81 research outputs found
Trapping of Single Atoms with Single Photons in Cavity QED
Two recent experiments have reported the trapping of individual atoms inside
optical resonators by the mechanical forces associated with single photons
[Hood et al., Science 287, 1447 (2000) and Pinkse et al., Nature 404, 365
(2000)]. Here we analyze the trapping dynamics in these settings, focusing on
two points of interest. Firstly, we investigate the extent to which
light-induced forces in these experiments are distinct from their free-space
counterparts. Secondly, we explore the quantitative features of the resulting
atomic motion and how these dynamics are mapped onto variations of the
intracavity field. Not surprisingly, qualitatively distinct atomic dynamics
arise as the coupling and dissipative rates are varied. For the experiment of
Hood et al., we show that atomic motion is largely conservative and is
predominantly in radial orbits transverse to the cavity axis. A comparison with
the free-space theory demonstrates that the fluctuations of the dipole force
are suppressed by an order of magnitude. This effect is based upon the
Jaynes-Cummings eigenstates of the atom-cavity system and represents
qualitatively new physics for optical forces at the single-photon level. By
contrast, even in a regime of strong coupling in the experiment of Pinkse et
al., there are only small quantitative distinctions between the free-space
theory and the quantum theory, so it is not clear that description of this
experiment as a novel single-quantum trapping effect is necessary. The atomic
motion is strongly diffusive, leading to an average localization time
comparable to the time for an atom to transit freely through the cavity and to
a reduction in the ability to infer aspects of the atomic motion from the
intracavity photon number.Comment: 19 pages, 22 figure files, REVTEX, corrected spelling, LaTeX now
produces postscript which includes figures, minor changes to figures. Final
version to be published in Physical Review A, expanded summary of results in
introduction, minor changes to figures and tex
Cavity cooling of a single atom
All conventional methods to laser-cool atoms rely on repeated cycles of
optical pumping and spontaneous emission of a photon by the atom. Spontaneous
emission in a random direction is the dissipative mechanism required to remove
entropy from the atom. However, alternative cooling methods have been proposed
for a single atom strongly coupled to a high-finesse cavity; the role of
spontaneous emission is replaced by the escape of a photon from the cavity.
Application of such cooling schemes would improve the performance of atom
cavity systems for quantum information processing. Furthermore, as cavity
cooling does not rely on spontaneous emission, it can be applied to systems
that cannot be laser-cooled by conventional methods; these include molecules
(which do not have a closed transition) and collective excitations of Bose
condensates, which are destroyed by randomly directed recoil kicks. Here we
demonstrate cavity cooling of single rubidium atoms stored in an intracavity
dipole trap. The cooling mechanism results in extended storage times and
improved localization of atoms. We estimate that the observed cooling rate is
at least five times larger than that produced by free-space cooling methods,
for comparable excitation of the atom
Commentary and Worked Examples to EN 1993-1-10 "Material Toughness and Through Thickness Properties" and Other Toughness Oriented Rules in EN 1993
This commentary gives explanations and worked examples to the design rules in Eurocode 3 that are influenced by the strength and toughness properties of the structural steels used. It is a commentary and background document to EN 1993-1-10 "Material toughness and through thickness properties" and its extension in EN 1993-1-12 "Design rules for high-strength steels", where toughness properties are explicitly addressed.
It however provides also background to other parts of EN 1993, e.g. to EN 1993-1-1 "Design of steel structures - Basic rules and rules for buildings", where the design rules are related only to strength properties as the yield strength and the tensile strength without explicitly mentioning the role of toughness that is hidden behind the resistance formulae. Finally it gives some comments to chapter 6 of EN 1998-1: "Design of structures for earthquake resistance - Part 1: General rules, seismic actions and rules for buildings".JRC.G.5-European laboratory for structural assessmen
Fast cavity-enhanced atom detection with low noise and high fidelity
Cavity quantum electrodynamics describes the fundamental interactions between
light and matter, and how they can be controlled by shaping the local
environment. For example, optical microcavities allow high-efficiency detection
and manipulation of single atoms. In this regime fluctuations of atom number
are on the order of the mean number, which can lead to signal fluctuations in
excess of the noise on the incident probe field. Conversely, we demonstrate
that nonlinearities and multi-atom statistics can together serve to suppress
the effects of atomic fluctuations when making local density measurements on
clouds of cold atoms. We measure atom densities below 1 per cavity mode volume
near the photon shot-noise limit. This is in direct contrast to previous
experiments where fluctuations in atom number contribute significantly to the
noise. Atom detection is shown to be fast and efficient, reaching fidelities in
excess of 97% after 10 us and 99.9% after 30 us.Comment: 7 pages, 4 figures, 1 table; extensive changes to format and
discussion according to referee comments; published in Nature Communications
with open acces
Інженерна комп’ютерна графіка
Розглянуто відомості про систему тривимірного моделювання
КОМПАС-3D при виконанні практичних завдань, побудову тривимірних
моделей деталей і складальних одиниць машин та обладнання, будівельних
споруд, а також про випуск асоціативних креслеників, розробку специфікацій,
експлікацій, інших текстових документів
Rotational master equation for cold laser-driven molecules
The equations of motion for the molecular rotation are derived for
vibrationally cold dimers that are polarized by off-resonant laser light. It is
shown that, by eliminating electronic and vibrational degrees of freedom, a
quantum master equation for the reduced rotational density operator can be
obtained. The coherent rotational dynamics is caused by stimulated Raman
transitions, whereas spontaneous Raman transitions lead to decoherence in the
motion of the quantized angular momentum. As an example the molecular dynamics
for the optical Kerr effect is chosen, revealing decoherence and heating of the
molecular rotation.Comment: 11 pages, 5 figures, to appear in Phys. Rev.
Double Beta Decay
We review recent developments in double-beta decay, focusing on what can be
learned about the three light neutrinos in future experiments. We examine the
effects of uncertainties in already measured neutrino parameters and in
calculated nuclear matrix elements on the interpretation of upcoming
double-beta decay measurements. We then review a number of proposed
experiments.Comment: Some typos corrected, references corrected and added. A less blurry
version of figure 3 is available from authors. 41 pages, 5 figures, submitted
to J. Phys.
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