2,768 research outputs found
Vortex macroscopic superpositions in ultracold bosons in a double-well potential
We study macroscopic superpositions in the orbital rather than the spatial
degrees of freedom, in a three-dimensional double-well system. We show that the
ensuing dynamics of interacting excited ultracold bosons, which in general
requires at least eight single-particle modes and Fock
vectors, is described by a surprisingly small set of many-body states. An
initial state with half the atoms in each well, and purposely excited in one of
them, gives rise to the tunneling of axisymmetric and transverse vortex
structures. We show that transverse vortices tunnel orders of magnitude faster
than axisymmetric ones and are therefore more experimentally accessible. The
tunneling process generates macroscopic superpositions only distinguishable by
their orbital properties and within experimentally realistic times.Comment: 9 pages, 6 figure
Symmetry breaking and singularity structure in Bose-Einstein condensates
We determine the trajectories of vortex singularities that arise after a
single vortex is broken by a discretely symmetric impulse in the context of
Bose-Einstein condensates in a harmonic trap. The dynamics of these
singularities are analyzed to determine the form of the imprinted motion. We
find that the symmetry-breaking process introduces two effective forces: a
repulsive harmonic force that causes the daughter trajectories to be ejected
from the parent singularity, and a Magnus force that introduces a torque about
the axis of symmetry. For the analytical non-interacting case we find that the
parent singularity is reconstructed from the daughter singularities after one
period of the trapping frequency. The interactions between singularities in the
weakly interacting system do not allow the parent vortex to be reconstructed.
Analytic trajectories were compared to the actual minima of the wavefunction,
showing less 0.5% error for impulse strength of (v=0.00005). We show that these
solutions are valid within the impulse regime for various impulse strengths
using numerical integration of the Gross-Pitaevskii equation. We also show that
the actual duration of the symmetry breaking potential does not significantly
change the dynamics of the system as long as the strength is below (v=0.0005).Comment: 14 pages, 10 figure
Tunneling, self-trapping and manipulation of higher modes of a BEC in a double well
We consider an atomic Bose-Einstein condensate trapped in a symmetric
one-dimensional double well potential in the four-mode approximation and show
that the semiclassical dynamics of the two ground state modes can be strongly
influenced by a macroscopic occupation of the two excited modes. In particular,
the addition of the two excited modes already unveils features related to the
effect of dissipation on the condensate. In general, we find a rich dynamics
that includes Rabi oscillations, a mixed Josephson-Rabi regime, self-trapping,
chaotic behavior, and the existence of fixed points. We investigate how the
dynamics of the atoms in the excited modes can be manipulated by controlling
the atomic populations of the ground states.Comment: 12 pages, 5 figure
Sharp crossover from composite fermionization to phase separation in mesoscopic mixtures of ultracold bosons
We show that a two-component mixture of a few repulsively interacting
ultracold atoms in a one-dimensional trap possesses very different quantum
regimes and that the crossover between them can be induced by tuning the
interactions in one of the species. In the composite fermionization regime,
where the interactions between both components are large, none of the species
show large occupation of any natural orbital. Our results show that by
increasing the interaction in one of the species, one can reach the
phase-separated regime. In this regime, the weakly interacting component stays
at the center of the trap and becomes almost fully phase coherent, while the
strongly interacting component is displaced to the edges of the trap. The
crossover is sharp, as observed in the in the energy and the in the largest
occupation of a natural orbital of the weakly interacting species. Such a
transition is a purely mesoscopic effect which disappears for large atom
numbers.Comment: 5 pages, 3 figure
Graded-index optical fiber emulator of an interacting three-atom system: illumination control of particle statistics and classical non-separability
We show that a system of three trapped ultracold and strongly interacting
atoms in one-dimension can be emulated using an optical fiber with a
graded-index profile and thin metallic slabs. While the wave-nature of single
quantum particles leads to direct and well known analogies with classical
optics, for interacting many-particle systems with unrestricted statistics such
analoga are not straightforward. Here we study the symmetries present in the
fiber eigenstates by using discrete group theory and show that, by spatially
modulating the incident field, one can select the atomic statistics, i.e.,
emulate a system of three bosons, fermions or two bosons or fermions plus an
additional distinguishable particle. We also show that the optical system is
able to produce classical non-separability resembling that found in the
analogous atomic system.Comment: 14 pages, 5 figure
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