1,604 research outputs found
Securing coherence rephasing with a pair of adiabatic rapid passages
Coherence rephasing is an essential step in quantum storage protocols that
use echo-based strategies. We present a thorough analysis on how two adiabatic
rapid passages (ARP) are able to rephase atomic coherences in an
inhomogeneously broadened ensemble. We consider both the cases of optical and
spin coherences, rephased by optical or radio-frequency (rf) ARPs,
respectively. We show how a rephasing sequence consisting of two ARPs in a
double-echo scheme is equivalent to the identity operator (any state can be
recovered), as long as certain conditions are fulfilled. Our mathematical
treatment of the ARPs leads to a very simple geometrical interpretation within
the Bloch sphere that permits a visual comprehension of the rephasing process.
We also identify the conditions that ensure the rephasing, finding that the
phase of the optical or rf ARP fields plays a key role in the capability of the
sequence to preserve the phase of the superposition state. This settles a
difference between optical and rf ARPs, since field phase control is not
readily guaranteed in the former case. We also provide a quantitative
comparison between -pulse and ARP rephasing efficiencies, showing the
superiority of the latter. We experimentally verify the conclusions of our
analysis through rf ARP rephasing sequencies performed on the rare-earth
ion-doped crystal Tm:YAG, of interest in quantum memories.Comment: 24 pages, 7 figure
Optical measurement of heteronuclear cross-relaxation interactions in Tm:YAG
We investigate cross-relaxation interactions between Tm and Al in Tm:YAG
using two optical methods: spectral holeburning and stimulated echoes. These
interactions lead to a reduction in the hyperfine lifetime at magnetic fields
that bring the Tm hyperfine transition into resonance with an Al transition. We
develop models for measured echo decay curves and holeburning spectra near a
resonance, which are used to show that the Tm-Al interaction has a resonance
width of 10~kHz and reduces the hyperfine lifetime to 0.5 ms. The antihole
structure is consistent with an interaction dominated by the Al nearest
neighbors at 3.0 Angstroms, with some contribution from the next nearest
neighbors at 3.6 Angstroms.Comment: 13 pages, 9 figure
Diseño y fabricación de un filtro pasabanda pasivo con lÃneas acopladas
[spa] Las señales electromagnéticas que ocupan la banda de frecuencias de radio (RF) se transmiten por lÃneas de transmisión, que son estructuras materiales capaces de dirigir la energÃa de un punto a otro del circuito. Debido al campo electromagnético generado por una señal RF, dos lÃneas de transmisión próximas pueden propagar parte de la energÃa que circula de una a la otra. Aprovechando estas propiedades de acoplamiento capacitivo e inductivo entre lÃneas, se ha diseñado, simulado y fabricado un filtro pasabanda pasivo realizado con lÃneas de transmisión
Prevalence of primary headaches: it is not the behavior, but still we have to pay attention to it!
A comprehensive approach to analyzing the XMM-Newton data of Seyfert 1 galaxies
Aims. We seek a comprehensive analysis of all the information provided by the
XMM-Newton satellite of the four Seyfert 1 galaxies ESO 359-G19, HE 1143-1810,
CTS A08.12, and Mrk 110, including the UV range, to characterize the different
components that are emitting and absorbing radiation in the vicinity of the
active nucleus.
Methods. The continuum emission was studied through the EPIC spectra by
taking advantage of the spectral range of these cameras. The high-resolution
RGS spectra were analyzed to characterize the absorbing and emission line
features that arise in the spectra of the sources. All these data, complemented
by information in the UV, are analyzed jointly in order to achieve a consistent
characterization of the observed features in each object.
Results. The continuum emission of the sources can be characterized either by
a combination of a power law and a black body for the weakest objects or by two
power law components for the brightest ones. The continuum is not absorbed by
neutral or ionized material in the line of sight to any of these sources. In
all of them we have identified a narrow Fe-Kalpha line at 6.4 keV. In ESO
559-G19 we also find an FeXXVI line at about 7 keV. In the soft X-rays band, we
identify only one OVII line in the spectra of HE 1143-1810 and CTS A08.12, and
two OVII-He alpha triplets and a narrow OVIII-Ly alpha emission line in Mrk
110.
Conclusions. Not detecting warm material in the line of sight to the low
state objects is due to intrinsically weaker or absent absorption in the line
of sight and not to a low signal-to-noise ratio in the data. Besides this, the
absence of clear emission lines cannot be fully attributed to dilution of those
lines by a strong continuum.Comment: 14 pages, 7 figures, 9 tables, accepted by A&
Spin coherence lifetime extension in Tm:YAG through dynamical decoupling
We report on spin coherence lifetime extension on Tm:YAG obtained
through dynamically decoupling the thulium spins from their magnetic
environment. The coherence lifetime reached with a Carr-Purcell-Meiboom-Gill
sequence revealed a 450-fold extension [ ms] with respect
to previously measured values. Comparison to a simple theoretical model allowed
us to estimate the correlation time of the fluctuations of the ground level
transition frequency to s at 1.7 K. For attaining efficient
decoupling sequences, we developed a strategy inspired by the
\emph{zero-first-order Zeeman} effect to minimize the large inhomogeneous
broadening of the ground level spin transition.Comment: 10 pages, 7 figure
Lifetime of sub-THz coherent acoustic phonons in a GaAs-AlAs superlattice
We measure the lifetime of the zone-center 340 GHz longitudinal phonon mode in a GaAs-AlAs superlattice excited and probed with femtosecond laser pulses. By comparing measurements conducted at room temperature and liquid nitrogen temperature, we separate the intrinsic (phonon-phonon scattering) and extrinsic contributions to phonon relaxation. The estimated room temperature intrinsic lifetime of 0.95 ns is compared to available calculations and experimental data for bulk GaAs. We conclude that ∼0.3 THz phonons are in the transition zone between Akhiezer and Landau-Rumer regimes of phonon-phonon relaxation at room temperature.United States. Dept. of Energy. Office of Basic Energy Sciences (Award DE-SC0001299)United States. Dept. of Energy (Grant DE-FG02-00ER15087
Calculation of The Band Gap Energy and Study of Cross Luminescence in Alkaline-Earth Dihalide Crystals
The band gap energy as well as the possibility of cross luminescence
processes in alkaline-earth dihalide crystals have been calculated using the ab
initio Perturbed-Ion (PI) model. The gap is calculated in several ways: as a
difference between one-electron energy eigenvalues and as a difference between
total energies of appropriate electronic states of the crystal, both at the HF
level and with inclusion of Coulomb correlation effects. In order to study the
possibility of ocurrence of cross luminescence in these materials, the energy
difference between the valence band and the upmost core band for some
representative crystals has been calculated. Both calculated band gap energies
and cross luminescence predictions compare very well with the available
experimental results.Comment: LaTeX file containing 8 pages plus 1 postscript figure. Final version
accepted for publication in The Journal of the Physical Society of Japan. It
contains a more complete list of references, as well as a more detailed
comparison with previous theoretical investigations on the subjec
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