Quantum Buckling

We study the mechanical buckling of a two dimensional membrane coated with a thin layer of superfluid. It is seen that a singularity (vortex or anti-vortex defect) in the phase of the quantum order parameter, distorts the membrane metric into a negative conical singularity surface, irrespective of the defect sign. The defect-curvature coupling and the observed instability is in striking contrast with classical elasticity where, the in-plane strain induced by positive (negative) disclinations is screened by a corresponding positive (negative) conical singularity surface. Defining a dimensionless ratio between superfluid stiffness and membrane bending modulus, we derive conditions under which the quantum buckling instability occurs. An ansatz for the resulting shape of the buckled membrane is analytically and numerically confirmed

Soliton attenuation and emergent hydrodynamics in fragile matter

Disordered packings of soft grains are fragile mechanical systems that loose rigidity upon lowering the external pressure towards zero. At zero pressure, we find that any infinitesimal strain-impulse propagates initially as a non-linear solitary wave progressively attenuated by disorder. We demonstrate that the particle fluctuations generated by the solitary-wave decay, can be viewed as a granular analogue of temperature. Their presence is manifested by two emergent macroscopic properties absent in the unperturbed granular packing: a finite pressure that scales with the injected energy (akin to a granular temperature) and an anomalous viscosity that arises even when the microscopic mechanisms of energy dissipation are negligible. Consistent with the interpretation of this state as a fluid-like thermalized state, the shear modulus remains zero. Further, we follow in detail the attenuation of the initial solitary wave identifying two distinct regimes : an initial exponential decay, followed by a longer power law decay and suggest simple models to explain these two regimes.Comment: 8 pages, 3 Figure

Enhanced Resolution of Lossy Interferometry by Coherent Amplification of Single Photons

In the quantum sensing context most of the efforts to design novel quantum techniques of sensing have been constrained to idealized, noise-free scenarios, in which effects of environmental disturbances could be neglected. In this work, we propose to exploit optical parametric amplification to boost interferometry sensitivity in the presence of losses in a minimally invasive scenario. By performing the amplification process on the microscopic probe after the interaction with the sample, we can beat the losses detrimental effect on the phase measurement which affects the single-photon state after its interaction with the sample, and thus improve the achievable sensitivity.Comment: 4 + 3 pages, 3 + 5 figure

Quantum to classical transition via fuzzy measurements on high gain spontaneous parametric down-conversion

We consider the high gain spontaneous parametric down-conversion in a non collinear geometry as a paradigmatic scenario to investigate the quantum-to-classical transition by increasing the pump power, that is, the average number of generated photons. The possibility of observing quantum correlations in such macroscopic quantum system through dichotomic measurement will be analyzed by addressing two different measurement schemes, based on different dichotomization processes. More specifically, we will investigate the persistence of non-locality in an increasing size n/2-spin singlet state by studying the change in the correlations form as $n$ increases, both in the ideal case and in presence of losses. We observe a fast decrease in the amount of Bell's inequality violation for increasing system size. This theoretical analysis is supported by the experimental observation of macro-macro correlations with an average number of photons of about 10^3. Our results enlighten the practical extreme difficulty of observing non-locality by performing such a dichotomic fuzzy measurement.Comment: 15 pages, 18 figure

LE PATOLOGIE DA SOVRACCARICO BIOMECCANICO DEGLI ARTI SUPERIORI: CONFRONTO FRA GRUPPI DI LAVORATORI AD ESPOSIZIONE VARIABILE.

Background: European and Italian statistics have reported in the past decade a significant increase of work-related musculoskeletal disorders including the construction sector. Objectives: To check this issue, the EPM Research Unit in collaboration with the Craftmanship Territorial Joint Committee in Bergamo, have started a research in the field of musculoskeletal disorders with special reference to lumbar spine and upper limbs. Methods: The health survey was carried out by ad hoc trained staff. Results: between November 2009 and November 2010, data on 2755 subjects with a variety of jobs were obtained, over 50% being masons. The whole sample and the group of masons were investigated and both exhibited prevalence of upper limb diseases definitely higher than the reference group of non-exposed subjects. At the same time, risk assessment on painters and carpenters was performed, showing very hogh levels of risk o upper limb biomechanical overload due to awkward postures and force application. Conclusions: Hence the need for active research to be included in the protocol of health surveillance (with appropriate clinical protocol), of upper limb and spine MSDs. They also highlight the need for other biomechanical overload exposure data aimed at reconstructing risk profiles (from biomechanical overload) but above all at identifying the technological and organizational solutions to erase this particular risk

A qualitative study on minority stress subjectively experienced by transgender and gender nonconforming people in Italy

A great amount of quantitative research has largely demonstrated that transgender and gender nonconforming (TGNC) people experience high rates of minority stress, against which they are able to exercise resilience and to use adaptive strategies buffering the negative effects of stress on health. Notwithstanding, qualitative investigations on how TGNC people subjectively experience minority stress are still scarce. This study aims at exploring the subjective experiences of minority stress through a focus group with 8 Italian TGNC individuals (5 male-to-female, 2 female-to-male, and 1 genderqueer; M = 25; SD = 5). Narratives were analyzed through the deductive thematic analysis. The analysis generated four main categories: (1) family rejection; (2) visibility of the body; (3) negative effects of family violence on health; and (4) integration of TGNC identity. Results offer an in-depth exploration of minority stress processes in TGNC people, as well as the impact of stress on health and adaptive strategies to face with stigma. Suggestions for clinical practice are discussed

General rules for bosonic bunching in multimode interferometers

We perform a comprehensive set of experiments that characterize bosonic bunching of up to 3 photons in interferometers of up to 16 modes. Our experiments verify two rules that govern bosonic bunching. The first rule, obtained recently in [1,2], predicts the average behavior of the bunching probability and is known as the bosonic birthday paradox. The second rule is new, and establishes a n!-factor quantum enhancement for the probability that all n bosons bunch in a single output mode, with respect to the case of distinguishable bosons. Besides its fundamental importance in phenomena such as Bose-Einstein condensation, bosonic bunching can be exploited in applications such as linear optical quantum computing and quantum-enhanced metrology.Comment: 6 pages, 4 figures, and supplementary material (4 pages, 1 figure

Heat transport in model jammed solids

We calculate numerically the normal modes of vibrations in 3D jammed packings of soft spheres as a function of the packing fraction and obtain the energy diffusivity, a spectral measure of transport that controls sound propagation and thermal conductivity. The crossover frequency between weak and strong phonon scattering is controlled by the coordination and shifts to zero as the system is decompressed towards the critical packing fraction at which rigidity is lost. Below the crossover, the diffusivity displays a power-law divergence with inverse frequency, which suggests that the vibrational modes are primarily transverse waves, weakly scattered by disorder. Above it, a large number of modes appear whose diffusivity plateaus at a nearly constant value independent of the inter-particle potential, before dropping to zero above the Anderson localization frequency. The thermal conductivity of a marginally jammed solid just above the rigidity threshold is calculated and related to the one measured experimentally at room temperature for most glasses.Comment: 15 pages, 7 figure