3,711 research outputs found
Pinning an Ion with an Intracavity Optical Lattice
We report one-dimensional pinning of a single ion by an optical lattice. The
lattice potential is produced by a standing-wave cavity along the rf-field-free
axis of a linear Paul trap. The ion's localization is detected by measuring its
fluorescence when excited by standing-wave fields with the same period, but
different spatial phases. The experiments agree with an analytical model of the
localization process, which we test against numerical simulations. For the best
localization achieved, the ion's average coupling to the cavity field is
enhanced from 50% to 81(3)% of its maximum possible value, and we infer that
the ion is bound in a lattice well with over 97% probability.Comment: 5 pages, 4 figures; Text edited for clarity, results unchange
Resonant enhancement of ultracold photoassociation rate by electric field induced anisotropic interaction
We study the effects of a static electric field on the photoassociation of a
heteronuclear atom-pair into a polar molecule. The interaction of permanent
dipole moment with a static electric field largely affects the ground state
continuum wave function of the atom-pair at short separations where
photoassociation transitions occur according to Franck-Condon principle.
Electric field induced anisotropic interaction between two heteronuclear ground
state atoms leads to scattering resonances at some specific electric fields.
Near such resonances the amplitude of scattering wave function at short
separation increases by several orders of magnitude. As a result,
photoaasociation rate is enhanced by several orders of magnitude near the
resonances. We discuss in detail electric field modified atom-atom scattering
properties and resonances. We calculate photoassociation rate that shows giant
enhancement due to electric field tunable anisotropic resonances. We present
selected results among which particularly important are the excitations of
higher rotational levels in ultracold photoassociation due to electric field
tunable resonances.Comment: 14 pages,9 figure
Cavity Assisted Nondestructive Laser Cooling of Atomic Qubits
We analyze two configurations for laser cooling of neutral atoms whose
internal states store qubits. The atoms are trapped in an optical lattice which
is placed inside a cavity. We show that the coupling of the atoms to the damped
cavity mode can provide a mechanism which leads to cooling of the motion
without destroying the quantum information.Comment: 12 page
The PCA Lens-Finder: application to CFHTLS
We present the results of a new search for galaxy-scale strong lensing
systems in CFHTLS Wide. Our lens-finding technique involves a preselection of
potential lens galaxies, applying simple cuts in size and magnitude. We then
perform a Principal Component Analysis of the galaxy images, ensuring a clean
removal of the light profile. Lensed features are searched for in the residual
images using the clustering topometric algorithm DBSCAN. We find 1098 lens
candidates that we inspect visually, leading to a cleaned sample of 109 new
lens candidates. Using realistic image simulations we estimate the completeness
of our sample and show that it is independent of source surface brightness,
Einstein ring size (image separation) or lens redshift. We compare the
properties of our sample to previous lens searches in CFHTLS. Including the
present search, the total number of lenses found in CFHTLS amounts to 678,
which corresponds to ~4 lenses per square degree down to i=24.8. This is
equivalent to ~ 60.000 lenses in total in a survey as wide as Euclid, but at
the CFHTLS resolution and depth.Comment: 21 pages, 12 figures, accepted for publication on A&
Dispersive Optical Interface Based on Nanofiber-Trapped Atoms
We dispersively interface an ensemble of one thousand atoms trapped in the
evanescent field surrounding a tapered optical nanofiber. This method relies on
the azimuthally-asymmetric coupling of the ensemble with the evanescent field
of an off-resonant probe beam, transmitted through the nanofiber. The resulting
birefringence and dispersion are significant; we observe a phase shift per atom
of \,1\,mrad at a detuning of six times the natural linewidth,
corresponding to an effective resonant optical density per atom of 0.027.
Moreover, we utilize this strong dispersion to non-destructively determine the
number of atoms.Comment: 4 pages, 4 figure
Fermi Surface of Metallic VO from Angle-Resolved Photoemission: Mid-level Filling of Bands
Using angle resolved photoemission spectroscopy (ARPES) we report the first
band dispersions and distinct features of the bulk Fermi surface (FS) in the
paramagnetic metallic phase of the prototypical metal-insulator transition
material VO. Along the -axis we observe both an electron pocket and
a triangular hole-like FS topology, showing that both V 3 and
states contribute to the FS. These results challenge the existing
correlation-enhanced crystal field splitting theoretical explanation for the
transition mechanism and pave the way for the solution of this mystery.Comment: 5 pages, 4 figures plus supplement 12 pages, 3 figures, 1 tabl
Transverse laser cooling of a thermal atomic beam of dysprosium
A thermal atomic beam of dysprosium (Dy) atoms is cooled using the
transition at 421 nm. The cooling is
done via a standing light wave orthogonal to the atomic beam. Efficient
transverse cooling to the Doppler limit is demonstrated for all observable
isotopes of dysprosium. Branching ratios to metastable states are demonstrated
to be . A scheme for enhancement of the
nonzero-nuclear-spin-isotope cooling, as well as a method for direct
identification of possible trap states, is proposed.Comment: 5 pages, 4 figures v2: 7 pages, 7 figure
Weak gravitational lensing with the Square Kilometre Array
We investigate the capabilities of various stages of the SKA to perform
world-leading weak gravitational lensing surveys. We outline a way forward to
develop the tools needed for pursuing weak lensing in the radio band. We
identify the key analysis challenges and the key pathfinder experiments that
will allow us to address them in the run up to the SKA. We identify and
summarize the unique and potentially very powerful aspects of radio weak
lensing surveys, facilitated by the SKA, that can solve major challenges in the
field of weak lensing. These include the use of polarization and rotational
velocity information to control intrinsic alignments, and the new area of weak
lensing using intensity mapping experiments. We show how the SKA lensing
surveys will both complement and enhance corresponding efforts in the optical
wavebands through cross-correlation techniques and by way of extending the
reach of weak lensing to high redshift.Comment: 19 pages, 6 figures. Cosmology Chapter, Advancing Astrophysics with
the SKA (AASKA14) Conference, Giardini Naxos (Italy), June 9th-13th 201
Critical behavior of repulsive linear -mers on triangular lattices
Monte Carlo (MC) simulations and finite-size scaling analysis have been
carried out to study the critical behavior in a submonolayer two-dimensional
gas of repulsive linear -mers on a triangular lattice at coverage
. A low-temperature ordered phase, characterized by a repetition of
alternating files of adsorbed -mers separated by adjacent empty sites,
is separated from the disordered state by a order-disorder phase transition
occurring at a finite critical temperature, . The MC technique was
combined with the recently reported Free Energy Minimization Criterion Approach
(FEMCA), [F. Rom\'a et al., Phys. Rev. B, 68, 205407, (2003)], to predict the
dependence of the critical temperature of the order-disorder transformation.
The dependence on of the transition temperature, , observed in MC
is in qualitative agreement with FEMCA. In addition, an accurate determination
of the critical exponents has been obtained for adsorbate sizes ranging between
and . For , the results reveal that the system does not belong
to the universality class of the two-dimensional Potts model with (,
monomers). Based on symmetry concepts, we suggested that the behavior observed
for and 3 could be generalized to include larger particle sizes ().Comment: 17 pages, 13 figure
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