537 research outputs found
Entanglement estimation in non-optimal qubit states
No full textThis is the author accepted manuscript. The final version is available from Elsevier via the DOI in this recordIn the last years, a relationship has been established between the quantum Fisher information (QFI) and quantum entanglement. In the case of two-qubit systems, all pure entangled states can be made useful for sub-shot-noise interferometry while their QFI meets a necessary and sufficient condition (Hyllus et al., 2010). In M-qubit systems, the QFI provides just a sufficient condition in the task of detecting the degree of entanglement of a generic state (Pezzé and Smerzi, 2009). In our work, we show analytically that, for a large class of one-parameter non-optimal two-qubit states, the maximally entangled states are associated with stationary points of the QFI, as a function of such parameter. We show, via numerical simulations, that this scenario is maintained for the generalisation of this class of states to a generic M-qubit system. Furthermore, we suggest a scheme for an interferometer able to detect the entanglement in a large class of two-spin states.QuantERAEuropean Commissio
Asymptotically Schwarzschild solutions in f (R) extension of general relativity
No full textWe address the question of how to build a class of f(R) extensions of General Relativity which are compatible with solar system experiments, without making any preliminary assumption on the properties of f. The aim is reached by perturbatively solving the modified Einstein equations around a Schwarzschild background and retrieving a posteriori the corresponding f(R). This turns out to be non analytical in R=0 and should be intended as the leading correction to the Einstein-Hilbert action in the low curvature limit. The parameters characterizing the f(R) class are then set by constraining the corrections to four different local tests with the observations. The result is a class of f(R) theories built up from a purely bottom-up approach and compatible with the local tests. At a more general level, this result can help constraining exact f(R) models working in Cosmology, since it provides the correct local limit. Further developments and possible extensions of the approach to Cosmology are also discussed
Modelli di dispersione atmosferica con scenari emissivi multipli - Una metodologia sistematica per la riduzione del numero di sorgenti
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Grapevine origin and diversity
No full textThis text is intended to be a brief discussion of some salient conceptual and methodological aspects concerning the cultivated grapevine (Vitis vinifera L). The essay, far from aiming to be exhaustive, strives instead to highlight original and significant steps taken by the international scientific community over the last thirty years to deepen the historical and biological path that this woody species, which has played an essential role in human history, has taken. Possible future scenarios involving genetic modifications to improve adaptive mechanisms are also discussed
PERFORMANCE OF DIFFERENT REGULATORS FOR PLANTS WITH RECYCLE
No full textPerformance of simple PI and model based (IMC) regulators for plants with recycle, are compared in control schemes with and without a recycle compensator. By considering different dynamic characteristic of the process, it is analysed in which cases the adoption of a compensator is necessary to eliminate completely the effect of recycle streams, both for set point tracking and for disturbance suppression. The robustness of the compensator in the presence of parametric uncertainty in the recycle model is also examined
Monitoraggio dell’Inquinamento Atmosferico con Modelli di Dispersione: un Metodo per l’Aggregazione delle Sorgenti Emissive
No full textIl Wine DNA fingerprinting (WDF): un’analisi molecolare per accertare la composizione varietale di un vino.
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