1,038 research outputs found
Mesoscopic ensembles of polar bosons in triple-well potentials
Mesoscopic dipolar Bose gases in triple-well potentials offer a minimal
system for the analysis of the long-range character of the dipole-dipole
interactions. We show that this long-range character may be clearly revealed by
a variety of possible ground-state phases. In addition, an appropriate control
of short-range and dipolar interactions may lead to novel scenarios for the
dynamics of atoms and polar molecules in lattices, including the dynamical
creation of mesoscopic Schr\"odinger cats, which may be employed as a source of
highly-nonclassical states for Heisenberg-limited interferometry.Comment: 4 pages, 3 figures. Identical to the published version, including
supplemental material (4 pages, 6 figures)
Parametric Amplification and Back-Action Noise Squeezing by a Qubit-Coupled Nanoresonator
We demonstrate the parametric amplification and noise squeezing of nanomechanical motion utilizing dispersive coupling
to a Cooper-pair box qubit. By modulating the qubit bias and resulting mechanical resonance shift, we achieve gain of 30 dB and
noise squeezing of 4 dB. This qubit-mediated effect is 3000 times more effective than that resulting from the weak nonlinearity of
capacitance to a nearby electrode. This technique may be used to prepare nanomechanical squeezed states
Modeling of Time-Varying (max,+) Systems by means of Weighted Timed Event Graphs
International audienceThe (max,+) theory allows to describe the behavior of Timed Event Graphs (TEG) with constant holding times. For time-varying systems, a class of First-In First-Out TEGs with periodic holding times has already been studied in the literature. We show here that such time-varying TEGs can be modeled by equivalent Weighted TEGs for which an input-output model exists. In summary, we can describe FIFO TEGs with periodic holding times by means of ultimately periodic formal series in a dioid denoted E * per ÎŽ
Vortex dynamics of rotating dipolar Bose-Einstein condensates
We study the influence of dipole-dipole interaction on the formation of
vortices in a rotating dipolar Bose-Einstein condensate (BEC) of Cr and
Dy atoms in quasi two-dimensional geometry. By numerically solving the
corresponding time-dependent mean-field Gross-Pitaevskii equation, we show that
the dipolar interaction enhances the number of vortices while a repulsive
contact interaction increases the stability of the vortices. Further, an
ordered vortex lattice of relatively large number of vortices is found in a
strongly dipolar BEC.Comment: 15 pages, 10 figures, 1 tabl
Nonlinear Schr\"odinger equation for a PT symmetric delta-functions double well
The time-independent nonlinear Schr\"odinger equation is solved for two
attractive delta-function shaped potential wells where an imaginary loss term
is added in one well, and a gain term of the same size but with opposite sign
in the other. We show that for vanishing nonlinearity the model captures all
the features known from studies of PT symmetric optical wave guides, e.g., the
coalescence of modes in an exceptional point at a critical value of the
loss/gain parameter, and the breaking of PT symmetry beyond. With the
nonlinearity present, the equation is a model for a Bose-Einstein condensate
with loss and gain in a double well potential. We find that the nonlinear
Hamiltonian picks as stationary eigenstates exactly such solutions which render
the nonlinear Hamiltonian itself PT symmetric, but observe coalescence and
bifurcation scenarios different from those known from linear PT symmetric
Hamiltonians.Comment: 16 pages, 9 figures, to be published in Journal of Physics
Evaporative Cooling of a Guided Rubidium Atomic Beam
We report on our recent progress in the manipulation and cooling of a
magnetically guided, high flux beam of atoms. Typically
atoms per second propagate in a magnetic guide providing a
transverse gradient of 800 G/cm, with a temperature K, at an
initial velocity of 90 cm/s. The atoms are subsequently slowed down to cm/s using an upward slope. The relatively high collision rate (5 s)
allows us to start forced evaporative cooling of the beam, leading to a
reduction of the beam temperature by a factor of ~4, and a ten-fold increase of
the on-axis phase-space density.Comment: 10 pages, 8 figure
Cardiac Surgery in Octogenarians; Peri-Operative Outcome and Long-Term Results
AIMS: Because the elderly are increasingly referred for operation, we reviewed the results of cardiac surgery in patients of 80 years or older. METHODS AND RESULTS: Records of 182 consecutive octogenarians who had had cardiac operations between 1992 and 1998 were reviewed. Follow-up was 100% complete. Seventy patients had coronary grafting (CABG), 70 aortic valve replacement, 30 aortic valve replacement+CABG, and 12 mitral valve repair/replacement. Rates of hospital death, stroke, and prolonged stay (>14 days) were as follows: CABG: 7 (10%), 2 (2.8%) and 41 (58%); aortic valve replacement: 6 (8.5%), 2 (2.8%) and 32 (45.7%); aortic valve replacement+CABG: 8 (26.5%), 1 (3.8%) and 14 (46.6%); mitral valve repair/replacement: 3 (25%), 1 (8.3%) and 5 (41.6%). Multivariate predictors (P<0.05) of hospital death were New York Heart Association functional class, urgent procedure, prolonged cardiopulmonary bypass time, and, after aortic valve replacement, previous percutaneous aortic valvuloplasty. Ascending aortic atheromatous disease was predictive of stroke, while pre-operative myocardial infarction was predictive of prolonged hospital stay. Actuarial 5-year survival was as follows: CABG, 65.8+/-8.8%; aortic valve replacement, 63.6+/-7.1%; aortic valve replacement+CABG, 62.4+/-6.8%; mitral valve repair/replacement, 57.1+/-5.6%; and total, 63.0+/-5.6%. Multivariate predictors of late death were pre-operative myocardial infarction, and urgent procedure. Ninety percent of long-term survivors were in New York Heart Association class I or II, and 87% believed having a heart operation after age 80 years was a good choice. CONCLUSION: Cardiac operations are successful in most octogenarians with increased hospital mortality, and longer hospital stay. Long-term survival and quality of life are good
Dynamics of gap solitons in a dipolar Bose-Einstein condensate on a three-dimensional optical lattice
We suggest and study the stable disk- and cigar-shaped gap solitons of a
dipolar Bose-Einstein condensate of Cr atoms localized in the lowest
band gap by three optical-lattice (OL) potentials along orthogonal directions.
The one-dimensional version of these solitons of experimental interest confined
by an OL along the dipole moment direction and harmonic traps in transverse
directions is also considered. Important dynamics of (i) breathing oscillation
of a gap soliton upon perturbation and (ii) dragging of a gap soliton by a
moving lattice along axial direction demonstrates the stability of gap
solitons. A movie clip of dragging of three-dimensional gap soliton is
included.Comment: To see the dragging movie clip please download sourc
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