5,913 research outputs found
Quantum Communication in Spin Systems With Long-Range Interactions
We calculate the fidelity of transmission of a single qubit between distant
sites on semi-infinite and finite chains of spins coupled via the magnetic
dipole interaction. We show that such systems often perform better than their
Heisenberg nearest-neighbour coupled counterparts, and that fidelities closely
approaching unity can be attained between the ends of finite chains without any
special engineering of the system, although state transfer becomes slow in long
chains. We discuss possible optimization methods, and find that, for any
length, the best compromise between the quality and the speed of the
communication is obtained in a nearly uniform chain of 4 spins.Comment: 15 pages, 8 eps figures, updated references, corrected text and
corrected figs. 1, 4 and
Assessment of Posidonia oceanica (L.) Delile conservation status by standard and putative approaches: the case study of Santa Marinella meadow (Italy, W Mediterranean)
The conservation status of the Posidonia oceanica meadow at Santa Marinella (Rome) was evaluated through both standard (bed density, leaf biometry, "A" coefficient, Leaf Area Index, rhizome production) and biochemical/genetic approaches (total phenol content and Random Amplified Polymorphic DNA marker). The bio-chemical/genetic results are in agreement with those obtained by standard approaches. The bed under study was ranked as a disturbed one, due to its low density, and high heterogeneity in leaf biometry, LAI values, "A" coefficient and primary production. This low quality ranking is confirmed by both mean phenol content in plants, quite high and scattered, and by the low genetic variability in the meadow, with a very high similarity of specimen at a local scale. Hence, these two putative approaches clearly identify the endangered conservation status of the meadow. They link plant biodiversity and ecophysiology to ecosystem 'health'. Furthermore, they are repeatable and standardizable and could be usefully introduced in meadows monitoring to check environmental quality
A Single Atom Transistor in a 1D Optical Lattice
We propose a scheme utilising a quantum interference phenomenon to switch the
transport of atoms in a 1D optical lattice through a site containing an
impurity atom. The impurity represents a qubit which in one spin state is
transparent to the probe atoms, but in the other acts as a single atom mirror.
This allows a single-shot quantum non-demolition measurement of the qubit spin.Comment: RevTeX 4, 5 Figures, 4 Page
Focusing New Ataxia Telangiectasia Therapeutic Approaches
Ataxia Telangiectasia (AT) is a rare worldwide disease inherited as autosomal recessive with a poor prognosis in its classical form. It is characterized by neurological impairment (progressive cerebellar ataxia, axonal peripheral neuropathy, oculomotor apraxia, and movement disorders such as dystonia, choreoathetosis, myoclonus, tremor, Parkinsonism), telangiectasias, recurrent sino pulmonary infections, proneness to cancer, increased alpha-fetoprotein and decreased IgA levels and radio hypersensitivity. AT is caused by biallelic mutations in ATM gene, which plays a pivotal role in the control of cell cycle and in the response to DNA double strand break damage and chromatin changes. The management of patients, as well as prognosis, depends on the severity of the phenotype; only symptomatic therapies are by now available. Here we discuss the classical and the new therapeutic approaches in the light of the most recent reports in the literature
What is a Gene? A Two Sided View
The need to account for all currently available experimental observations
concerning the gene nature, has reshaped the concept of gene turning it from the
essentially mechanistic unit, predominant during the '70s, into a quite abstract
open and generalized entity, whose contour appears less defined as compared to the
past. Here we propose the essence of the gene to be considered double faced. In
this respect genotypic and phenotypic entities of a gene would coexist and mix
reciprocally. This harmonizes present knowledge with current definitions and
predisposes for remodelling of our thinking as a consequence of future discoveries.
A two sided view of the gene also allows to combine the genetic and epigenetic
aspects in a unique solution, being structural and functional at the same time and
simultaneously able to include the different levels in an overlapping unicum
Determination of folic acid using biosensors: a short review of recent progress
Folic acid (FA) is the synthetic surrogate of the essential B vitamin folate, alternatively named folacin, pteroylglutamic acid or vitamin B-9. FA is an electroactive compound that helps our body to create and keep our cells healthy: it acts as the main character in a variety of synthetic biological reactions such as the synthesis of purines, pyrimidine (thus being indirectly implied in DNA synthesis), fixing and methylation of DNA. Therefore, physiological folate deficiency may be responsible for severe degenerative conditions, including neural tube defects in developing embryos and megaloblastic anaemia at any age. Moreover, being a water-soluble molecule, it is constantly lost and has to be reintegrated daily; for this reason, FA supplements and food fortification are, nowadays, extremely diffused and well-established practices. Consequently, accurate, reliable and precise analytical techniques are needed to exactly determine FA concentration in various media. Thus, the aim of this review is to report on research papers of the past 5 years (2016-2020) dealing with rapid and low-cost electrochemical determination of FA in food or biological fluid samples
Polarization entangled photon-pair source based on quantum nonlinear photonics and interferometry
We present a versatile, high-brightness, guided-wave source of polarization
entangled photons, emitted at a telecom wavelength. Photon-pairs are generated
using an integrated type-0 nonlinear waveguide, and subsequently prepared in a
polarization entangled state via a stabilized fiber interferometer. We show
that the single photon emission wavelength can be tuned over more than 50 nm,
whereas the single photon spectral bandwidth can be chosen at will over more
than five orders of magnitude (from 25 MHz to 4 THz). Moreover, by performing
entanglement analysis, we demonstrate a high degree of control of the quantum
state via the violation of the Bell inequalities by more than 40 standard
deviations. This makes this scheme suitable for a wide range of quantum optics
experiments, ranging from fundamental research to quantum information
applications. We report on details of the setup, as well as on the
characterization of all included components, previously outlined in F. Kaiser
et al. (2013 Laser Phys. Lett. 10, 045202).Comment: 16 pages, 7 figure
New strategy for the cleaning of paper artworks: A smart combination of gels and biosensors
n this work an outlook on the design and application, in the cultural heritage field, of new tools for diagnostic and cleaning use, based on biocompatible hydrogels and electrochemical sensors, is reported. The use of hydrogels is intriguing because it does not require liquid treatment that could induce damage on artworks, while electrochemical biosensors not only are easy to prepare, but also can be selective for a specific compound and therefore are suitable for monitoring the cleaning process. In the field of restoration of paper artworks, more efforts have to be done in order to know how to perform the best way for an effective restoration. Rigid Gellan gel, made up of Gellan gum and calcium acetate, was proposed as a paper cleaning treatment, and selective biosensors for substances to be removed from this gel have been obtained by choosing the appropriate enzymes to be immobilized. Using this approach, it is possible to know when the cleanup process will be completed, avoiding lengthy and sometimes unnecessary cleaning material applications
Topological p_x+ip_y Superfluid Phase of Fermionic Polar Molecules
We discuss the topological p_x+ip_y superfluid phase in a 2D gas of
single-component fermionic polar molecules dressed by a circularly polarized
microwave field. This phase emerges because the molecules may interact with
each other via a potential V_0(r) that has an attractive dipole-dipole 1/r^3
tail, which provides p-wave superfluid pairing at fairly high temperatures. We
calculate the amplitude of elastic p-wave scattering in the potential V_0(r)
taking into account both the anomalous scattering due to the dipole-dipole tail
and the short-range contribution. This amplitude is then used for the
analytical and numerical solution of the renormalized BCS gap equation which
includes the second order Gor'kov-Melik-Barkhudarov corrections and the
correction related to the effective mass of the quasiparticles. We find that
the critical temperature T_c can be varied within a few orders of magnitude by
modifying the short-range part of the potential V_0(r). The decay of the system
via collisional relaxation of molecules to dressed states with lower energies
is rather slow due to the necessity of a large momentum transfer. The presence
of a constant transverse electric field reduces the inelastic rate, and the
lifetime of the system can be of the order of seconds even at 2D densities ~
10^9 cm^{-2}. This leads to T_c of up to a few tens of nanokelvins and makes it
realistic to obtain the topological p_x+ip_y phase in experiments with
ultracold polar molecules.Comment: 15 pages, 9 figures, published versio
Ground state cooling of atoms in optical lattices
We propose two schemes for cooling bosonic and fermionic atoms that are
trapped in a deep optical lattice. The first scheme is a quantum algorithm
based on particle number filtering and state dependent lattice shifts. The
second protocol alternates filtering with a redistribution of particles by
means of quantum tunnelling. We provide a complete theoretical analysis of both
schemes and characterize the cooling efficiency in terms of the entropy. Our
schemes do not require addressing of single lattice sites and use a novel
method, which is based on coherent laser control, to perform very fast
filtering.Comment: 12 pages, 7 figure
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