2,552 research outputs found
Entanglement measurement of the quadrature components without the homodyne detection in the spatially multi-mode far-field
We consider the measuring procedure that in principle allows to avoid the
homodyne detection for the simultaneous selection of both quadrature components
in the far-field. The scheme is based on the use of the coherent sources of the
non-classical light. The possibilities of the procedure are illustrated on the
basis of the use of pixellised sources, where the phase-locked sub-Poissonian
lasers or the degenerate optical parametric oscillator generating above
threshold are chosen as the pixels. The theory of the pixellised source of the
spatio-temporal squeezed light is elaborated as a part of this investigation.Comment: 11 pages, 5 figures, RevTeX4. Submitted to Phys. Rev.
Determination of two-body potentials from n-body spectra
We show how the two-body potential may be uniquely determined from n-body
spectra where the hypercentral approximation is valid. We illustrate this by
considering an harmonic oscillator potential which has been altered by changing
the energy or normalisation constant of the ground state of the n-body system
and finding how this modifies the two-body potential. It is shown that with
increasing number of particles the spectrum must be known more precisely to
obtain the two-body potential to the same degree of accuracy.Comment: 13 pages of text (LATEX), 3 figures (not included, available from
authors), NIKHEF-93-P
Zeeman slowers made simple with permanent magnets in a Halbach configuration
We describe a simple Zeeman slower design using permanent magnets. Contrary
to common wire-wound setups no electric power and water cooling are required.
In addition, the whole system can be assembled and disassembled at will. The
magnetic field is however transverse to the atomic motion and an extra repumper
laser is necessary. A Halbach configuration of the magnets produces a high
quality magnetic field and no further adjustment is needed. After optimization
of the laser parameters, the apparatus produces an intense beam of slow and
cold 87Rb atoms. With a typical flux of 1 - 5 \times 10^10 atoms/s at 30 ms^-1,
our apparatus efficiently loads a large magneto-optical trap with more than
10^10 atoms in one second, which is an ideal starting point for degenerate
quantum gases experiments.Comment: 8+6 pages (article + appendices: calculation details, probe and oven
description, pictures), 18 figures, supplementary material (movie,
Mathematica programs and technical drawings
Independent nonclassical tests for states and measurements in the same experiment
We show that one single experiment can test simultaneously and independently
both the nonclassicality of states and measurements by the violation or
fulfillment of classical bounds on the statistics. Nonideal measurements
affected by imperfections can be characterized by two bounds depending on
whether we test the ideal measurement or the real one.Comment: 9 pages, 3 figures. Proceedings of 17th CEWQO 201
Change in acetabular version after lumbar pedicle subtraction osteotomy to correct post-operative flat back: EOSÂź measurements of 38Â acetabula
AbstractBackgroundAbnormalities in acetabular orientation can promote the development of hip osteoarthritis, femoro-acetabular impingement, or even acetabular cup malposition. The objective of the present study was to determine whether pedicle substraction osteotomy (PSO) to correct sagittal spinal imbalance affected acetabular orientation.HypothesisPSO performed to correct sagittal spinal imbalance affects acetabular orientation by changing the pelvic parameters.Materials and methodsThis was a descriptive study in which two observers measured the acetabular parameters on both sides in 19 patients (38 acetabula) before and after PSO for post-operative flat-back syndrome. Mean time from PSO to post-operative measurements was 19months. Measurements were taken twice at a 2-week interval, on standing images obtained using the EOSŸ imaging system and sterEOSŸ software to obtain 3D reconstructions of synchronised 2D images. Acetabular anteversion and inclination were measured relative to the vertical plane. Mean pre-PSO and post-PSO values were compared using the paired t-test, and P values lower than 0.05 were considered significant. To assess inter-observer and intra-observer reproducibility, we computed the intra-class correlation coefficients (ICCs).ResultsThe measurements showed significant acetabular retroversion after PSO, of 7.6° on the right and 6.5° on the left (P<0.001). Acetabular inclination diminished significantly, by 4.5° on the right and 2.5° on the left (P<0.01). Inclination of the anterior pelvic plane decreased by 8.4° (P<0.01). Pelvic incidence was unchanged, whereas sacral slope increased by 10.5° (P<0.001) and pelvic tilt decreased by 10.9° (P<0.001). The ICC was 0.98 for both inter-observer and intra-observer reproducibility.ConclusionChanging the sagittal spinal alignment modifies both the pelvic and the acetabular parameters. PSO significantly increases sacral slope, thus inducing anterior pelvic tilt with significant acetabular retroversion. The measurements obtained using sterEOSŸ showed good inter-observer and intra-observer reproducibility. To our knowledge, this is the first study of changes in acetabular version after PSO
Entanglement and squeezing in a two-mode system: theory and experiment
We report on the generation of non separable beams produced via the
interaction of a linearly polarized beam with a cloud of cold cesium atoms
placed in an optical cavity. We convert the squeezing of the two linear
polarization modes into quadrature entanglement and show how to find out the
best entanglement generated in a two-mode system using the inseparability
criterion for continuous variable [Duan et al., Phys. Rev. Lett. 84, 2722
(2000)]. We verify this method experimentally with a direct measurement of the
inseparability using two homodyne detections. We then map this entanglement
into a polarization basis and achieve polarization entanglement.Comment: submitted to J. Opt. B for a Special Issue on Foundations of Quantum
Optic
Radiation-pressure cooling and optomechanical instability of a micro-mirror
Recent experimental progress in table-top experiments or gravitational-wave
interferometers has enlightened the unique displacement sensitivity offered by
optical interferometry. As the mirrors move in response to radiation pressure,
higher power operation, though crucial for further sensitivity enhancement,
will however increase quantum effects of radiation pressure, or even jeopardize
the stable operation of the detuned cavities proposed for next-generation
interferometers. The appearance of such optomechanical instabilities is the
result of the nonlinear interplay between the motion of the mirrors and the
optical field dynamics. In a detuned cavity indeed, the displacements of the
mirror are coupled to intensity fluctuations, which modifies the effective
dynamics of the mirror. Such "optical spring" effects have already been
demonstrated on the mechanical damping of an electromagnetic waveguide with a
moving wall, on the resonance frequency of a specially designed flexure
oscillator, and through the optomechanical instability of a silica
micro-toroidal resonator. We present here an experiment where a
micro-mechanical resonator is used as a mirror in a very high-finesse optical
cavity and its displacements monitored with an unprecedented sensitivity. By
detuning the cavity, we have observed a drastic cooling of the micro-resonator
by intracavity radiation pressure, down to an effective temperature of 10 K. We
have also obtained an efficient heating for an opposite detuning, up to the
observation of a radiation-pressure induced instability of the resonator.
Further experimental progress and cryogenic operation may lead to the
experimental observation of the quantum ground state of a mechanical resonator,
either by passive or active cooling techniques
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