Hierarchichal-segmented AO in order to attain wide field compensation in the visible on an 8m class telescope

We describe the preliminary optimized layout for a partially optimized concept of an optical-8m class VLT-like 2x2 segmented camera where each channel is assisted by an equivalent of an MCAO system where the ground layer correction is commonly employed while the high altitude ones is performed in an open-loop fashion. While we derive the basic relationships among the Field of View and attainable correction with a pre-defined choice for the hardware, we discuss sky coverage and wavefront sensing issues employing natural and artificial references, involving the latest stateof-the-art in the development of wavefront sensing. We show that a flexible approach allow for a compensated Field of View that is variable and can be properly tuned matching the current turbulence situation and the requirement in term of quality of the compensation. A preliminary description of the overall optomechanical package is given as well along with a rough estimates of the efforts required to translates such a concept into reality.Comment: 6 pages, 4 figures, in AO4ELT5 Proceeding

Multiple Spatial Frequencies Pyramid WaveFront Sensing

A modification of the pyramid wavefront sensor is described. In this conceptually new class of devices, the perturbations are split at the level of the focal plane depending upon their spatial frequencies, and then measured separately. The aim of this approach is to increase the accuracy in the determination of some range of spatial frequency perturbations, or a certain classes of modes, disentangling them from the noise associated to the Poissonian fluctuations of the light coming from the perturbations outside of the range of interest or from the background in the pupil planes; the latter case specifically when the pyramid wavefront sensor is used with a large modulation. While the limits and the effectiveness of this approach should be further investigated, a number of variations on the concept are shown, including a generalization of the spatial filtering in the point-diffraction wavefront sensor. The simplest application, a generalization to the pyramid of the well-known spatially filtering in wavefront sensing, is showing promise as a significant limiting magnitude advance. Applications are further speculated in the area of extreme adaptive optics and when serving spectroscopic instrumentation where “light in the bucket” rather than Strehl performance is required

A Holographic Diffuser Generalised Optical Differentiation Wavefront Sensor

The wavefront sensors used today at the biggest World's telescopes have either a high dynamic range or a high sensitivity, and they are subject to a linear trade off between these two parameters. A new class of wavefront sensors, the Generalised Optical Differentiation Wavefront Sensors, has been devised, in a way not to undergo this linear trade off and to decouple the dynamic range from the sensitivity. This new class of WFSs is based on the light filtering in the focal plane from a dedicated amplitude filter, which is a hybrid between a linear filter, whose physical dimension is related to the dynamic range, and a step in the amplitude, whose size is related to the sensitivity. We propose here a possible technical implementation of this kind of WFS, making use of a simple holographic diffuser to diffract part of the light in a ring shape around the pin of a pyramid wavefront sensor. In this way, the undiffracted light reaches the pin of the pyramid, contributing to the high sensitivity regime of the WFS, while the diffused light is giving a sort of static modulation of the pyramid, allowing to have some signal even in high turbulence conditions. The holographic diffuser zeroth order efficiency is strictly related to the sensitivity of the WFS, while the diffusing angle of the diffracted light gives the amount of modulation and thus the dynamic range. By properly choosing these two parameters it is possible to build a WFS with high sensitivity and high dynamic range in a static fashion. Introducing dynamic parts in the setup allows to have a set of different diffuser that can be alternated in front of the pyramid, if the change in the seeing conditions requires it.Comment: 11 pages, 5 figure

Ingot Laser Guide Stars Wavefront Sensing

We revisit one class of z-invariant WaveFront sensor where the LGS is fired aside of the telescope aperture. In this way there is a spatial dependence on the focal plane with respect to the height where the resonant scattering occurs. We revise the basic parameters involving the geometry and we propose various merit functions to define how much improvement can be attained by a z-invariant approach. We show that refractive approaches are not viable and we discuss several solutions involving reflective ones in what has been nicknamed "ingot wavefront sensor" discussing the degrees of freedom required to keep tracking and the basic recipe for the optical design.Comment: 6 pages, 4 figures, AO4ELT5 Conference Proceeding, 201

Precautionary advice about mobile phones: Public understandings and intended responses

The official published version can be obtained from the link below - Copyright @ Taylor & FrancisThere is a widespread academic and policy debate about public responses to precaution in public health campaigns. This paper explores these issues in relation to the precautionary stance adopted in the UK around the regulation of mobile telecommunications. The aim of the paper is to examine the nature of attitudes to precaution, and the way in which these, along with other relevant variables, relate to the intention to adopt relevant behaviours. The results from an experimental study (n = 173) indicate that people distinguish between two dimensions of precaution: firstly in relation to its value or necessity per se and secondly as anchored to notions of governance. The two variables differentially relate to other variables including trust and uncertainty, and are predictive of intended behaviour change indirectly, through worry about mobile phone risks. Precautionary advice was generally interpreted as causing concern rather than providing reassurance. The results suggest that precaution may be considered a valuable stance but this does not mean that it is seen as good governance or that it will reduce concern. Whilst the discourse of precaution is aimed at reducing concern, it appears that the uptake of relevant behaviours is largely triggered by worry

Machine learning for quantum error mitigation on NISQ devices

Il Quantum Error Mitigation (QEM) è un insieme di tecniche utilizzate per ridurre l'impatto del rumore nel calcolo quantistico senza la necessità di implementare specifici protocolli per una completa rimozione degli errori, come avviene invece nel caso del Quantum Error Correction (QEC). Questo approccio mira a migliorare le prestazioni degli algoritmi mitigando gli effetti indesiderati del rumore che caratterizzano i computer quantistici odierni, appartenenti alla cosidetta classe Noisy Intermediate-Scale Quantum (NISQ). Nel contesto del calcolo quantistico \textit{gate-based}, questa tesi introduce un innovativo approccio al QEM basato su tecniche di Machine Learning (ML). In particolare, viene proposta una semplice rete neurale classica (architettura dell'autoencoder) in grado di imparare uno specifico modello di rumore dai dati forniti. Dopo una prima fase, che prevede la preparazione di un dataset eseguendo la simulazione di diversi circuiti quantistici, la rete neurale viene allenata per l'identificazione e mitigazione degli effetti del rumore quantistico sull'istogramma misurato. L'efficacia del modello è poi validata calcolando una metrica per confrontare ogni coppia di istogrammi \textit{rumoroso} e \textit{mitigato} con la corrispondente distribuzione di probabilità ideale. I promettenti risultati ottenuti aprono nuove prospettive per applicazioni del QEM in contesti sperimentali anche più avanzati, contribuendo alla crescita e alla maturazione della computazione quantistica

Imaginary latent variables: Empirical testing for detecting deficiency in reflective measures

Imaginary latent variables are variables with negative variances and have been used to implement constraints in measurement models. This article aimed to advance this practice and rationalize the imaginary latent variables as a method to detect possible latent deficiencies in measurement models. This rationale is based on the theory of complex numbers used in the measurement process of common factor model–based structural equation modeling. Modeling an imaginary latent variable produces a potential deficiency within its relative reflective measures through a considerable reduction in common variance indicating the most affected indicator(s)