5,025 research outputs found
Accurate control of a Bose-Einstein condensate by managing the atomic interaction
We exploit the variation of the atomic interaction in order to move
ultra-cold atoms across an AC-driven periodic lattice. By breaking relevant
symmetries, a gathering of atoms is achieved. Accurate control of the gathered
atoms positions can be demonstrated via the control of the atomic localization
process. The localization process is analyzed with the help of the nonlinear
Floquet states where the Landau-Zener tunneling between states is observed and
controlled. Transport effects in the presence of disorder are discussed.Comment: 14 pages, 5 Figures, PACS numbers: 03.75.Lm, 05.60.-k, 63.20.P
Many-Body Coherent Destruction of Tunneling
A new route to coherent destruction of tunneling is established by
considering a monochromatic fast modulation of the self-interaction strength of
a many-boson system. The modulation can be tuned such that only an arbitrarily,
a priori prescribed number of particles are allowed to tunnel. The associated
tunneling dynamics is sensitive to the odd or even nature of the number of
bosons.Comment: 4 pages, 3 figures, accepted for publication in Phys. Rev. Let
Three-dimensional localized-delocalized Anderson transition in the time domain
Systems which can spontaneously reveal periodic evolution are dubbed time
crystals. This is in analogy with space crystals that display periodic behavior
in configuration space. While space crystals are modelled with the help of
space periodic potentials, crystalline phenomena in time can be modelled by
periodically driven systems. Disorder in the periodic driving can lead to
Anderson localization in time: the probability for detecting a system at a
fixed point of configuration space becomes exponentially localized around a
certain moment in time. We here show that a three-dimensional system exposed to
a properly disordered pseudo-periodic driving may display a
localized-delocalized Anderson transition in the time domain, in strong analogy
with the usual three-dimensional Anderson transition in disordered systems.
Such a transition could be experimentally observed with ultra-cold atomic
gases.Comment: version accepted for publication in Phys. Rev. Lett., supplemental
material include
Inhomogeneous soliton ratchets under two ac forces
We extend our previous work on soliton ratchet devices [L. Morales-Molina et
al., Eur. Phys. J. B 37, 79 (2004)] to consider the joint effect of two ac
forces including non-harmonic drivings, as proposed for particle ratchets by
Savele'v et al. [Europhys. Lett. 67}, 179 (2004); Phys. Rev. E {\bf 70} 066109
(2004)]. Current reversals due to the interplay between the phases, frequencies
and amplitudes of the harmonics are obtained. An analysis of the effect of the
damping coefficient on the dynamics is presented. We show that solitons give
rise to non-trivial differences in the phenomenology reported for particle
systems that arise from their extended character. A comparison with soliton
ratchets in homogeneous systems with biharmonic forces is also presented. This
ratchet device may be an ideal candidate for Josephson junction ratchets with
intrinsic large damping
Ratchet behavior in nonlinear Klein-Gordon systems with point-like inhomogeneities
We investigate the ratchet dynamics of nonlinear Klein-Gordon kinks in a
periodic, asymmetric lattice of point-like inhomogeneities. We explain the
underlying rectification mechanism within a collective coordinate framework,
which shows that such system behaves as a rocking ratchet for point particles.
Careful attention is given to the kink width dynamics and its role in the
transport. We also analyze the robustness of our kink rocking ratchet in the
presence of noise. We show that the noise activates unidirectional motion in a
parameter range where such motion is not observed in the noiseless case. This
is subsequently corroborated by the collective variable theory. An explanation
for this new phenomenom is given
Harnessing synthetic gauge fields for maximally entangled state generation
We study the generation of entanglement between two species of neutral cold
atoms living on an optical ring lattice, where each group of particles can be
described by a -dimensional Hilbert space (quit). Synthetic magnetic
fields are exploited to create an entangled state between the pair of quits.
Maximally entangled eigenstates are found for well defined values of the
Aharonov-Bohm phase, which are zero energy eigenstates of both the kinetic and
interacting parts of the Bose-Hubbard Hamiltonian, making them quite
exceptional and robust against certain non-perturbative fluctuations of the
Hamiltonian. We propose a protocol to reach the maximally entangled state (MES)
by starting from an initially prepared ground state. Also, an indirect method
to detect the MES by measuring the current of the particles is proposed.Comment: 10 pages, 3 figure
Current and entanglement in a Bose-Hubbard lattice
We study the generation of entanglement for interacting cold atoms in an
optical lattice. The entanglement is generated by managing the interaction
between two distinct atomic species. It is found that the current of one of the
species can be used as a good indicator of entanglement generation. The
thermalization process between the species is also shown to be closely related
to the evolution of the current.Comment: 10 pages, 5 figure
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