensional Schr\"odinger equation.Comment: 13 pages, 6 figure
Spin and Orbital angular momentum propagation in anisotropic media: theory
This paper is devoted to study the propagation of light beams carrying
orbital angular momentum in optically anisotropic media. We first review some
properties of homogeneous anisotropic media, and describe how the paraxial
formalism is modified in order to proceed with a new approach dealing with a
general setting of paraxial propagation along uniaxial inhomogeneous media.
This approach is suitable for describing the space-variant-optical-axis phase
plates
Entanglement in spatial adiabatic processes for interacting atoms
We study the dynamics of the non-classical correlations for few atom systems
in the presence of strong interactions for a number of recently developed
adiabatic state preparation protocols. We show that entanglement can be created
in a controlled fashion and can be attributed to two distinct sources, the
atom-atom interaction and the distribution of atoms among different traps.Comment: 9 pages, 3 figure