5,583 research outputs found
Efficient quantum simulation of fermionic and bosonic models in trapped ions
We analyze the efficiency of quantum simulations of fermionic and bosonic
models in trapped ions. In particular, we study the optimal time of entangling
gates and the required number of total elementary gates. Furthermore, we
exemplify these estimations in the light of quantum simulations of quantum
field theories, condensed-matter physics, and quantum chemistry. Finally, we
show that trapped-ion technologies are a suitable platform for implementing
quantum simulations involving interacting fermionic and bosonic modes, paving
the way for overcoming classical computers in the near future.Comment: 13 pages, 3 figures. Published in EPJ Quantum Technolog
Notas a "Voces castellanas y su equivalencia en valenciano. Voces valencianas y su equivalencia en castellano" por C.M.G., de 1825
En este artículo se estudia el primer diccionario bilingüe valenciano-castellano, castellano-valenciano, de 1825, escrito por un autor anónimo C.M.G., inédito hasta ahora. Este diccionario presenta un gran interés dialectal, sociolingüístico e histórico. Seguramente fue escrito por un autor del norte de Castellón, como demuestran las particularidades dialectales del texto. Contiene más de 2000 voces, una parte de las cuales avanzan su fecha de registro en los diccionarios o añade nuevas acepciones a las conocidas en la lexicografía catalana. In this aricle is studied the first ever bilingual Valencian-Spanish, Spanish-Valencian dictionary, dated in 1825, by an anonymous author –C.M.G.-, never edited until nowadays. Such dictionary shows such a great dialectal, sociolinguistical, and historical value, the most sure is that it was written by a valencian author original from the north of Castelló as some characteristics common in the local dialect prove, and it contains more than 2000 vocies, which, part of them move the first known date of such entries to earlier dates in time, and others are new meanings for the existing registers in the catalan lexicography dictionaries
Acceleration of cosmic rays and gamma-ray emission from supernova remnants in the Galaxy
Galactic cosmic rays are believed to be accelerated at supernova remnant
shocks. Though very popular and robust, this conjecture still needs a
conclusive proof. The strongest support to this idea is probably the fact that
supernova remnants are observed in gamma-rays, which are indeed expected as the
result of the hadronic interactions between the cosmic rays accelerated at the
shock and the ambient gas. However, also leptonic processes can, in most cases,
explain the observed gamma-ray emission. This implies that the detections in
gamma rays do not necessarily mean that supernova remnants accelerate cosmic
ray protons. To overcome this degeneracy, the multi-wavelength emission (from
radio to gamma rays) from individual supernova remnants has been studied and in
a few cases it has been possible to ascribe the gamma-ray emission to one of
the two processes (hadronic or leptonic). Here we adopt a different approach
and, instead of a case-by-case study we aim for a population study and we
compute the number of supernova remnants which are expected to be seen in TeV
gamma rays above a given flux under the assumption that these objects indeed
are the sources of cosmic rays. The predictions found here match well with
current observational results, thus providing a novel consistency check for the
supernova remnant paradigm for the origin of galactic cosmic rays. Moreover,
hints are presented for the fact that particle spectra significantly steeper
than E^-2 are produced at supernova remnants. Finally, we expect that several
of the supernova remnants detected by H.E.S.S. in the survey of the galactic
plane should exhibit a gamma-ray emission dominated by hadronic processes (i.e.
neutral pion decay). The fraction of the detected remnants for which the
leptonic emission dominates over the hadronic one depends on the assumed values
of the physical parameters and can be as high as roughly a half.Comment: 14 pages, 4 figures, 4 tables, submitted to MNRA
Temperature dependence of spin diffusion length and spin Hall angle in Au and Pt
We have studied the spin transport and the spin Hall effect as a function of
temperature for platinum (Pt) and gold (Au) in lateral spin valve structures.
First, by using the spin absorption technique, we extract the spin diffusion
length of Pt and Au. Secondly, using the same devices, we have measured the
spin Hall conductivity and analyzed its evolution with temperature to identify
the dominant scattering mechanisms behind the spin Hall effect. This analysis
confirms that the intrinsic mechanism dominates in Pt whereas extrinsic effects
are more relevant in Au. Moreover, we identify and quantify the phonon-induced
skew scattering. We show that this contribution to skew scattering becomes
relevant in metals such as Au, with a low residual resistivity.Comment: 13 pages, 5 figure
Tailoring palladium nanocontacts by electromigration
Electromigration is employed in nanoelectronics for transforming narrow metallic wires into electrodes separated by a few nanometers gap. In this work, we fabricate either nanoconstrictions or nanogap electrodes by performing electromigration in palladium nanowires. The device resistance and the cross section of the initial nanowires allow us to regulate the conditions for transforming deterministically each nanowire in a specific final device. The resulting samples show unique electrical transport characteristics and could be used in multiple nanoelectronics research applications, from ballistic transport to electrodes for single molecular devices.Fil: Arzubiaga, Libe. CIC nanoGUNE; EspañaFil: Golmar, Federico. Instituto Nacional de Tecnología Industrial; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Llopis, Roger. CIC nanoGUNE; EspañaFil: Casanova, Félix. CIC nanoGUNE; España. Basque Foundation for Science; EspañaFil: Hueso, Luis E.. CIC nanoGUNE; España. Basque Foundation for Science; Españ
Algorithmic quantum simulation of memory effects
We propose a method for the algorithmic quantum simulation of memory effects
described by integrodifferential evolution equations. It consists in the
systematic use of perturbation theory techniques and a Markovian quantum
simulator. Our method aims to efficiently simulate both completely positive and
nonpositive dynamics without the requirement of engineering non-Markovian
environments. Finally, we find that small error bounds can be reached with
polynomially scaling resources, evaluated as the time required for the
simulation
Deep Strong Coupling Regime of the Jaynes-Cummings model
We study the quantum dynamics of a two-level system interacting with a
quantized harmonic oscillator in the deep strong coupling regime (DSC) of the
Jaynes-Cummings model, that is, when the coupling strength g is comparable or
larger than the oscillator frequency w (g/w > 1). In this case, the
rotating-wave approximation cannot be applied or treated perturbatively in
general. We propose an intuitive and predictive physical frame to describe the
DSC regime where photon number wavepackets bounce back and forth along parity
chains of the Hilbert space, while producing collapse and revivals of the
initial population. We exemplify our physical frame with numerical and
analytical considerations in the qubit population, photon statistics, and
Wigner phase space.Comment: Published version, note change of title: DSC regime of the JC mode
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