84 research outputs found
Random quantum channels I: graphical calculus and the Bell state phenomenon
This paper is the first of a series where we study quantum channels from the
random matrix point of view. We develop a graphical tool that allows us to
compute the expected moments of the output of a random quantum channel. As an
application, we study variations of random matrix models introduced by Hayden
\cite{hayden}, and show that their eigenvalues converge almost surely. In
particular we obtain for some models sharp improvements on the value of the
largest eigenvalue, and this is shown in a further work to have new
applications to minimal output entropy inequalities.Comment: Several typos were correcte
Generating random density matrices
We study various methods to generate ensembles of random density matrices of
a fixed size N, obtained by partial trace of pure states on composite systems.
Structured ensembles of random pure states, invariant with respect to local
unitary transformations are introduced. To analyze statistical properties of
quantum entanglement in bi-partite systems we analyze the distribution of
Schmidt coefficients of random pure states. Such a distribution is derived in
the case of a superposition of k random maximally entangled states. For another
ensemble, obtained by performing selective measurements in a maximally
entangled basis on a multi--partite system, we show that this distribution is
given by the Fuss-Catalan law and find the average entanglement entropy. A more
general class of structured ensembles proposed, containing also the case of
Bures, forms an extension of the standard ensemble of structureless random pure
states, described asymptotically, as N \to \infty, by the Marchenko-Pastur
distribution.Comment: 13 pages in latex with 8 figures include
A Search for New Galactic Magnetars in Archival Chandra and XMM-Newton Observations
We present constraints on the number of Galactic magnetars, which we have
established by searching for sources with periodic variability in 506 archival
Chandra observations and 441 archival XMM-Newton observations of the Galactic
plane (|b|<5 degree). Our search revealed four sources with periodic
variability on time scales of 200-5000 s, all of which are probably accreting
white dwarfs. We identify 7 of 12 known Galactic magnetars, but find no new
examples with periods between 5 and 20 s. We convert this non-detection into
limits on the total number of Galactic magnetars by computing the fraction of
the young Galactic stellar population that was included in our survey. We find
that easily-detectable magnetars, modeled after persistent anomalous X-ray
pulsars, could have been identified in 5% of the Galactic spiral arms by mass.
If we assume there are 3 previously-known examples within our random survey,
then there are 59 (+92,-32) in the Galaxy. Transient magnetars in quiescence
could have been identified throughout 0.4% of the spiral arms, and the lack of
new examples implies that <540 exist in the Galaxy (90% confidence). Similar
constraints are found by considering the detectability of transient magnetars
in outburst by current and past X-ray missions. For assumed lifetimes of 1e4
yr, we find that the birth rate of magnetars could range between 0.003 and 0.06
per year. Therefore, the birth rate of magnetars is at least 10% of that for
normal radio pulsars. The magnetar birth rate could exceed that of radio
pulsars, unless the lifetimes of transient magnetars are >1e5 yr. Obtaining
better constraints will require wide-field X-ray or radio searches for
transient X-ray pulsars similar to XTE J1810--197, AX J1845.0--0250, CXOU
J164710.2--455216, and 1E 1547.0-5408.Comment: 16 pages, 10 figures, one with a bit of color. submitted to Ap
Assessment of the technological performance of some Saccharomyces and non-Saccharomyces indigenous yeast strains
The study aimed to assess the technological potential of four indigenous Saccharomyces cerevisiae strains (S. cer. 4.1.11, S. cer. 4.3, S. cer. 4.6 and S. cer. 4.10), as possible sources for starter cultures. The experiments were carried out at micropilot level on the natural must of 'Fetească albă' cultivar. The evaluation of the yeasts was carried out according to the chemical parameters and volatile compounds analysed in the obtained wines compared to the wine obtained with a commercial starter culture (CSC). The values of the main physico-chemical parameters analyzed
in the obtained wines were similar to those determined in the control wine. The average values of the volatile compounds with positive impact on the wine aroma
ranged within the interval 177.46 - 217.81 mg/L, a higher value compared to the control wine, respectively 166.33 mg/L. The use of the indigenous strain Torulospora
delbrueckii (T.d 10) in association with the strains S. cer. 4.1.11 or S. cer. 4.10 led to an increase of 12.56%, respectively 8.30% in glycerol concentrations, as well as an
increase of 11.94% to 14.49% in the average concentration of volatile compounds. Harnessing the oenological potential of the yeasts tested in sequential fermentations
proved dependent on the time allowed for the development of the strain T.d 10, namely 24 and 48 hours, as well as on the yeasts used. Thus, in the wines obtained by the association T.d 10/ S. cer. 4.10, in which the development of the culture T.d 10 was carried out for 48 hours, we noticed an increase of 12.52% and, respectively 32.95%, in the average of volatile compounds, compared to the monoculture wine for the same S. cer. 4.10 strain and to the control wine (CSC)
Random graph states, maximal flow and Fuss-Catalan distributions
For any graph consisting of vertices and edges we construct an
ensemble of random pure quantum states which describe a system composed of
subsystems. Each edge of the graph represents a bi-partite, maximally entangled
state. Each vertex represents a random unitary matrix generated according to
the Haar measure, which describes the coupling between subsystems. Dividing all
subsystems into two parts, one may study entanglement with respect to this
partition. A general technique to derive an expression for the average
entanglement entropy of random pure states associated to a given graph is
presented. Our technique relies on Weingarten calculus and flow problems. We
analyze statistical properties of spectra of such random density matrices and
show for which cases they are described by the free Poissonian
(Marchenko-Pastur) distribution. We derive a discrete family of generalized,
Fuss-Catalan distributions and explicitly construct graphs which lead to
ensembles of random states characterized by these novel distributions of
eigenvalues.Comment: 37 pages, 24 figure
Valorizing intangible cultural heritage through community-based tourism in Lăpuș Land, Transylvania
Community-based tourism has been promoted as a means of
development whereby the social, environmental and economic needs of local communities are met through the offering of a tourism product. Local culture may be a community’s most valuable asset for tourism if planned and managed properly. Its intangible cultural heritage may provide a community with a competitive advantage and uniqueness, one that differentiates it from all other communities. However, with increasing commodification of tourism, many smaller rural communities face several challenges in developing community-based tourism. The present paper explores the concept of community-based tourism, as a basis for the valorization of intangible cultural heritage, with a special focus on a regional tourist destination in Romania. Aiming to identify tourists’ experience, a research was conducted among Japanese visitors who discovered the intangible cultural heritage of the studied area during an academic summer camp
Random matrix techniques in quantum information theory
The purpose of this review article is to present some of the latest
developments using random techniques, and in particular, random matrix
techniques in quantum information theory. Our review is a blend of a rather
exhaustive review, combined with more detailed examples -- coming from research
projects in which the authors were involved. We focus on two main topics,
random quantum states and random quantum channels. We present results related
to entropic quantities, entanglement of typical states, entanglement
thresholds, the output set of quantum channels, and violations of the minimum
output entropy of random channels
Radical heminephrectomy for left sided upper pole renal tumor on horseshoe kidney – case report and review of the literature
Ion Chiricuţă Oncological Institute Cluj Napoca, Al V-lea Congres de Urologie, Dializă şi Transplant Renal din Republica Moldova cu participare internaţională (1-13 iunie 2011)Abstract Tumoral pathology of the horseshoe kidney is a rare pathology, only half of the tumors represent renal cell carcinoma. We will present the case of a 45 year old man known with horseshoe kidney diagnosed with a large renal tumor on the left side. CT angiography was performed preoperatively to asses the vascular anomalies of the renal pedicle and it was used for planning the surgical approach. The approach was transperitoneal by subcostal incision with lateral paramedian extension
Random repeated quantum interactions and random invariant states
We consider a generalized model of repeated quantum interactions, where a
system is interacting in a random way with a sequence of
independent quantum systems . Two types of randomness
are studied in detail. One is provided by considering Haar-distributed
unitaries to describe each interaction between and
. The other involves random quantum states describing each copy
. In the limit of a large number of interactions, we present
convergence results for the asymptotic state of . This is achieved
by studying spectral properties of (random) quantum channels which guarantee
the existence of unique invariant states. Finally this allows to introduce a
new physically motivated ensemble of random density matrices called the
\emph{asymptotic induced ensemble}
Dry Bacterial Cellulose and Carboxymethyl Cellulose formulations with interfacial-active performance: processing conditions and redispersion
Dry or powdered formulations of food additives facilitate transportation, storage, preservation and handling. In this work, dry formulations of bacterial cellulose and carboxymethyl cellulose (BC:CMC), easily redispersible and preserving the functionality of the never-dried dispersions are reported. Different processing parameters and their effect on the materials properties were evaluated, namely: (i) wet-grinding of BC (Hand-blender, Microcut Head Impeller, High-pressure Homogenizer), (ii) drying of BC:CMC mixtures (fast drying at130 °C and slow drying at 80 °C) and subsequent (iii) comminution to different particle sizes. The dispersibility of the obtained BC:CMC powders was evaluated, and their functionality after redispersion was assessed by measuring the dynamic viscosity, the effect in oil/water interfacial tension (liquidliquid system) and the stabilization of cocoa in milk (solidliquid system). The size of BC fibre bundles was of paramount relevance to its stabilizing ability in multiphasic systems. A more extensive wet-grinding of the BC fibres was accompanied by a loss in the BC:CMC functionality, related to the increasingly smaller size of the BC bundles. Indeed, as the Dv (50) of the wet BC bundles was reduced from 1228 to 55 µm, the BC:CMC viscosity profile dropped and the effect on interfacial tension decreased. This effect was observed both on the never-dried and dry BC:CMC formulations. On the other hand, the drying method did not play a major effect in the materials properties. In a benchmarking study, the BC:CMC formulations, at a low concentration (0.15%), had better stabilizing ability of the cocoa particles than several commercial cellulose products.Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10570-020-03211-9) contains supplementary material, which is available to authorized users.This study was supported by FCT under
the scope of the strategic funding of UID/BIO/04469/2019 unit
and BioTecNorte operation (NORTE-01-0145-FEDER000004) funded by the European Regional Development Fund
under the scope of Norte2020-Programa Operacional Regional
do Norte. Daniela Martins also gratefully acknowledges FCT for
the PhD scholarship, reference SFRH/BD/115917/2016.info:eu-repo/semantics/publishedVersio
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