Photon Self-Induced Spin to Orbital Conversion in TGG crystal at high laser power

In this paper, we present experimental evidence of a newly discovered third-order nonlinear optical process Self-Induced Spin-to-Orbital Conversion (SISTOC) of the photon angular momentum. This effect is the physical mechanism at the origin of the depolarization of very intense laser beams propagating in isotropic materials. The SISTOC process, like self-focusing, is triggered by laser heating leading to a radial temperature gradient in the medium. In this work we tested the occurrence of SISTOC in a terbium gallium garnet (TGG) rod for an impinging laser power of about 100~W. To study the SISTOC process we used different techniques: polarization analysis, interferometry and tomography of the photon orbital angular momentum. Our results confirm, in particular, that the apparent depolarization of the beam is due to the occurrence of maximal entanglement between the spin and orbital angular momentum of the photons undergoing the SISTOC process. This explanation of the true nature of the depolarization mechanism could be of some help in finding novel methods to reduce or to compensate for this usually unwanted depolarization effect in all cases where very high laser power and good beam quality are required.Comment: 6 pages, 10 figures, submitte

COBE Observations of the Microwave Counterparts of Gamma Ray Bursts

We have used the data from the COBE satellite to search for delayed microwave emission (31 - 90 GHz) from Gamma Ray Bursts (GRBs). The large $7^\circ$ beam of COBE is well matched to the large positional uncertainties in the GRB locations, although it also means that fluxes from (point source) GRB objects will be diluted. In view of this we are doing a statistical search of the GRBs which occurred during the currently released COBE DMR data (years 1990 and 1991), which overlap $\sim 200$ GRBs recorded by GRO. Here we concentrate on just the top 10 GRBs (in peak counts/second). We obtain the limits on the emission by comparing the COBE fluxes before and after the GRB at the GRB location. Since it is thought that the microwave emission should lag the GRB event, we have searched the GRB position for emission in the few months following the GRB occurrence.Comment: 5 pages, LaTE

COMPASS: a 2.6m telescope for CMBR polarization studies

COMPASS (COsmic Microwave Polarization at Small Scale) is an experiment devoted to measuring the polarization of the CMBR. Its design and characteristics are presented

Spin-orbit hybrid entanglement of photons and quantum contextuality

We demonstrate electromagnetic quantum states of single photons and of correlated photon pairs exhibiting "hybrid" entanglement between spin and orbital angular momentum. These states are obtained from entangled photon pairs emitted by spontaneous parametric down conversion, by employing a $q$-plate for coupling the spin and orbital degrees of freedom of a photon. Entanglement and contextual quantum behavior (that is also non-local, in the case of photon pairs) is demonstrated by the reported violation of the Clauser-Horne-Shimony-Holt inequality. In addition a classical analog of the hybrid spin-orbit photonic entanglement is reported and discussed.Comment: 5 pages, 3 figure

Detection of Zak phases and topological invariants in a chiral quantum walk of twisted photons

Topological insulators are fascinating states of matter exhibiting protected edge states and robust quantized features in their bulk. Here, we propose and validate experimentally a method to detect topological properties in the bulk of one-dimensional chiral systems. We first introduce the mean chiral displacement, and we show that it rapidly approaches a multiple of the Zak phase in the long time limit. Then we measure the Zak phase in a photonic quantum walk, by direct observation of the mean chiral displacement in its bulk. Next, we measure the Zak phase in an alternative, inequivalent timeframe, and combine the two windings to characterize the full phase diagram of this Floquet system. Finally, we prove the robustness of the measure by introducing dynamical disorder in the system. This detection method is extremely general, as it can be applied to all one-dimensional platforms simulating static or Floquet chiral systems.Comment: 10 pages, 7 color figures (incl. appendices) Close to the published versio

Vortex and half-vortex dynamics in a spinor quantum fluid of interacting polaritons

Spinorial or multi-component Bose-Einstein condensates may sustain fractional quanta of circulation, vorticant topological excitations with half integer windings of phase and polarization. Matter-light quantum fluids, such as microcavity polaritons, represent a unique test bed for realising strongly interacting and out-of-equilibrium condensates. The direct access to the phase of their wavefunction enables us to pursue the quest of whether half vortices ---rather than full integer vortices--- are the fundamental topological excitations of a spinor polariton fluid. Here, we are able to directly generate by resonant pulsed excitations, a polariton fluid carrying either the half or full vortex states as initial condition, and to follow their coherent evolution using ultrafast holography. Surprisingly we observe a rich phenomenology that shows a stable evolution of a phase singularity in a single component as well as in the full vortex state, spiraling, splitting and branching of the initial cores under different regimes and the proliferation of many vortex anti-vortex pairs in self generated circular ripples. This allows us to devise the interplay of nonlinearity and sample disorder in shaping the fluid and driving the phase singularities dynamicsComment: New version complete with revised modelization, discussion and added material. 8 pages, 7 figures. Supplementary videos: https://drive.google.com/folderview?id=0B0QCllnLqdyBfmc2ai0yVF9fa2g2VnZodGUwemVkLThBb3BoOVRKRDJMS2dUdjlZdkRTQk

SARS-CoV-2 and companion animals: sources of information and communication campaign during the COVID-19 pandemic in Italy

This study analyzed data on the sources and the level of Italians’ awareness on the risk of infection by SARS-CoV-2 at the human–animal interface. Data were collected through a survey-type investigation on a representative sample of the Italian population. Forty-five percent of the interviewees were aware that companion animals could be infected by SARS-CoV-2. However, 29.8% were familiar with preventive measures to adopt to avoid viral transmission between infected humans and companion animals, and only 20.7% knew which companion animals could be at risk of infection. Higher awareness regarding the risk of SARS-CoV-2 transmission between animals and humans (51.7%) and the measures to prevent it (33.3%) was detected among companion animals’ owners. Notably, 40.4% of interviewees were not informed at all. Television broadcasts (26.4%) represented the main source of information, while only 3.5% of the interviewees relied on veterinarians, of which 31.9% considered this source of information as the most trustworthy. Overall, 72.4% of Italians recognized that the communication campaign on COVID-19 and companion animals was inadequate. This survey highlights the need for increasing the public awareness of the risk of companion animals being infected with SARS-CoV-2 and the involvement of professionals in the public communication on zoonoses. © 2023 by the authors

Chirality effects on the IRMPD spectra of basket resorcinarene/nucleoside complexes

The IRMPD spectra of the ESI-formed proton-bound complexes of the R,R,R,R- and S,S,S,S-enantiomers of a bis(diamido)-bridged basket resorcin[4]arene (R and S) with cytosine (1), cytidine (2), and cytarabine (3) were measured in the region 2800– 3600 cm1. Comparison of the IRMPD spectra with the corresponding ONIOM (B3LYP/6-31(d):UFF)-calculated absorption frequencies allowed the assessment of the vibrational modes that are responsible for the observed spectroscopic features. All of the complexes investigated, apart from [R·H·3]+, showed similar IRMPD spectra, which points to similar structural and conformational landscapes. Their IRMPD spectra agree with the formation of several isomeric structures in the ESI source, wherein the N(3)-protonated guest establishes noncovalent interactions with the host amidocarbonyl groups that are either oriented inside the host cavity or outside it between one of the bridged side-chains and the upper aromatic nucleus. The IRMPD spectrum of the [R·H·3]+ complex was clearly different from the others. This difference is attributed to the effect of intramolecular hydrogen bonding interactions between the C(2’)-OH group and the aglycone oxygen atom of the nucleosidic guest upon repulsive interactions between the same oxygen atom and the aromatic rings of the host