111 research outputs found
Economical Phase-Covariant Cloning of Qudits
We derive the optimal N to M phase-covariant quantum cloning for equatorial
states in dimension d with M=kd+N, k integer. The cloning maps are optimal for
both global and single-qudit fidelity. The map is achieved by an ``economical''
cloning machine, which works without ancilla.Comment: 10 pages revtex4, 7 figures, replaced with modified versio
Optimal Time-Reversal of Multi-phase Equatorial States
Even though the time-reversal is unphysical (it corresponds to the complex
conjugation of the density matrix), for some restricted set of states it can be
achieved unitarily, typically when there is a common de-phasing in a n-level
system. However, in the presence of multiple phases (i. e. a different
de-phasing for each element of an orthogonal basis occurs) the time reversal is
no longer physically possible. In this paper we derive the channel which
optimally approaches in fidelity the time-reversal of multi-phase equatorial
states in arbitrary (finite) dimension. We show that, in contrast to the
customary case of the Universal-NOT on qubits (or the universal conjugation in
arbitrary dimension), the optimal phase covariant time-reversal for equatorial
states is a nonclassical channel, which cannot be achieved via a
measurement/preparation procedure. Unitary realizations of the optimal
time-reversal channel are given with minimal ancillary dimension, exploiting
the simplex structure of the optimal maps.Comment: 7 pages, minor change
Superbroadcasting and classical information
We address the problem of broadcasting N copies of a generic qubit state to
M>N copies by estimating its direction and preparing a suitable output state
according to the outcome of the estimate. This semiclassical broadcasting
protocol is more restrictive than a general one, since it requires an
intermediate step where classical information is extracted and processed.
However, we prove that a suboptimal superbroadcasting, namely broadcasting with
simultaneous purification of the local output states with respect to the input
ones, is possible. We show that in the asymptotic limit of the
purification rate converges to the optimal one, proving the conjecture that
optimal broadcasting and state estimation are asymptotically equivalent. We
also show that it is possible to achieve superbroadcasting with simultaneous
inversion of the Bloch vector direction (universal NOT). We prove that in this
case the semiclassical procedure of state estimation and preparation turns out
to be optimal. We finally analyse semiclassical superbroadcasting in the
phase-covariant case.Comment: 9 pages, 2 figure
Universal and phase covariant superbroadcasting for mixed qubit states
We describe a general framework to study covariant symmetric broadcasting
maps for mixed qubit states. We explicitly derive the optimal N to M
superbroadcasting maps, achieving optimal purification of the single-site
output copy, in both the universal and the phase covariant cases. We also study
the bipartite entanglement properties of the superbroadcast states.Comment: 19 pages, 8 figures, strictly related to quant-ph/0506251 and
quant-ph/051015
Predicting global usages of resources endowed with local policies
The effective usages of computational resources are a primary concern of
up-to-date distributed applications. In this paper, we present a methodology to
reason about resource usages (acquisition, release, revision, ...), and
therefore the proposed approach enables to predict bad usages of resources.
Keeping in mind the interplay between local and global information occurring in
the application-resource interactions, we model resources as entities with
local policies and global properties governing the overall interactions.
Formally, our model takes the shape of an extension of pi-calculus with
primitives to manage resources. We develop a Control Flow Analysis computing a
static approximation of process behaviour and therefore of the resource usages.Comment: In Proceedings FOCLASA 2011, arXiv:1107.584
Italian mitochondrial DNA database: results of a collaborative exercise and proficiency testing
Abstract This work is a review of a collaborative exercise on mtDNA analysis undertaken by the Italian working group (Ge.F.I.). A total of 593 samples from 11 forensic genetic laboratories were subjected to hypervariable region (HVS-I/HVS-II) sequence analysis. The raw lane data were sent to MtDNA Population Database (EMPOP) for an independent evaluation. For the inclusion of data for the Italian database, quality assurance procedures were applied to the control region profiles. Only eight laboratories with a final population sample of 395 subjects passed the quality conformance test. Control region haplogroup (hg) assignments were confirmed by restriction fragment length polymorphism (RFLP) typing of the most common European hg-diagnostic sites. A total of 306 unique haplotypes derived from the combined analysis of control and coding region polymorphisms were found; the most common haplotype -CRS, 263, 309.1C, 315.1C/ÂŹ7025 AluI-was shared by 20 subjects. The majority of mtDNAs detected in the Italian population fell into the most common wes
Generalised quantum weakest preconditions
Generalisation of the quantum weakest precondition result of D'Hondt and
Panangaden is presented. In particular the most general notion of quantum
predicate as positive operator valued measure (POVM) is introduced. The
previously known quantum weakest precondition result has been extended to cover
the case of POVM playing the role of a quantum predicate. Additionally, our
result is valid in infinite dimension case and also holds for a quantum
programs defined as a positive but not necessary completely positive
transformations of a quantum states.Comment: 7 pages, no figures, added references, changed conten
Dynamic measurement of the height and volume of migrating cells by a novel fluorescence microscopy technique
We propose a new technique to measure the volume of adherent migrating cells. The method is based on a negative staining where a fluorescent, non cell-permeant dye is added to the extracellular medium. The specimen is observed with a conventional fluorescence microscope in a chamber of uniform height. Given that the fluorescence signal depends on the thickness of the emitting layer, the objects excluding the fluorescent dye (i.e., cells) appear dark, and the decrease of the fluorescent signal with respect to the background is expected to give information about the height and the volume of the object. Using a glass microfabricated pattern with steps of defined heights, we show that the drop in fluorescence intensity is indeed proportional to the height of the step and obtain calibration curves relating fluorescence intensity to height. The technique, termed fluorescence displacement method, is further validated by comparing our measurements with the ones obtained by atomic force microscopy (AFM). We apply our method to measure the real-time volume dynamics of migrating fish epidermal keratocytes subjected to osmotic stress. The fluorescence displacement technique allows fast and precise monitoring of cell height and volume, thus providing a valuable tool for characterizing the three-dimensional behaviour of migrating cells
The Activity of Special Continuity Care Units in the City of Florence During the COVID-19 Pandemic
Objectives: Worldwide, countries adopted different strategies in primary care (PC) to cope with the COVID-19 pandemic. This study aims to describe and evaluate the functions and activity load of a specific PC organizational model called âSpecial Continuity Care Unitsâ (SCCU) in Florence, Italy, and to investigate the characteristics of the COVID-19 patients assisted by the service.Methods: The retrospective cross-sectional design used daily updated reports by SCCU team members to evaluate the activity load. The retrospective cohort study analyzed data of the demographics, clinical characteristics, and process outcomes of patients assisted during the second pandemic wave.Results: The analysis shows how the service activity load changed along with the epidemiological trend. Regarding people assisted by the SCCU, the median follow-up duration of symptoms was 6Â days; male gender and being symptomatic were predictors of hospitalization.Conclusion: Some key characteristics can be described as indispensable in PC services facing health emergencies: model flexibility, the availability of resources, networking among services to enhance coordination and resource optimization, and close collaboration with general practitioners
- âŠ