1,342 research outputs found
Blueprint of a Molecular Spin Quantum Processor
The implementation of a universal quantum processor still poses fundamental
issues related to error mitigation and correction, which demand to investigate
also platforms and computing schemes alternative to the main stream. A
possibility is offered by employing multi-level logical units (qudits),
naturally provided by molecular spins. Here we present the blueprint of a
Molecular Spin Quantum Processor consisting of single Molecular Nanomagnets,
acting as qudits, placed within superconducting resonators adapted to the size
and interactions of these molecules to achieve a strong single spin to photon
coupling. We show how to implement a universal set of gates in such a platform
and to readout the final qudit state. Single-qudit unitaries (potentially
embedding multiple qubits) are implemented by fast classical drives, while a
novel scheme is introduced to obtain two-qubit gates via resonant photon
exchange. The latter is compared to the dispersive approach, finding in general
a significant improvement. The performance of the platform is assessed by
realistic numerical simulations of gate sequences, such as Deutsch-Josza and
quantum simulation algorithms. The very good results demonstrate the
feasibility of the molecular route towards a universal quantum processor.Comment: 16 pages, 11 figures. Accepted in Physical Review Applie
Dynamical mass of the Ophiuchus intermediate-mass stellar system S1 with DYNAMO-VLBA
We report dynamical mass measurements of the individual stars in the most
luminous and massive stellar member of the nearby Ophiuchus star-forming
region, the young tight binary system S1. We combine 28 archival datasets with
seven recent, proprietary VLBA observations obtained as part of the
\textit{Dynamical Masses of Young Stellar Multiple Systems with the VLBA}
project (DYNAMO--VLBA), to constrain the astrometric and orbital parameters of
the system, and recover high accuracy dynamical masses. The primary component,
S1A, is found to have a mass of 4.110.10~M, significantly less
than the typical value, ~6~M previously reported in the
literature. We show that the spectral energy distribution of S1A can be
reproduced by a reddened blackbody with a temperature between roughly 14,000~K
and 17,000~K. According to evolutionary models, this temperature range
corresponds to stellar masses between 4~M and 6~M so the SED is
not a priori inconsistent with the dynamical mass of S1A. The luminosity of S1
derived from SED-fitting, however, is only consistent with models for stellar
masses above 5~M. Thus, we cannot reconcile the evolutionary models
with the dynamical mass measurement of S1A: the models consistent with the
location of S1A in the HR diagram correspond to masses at least 25\% higher
than the dynamical mass. For the secondary component, S1B, a mass of
0.831~~0.014~M is determined, consistent with a low-mass young
star. While the radio flux of S1A remains roughly constant throughout the
orbit, the flux of S1B is found to be higher near the apastron
Twenty years of ground-based NDACC FTIR spectrometry at Izaña Observatory-overview and long-term comparison to other techniques
High-resolution Fourier transform infrared (FTIR) solar observations are particularly relevant for climate studies, as they allow atmospheric gaseous composition and multiple climate processes to be monitored in detail. In this context, the present paper provides an overview of 20 years of FTIR measurements taken in the framework of the NDACC (Network for the Detection of Atmospheric Composition Change) from 1999 to 2018 at the subtropical Izaña Observatory (IZO, Spain). Firstly, long-term instrumental performance is comprehensively assessed, corroborating the temporal stability and reliable instrumental characterization of the two FTIR spectrometers installed at IZO since 1999. Then, the time series of all trace gases contributing to NDACC at IZO are presented (i.e. CH, CH, ClONO, CO, HCl, HCN, HCO, HF, HNO, NO, NO, NO, O, carbonyl sulfide (OCS), and water vapour isotopologues HO, HO, and HDO), reviewing the major accomplishments drawn from these observations. In order to examine the quality and long-term consistency of the IZO FTIR observations, a comparison of those NDACC products for which other high-quality measurement techniques are available at IZO has been performed (i.e. CH, CO, HO, NO, NO, and O). This quality assessment was carried out on different timescales to examine what temporal signals are captured by the FTIR records, and to what extent. After 20 years of operation, the IZO NDACC FTIR observations have been found to be very consistent and reliable over time, demonstrating great potential for climate research. Long-term NDACC FTIR data sets, such as IZO, are indispensable tools for the investigation of atmospheric composition trends, multi-year phenomena, and complex climate feedback processes, as well as for the validation of past and present space-based missions and chemistry climate models
Experimental and theoretical study of α–Eu2(MoO4)3 under compression
The compression process in the α-phase of europium trimolybdate was revised employing
several experimental techniques. X-ray diffraction (using synchrotron and laboratory radiation
sources), Raman scattering and photoluminescence experiments were performed up to a
maximum pressure of 21 GPa. In addition, the crystal structure and Raman mode frequencies
have been studied by means of first-principles density functional based methods. Results
suggest that the compression process of α-Eu2(MoO4)3 can be described by three stages.
Below 8 GPa, the α-phase suffers an isotropic contraction of the crystal structure. Between
8 and 12 GPa, the compound undergoes an anisotropic compression due to distortion and
rotation of the MoO4 tetrahedra. At pressures above 12 GPa, the amorphization process starts
without any previous occurrence of a crystalline-crystalline phase transition in the whole range
of pressure. This behavior clearly differs from the process of compression and amorphization
in trimolybdates with β′-phase and tritungstates with α-phase.We thank Diamond Light Source for access to beamline I15 (EE1746) that contributed to the results presented here. Part of the diffraction measurements were performed at the 'Servicio Integrado de Difraccion de Rayos X (SIDIX)' of University of La Laguna. This work has been supported by Ministerio de Economia y Competitividad of Spain (MINECO) for the research projects through the National Program of Materials (MAT2010-21270-C04-01/02/03/04, MAT2013-46649-C41/2/3/4-P and MAT2013-43319-P), the Consolider-Ingenio 2010 MALTA (CSD2007-00045), the project of Generalitat Valenciana (GVA-ACOMP/2014/243) and by the European Union FEDER funds. C Guzman-Afonso wishes to thank ACIISI and FSE for a fellowship. J A Sans thanks the FPI and 'Juan de la Cierva' programs for fellowships.Guzmán-Afonso, C.; León-Luis, S.; Sans-Tresserras, JÁ.; González -Silgo, C.; Rodríguez-Hernández, P.; Radescu, S.; muñoz, A.... (2015). Experimental and theoretical study of α–Eu2(MoO4)3 under compression. Journal of Physics: Condensed Matter. 27(46):465401-1-465401-11. https://doi.org/10.1088/0953-8984/27/46/465401S465401-1465401-11274
Internal consistency of the Regional Brewer Calibration Centre for Europe triad during the period 2005–2016
Total ozone column measurements can be made using Brewer spectrophotometers,
which are calibrated periodically in intercomparison campaigns with respect
to a reference instrument. In 2003, the Regional Brewer Calibration Centre
for Europe (RBCC-E) was established at the Izaña Atmospheric Research
Center (Canary Islands, Spain), and since 2011 the RBCC-E has transferred its
calibration based on the Langley method using travelling standard(s) that are
wholly and independently calibrated at Izaña. This work is focused on
reporting the consistency of the measurements of the RBCC-E triad (Brewer
instruments #157, #183 and #185) made at the Izaña Atmospheric
Observatory during the period 2005–2016. In order to study the long-term
precision of the RBCC-E triad, it must be taken into account that each Brewer
takes a large number of measurements every day and, hence, it becomes
necessary to calculate a representative value of all of them. This value was
calculated from two different methods previously used to study the long-term
behaviour of the world reference triad (Toronto triad) and Arosa triad.
Applying their procedures to the data from the RBCC-E triad allows the
comparison of the three instruments. In daily averages, applying the
procedure used for the world reference triad, the RBCC-E triad presents a
relative standard deviation equal to σ  =  0.41 %, which is
calculated as the mean of the individual values for each Brewer
(σ157  =  0.362 %, σ183  =  0.453 % and
σ185  =  0.428 %). Alternatively, using the procedure used
to analyse the Arosa triad, the RBCC-E presents a relative standard deviation
of about σ  =  0.5 %. In monthly averages, the method used for
the data from the world reference triad gives a relative standard deviation
mean equal to σ  =  0.3 % (σ157  =  0.33 %,
σ183  =  0.34 % and σ185  =  0.23 %).
However, the procedure of the Arosa triad gives monthly values of
σ  =  0.5 %. In this work, two ozone data sets are analysed:
the first includes all the ozone measurements available, while the second
only includes the simultaneous measurements of all three instruments.
Furthermore, this paper also describes the Langley method used to determine
the extraterrestrial constant (ETC) for the RBCC-E triad, the necessary first
step toward accurate ozone calculation. Finally, the short-term or intraday
consistency is also studied to identify the effect of the solar zenith angle
on the precision of the RBCC-E triad.</p
Very high energy particle acceleration powered by the jets of the microquasar SS 433
SS 433 is a binary system containing a supergiant star that is overflowing
its Roche lobe with matter accreting onto a compact object (either a black hole
or neutron star). Two jets of ionized matter with a bulk velocity of
extend from the binary, perpendicular to the line of sight, and
terminate inside W50, a supernova remnant that is being distorted by the jets.
SS 433 differs from other microquasars in that the accretion is believed to be
super-Eddington, and the luminosity of the system is erg
s. The lobes of W50 in which the jets terminate, about 40 pc from the
central source, are expected to accelerate charged particles, and indeed radio
and X-ray emission consistent with electron synchrotron emission in a magnetic
field have been observed. At higher energies (>100 GeV), the particle fluxes of
rays from X-ray hotspots around SS 433 have been reported as flux
upper limits. In this energy regime, it has been unclear whether the emission
is dominated by electrons that are interacting with photons from the cosmic
microwave background through inverse-Compton scattering or by protons
interacting with the ambient gas. Here we report TeV -ray observations
of the SS 433/W50 system where the lobes are spatially resolved. The TeV
emission is localized to structures in the lobes, far from the center of the
system where the jets are formed. We have measured photon energies of at least
25 TeV, and these are certainly not Doppler boosted, because of the viewing
geometry. We conclude that the emission from radio to TeV energies is
consistent with a single population of electrons with energies extending to at
least hundreds of TeV in a magnetic field of ~micro-Gauss.Comment: Preprint version of Nature paper. Contacts: S. BenZvi, B. Dingus, K.
Fang, C.D. Rho , H. Zhang, H. Zho
All-particle cosmic ray energy spectrum measured by the HAWC experiment from 10 to 500 TeV
We report on the measurement of the all-particle cosmic ray energy spectrum
with the High Altitude Water Cherenkov (HAWC) Observatory in the energy range
10 to 500 TeV. HAWC is a ground based air-shower array deployed on the slopes
of Volcan Sierra Negra in the state of Puebla, Mexico, and is sensitive to
gamma rays and cosmic rays at TeV energies. The data used in this work were
taken from 234 days between June 2016 to February 2017. The primary cosmic-ray
energy is determined with a maximum likelihood approach using the particle
density as a function of distance to the shower core. Introducing quality cuts
to isolate events with shower cores landing on the array, the reconstructed
energy distribution is unfolded iteratively. The measured all-particle spectrum
is consistent with a broken power law with an index of prior to
a break at ) TeV, followed by an index of . The
spectrum also respresents a single measurement that spans the energy range
between direct detection and ground based experiments. As a verification of the
detector response, the energy scale and angular resolution are validated by
observation of the cosmic ray Moon shadow's dependence on energy.Comment: 16 pages, 11 figures, 4 tables, submission to Physical Review
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