3,962 research outputs found
Shot Noise in Gravitational-Wave Detectors with Fabry-Perot Arms
Shot-noise-limited sensitivity is calculated for gravitational-wave interferometers with Fabry–Perot arms, similar to those being installed at the Laser Interferometer Gravitational-Wave Observatory (LIGO) and the Italian–French Laser Interferometer Collaboration (VIRGO) facility. This calculation includes the effect of nonstationary shot noise that is due to phase modulation of the light. The resulting formula is experimentally verified by a test interferometer with suspended mirrors in the 40-m arms
16 x 25 Ge:Ga Detector Arrays for FIFI LS
We are developing two-dimensional 16 x 25 pixel detector arrays of both
unstressed and stressed Ge:Ga photoconductive detectors for far-infrared
astronomy from SOFIA. The arrays, based on earlier 5 x 5 detector arrays used
on the KAO, will be for our new instrument, the Far Infrared Field Imaging Line
Spectrometer (FIFI LS). The unstressed Ge:Ga detector array will cover the
wavelength range from 40 to 120 microns, and the stressed Ge:Ga detector array
from 120 to 210 microns. The detector arrays will be operated with multiplexed
integrating amplifiers with cryogenic readout electronics located close to the
detector arrays. The design of the stressed detector array and results of
current measurements on several prototype 16 pixel linear arrays are reported.
They demonstrate the feasibility of the current concept. ***This paper does not
include Figures due to astro-ph size limitations. Please download entire file
at http://fifi-ls.mpe-garching.mpg.de/spie.det.ps.gz ***Comment: 8 pages, SPIE Proceedings, Astronomical Telescopes and
Instrumentation 200
Motional sidebands and direct measurement of the cooling rate in the resonance fluorescence of a single trapped ion
Resonance fluorescence of a single trapped ion is spectrally analyzed using a
heterodyne technique. Motional sidebands due to the oscillation of the ion in
the harmonic trap potential are observed in the fluorescence spectrum. From the
width of the sidebands the cooling rate is obtained and found to be in
agreement with the theoretical prediction.Comment: 4 pages, 4 figures. Final version after minor changes, 1 figure
replaced; to be published in PRL, July 10, 200
Electromagnetic multipole theory for optical nanomaterials
Optical properties of natural or designed materials are determined by the
electromagnetic multipole moments that light can excite in the constituent
particles. In this work we present an approach to calculate the multipole
excitations in arbitrary arrays of nanoscatterers in a dielectric host medium.
We introduce a simple and illustrative multipole decomposition of the electric
currents excited in the scatterers and link this decomposition to the classical
multipole expansion of the scattered field. In particular, we find that
completely different multipoles can produce identical scattered fields. The
presented multipole theory can be used as a basis for the design and
characterization of optical nanomaterials
Loading a vapor cell magneto-optic trap using light-induced atom desorption
Low intensity white light was used to increase the loading rate of Rb
atoms into a vapor cell magneto-optic trap by inducing non-thermal desorption
of Rb atoms from the stainless steel walls of the vapor cell. An increased Rb
partial pressure reached a new equilibrium value in less than 10 seconds after
switching on the broadband light source. After the source was turned off, the
partial pressure returned to its previous value in times as short as 10
seconds.Comment: 7 pages, 6 figure
Family Socioeconomic Status and Ethnicity, Acculturation and Enculturation, and Parent Beliefs about Child Behavior, Learning Methods, and Parenting Roles
Relationships between family socioeconomic status and ethnicity, acculturation and enculturation, and parent beliefs about desired child behavior, child learning methods, and parenting roles in children’s learning desired behavior were examined in a study of 207 parents of preschoolers from seven ethnic and cultural groups. Different subgroups of participants were identified from patterns of acculturation and enculturation. Family ethnicity, family SES, and acculturation were differentially related to the parent beliefs whereas enculturation and combinations of acculturation and enculturation were unrelated to beliefs. Findings are discussed in terms of the high degree of specificity in the relationships between the predictor variables and parent beliefs about child behavior, learning methods, and parenting roles. The results are consistent with an individual-oriented concept of culture. Cautions are therefore raised in terms of overgeneralizations about attributing traditional beliefs broadly to families from the same ethnic or cultural group
Quantum damping of position due to energy measurements
Quantum theory for measurements of energy is introduced and its consequences
for the average position of monitored dynamical systems are analyzed. It turns
out that energy measurements lead to a localization of the expectation values
of other observables. This is manifested, in the case of position, as a damping
of the motion without classical analogue. Quantum damping of position for an
atom bouncing on a reflecting surface in presence of a homogeneous
gravitational field is dealt in detail and the connection with an experiment
already performed in the classical regime is studied. We show that quantum
damping is testable provided that the same measurement strength obtained in the
experimental verification of the quantum Zeno effect in atomic spectroscopy [W.
M. Itano et al., Phys. Rev. A {\bf 41}, 2295 (1990)] is made available.Comment: 19 pages + 4 figures available upon request; Plain REVTeX; To be
published in Phys. Rev.
Atomic multipole relaxation rates near surfaces
The spontaneous relaxation rates for an atom in free space and close to an
absorbing surface are calculated to various orders of the electromagnetic
multipole expansion. The spontaneous decay rates for dipole, quadrupole and
octupole transitions are calculated in terms of their respective primitive
electric multipole moments and the magnetic relaxation rate is calculated for
the dipole and quadrupole transitions in terms of their respective primitive
magnetic multipole moments. The theory of electromagnetic field quantization in
magnetoelectric materials is used to derive general expressions for the decay
rates in terms of the dyadic Green function. We focus on the decay rates in
free space and near an infinite half space. For the decay of atoms near to an
absorbing dielectric surface we find a hierarchy of scaling laws depending on
the atom-surface distance z.Comment: Updated to journal version. 16 page
Forces between a single atom and its distant mirror image
An excited-state atom whose emitted light is back-reflected by a distant
mirror can experience trapping forces, because the presence of the mirror
modifies both the electromagnetic vacuum field and the atom's own radiation
reaction field. We demonstrate this mechanical action using a single trapped
barium ion. We observe the trapping conditions to be notably altered when the
distant mirror is shifted by an optical wavelength. The well-localised barium
ion enables the spatial dependence of the forces to be measured explicitly. The
experiment has implications for quantum information processing and may be
regarded as the most elementary optical tweezers.Comment: 4 pages, 5 figures, published versio
Guiding Neutral Atoms with a Wire
We demonstrate guiding of cold neutral atoms along a current carrying wire.
Atoms either move in Kepler-like orbits around the wire or are guided in a
potential tube on the side of the wire which is created by applying an
additional homogeneous bias field. These atom guides are very versatile and
promising for applications in atom optics.Comment: 4 pages, 6 figures, submitted to PR
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