404 research outputs found
Applications of Integrated Magnetic Microtraps
Lithographically fabricated circuit patterns can provide magnetic guides and
microtraps for cold neutral atoms. By combining several such structures on the
same ceramic substrate, we have realized the first ``atom chips'' that permit
complex manipulations of ultracold trapped atoms or de Broglie wavepackets. We
show how to design magnetic potentials from simple conductor patterns and we
describe an efficient trap loading procedure in detail. Applying the design
guide, we describe some new microtrap potentials, including a trap which
reaches the Lamb-Dicke regime for rubidium atoms in all three dimensions, and a
rotatable Ioffe-Pritchard trap, which we also demonstrate experimentally.
Finally, we demonstrate a device allowing independent linear positioning of two
atomic clouds which are very tightly confined laterally. This device is well
suited for the study of one-dimensional collisions.Comment: 10 pages, 17 figure
Trapped-Atom-Interferometer in a Magnetic Microtrap
We propose a configuration of a magnetic microtrap which can be used as an
interferometer for three-dimensionally trapped atoms. The interferometer is
realized via a dynamic splitting potential that transforms from a single well
into two separate wells and back. The ports of the interferometer are
neighboring vibrational states in the single well potential. We present a
one-dimensional model of this interferometer and compute the probability of
unwanted vibrational excitations for a realistic magnetic potential. We
optimize the speed of the splitting process in order suppress these excitations
and conclude that such interferometer device should be feasible with currently
available microtrap technique.Comment: 6 pages, 6 figures, submitted to PR
Intravenöse Infusion flĂŒchtiger FettsĂ€uren als Stoffwechselbelastungstest zur ĂberprĂŒfung möglicher Butafosfanwirkungen auf den Energiestoffwechsel des Rindes
Process tomography of ion trap quantum gates
A crucial building block for quantum information processing with trapped ions
is a controlled-NOT quantum gate. In this paper, two different sequences of
laser pulses implementing such a gate operation are analyzed using quantum
process tomography. Fidelities of up to 92.6(6)% are achieved for single gate
operations and up to 83.4(8)% for two concatenated gate operations. By process
tomography we assess the performance of the gates for different experimental
realizations and demonstrate the advantage of amplitude--shaped laser pulses
over simple square pulses. We also investigate whether the performance of
concatenated gates can be inferred from the analysis of the single gates
Trapping and coherent manipulation of a Rydberg atom on a microfabricated device: a proposal
We propose to apply atom-chip techniques to the trapping of a single atom in
a circular Rydberg state. The small size of microfabricated structures will
allow for trap geometries with microwave cut-off frequencies high enough to
inhibit the spontaneous emission of the Rydberg atom, paving the way to
complete control of both external and internal degrees of freedom over very
long times. Trapping is achieved using carefully designed electric fields,
created by a simple pattern of electrodes. We show that it is possible to
excite, and then trap, one and only one Rydberg atom from a cloud of ground
state atoms confined on a magnetic atom chip, itself integrated with the
Rydberg trap. Distinct internal states of the atom are simultaneously trapped,
providing us with a two-level system extremely attractive for atom-surface and
atom-atom interaction studies. We describe a method for reducing by three
orders of magnitude dephasing due to Stark shifts, induced by the trapping
field, of the internal transition frequency. This allows for, in combination
with spin-echo techniques, maintenance of an internal coherence over times in
the second range. This method operates via a controlled light shift rendering
the two internal states' Stark shifts almost identical. We thoroughly identify
and account for sources of imperfection in order to verify at each step the
realism of our proposal.Comment: Accepted in EPJ
Breakdown of superfluidity of an atom laser past an obstacle
The 1D flow of a continuous beam of Bose-Einstein condensed atoms in the
presence of an obstacle is studied as a function of the beam velocity and of
the type of perturbing potential (representing the interaction of the obstacle
with the atoms of the beam). We identify the relevant regimes:
stationary/time-dependent and superfluid/dissipative; the absence of drag is
used as a criterion for superfluidity. There exists a critical velocity below
which the flow is superfluid. For attractive obstacles, we show that this
critical velocity can reach the value predicted by Landau's approach. For
penetrable obstacles, it is shown that superfluidity is recovered at large beam
velocity. Finally, enormous differences in drag occur when switching from
repulsive to attractive potential.Comment: 15 pages, 6 figure
Trapping cold atoms near carbon nanotubes: thermal spin flips and Casimir-Polder potential
We investigate the possibility to trap ultracold atoms near the outside of a
metallic carbon nanotube (CN) which we imagine to use as a miniaturized
current-carrying wire. We calculate atomic spin flip lifetimes and compare the
strength of the Casimir-Polder potential with the magnetic trapping potential.
Our analysis indicates that the Casimir-Polder force is the dominant loss
mechanism and we compute the minimum distance to the carbon nanotube at which
an atom can be trapped.Comment: 8 pages, 3 figure
Coherence length of an elongated condensate: a study by matter-wave interferometry
We measure the spatial correlation function of Bose-Einstein condensates in
the cross-over region between phase-coherent and strongly phase-fluctuating
condensates. We observe the continuous path from a gaussian-like shape to an
exponential-like shape characteristic of one-dimensional phase-fluctuations.
The width of the spatial correlation function as a function of the temperature
shows that the condensate coherence length undergoes no sharp transition
between these two regimes.Comment: 8 pages, 6 figure, submitted to EPJ
Analysis of an atom laser based on the spatial control of the scattering length
In this paper we analyze atom lasers based on the spatial modulation of the
scattering length of a Bose-Einstein Condensate. We demonstrate, through
numerical simulations and approximate analytical methods, the controllable
emission of matter-wave bursts and study the dependence of the process on the
spatial dependence of the scattering length along the axis of emission. We also
study the role of an additional modulation of the scattering length in time.Comment: Submitted to Phys. Rev.
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