5,652 research outputs found
Limit quantum efficiency for violation of Clauser-Horne Inequality for qutrits
In this paper we present the results of numerical calculations about the
minimal value of detection efficiency for violating the Clauser - Horne
inequality for qutrits. Our results show how the use of non-maximally entangled
states largely improves this limit respect to maximally entangled ones. A
stronger resistance to noise is also found.Comment: Phys. Rev. A in pres
Nonequilibrium transitions induced by multiplicative noise
A new simple model exhibiting a noise-induced ordering transition (NIOT) and
a noise-induced disordering transition (NIDT), in which the noise is purely
multiplicative, is presented. Both transitions are found in two as well as in
one dimension (where they had not been previously reported). We show
analytically and numerically that the critical behavior of these two
transitions is described by the so called multiplicative noise(MN) universality
class. A computation of the set of critical exponents is presented in both
, and (where they have not been previously measured).Comment: 4 pages, 2 figures, Late
Role of heat and mechanical treatments in the fabrication of superconducting Ba0.6K0.4Fe2As2 ex-situ Powder-In-Tube tapes
Among the recently discovered Fe-based superconducting compounds, the
(K,Ba)Fe2As2 phase is attracting large interest within the scientific community
interested in conductor developments. In fact, after some years of development,
critical current densities Jc of about 105 A/cm2 at fields up to more than 10 T
have been obtained in powder in tube (PIT) processed wires and tapes. Here we
explore the crucial points in the wire/tape fabrication by means of the ex-situ
PIT method. We focus on scaling up processes which are crucial for the
industrial fabrication. We analyzed the effects on the microstructure of the
different heat and mechanical treatments. By an extensive microstructural
analysis correlated with the transport properties we addressed the issues
concerning the phase purity, the internal porosity and crack formation in the
superconducting core region. Our best conductors with a filling factor of about
30 heat treated at 800 C exhibited Tc = 38 K the highest value measured in such
kind of superconducting tape. The microstructure analysis shows clean and well
connected grain boundaries but rather poor density: The measured Jc of about 3
x 10^4 A/cm2 in self-field is suppressed by less than a factor 7 at 7 T. Such
not yet optimized Jc values can be accounted for by the reduced density while
the moderate in-field suppression and a rather high n-factor confirm the high
homogeneity and uniformity of these tapes
Quantum correlation dynamics in photosynthetic processes assisted by molecular vibrations
During the long course of evolution, nature has learnt how to exploit quantum
effects. In fact, recent experiments reveal the existence of quantum processes
whose coherence extends over unexpectedly long time and space ranges. In
particular, photosynthetic processes in light-harvesting complexes display a
typical oscillatory dynamics ascribed to quantum coherence. Here, we consider
the simple model where a dimer made of two chromophores is strongly coupled
with a quasi-resonant vibrational mode. We observe the occurrence of wide
oscillations of genuine quantum correlations, between electronic excitations
and the environment, represented by vibrational bosonic modes. Such a quantum
dynamics has been unveiled through the calculation of the negativity of
entanglement and the discord, indicators widely used in quantum information for
quantifying the resources needed to realize quantum technologies. We also
discuss the possibility of approximating additional weakly-coupled off-resonant
vibrational modes, simulating the disturbances induced by the rest of the
environment, by a single vibrational mode.
Within this approximation, one can show that the off-resonant bath behaves
like a classical source of noise
Exhaust Energy Recovery with Variable Geometry Turbine to Reduce Fuel Consumption for Microcars
The objective proposed by EU to reduce by about 4%/year CO2 emission of internal combustion engines for
the next years up to 2030, requires to increase the engine efficiency and accordingly improving the technology.
In this framework, hybrid powertrains can have the possibility of a deep market penetration since they may recover energy during brake, allow the engine to operate in better efficiency conditions and with less transients, Moreover, they can recover a large amount of energy lost through the exhaust and use it to reduce fuel consumption.
This paper concerns the modification of a conventional two in-line cylinders Diesel engine (440 cm3) adding a variable geometry turbine (VGT) coupled with a generator. The turbine is used to recover exhaust gas energy that otherwise would be lost.
The generator, connected to the turbo shaft, converts mechanical energy into electrical energy and is used to charge the vehicle battery or the auxiliaries. The aim of this work is reducing fuel consumption by replacing the alternator with a kind of electric turbo-compounding system to drive vehicle auxiliaries. If the selected turbine recovers enough energy to power auxiliaries, the alternator, which usually has low efficiency, can be removed. Along these lines, fuel consumption savings can be achieved. At a later stage, a microcar has been tested on WLTC (Class 1) driving cycle. The results show fuel consumption reduction of 6 to 9%, depending on VGT size. Indeed, four different VGT sizes have been analyzed to choose the optimal configuration that reflects a compromise between energy recovery and fuel consumption reductions
Toward third order ghost imaging with thermal light
Recently it has been suggested that an enhancement in the visibility of ghost
images obtained with thermal light can be achieved exploiting higher order
correlations [3]. This paper reports on the status of an higher order ghost
imaging experiment carried on at INRIM labs exploiting a pseudo-thermal source
and a CCD camera.Comment: To be published in Proceedings of Recent advances in Foundations of
Quantum Mechanics and Quantum Informatio
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