5,068 research outputs found
Generation and detection of a sub-Poissonian atom number distribution in a one-dimensional optical lattice
We demonstrate preparation and detection of an atom number distribution in a
one-dimensional atomic lattice with the variance dB below the Poissonian
noise level. A mesoscopic ensemble containing a few thousand atoms is trapped
in the evanescent field of a nanofiber. The atom number is measured through
dual-color homodyne interferometry with a pW-power shot noise limited probe.
Strong coupling of the evanescent probe guided by the nanofiber allows for a
real-time measurement with a precision of atoms on an ensemble of some
atoms in a one-dimensional trap. The method is very well suited for
generating collective atomic entangled or spin-squeezed states via a quantum
non-demolition measurement as well as for tomography of exotic atomic states in
a one-dimensional lattice
Few-body resonances of unequal-mass systems with infinite interspecies two-body s-wave scattering length
Two-component Fermi and Bose gases with infinitely large interspecies s-wave
scattering length exhibit a variety of intriguing properties. Among these
are the scale invariance of two-component Fermi gases with equal masses, and
the favorable scaling of Efimov features for two-component Bose gases and
Bose-Fermi mixtures with unequal masses. This paper builds on our earlier work
[D. Blume and K. M. Daily, arXiv:1006.5002] and presents a detailed discussion
of our studies of small unequal-mass two-component systems with infinite
in the regime where three-body Efimov physics is absent. We report on
non-universal few-body resonances. Just like with two-body systems on
resonance, few-body systems have a zero-energy bound state in free space and a
diverging generalized scattering length. Our calculations are performed within
a non-perturbative microscopic framework and investigate the energetics and
structural properties of small unequal-mass two-component systems as functions
of the mass ratio , and the numbers and of heavy and
light atoms. For purely attractive Gaussian two-body interactions, we find that
the and systems exhibit three-body and four-body
resonances at mass ratios and 10.4(2), respectively. The
three- and four-particle systems on resonance are found to be large. This
suggests that the corresponding wave function has relatively small overlap with
deeply-bound dimers, trimers or larger clusters and that the three- and
four-body systems on resonance have a comparatively long lifetime. Thus, it
seems feasible that the features discussed in this paper can be probed
experimentally with present-day technology.Comment: 17 pages, 17 figure
Capacitive coupling of atomic systems to mesoscopic conductors
We describe a technique that enables a strong, coherent coupling between
isolated neutral atoms and mesoscopic conductors. The coupling is achieved by
exciting atoms trapped above the surface of a superconducting transmission line
into Rydberg states with large electric dipole moments, that induce voltage
fluctuations in the transmission line. Using a mechanism analogous to cavity
quantum electrodynamics an atomic state can be transferred to a long-lived mode
of the fluctuating voltage, atoms separated by millimeters can be entangled, or
the quantum state of a solid state device can be mapped onto atomic or photonic
states.Comment: 4 pages, including one figure. v2: Improved discussion of surface
effect
Bogoliubov theory of entanglement in a Bose-Einstein condensate
We consider a Bose-Einstein condensate which is illuminated by a short
resonant light pulse that coherently couples two internal states of the atoms.
We show that the subsequent time evolution prepares the atoms in an interesting
entangled state called a spin squeezed state. This evolution is analysed in
detail by developing a Bogoliubov theory which describes the entanglement of
the atoms. Our calculation is a consistent expansion in , where
is the number of particles in the condensate, and our theory predict that it is
possible to produce spin squeezing by at least a factor of . Within
the Bogoliubov approximation this result is independent of temperature.Comment: 14 pages, including 5 figures, minor changes in the presentatio
Depression in COPD â management and quality of life considerations
Depression is common in COPD patients. Around 40% are affected by severe depressive symptoms or clinical depression. It is not easy to diagnose depression in COPD patients because of overlapping symptoms between COPD and depression. However, the six-item Hamilton Depression Subscale appears to be a useful screening tool. Quality of life is strongly impaired in COPD patients and patientsâ quality of life emerges to be more correlated with the presence of depressive symptoms than with the severity of COPD. Nortriptyline and imipramine are effective in the treatment of depression, but little is known about the usefulness of newer antidepressants. In patients with milder depression, pulmonary rehabilitation as well as cognitive-behavioral therapy are effective. Little is known about the long-term outcome in COPD patients with co-morbid depression. Preliminary data suggest that co-morbid depression may be an independent protector for mortality
Differential Measurement of Trident Production in Strong Electromagnetic Fields
In this paper, we present experimental results and numerical simulations of
trident production, , in a strong electromagnetic
field. The experiment was conducted at CERN for the purpose of probing the
strong-field parameter up to 2.4, using a 200 GeV electron beam
penetrating a 400 m thick germanium crystal oriented along the axis. For the current experimental parameters we found that the
trident process is primarily a two-step process, and show remarkable agreement
between theoretical predictions and experimental data. This paper is an
extension of the previously published paper (Phys. Rev. Lett. 130, 071601
(2023)) and features new analysis differential in the energy of the produced
positron and electron in the trident process. Even for the more demanding
differential analysis, we find good agreement between theoretical predictions
and experimental data, while a slight discrepancy is found in the high energy
tail of the trident spectrum. This discrepancy could be an indication of the
direct process, but further investigation is needed due to the large
uncertainties in this part of the spectrum. Finally we present a suggestion for
a future experiment, aiming to probe the direct process using thin crystals
Band Positions Used for On-Line Crystallographic Orientation Determination from Electron Back Scattering Patterns
A computer procedure for on-line analysis of electron back scattering patterns (EBSP) has been developed. An experimental EBSP is computer recorded and displayed on a computer monitor. The user identifies the positions of at least two bands in the EBSP with a cursor. Based on this input the computer calculates possible crystallographic orientations. The corresponding EBSPs are simulated and superimposed on the experimental EBSP. The correct crystallographic orientation is determined from a comparison between the experimental and simulated EBSPs. Typically, the analysis takes a 10-30 seconds per pattern. Advantages with the present procedure are that it can be applied for any crystal symmetry, that it requires no knowledge about electron diffraction maps, that it can be used for EBSPs with relatively low contrast, and that the indexing is very precise. For relative orientation measurements the accuracy is found to be within range 0.05°-0.20°, whereas, for repeated measurements of a given grain after complete remounting of sample and EBSP equipment, it was determined to be 0.5°. Furthermore, the procedure facilitates fully automatic pattern recognition
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