152 research outputs found
Ultralong-Range Rydberg Molecules in a Divalent-Atomic System
We report the creation of ultralong-range Sr molecules comprising one
ground-state atom and one atom in a Rydberg state
for ranging from 29 to 36. Molecules are created in a trapped ultracold
atomic gas using two-photon excitation near resonant with the
intermediate state, and their formation is detected through ground-state atom
loss from the trap. The observed molecular binding energies are fit with the
aid of first-order perturbation theory that utilizes a Fermi pseudopotential
with effective -wave and -wave scattering lengths to describe the
interaction between an excited Rydberg electron and a ground-state Sr atom.Comment: 5 pages, 2 figure
Many-body quantum chaos in stroboscopically-driven cold atoms
Seeking signatures of quantum chaos in experimentally realizable many-body
systems is of vigorous interest. In such systems, the spectral form factor
(SFF), defined as the Fourier transform of two-level spectral correlation
function, is known to exhibit random matrix theory (RMT) behaviors, namely a
'ramp' followed by a 'plateau' in sufficiently late time. Recently, a generic
early-time deviation from the RMT behavior, which we call the 'bump', has been
shown to exist in random quantum circuits and spin chains as toy models for
many-body quantum chaotic systems. Here we demonstrate the existence of the
'bump-ramp-plateau' behavior in the SFF for a number of paradigmatic,
stroboscopically-driven cold atom models of interacting bosons in optical
lattices and spinor condensates. We find that the scaling of the many-body
Thouless time -- the time of the onset of the (RMT) ramp
behavior -- and the increase of the bump amplitude in atom number are
significantly slower in (effectively 0D) chaotic spinor gases than in 1D
optical lattices, demonstrating the role of locality in many-body quantum
chaos. Moreover, scaling and the bump amplitude are more
sensitive to variations in atom number than the system size regardless of the
hyperfine structure, the symmetry classes, or the choice of the driving
protocol. We obtain scaling functions of SFF which suggest power-law behavior
for the bump regime in quantum chaotic cold-atom systems. Finally, we propose
an interference measurement protocol to probe SFF in the laboratory.Comment: 10 pages, 7 figures, supplementary materia
Probing Nonlocal Spatial Correlations in Quantum Gases with Ultra-long-range Rydberg Molecules
We present photo-excitation of ultra-long-range Rydberg molecules as a probe
of spatial correlations in quantum gases. Rydberg molecules can be created with
well-defined internuclear spacing, set by the radius of the outer lobe of the
Rydberg electron wavefunction . By varying the principal quantum number
of the target Rydberg state, the molecular excitation rate can be used to
map the pair-correlation function of the trapped gas . We
demonstrate this with ultracold Sr gases and probe pair-separation length
scales ranging from , which are on the order of the
thermal de Broglie wavelength for temperatures around 1 K. We observe
bunching for a single-component Bose gas of Sr and anti-bunching due to
Pauli exclusion at short distances for a polarized Fermi gas of Sr,
revealing the effects of quantum statistics.Comment: 6 pages, 5 figure
Creation of Rydberg Polarons in a Bose Gas
We report spectroscopic observation of Rydberg polarons in an atomic Bose
gas. Polarons are created by excitation of Rydberg atoms as impurities in a
strontium Bose-Einstein condensate. They are distinguished from previously
studied polarons by macroscopic occupation of bound molecular states that arise
from scattering of the weakly bound Rydberg electron from ground-state atoms.
The absence of a -wave resonance in the low-energy electron-atom scattering
in Sr introduces a universal behavior in the Rydberg spectral lineshape and in
scaling of the spectral width (narrowing) with the Rydberg principal quantum
number, . Spectral features are described with a functional determinant
approach (FDA) that solves an extended Fr\"{o}hlich Hamiltonian for a mobile
impurity in a Bose gas. Excited states of polyatomic Rydberg molecules
(trimers, tetrameters, and pentamers) are experimentally resolved and
accurately reproduced with FDA.Comment: 5 pages, 3 figure
Impact of vitamin C supplementation on post-cardiac surgery ICU and hospital length of stay
Background: Prolonged intensive care unit (ICU) and hospital stay after cardiac surgery is vitally important and is influenced by both intraoperative and postoperative factors.Objectives: This randomized clinical trial study was designed to assess whether vitamin C supplementation could reduce the length of ICU and hospital stay in post-cardiac surgery patients.Patients and Methods: Two hundred and ninety patients scheduled for adult cardiac surgery including coronary, valve and congenital operations were randomized into two groups: an intervention group, who received 2 g of vitamin C (ascorbic acid) intravenously, immediately before surgery in the operating theatre, followed by 1 g daily oral doses for the first 4 postoperative days; and a placebo group,who received an equal number of identical tablets in the same shape and size. Results: Hospital length of stay was significantly different between the two groups (10.17 ± 4.63 days in the intervention group vs. 12 ± 4.51 days in the placebo group; P = 0.01), while there was no significant difference in the ICU stay between the groups (3.42 ± 1.06 days in intervention group vs. 3.43 ± 1.09 days in the placebo group; P = 0.88). There were significant differences in the intubation time and the drainage volume in the ICU and the first 24 postoperative hours between the two groups (P for both = 0.003). Conclusions: Vitamin C can decrease the length of hospital stay, drainage volume in the ICU and in the first 24 postoperative hours, intubation time and some complications in patients after cardiac surgery; perhaps by decreasing inflammatory factors. Background: Prolonged intensive care unit (ICU) and hospital stay after cardiac surgery is vitally important and is influenced by both intraoperative and postoperative factors.Objectives: This randomized clinical trial study was designed to assess whether vitamin C supplementation could reduce the length of ICU and hospital stay in post-cardiac surgery patients.Patients and Methods: Two hundred and ninety patients scheduled for adult cardiac surgery including coronary, valve and congenital operations were randomized into two groups: an intervention group, who received 2 g of vitamin C (ascorbic acid) intravenously, immediately before surgery in the operating theatre, followed by 1 g daily oral doses for the first 4 postoperative days; and a placebo group,who received an equal number of identical tablets in the same shape and size. Results: Hospital length of stay was significantly different between the two groups (10.17 ± 4.63 days in the intervention group vs. 12 ± 4.51 days in the placebo group; P = 0.01), while there was no significant difference in the ICU stay between the groups (3.42 ± 1.06 days in intervention group vs. 3.43 ± 1.09 days in the placebo group; P = 0.88). There were significant differences in the intubation time and the drainage volume in the ICU and the first 24 postoperative hours between the two groups (P for both = 0.003). Conclusions: Vitamin C can decrease the length of hospital stay, drainage volume in the ICU and in the first 24 postoperative hours, intubation time and some complications in patients after cardiac surgery; perhaps by decreasing inflammatory factors. © 2015, Iranian Society of Regional Anesthesia and Pain Medicine (ISRAPM)
Dilated cardiomyopathy as a rare presentation of the pulmonary sequestration: A case report with aberrant vessel from aorta to left lower pulmonary lobe
Late onset non-ischemic cardiomyopathy is a rare manifestation of the presence of aberrant vessel from descending thoracic aorta to left lower lobe of lung. This congenital anomaly is associated with pulmonary sequestration. Our case was a 23-year-old male who was under observation since the age of 19 years for evaluation of shortness of breath, functional class II. He had history of professional athletic training and he denied consumption of any compound. Ejection fraction had deteriorated during three years from 45�50 to 40 and left ventricular size increased from normal size to mild enlargement. Cardiac computed tomography showed presence of aberrant artery from descending aorta to left lower pulmonary lobe with pulmonary sequestration. His cardiac function improved after successful coil embolization of aberrant vessel. In conclusion, pulmonary sequestration and aberrant pulmonary supply from aorta should be considered as a rare cause of dilated cardiomyopathy which can be reversible by proper intervention. © 2019 Japanese College of Cardiolog
Quantum Phases of Dipolar Bosons in Bilayer Geometry
We investigate the quantum phases of hard-core dipolar bosons confined to a
square lattice in a bilayer geometry. Using exact theoretical techniques, we
discuss the many-body effects resulting from pairing of particles across layers
at finite density, including a novel pair supersolid phase, superfluid and
solid phases. These results are of direct relevance to experiments with polar
molecules and atoms with large magnetic dipole moments trapped in optical
lattices.Comment: 7 pages, 5 figure
Geometry and symmetries of multi-particle systems
The quantum dynamical evolution of atomic and molecular aggregates, from
their compact to their fragmented states, is parametrized by a single
collective radial parameter. Treating all the remaining particle coordinates in
d dimensions democratically, as a set of angles orthogonal to this collective
radius or by equivalent variables, bypasses all independent-particle
approximations. The invariance of the total kinetic energy under arbitrary
d-dimensional transformations which preserve the radial parameter gives rise to
novel quantum numbers and ladder operators interconnecting its eigenstates at
each value of the radial parameter.
We develop the systematics and technology of this approach, introducing the
relevant mathematics tutorially, by analogy to the familiar theory of angular
momentum in three dimensions. The angular basis functions so obtained are
treated in a manifestly coordinate-free manner, thus serving as a flexible
generalized basis for carrying out detailed studies of wavefunction evolution
in multi-particle systems.Comment: 37 pages, 2 eps figure
The variable phase method used to calculate and correct scattering lengths
It is shown that the scattering length can be obtained by solving a Riccati
equation derived from variable phase theory. Two methods of solving it are
presented. The equation is used to predict how long-range interactions
influence the scattering length, and upper and lower bounds on the scattering
length are determined. The predictions are compared with others and it is shown
how they may be obtained from secular perturbation theory.Comment: 7 pages including 3 figure
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