1,248 research outputs found
Raman transitions between hyperfine clock states in a magnetic trap
We present our experimental investigation of an optical Raman transition
between the magnetic clock states of Rb in an atom chip magnetic trap.
The transfer of atomic population is induced by a pair of diode lasers which
couple the two clock states off-resonantly to an intermediate state manifold.
This transition is subject to destructive interference of two excitation paths,
which leads to a reduction of the effective two-photon Rabi-frequency.
Furthermore, we find that the transition frequency is highly sensitive to the
intensity ratio of the diode lasers. Our results are well described in terms of
light shifts in the multi-level structure of Rb. The differential light
shifts vanish at an optimal intensity ratio, which we observe as a narrowing of
the transition linewidth. We also observe the temporal dynamics of the
population transfer and find good agreement with a model based on the system's
master equation and a Gaussian laser beam profile. Finally, we identify several
sources of decoherence in our system, and discuss possible improvements.Comment: 10 pages, 7 figure
Radiation effects in silicon solar cells Quarterly report
Effect of lithium on production and annealing of damage in silico
Radiation effects in silicon solar cells Quarterly progress report, 1 Jul. - 30 Sep. 1970
Defects responsible for degradation in output of silicon solar cells irradiated by space radiatio
Trapping of Rydberg Atoms in Tight Magnetic Microtraps
We explore the possibility to trap Rydberg atoms in tightly confining
magnetic microtraps. The trapping frequencies for Rydberg atoms are expected to
be influenced strongly by magnetic field gradients. We show that there are
regimes where Rydberg atoms can be trapped. Moreover, we show that so-called
magic trapping conditions can be found for certain states of rubidium, where
both Rydberg atoms and ground state atoms have the same trapping frequencies.
Magic trapping is highly beneficial for implementing quantum gate operations
that require long operation times
On the differential geometry of curves in Minkowski space
We discuss some aspects of the differential geometry of curves in Minkowski
space. We establish the Serret-Frenet equations in Minkowski space and use them
to give a very simple proof of the fundamental theorem of curves in Minkowski
space. We also state and prove two other theorems which represent Minkowskian
versions of a very known theorem of the differential geometry of curves in
tridimensional Euclidean space. We discuss the general solution for torsionless
paths in Minkowki space. We then apply the four-dimensional Serret-Frenet
equations to describe the motion of a charged test particle in a constant and
uniform electromagnetic field and show how the curvature and the torsions of
the four-dimensional path of the particle contain information on the
electromagnetic field acting on the particle.Comment: 10 pages. Typeset using REVTE
Polar distortions in hydrogen bonded organic ferroelectrics
Although ferroelectric compounds containing hydrogen bonds were among the
first to be discovered, organic ferroelectrics are relatively rare. The
discovery of high polarization at room temperature in croconic acid [Nature
\textbf{463}, 789 (2010)] has led to a renewed interest in organic
ferroelectrics. We present an ab-initio study of two ferroelectric organic
molecular crystals, 1-cyclobutene-1,2-dicarboxylic acid (CBDC) and
2-phenylmalondialdehyde (PhMDA). By using a distortion-mode analysis we shed
light on the microscopic mechanisms contributing to the polarization, which we
find to be as large as 14.3 and 7.0\,C/cm for CBDC and PhMDA
respectively. These results suggest that it may be fruitful to search among
known but poorly characterized organic compounds for organic ferroelectrics
with enhanced polar properties suitable for device applications.Comment: Submitte
Controlling Stray Electric Fields on an Atom Chip for Rydberg Experiments
Experiments handling Rydberg atoms near surfaces must necessarily deal with
the high sensitivity of Rydberg atoms to (stray) electric fields that typically
emanate from adsorbates on the surface. We demonstrate a method to modify and
reduce the stray electric field by changing the adsorbates distribution. We use
one of the Rydberg excitation lasers to locally affect the adsorbed dipole
distribution. By adjusting the averaged exposure time we change the strength
(with the minimal value less than at
from the chip) and even the sign of the perpendicular field component. This
technique is a useful tool for experiments handling Ryberg atoms near surfaces,
including atom chips
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