166 research outputs found
Trapping of Neutral Rubidium with a Macroscopic Three-Phase Electric Trap
We trap neutral ground-state rubidium atoms in a macroscopic trap based on
purely electric fields. For this, three electrostatic field configurations are
alternated in a periodic manner. The rubidium is precooled in a magneto-optical
trap, transferred into a magnetic trap and then translated into the electric
trap. The electric trap consists of six rod-shaped electrodes in cubic
arrangement, giving ample optical access. Up to 10^5 atoms have been trapped
with an initial temperature of around 20 microkelvin in the three-phase
electric trap. The observations are in good agreement with detailed numerical
simulations.Comment: 4 pages, 4 figure
Tunable gauge potential for neutral and spinless particles in driven lattices
We present a universal method to create a tunable, artificial vector gauge
potential for neutral particles trapped in an optical lattice. The necessary
Peierls phase of the hopping parameters between neighboring lattice sites is
generated by applying a suitable periodic inertial force such that the method
does not rely on any internal structure of the particles. We experimentally
demonstrate the realization of such artificial potentials, which generate
ground state superfluids at arbitrary non-zero quasi-momentum. We furthermore
investigate possible implementations of this scheme to create tuneable magnetic
fluxes, going towards model systems for strong-field physics
Minimally-destructive detection of magnetically-trapped atoms using frequency-synthesised light
We present a technique for atomic density measurements by the off-resonant
phase-shift induced on a two-frequency, coherently-synthesised light beam. We
have used this scheme to measure the column density of a magnetically trapped
atom cloud and to monitor oscillations of the cloud in real time by making over
a hundred non-destructive local density measurments. For measurements using
pulses of 10,000-100,000 photons lasting ~10 microsecond, the precision is
limited by statistics of the photons and the photodiode avalanche. We explore
the relationship between measurement precision and the unwanted loss of atoms
from the trap and introduce a figure of merit that characterises it. This
method can be used to probe the density of a BEC with minimal disturbance of
its phase.Comment: Submitted to New Journal of Physic
A compact and robust diode laser system for atom interferometry on a sounding rocket
We present a diode laser system optimized for laser cooling and atom
interferometry with ultra-cold rubidium atoms aboard sounding rockets as an
important milestone towards space-borne quantum sensors. Design, assembly and
qualification of the system, combing micro-integrated distributed feedback
(DFB) diode laser modules and free space optical bench technology is presented
in the context of the MAIUS (Matter-wave Interferometry in Microgravity)
mission.
This laser system, with a volume of 21 liters and total mass of 27 kg, passed
all qualification tests for operation on sounding rockets and is currently used
in the integrated MAIUS flight system producing Bose-Einstein condensates and
performing atom interferometry based on Bragg diffraction. The MAIUS payload is
being prepared for launch in fall 2016.
We further report on a reference laser system, comprising a rubidium
stabilized DFB laser, which was operated successfully on the TEXUS 51 mission
in April 2015. The system demonstrated a high level of technological maturity
by remaining frequency stabilized throughout the mission including the rocket's
boost phase
Quantum simulation of frustrated magnetism in triangular optical lattices
Magnetism plays a key role in modern technology as essential building block
of many devices used in daily life. Rich future prospects connected to
spintronics, next generation storage devices or superconductivity make it a
highly dynamical field of research. Despite those ongoing efforts, the
many-body dynamics of complex magnetism is far from being well understood on a
fundamental level. Especially the study of geometrically frustrated
configurations is challenging both theoretically and experimentally. Here we
present the first realization of a large scale quantum simulator for magnetism
including frustration. We use the motional degrees of freedom of atoms to
comprehensively simulate a magnetic system in a triangular lattice. Via a
specific modulation of the optical lattice, we can tune the couplings in
different directions independently, even from ferromagnetic to
antiferromagnetic. A major advantage of our approach is that standard
Bose-Einstein-condensate temperatures are sufficient to observe magnetic
phenomena like N\'eel order and spin frustration. We are able to study a very
rich phase diagram and even to observe spontaneous symmetry breaking caused by
frustration. In addition, the quantum states realized in our spin simulator are
yet unobserved superfluid phases with non-trivial long-range order and
staggered circulating plaquette currents, which break time reversal symmetry.
These findings open the route towards highly debated phases like spin-liquids
and the study of the dynamics of quantum phase transitions.Comment: 5 pages, 4 figure
Non-Destructive Probing of Rabi Oscillations on the Cesium Clock Transition near the Standard Quantum Limit
We report on non-destructive observation of Rabi oscillations on the Cs clock
transition. The internal atomic state evolution of a dipole-trapped ensemble of
cold atoms is inferred from the phase shift of a probe laser beam as measured
using a Mach-Zehnder interferometer. We describe a single color as well as a
two-color probing scheme. Using the latter, measurements of the collective
pseudo-spin projection of atoms in a superposition of the clock states are
performed and the observed spin fluctuations are shown to be close to the
standard quantum limit.Comment: 4 pages, 4 figures, accepted for publication in Physical Review
Letter
Efficient Guiding of Cold Atoms though a Photonic Band Gap Fiber
We demonstrate the first guiding of cold atoms through a 88 mm long piece of
photonic band gap fiber. The guiding potential is created by a far-off
resonance dipole trap propagating inside the fiber with a hollow core of 12 mu
m. We load the fiber from a dark spot 85-Rb magneto optical trap and observe a
peak flux of more than 10^5 atoms/s at a velocity of 1.5 m/s. With an
additional reservoir optical dipole trap, a constant atomic flux of 1.5 10^4
atoms/s is sustained for more than 150\,ms. These results open up interesting
possibilities to study nonlinear light-matter interaction in a nearly
one-dimensional geometry and pave the way for guided matter wave
interferometry.Comment: 8 pages, 3 figure
Quantum phase transition to unconventional multi-orbital superfluidity in optical lattices
Orbital physics plays a significant role for a vast number of important
phenomena in complex condensed matter systems such as high-T
superconductivity and unconventional magnetism. In contrast, phenomena in
superfluids -- especially in ultracold quantum gases -- are commonly well
described by the lowest orbital and a real order parameter. Here, we report on
the observation of a novel multi-orbital superfluid phase with a {\it complex}
order parameter in binary spin mixtures. In this unconventional superfluid, the
local phase angle of the complex order parameter is continuously twisted
between neighboring lattice sites. The nature of this twisted superfluid
quantum phase is an interaction-induced admixture of the p-orbital favored by
the graphene-like band structure of the hexagonal optical lattice used in the
experiment. We observe a second-order quantum phase transition between the
normal superfluid (NSF) and the twisted superfluid phase (TSF) which is
accompanied by a symmetry breaking in momentum space. The experimental results
are consistent with calculated phase diagrams and reveal fundamentally new
aspects of orbital superfluidity in quantum gas mixtures. Our studies might
bridge the gap between conventional superfluidity and complex phenomena of
orbital physics.Comment: 5 pages, 4 figure
Interferometry with Bose-Einstein Condensates in Microgravity
Atom interferometers covering macroscopic domains of space-time are a
spectacular manifestation of the wave nature of matter. Due to their unique
coherence properties, Bose-Einstein condensates are ideal sources for an atom
interferometer in extended free fall. In this paper we report on the
realization of an asymmetric Mach-Zehnder interferometer operated with a
Bose-Einstein condensate in microgravity. The resulting interference pattern is
similar to the one in the far-field of a double-slit and shows a linear scaling
with the time the wave packets expand. We employ delta-kick cooling in order to
enhance the signal and extend our atom interferometer. Our experiments
demonstrate the high potential of interferometers operated with quantum gases
for probing the fundamental concepts of quantum mechanics and general
relativity.Comment: 8 pages, 3 figures; 8 pages of supporting materia
Mutation in NSUN2, which Encodes an RNA Methyltransferase, Causes Autosomal-Recessive Intellectual Disability
Causes of autosomal-recessive intellectual disability (ID) have, until very recently, been under researched because of the high degree of genetic heterogeneity. However, now that genome-wide approaches can be applied to single multiplex consanguineous families, the identification of genes harboring disease-causing mutations by autozygosity mapping is expanding rapidly. Here, we have mapped a disease locus in a consanguineous Pakistani family affected by ID and distal myopathy. We genotyped family members on genome-wide SNP microarrays and used the data to determine a single 2.5 Mb homozygosity-by-descent (HBD) locus in region 5p15.32–p15.31; we identified the missense change c.2035G>A (p.Gly679Arg) at a conserved residue within NSUN2. This gene encodes a methyltransferase that catalyzes formation of 5-methylcytosine at C34 of tRNA-leu(CAA) and plays a role in spindle assembly during mitosis as well as chromosome segregation. In mouse brains, we show that NSUN2 localizes to the nucleolus of Purkinje cells in the cerebellum. The effects of the mutation were confirmed by the transfection of wild-type and mutant constructs into cells and subsequent immunohistochemistry. We show that mutation to arginine at this residue causes NSUN2 to fail to localize within the nucleolus. The ID combined with a unique profile of comorbid features presented here makes this an important genetic discovery, and the involvement of NSUN2 highlights the role of RNA methyltransferase in human neurocognitive development
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