211 research outputs found
Fechando hueso cremado: la base cientÃfica
A new method of obtaining absolute chronology dates out of burnt or cremated bone is presented. The authors explain their recent experiments and give promising results.Los autores presentan un nuevo método para obtener fechas de datación absoluta a partir de restos de hueso sometidos a diferentes grados de combustión y explican algunas de sus recientes experiencias y los resultados obtenidos
Compound Josephson-junction coupler for flux qubits with minimal crosstalk
This is the published version, also available here: http://dx.doi.org/10.1103/PhysRevB.80.052506.An improved tunable coupling element for building networks of coupled rf-superconducting quantum interference device (rf-SQUID) flux qubits has been experimentally demonstrated. This new form of coupler, based on the compound Josephson-junction rf-SQUID, provides a sign and magnitude tunable mutual inductance between qubits with minimal nonlinear crosstalk from the coupler tuning parameter into the qubits. Quantitative agreement is shown between an effective one-dimensional model of the coupler’s potential and measurements of the coupler persistent current and susceptibility
Entanglement in a quantum annealing processor
Entanglement lies at the core of quantum algorithms designed to solve
problems that are intractable by classical approaches. One such algorithm,
quantum annealing (QA), provides a promising path to a practical quantum
processor. We have built a series of scalable QA processors consisting of
networks of manufactured interacting spins (qubits). Here, we use qubit
tunneling spectroscopy to measure the energy eigenspectrum of two- and
eight-qubit systems within one such processor, demonstrating quantum coherence
in these systems. We present experimental evidence that, during a critical
portion of QA, the qubits become entangled and that entanglement persists even
as these systems reach equilibrium with a thermal environment. Our results
provide an encouraging sign that QA is a viable technology for large-scale
quantum computing.Comment: 13 pages, 8 figures, contact corresponding author for Supplementary
Informatio
The 10 Meter South Pole Telescope
The South Pole Telescope (SPT) is a 10 m diameter, wide-field, offset
Gregorian telescope with a 966-pixel, multi-color, millimeter-wave, bolometer
camera. It is located at the Amundsen-Scott South Pole station in Antarctica.
The design of the SPT emphasizes careful control of spillover and scattering,
to minimize noise and false signals due to ground pickup. The key initial
project is a large-area survey at wavelengths of 3, 2 and 1.3 mm, to detect
clusters of galaxies via the Sunyaev-Zeldovich effect and to measure the
small-scale angular power spectrum of the cosmic microwave background (CMB).
The data will be used to characterize the primordial matter power spectrum and
to place constraints on the equation of state of dark energy. A
second-generation camera will measure the polarization of the CMB, potentially
leading to constraints on the neutrino mass and the energy scale of inflation.Comment: 47 pages, 14 figures, updated to match version to be published in
PASP 123 903 (May, 2011
Galaxy clusters discovered with a Sunyaev-Zel'dovich effect survey
The South Pole Telescope (SPT) is conducting a Sunyaev-Zel'dovich (SZ) effect
survey over large areas of the southern sky, searching for massive galaxy
clusters to high redshift. In this preliminary study, we focus on a 40
square-degree area targeted by the Blanco Cosmology Survey (BCS), which is
centered roughly at right ascension 5h30m, declination -53 degrees. Over two
seasons of observations, this entire region has been mapped by the SPT at 95
GHz, 150 GHz, and 225 GHz. We report the four most significant SPT detections
of SZ clusters in this field, three of which were previously unknown and,
therefore, represent the first galaxy clusters discovered with an SZ survey.
The SZ clusters are detected as decrements with greater than 5-sigma
significance in the high-sensitivity 150 GHz SPT map. The SZ spectrum of these
sources is confirmed by detections of decrements at the corresponding locations
in the 95 GHz SPT map and non-detections at those locations in the 225 GHz SPT
map. Multiband optical images from the BCS survey demonstrate significant
concentrations of similarly colored galaxies at the positions of the SZ
detections. Photometric redshift estimates from the BCS data indicate that two
of the clusters lie at moderate redshift (z ~ 0.4) and two at high redshift (z
>~ 0.8). One of the SZ detections was previously identified as a galaxy cluster
using X-ray data from the ROSAT All-Sky Survey (RASS). Potential RASS
counterparts (not previously identified as clusters) are also found for two of
the new discoveries. These first four galaxy clusters are the most significant
SZ detections from a subset of the ongoing SPT survey. As such, they serve as a
demonstration that SZ surveys, and the SPT in particular, can be an effective
means for finding galaxy clusters.Comment: 11 pages, 3 figures, revised to match published version, uses
emulateap
Non-parametric modeling of the intra-cluster gas using APEX-SZ bolometer imaging data
We demonstrate the usability of mm-wavelength imaging data obtained from the
APEX-SZ bolometer array to derive the radial temperature profile of the hot
intra-cluster gas out to radius r_500 and beyond. The goal is to study the
physical properties of the intra-cluster gas by using a non-parametric
de-projection method that is, aside from the assumption of spherical symmetry,
free from modeling bias. We use publicly available X-ray imaging data from the
XMM-Newton observatory and our Sunyaev-Zel'dovich Effect (SZE) imaging data
from the APEX-SZ experiment at 150 GHz to de-project the density and
temperature profiles for the relaxed cluster Abell 2204. We derive the gas
density, temperature and entropy profiles assuming spherical symmetry, and
obtain the total mass profile under the assumption of hydrostatic equilibrium.
For comparison with X-ray spectroscopic temperature models, a re-analysis of
the recent Chandra observation is done with the latest calibration updates.
Using the non-parametric modeling we demonstrate a decrease of gas temperature
in the cluster outskirts, and also measure the gas entropy profile. These
results are obtained for the first time independently of X-ray spectroscopy,
using SZE and X-ray imaging data. The contribution of the SZE systematic
uncertainties in measuring T_e at large radii is shown to be small compared to
the Chandra systematic spectroscopic errors. The upper limit on M_200 derived
from the non-parametric method is consistent with the NFW model prediction from
weak lensing analysis.Comment: Replaced with the published version; A&A 519, A29 (2010
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