Study of the propagation and detection of the orbital angular momentum of light for astrophysical applications

The aim of this work is to study the propagation of orbital angular momentum (OAM) of light for astrophysical applications and a method for OAM detection with optical telescopes. The thesis deals with the study of the orbital angular momentum (OAM) as a new observable for astronomers, which could give additional information with respect to those already inferred from the analysis of the intensity, frequency and polarization of light. Indeed, the main purpose of this work is to highlight that light can have a much more complex structure, and therefore can transport much more information. In particular, firstly we show that OAM can be imparted to light from interstellar media with a perturbed electron density function in the plane perpendicular to the propagation direction, revealing that the study of OAM could give information about the spatial structures of the traversed inhomogeneous media. The second part of the thesis deals with an experimental verification of the preservation of orbital angular momentum even for uncorrelated non-monochromatic wave beams, showing that this observable of light is preserved, thus we can aim at detecting it. Finally, if OAM can transport information, and if it is preserved in propagation, the obvious consequence is the study of its detection, in particular by an OAM mode sorter fitted to optical telescopes

Free-space quantum key distribution by rotation-invariant twisted photons

Twisted photons are photons carrying a well-defined nonzero value of orbital angular momentum (OAM). The associated optical wave exhibits a helical shape of the wavefront (hence the name) and an optical vortex at the beam axis. The OAM of light is attracting a growing interest for its potential in photonic applications ranging from particle manipulation, microscopy and nanotechnologies, to fundamental tests of quantum mechanics, classical data multiplexing and quantum communication. Hitherto, however, all results obtained with optical OAM were limited to laboratory scale. Here we report the experimental demonstration of a link for free-space quantum communication with OAM operating over a distance of 210 meters. Our method exploits OAM in combination with optical polarization to encode the information in rotation-invariant photonic states, so as to guarantee full independence of the communication from the local reference frames of the transmitting and receiving units. In particular, we implement quantum key distribution (QKD), a protocol exploiting the features of quantum mechanics to guarantee unconditional security in cryptographic communication, demonstrating error-rate performances that are fully compatible with real-world application requirements. Our results extend previous achievements of OAM-based quantum communication by over two orders of magnitudes in the link scale, providing an important step forward in achieving the vision of a worldwide quantum network

Encoding many channels in the same frequency through radio vorticity: first experimental test

We have shown experimentally that it is possible to propagate and use the properties of twisted non-monochromatic incoherent radio waves to simultaneously transmit to infinity more radio channels on the same frequency band by encoding them in different orbital angular momentum states. This novel radio technique allows the implementation of, at least in principle, an infinite number of channels on one and the same frequency, even without using polarization or dense coding techniques. An optimal combination of all these physical properties and techniques represents a solution for the problem of radio band congestion. Our experimental findings show that the vorticity of each twisted electromagnetic wave is preserved after the propagation, paving the way for entirely new paradigms in radio communication protocols.Comment: 17 pages, 6 figures, with a public experiment, three audio files in mp3 forma

SARS-CoV-2 Breakthrough Infections: Incidence and Risk Factors in a Large European Multicentric Cohort of Health Workers

The research aimed to investigate the incidence of SARS-CoV-2 breakthrough infections and their determinants in a large European cohort of more than 60,000 health workers

Study of the propagation and detection of the orbital angular momentum of light for astrophysical applications

The aim of this work is to study the propagation of orbital angular momentum (OAM) of light for astrophysical applications and a method for OAM detection with optical telescopes. The thesis deals with the study of the orbital angular momentum (OAM) as a new observable for astronomers, which could give additional information with respect to those already inferred from the analysis of the intensity, frequency and polarization of light. Indeed, the main purpose of this work is to highlight that light can have a much more complex structure, and therefore can transport much more information. In particular, firstly we show that OAM can be imparted to light from interstellar media with a perturbed electron density function in the plane perpendicular to the propagation direction, revealing that the study of OAM could give information about the spatial structures of the traversed inhomogeneous media. The second part of the thesis deals with an experimental verification of the preservation of orbital angular momentum even for uncorrelated non-monochromatic wave beams, showing that this observable of light is preserved, thus we can aim at detecting it. Finally, if OAM can transport information, and if it is preserved in propagation, the obvious consequence is the study of its detection, in particular by an OAM mode sorter fitted to optical telescopes.Lo scopo di questo lavoro è analizzare la propagazione del momento angolare orbitale (OAM) della luce per applicazioni astrofisiche e studiarne un metodo per la rilevazione con telescopi ottici. La tesi si occupa dello studio del momento angolare orbitale come un nuovo osservabile per gli astronomi, che potrebbe dare informazioni aggiuntive rispetto a quelle già deducibili dall'analisi della intensità, frequenza e polarizzazione della luce. Infatti, lo scopo principale di questo lavoro è di evidenziare come la luce possa avere una struttura molto più complessa, e quindi trasportare molte più informazioni. Inizialmente si dimostra che mezzi interstellari con una funzione di densità elettronica inomogenea nel piano perpendicolare alla direzione di propagazione della luce che li attraversa, possono conferire OAM. Ciò indica che lo studio dell' OAM può fornire informazioni sulle strutture spaziali dei mezzi attraversati non omogenei. Nella seconda parte della tesi viene esposta una verifica sperimentale della conservazione del momento angolare orbitale, anche per fasci d'onda non monocromatici e non coerenti . Viene così dimostrando che questo osservabile della luce si conserva, consentendone la rilevazione. Infine, osservato che l'OAM può trasportare informazioni, e che si conserva nella propagazione, si propone lo studio di un metodo per rivelarlo, in particolare di un uno spettrografo OAM per telescopi ottici

National minimum standards for care homes for younger adults

Added title from cover in Welsh: Y safonau gofynnol cenedlaethol ar gyfer cartrefi gofal i oedolion iau. Parallel text in English and Welsh, printed tete-becheAvailable from British Library Document Supply Centre- DSC:m03/11717 / BLDSC - British Library Document Supply CentreSIGLEGBUnited Kingdo

Reply to Comment on \u2018Encoding many channels on the same frequency through radio vorticity: first experimental test\u2019

Our recent paper (Tamburini et al 2012 New J. Phys. 14 033001), which presented results from outdoor experiments that demonstrate that it is physically feasible to simultaneously transmit different states of the newly recognized electromagnetic (EM) quantity orbital angular momentum (OAM) at radio frequencies into the far zone and to identify these states there, has led to a comment (Tamagnone et al 2012 New J. Phys. 14 118001). These authors discuss whether our investigations can be regarded as a particular implementation of the multiple-input\u2013multiple-output (MIMO) technique. Clearly, our experimental confirmation of a theoretical prediction, first made almost a century ago (Abraham 1914 Phys. Z. XV 914\u20138), that the total EM angular momentum (a pseudovector of dimension length 7 mass 7 velocity) can propagate over huge distances, is essentially different from\u2014and conceptually incompatible with\u2014the fact that there exist engineering techniques that can enhance the spectral capacity of EM linear momentum (an ordinary vector of dimension mass 7 velocity). Our OAM experiments (Tamburini et al 2012 New J. Phys. 14 033001; Tamburini et al 2011 Appl. Phys. Lett. 99 204102\u20133) confirm the availability of a new physical layer for real-world radio communications based on EM rotational degrees of freedom. The next step is to develop new protocols and techniques for high spectral density on this new physical layer. This includes MIMO-like and other, more efficient, techniques

Light's orbital angular momentum and optical vortices for astronomical coronagraphy from ground and space telescopes

The properties of optical vortices produced with spiral phase plates have recently found interesting applications in astronomical coronagraphy. Here we review the characteristics of the optical vortex coronagraph. Our simulations show that the intensity of an on-axis star can be fainted by 10 orders of magnitude, thus allowing the detection of close faint sources like extrasolar planets. We also discuss the expected coronagraphic performances achievable with a stepped spiral phase plate