Bragg spectroscopy of quantum gases: Exploring physics in one dimension

This thesis has been aimed at investigating the dynamical properties of one-dimensional gaseous nanowires, realized by trapping ultracold gases in laser-light lattice structures. The project was carried out at the European laboratory LENS in Florence, also with international collaborations. In recent years, one-dimensional systems have attracted great interest in different fields of physics, material science and chemistry, owing to their peculiar features: In this work, probing the response of the system to inelastic light-scattering experiments – Bragg spectroscopy – has allowed to explore the dynamics and the correlations inside these structures and the quantum phase-transition from superfluid to insulator, occurring due to inter-particle interactions

Noise spectroscopy of a quantum-classical environment with a diamond qubit

Knowing a quantum system's environment is critical for its practical use as a quantum device. Qubit sensors can reconstruct the noise spectral density of a classical bath, provided long enough coherence time. Here we present a protocol that can unravel the characteristics of a more complex environment, comprising both unknown coherently coupled quantum systems, and a larger quantum bath that can be modeled as a classical stochastic field. We exploit the rich environment of a Nitrogen-Vacancy center in diamond, tuning the environment behavior with a bias magnetic field, to experimentally demonstrate our method. We show how to reconstruct the noise spectral density even when limited by relatively short coherence times, and identify the local spin environment. Importantly, we demonstrate that the reconstructed model can have predictive power, describing the spin qubit dynamics under control sequences not used for noise spectroscopy, a feature critical for building robust quantum devices. At lower bias fields, where the effects of the quantum nature of the bath are more pronounced, we find that more than a single classical noise model are needed to properly describe the spin coherence under different controls, due to the back action of the qubit onto the bath.Comment: Main text: 5 pages, 5 figures. Supplemental material: 7 pages, 7 figures, 4 table

Enhancing User-Engagement in the Design Process through Augmented Reality Applications

Augmented Reality (AR) technologies are often perceived as the most impactful method to enhance the communication between the designer and the client during the iterative design process. However, the significance of designing the User Interface (UI) and the User Experience (UX) are often underestimated. To intercede, this research aims to employ new and existing techniques to develop UI's, and comparatively assess ``the accuracy and completeness with which specified users can achieve specified goals in particular environments'' (Stone, 2005) - a notion this research delineates as `effectiveness'. Prompted by the work of key scholars, the developed UI's were assessed through the lens of existing UI evaluation techniques, including: Usability Heuristics (Nielsen, 1994) and Visual and Cognitive Heuristics (Zuk and Carpendale, 2006). In partnership with PTW Architects, characteristics such as the rapidity and complexity of interactions, in conjunction with the interface's simplicity and intuitiveness, were extracted from 15 trials underwent by architectural practitioners. The outcomes of this research highlights strategies for the effective development of user interface design for mobile augmented reality applications

Quasiparticle dynamics in a Bose insulator probed by inter-band Bragg spectroscopy

We investigate experimentally and theoretically the dynamical properties of a Mott insulator in decoupled one-dimensional chains. Using a theoretical analysis of the Bragg excitation scheme we show that the spectrum of inter-band transitions holds information on the single-particle Green's function of the insulator. In particular the existence of particle-hole coherence due to quantum fluctuations in the Mott state is clearly seen in the Bragg spectra and quantified. Finally we propose a scheme to directly measure the full, momentum resolved spectral function as obtained in angle-resolved photoemission spectroscopy of solids.Comment: The new version contains improved theoretical treatment and data analysi

Kirkwood-Dirac quasiprobability approach to the statistics of incompatible observables

Recent work has revealed the central role played by the Kirkwood-Dirac quasiprobability (KDQ) as a tool to properly account for non-classical features in the context of condensed matter physics (scrambling, dynamical phase transitions) metrology (standard and post-selected), thermodynamics (power output and fluctuation theorems), foundations (contextuality, anomalous weak values) and more. Given the growing relevance of the KDQ across the quantum sciences, our aim is two-fold: First, we highlight the role played by quasiprobabilities in characterizing the statistics of quantum observables and processes in the presence of measurement incompatibility. In this way, we show how the KDQ naturally underpins and unifies quantum correlators, quantum currents, Loschmidt echoes, and weak values. Second, we provide novel theoretical and experimental perspectives by discussing a wide variety of schemes to access the KDQ and its non-classicality features

Bodily Expression of Social Initiation Behaviors in ASC and non-ASC children: Mixed Reality vs. LEGO Game Play

This study is part of a larger project that showed the potential of our mixed reality (MR) system in fostering social initiation behaviors in children with Autism Spectrum Condition (ASC). We compared it to a typical social intervention strategy based on construction tools, where both mediated a face-to-face dyadic play session between an ASC child and a non-ASC child. In this study, our first goal is to show that an MR platform can be utilized to alter the nonverbal body behavior between ASC and non-ASC during social interaction as much as a traditional therapy setting (LEGO). A second goal is to show how these body cues differ between ASC and non-ASC children during social initiation in these two platforms. We present our first analysis of the body cues generated under two conditions in a repeated-measures design. Body cue measurements were obtained through skeleton information and characterized in the form of spatio-temporal features from both subjects individually (e.g. distances between joints and velocities of joints), and interpersonally (e.g. proximity and visual focus of attention). We used machine learning techniques to analyze the visual data of eighteen trials of ASC and non-ASC dyads. Our experiments showed that: (i) there were differences between ASC and non-ASC bodily expressions, both at individual and interpersonal level, in LEGO and in the MR system during social initiation; (ii) the number of features indicating differences between ASC and non-ASC in terms of nonverbal behavior during initiation were higher in the MR system as compared to LEGO; and (iii) computational models evaluated with combination of these different features enabled the recognition of social initiation type (ASC or non-ASC) from body features in LEGO and in MR settings. We did not observe significant differences between the evaluated models in terms of performance for LEGO and MR environments. This might be interpreted as the MR system encouraging similar nonverbal behaviors in children, perhaps more similar than the LEGO environment, as the performance scores in the MR setting are lower as compared to the LEGO setting. These results demonstrate the potential benefits of full body interaction and MR settings for children with ASC.EPSR

MicroRNAs targeting oncogenes are down-regulated in pancreatic malignant transformation from benign tumors

BACKGROUND MicroRNA (miRNA) expression profiles have been described in pancreatic ductal adenocarcinoma (PDAC), but these have not been compared with pre-malignant pancreatic tumors. We wished to compare the miRNA expression signatures in pancreatic benign cystic tumors (BCT) of low and high malignant potential with PDAC, in order to identify miRNAs deregulated during PDAC development. The mechanistic consequences of miRNA dysregulation were further evaluated. METHODS Tissue samples were obtained at a tertiary pancreatic unit from individuals with BCT and PDAC. MiRNA profiling was performed using a custom microarray and results were validated using RT-qPCR prior to evaluation of miRNA targets. RESULTS Widespread miRNA down-regulation was observed in PDAC compared to low malignant potential BCT. We show that amongst those miRNAs down-regulated, miR-16, miR-126 and let-7d regulate known PDAC oncogenes (targeting BCL2, CRK and KRAS respectively). Notably, miR-126 also directly targets the KRAS transcript at a "seedless" binding site within its 3'UTR. In clinical specimens, miR-126 was strongly down-regulated in PDAC tissues, with an associated elevation in KRAS and CRK proteins. Furthermore, miR-21, a known oncogenic miRNA in pancreatic and other cancers, was not elevated in PDAC compared to serous microcystic adenoma (SMCA), but in both groups it was up-regulated compared to normal pancreas, implicating early up-regulation during malignant change. CONCLUSIONS Expression profiling revealed 21 miRNAs down-regulated in PDAC compared to SMCA, the most benign lesion that rarely progresses to invasive carcinoma. It appears that miR-21 up-regulation is an early event in the transformation from normal pancreatic tissue. MiRNA expression has the potential to distinguish PDAC from normal pancreas and BCT. Mechanistically the down-regulation of miR-16, miR-126 and let-7d promotes PDAC transformation by post-transcriptional up-regulation of crucial PDAC oncogenes. We show that miR-126 is able to directly target KRAS; re-expression has the potential as a therapeutic strategy against PDAC and other KRAS-driven cancers