166 research outputs found
Guiding Neutral Atoms with a Wire
We demonstrate guiding of cold neutral atoms along a current carrying wire.
Atoms either move in Kepler-like orbits around the wire or are guided in a
potential tube on the side of the wire which is created by applying an
additional homogeneous bias field. These atom guides are very versatile and
promising for applications in atom optics.Comment: 4 pages, 6 figures, submitted to PR
Observation of decoherence with a movable mirror
Recently it has been proposed to use parity as a measure of the mechanism
behind decoherence or the transformation from quantum to classical. Here, we
show that the proposed experiment is more feasible than previously thought, as
even an initial thermal state would exhibit the hypothesized symmetry breaking.Comment: Proceedings of the Lake Garda "quantum puzzles" conferenc
Multiple scattering of matter waves: an analytic model of the refractive index for atomic and molecular gases
We present an analytic model of the refractive index for matter waves
propagating through atomic or molecular gases. The model, which combines a WKB
treatment of the long range attraction with the Fraunhofer model treatment of
the short range repulsion, furnishes a refractive index in compelling agreement
with recent experiments of Jacquey et al. [Phys. Rev. Lett. 98, 240405 (2007)]
on Li atom matter waves passing through dilute noble gases. We show that the
diffractive contribution, which arises from scattering by a two dimensional
"hard core" of the potential, is essential for obtaining a correct imaginary
part of the refractive index.Comment: 5 pages, 1 figure, 2 table
Atom Chips
Atoms can be trapped and guided using nano-fabricated wires on surfaces,
achieving the scales required by quantum information proposals. These Atom
Chips form the basis for robust and widespread applications of cold atoms
ranging from atom optics to fundamental questions in mesoscopic physics, and
possibly quantum information systems
Fault-tolerant quantum repeater with atomic ensembles and linear optics
We present a detailed analysis of a new robust quantum repeater architecture
building on the original DLCZ protocol [L.M. Duan \textit{et al.}, Nature
(London) \textbf{414}, 413 (2001)]. The new architecture is based on two-photon
Hong-Ou-Mandel-type interference which relaxes the long-distance
interferometric stability requirements by about 7 orders of magnitude, from
sub-wavelength for the single photon interference required by DLCZ to the
coherence length of the photons, thereby removing the weakest point in the DLCZ
schema. Our proposal provides an exciting possibility for robust and realistic
long-distance quantum communication.Comment: Comments are welcome, to appear in Phys. Rev. A, accepted versio
Atom Chips: Fabrication and Thermal Properties
Neutral atoms can be trapped and manipulated with surface mounted microscopic
current carrying and charged structures. We present a lithographic fabrication
process for such atom chips based on evaporated metal films. The size limit of
this process is below 1m. At room temperature, thin wires can carry more
than 10A/cm current density and voltages of more than 500V. Extensive
test measurements for different substrates and metal thicknesses (up to 5
m) are compared to models for the heating characteristics of the
microscopic wires. Among the materials tested, we find that Si is the best
suited substrate for atom chips
First measurements of the index of refraction of gases for lithium atomic waves
We report here the first measurements of the index of refraction of gases for
lithium waves. Using an atom interferometer, we have measured the real and
imaginary part of the index of refraction for argon, krypton and xenon, as
a function of the gas density for several velocities of the lithium beam. The
linear dependence of with the gas density is well verified. The total
collision cross-section deduced from the imaginary part is in very good
agreement with traditional measurements of this quantity. Finally, as predicted
by theory, the real and imaginary parts of and their ratio
exhibit glory oscillations
Quantum gates with neutral atoms: Controlling collisional interactions in time dependent traps
We theoretically study specific schemes for performing a fundamental
two-qubit quantum gate via controlled atomic collisions by switching
microscopic potentials. In particular we calculate the fidelity of a gate
operation for a configuration where a potential barrier between two atoms is
instantaneously removed and restored after a certain time. Possible
implementations could be based on microtraps created by magnetic and electric
fields, or potentials induced by laser light.Comment: 10 pages, 3 figure
Test of the isotopic and velocity selectivity of a lithium atom interferometer by magnetic dephasing
A magnetic field gradient applied to an atom interferometer induces a
-dependent phase shift which results in a series of decays and revivals of
the fringe visibility. Using our lithium atom interferometer based on Bragg
laser diffraction, we have measured the fringe visibility as a function of the
applied gradient. We have thus tested the isotopic selectivity of the
interferometer, the velocity selective character of Bragg diffraction for
different diffraction orders as well as the effect of optical pumping of the
incoming atoms. All these observations are qualitatively understood but a
quantitative analysis requires a complete model of the interferometer
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