8,472 research outputs found
The PlySs9 endolysin and its amidase subdomain reveal potential roles in the treatment of Gram-positive bovine mastitis
Observation of Stueckelberg oscillations in dipole-dipole interactions
We have observed Stueckelberg oscillations in the dipole-dipole interaction
between Rydberg atoms with an externally applied radio-frequency field. The
oscillating RF field brings the interaction between cold Rydberg atoms in two
separated volumes into resonance. We observe multi-photon transitions when
varying the amplitude of the RF-field and the static electric field offset. The
angular momentum states we use show a quadratic Stark shift, which leads to a
fundamentally different behavior than linearly shifting states. Both cases are
studied theoretically using the Floquet approach and are compared. The
amplitude of the sidebands, related to the interaction strength, is given by
the Bessel function in the linearly shifting case and by the generalized Bessel
function in the quadratically shifting case. The oscillatory behavior of both
functions corresponds to Stueckelberg oscillations, an interference effect
described by the semi-classical Landau-Zener-Stueckelberg model. The
measurements prove coherent dipole-dipole interaction during at least 0.6
micro-seconds
Designs of magnetic atom-trap lattices for quantum simulation experiments
We have designed and realized magnetic trapping geometries for ultracold
atoms based on permanent magnetic films. Magnetic chip based experiments give a
high level of control over trap barriers and geometric boundaries in a compact
experimental setup. These structures can be used to study quantum spin physics
in a wide range of energies and length scales. By introducing defects into a
triangular lattice, kagome and hexagonal lattice structures can be created.
Rectangular lattices and (quasi-)one-dimensional structures such as ladders and
diamond chain trapping potentials have also been created. Quantum spin models
can be studied in all these geometries with Rydberg atoms, which allow for
controlled interactions over several micrometers. We also present some
nonperiodic geometries where the length scales of the traps are varied over a
wide range. These tapered structures offer another way to transport large
numbers of atoms adiabatically into subwavelength traps and back.Comment: 9 pages, 10 figure
High-Precision Measurement of Rydberg State Hyperfine Splitting in a Room-Temperature Vapour Cell
We present direct measurements of the hyperfine splitting of Rydberg states
in rubidium 87 using Electromagnetically Induced Transparency (EIT)
spectroscopy in a room-temperature vapour cell. With this method, and in spite
of Doppler-broadening, line-widths of 3.7 MHz FWHM, i.e. significantly below
the intermediate state natural linewidth are reached. This allows resolving
hyperfine splittings for Rydberg s-states with n=20...24. With this method we
are able to determine Rydberg state hyperfine splittings with an accuracy of
approximately 100 kHz. Ultimately our method allows accuracies of order 5 kHz
to be reached. Furthermore we present a direct measurement of
hyperfine-resolved Rydberg state Stark-shifts. These results will be of great
value for future experiments relying on excellent knowledge of Rydberg-state
energies an
Cold trapped atoms detected with evanescent waves
We demonstrate the in situ detection of cold 87 Rb atoms near a dielectric
surface using the absorption of a weak, resonant evanescent wave. We have used
this technique in time of flight experiments determining the density of atoms
falling on the surface. A quantitative understanding of the measured curve was
obtained using a detailed calculation of the evanescent intensity distribution.
We have also used it to detect atoms trapped near the surface in a
standing-wave optical dipole potential. This trap was loaded by inelastic
bouncing on a strong, repulsive evanescent potential. We estimate that we trap
1.5 x 10 4 atoms at a density 100 times higher than the falling atoms.Comment: 5 pages, 3 figure
Fisrt report of indigenous Dermacentor reticulatus populations in Belgium and preliminary study on associated Babesiosis pathogens
Bounds on relative entropy of entanglement for multi-party systems
We present upper and lower bounds to the relative entropy of entanglement of
multi-party systems in terms of the bi-partite entanglements of formation and
distillation and entropies of various subsystems. We point out implications of
our results to the local reversible convertibility of multi-party pure states
and discuss their physical basis in terms of deleting of information.Comment: 4 pages, no figure
On the derivation of SPH schemes for shocks through inhomogeneous media
Smoothed Particle Hydrodynamics (SPH) is typically used for the simulation of shock propagation through solid media, commonly observed during hypervelocity impacts. Although schemes for impacts into monolithic structures have been studied using SPH, problems occur when multimaterial structures are considered. This study begins from a variational framework and builds schemes for multiphase compressible problems, coming from different density estimates. Algorithmic details are discussed and results are compared upon three one-dimensional Riemann problems of known behavior
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