Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 22
Filtrar
Más filtros










Base de datos
Intervalo de año de publicación
1.
Epilepsy Res ; 154: 86-89, 2019 08.
Artículo en Inglés | MEDLINE | ID: mdl-31112901

RESUMEN

BACKGROUND: Geographic isolates are the ideal setting to study the genetic background and the epidemiology of epilepsy. There are only few published reports on the epidemiology of pediatric epilepsy in geographic isolates. METHODS: This study was performed in the Ischia island, district of Napoli (Southern Italy). The local population includes 61,086 individuals, 8381 of them aged from 0 to 14 years. We included children with two or more unprovoked seizures or one unprovoked seizure associated to a high risk of relapse, observed from 2004 to 2017. Neonatal, febrile and acute symptomatic seizures were excluded. Eligible patients were identified through the local pediatricians' medical records. All probands and their parents underwent a face-to-face interview. Clinical charts were reviewed and electroclinical diagnoses were confirmed by two authors (AC, VB). RESULTS: Thirty-six children and adolescents were included. Overall, the prevalence of epilepsy in the Ischia island was 4.3 per 1,000 (95% CI 3.0-5.9). Incidence was 51.7 per 100,000 person-years (95% CI 36.2-71.6). Sixteen (44.4%) patients had a genetic (idiopathic) origin and 20 (55.6%) a symptomatic (structural/metabolic) etiology. Nine probands (25%) had at least one family member with epilepsy (including third-degree relatives). Their pedigrees were suggestive of dominant inheritance in six and of recessive inheritance in three families. CONCLUSIONS: The epidemiological features of pediatric epilepsy in this geographic isolate are similar to the general population. A family history was reported in one fourth of the patients with a wide clinical heterogeneity, likely reflecting genetic heterogeneity in this population.


Asunto(s)
Epilepsia/epidemiología , Epilepsia/genética , Familia , Adolescente , Niño , Preescolar , Análisis por Conglomerados , Epilepsia/diagnóstico , Femenino , Mapeo Geográfico , Humanos , Lactante , Italia/epidemiología , Masculino
2.
Phys Rev Lett ; 122(1): 013601, 2019 Jan 11.
Artículo en Inglés | MEDLINE | ID: mdl-31012655

RESUMEN

Structured photons are nowadays an important resource in classical and quantum optics due to the richness of properties they show under propagation, focusing, and in their interaction with matter. Vectorial modes of light in particular, a class of modes where the polarization varies across the beam profile, have already been used in several areas ranging from microscopy to quantum information. One of the key ingredients needed to exploit the full potential of complex light in the quantum domain is the control of quantum interference, a crucial resource in fields like quantum communication, sensing, and metrology. Here we report a tunable Hong-Ou-Mandel interference between vectorial modes of light. We demonstrate how a properly designed spin-orbit device can be used to control quantum interference between vectorial modes of light by simply adjusting the device parameters and no need of interferometric setups. We believe our result can find applications in fundamental research and quantum technologies based on structured light by providing a new tool to control quantum interference in a compact, efficient, and robust way.

3.
Phys Rev Lett ; 121(17): 173901, 2018 Oct 26.
Artículo en Inglés | MEDLINE | ID: mdl-30411929

RESUMEN

In this work, we experimentally show that quantum entanglement can be symmetry protected in the interaction with a single subwavelength plasmonic nanoaperture, with a total volume of V∼0.2λ^{3}. In particular, we experimentally demonstrate that two-photon entanglement can be either completely preserved or completely lost after the interaction with the nanoaperture, solely depending on the relative phase between the quantum states. We achieve this effect by using specially engineered two-photon states to match the properties of the nanoaperture. In this way we can access a symmetry protected state, i.e., a state constrained by the geometry of the interaction to retain its entanglement. In spite of the small volume of interaction, we show that the symmetry protected entangled state retains its main properties. This connection between nanophotonics and quantum optics probes the fundamental limits of the phenomenon of quantum interference.

4.
Phys Rev Lett ; 121(14): 140501, 2018 Oct 05.
Artículo en Inglés | MEDLINE | ID: mdl-30339412

RESUMEN

Quantum teleportation establishes a correspondence between an entangled state shared by two separate parties that can communicate classically and the presence of a quantum channel connecting the two parties. The standard benchmark for quantum teleportation, based on the average fidelity between the input and output states, indicates that some entangled states do not lead to channels which can be certified to be quantum. It was recently shown that if one considers a finer-grained witness, then all entangled states can be certified to produce a nonclassical teleportation channel. Here we experimentally demonstrate a complete characterization of a new family of such witnesses, of the type proposed in Phys. Rev. Lett. 119, 110501 (2017)PRLTAO0031-900710.1103/PhysRevLett.119.110501 under different conditions of noise. We report nonclassical teleportation using quantum states that cannot achieve average fidelity of teleportation above the classical limit. We further use the violation of these witnesses to estimate the negativity of the shared state. Our results have fundamental implications in quantum information protocols and may also lead to new applications and quality certification of quantum technologies.

5.
ACS Photonics ; 4(11): 2807-2812, 2017 Nov 15.
Artículo en Inglés | MEDLINE | ID: mdl-29250573

RESUMEN

In classical physics, properties of objects exist independently of the context, i.e., whether and how measurements are performed. Quantum physics showed this assumption to be wrong, and that Nature is indeed "contextual". Contextuality has been observed in the simplest physical systems, such as single particles, and plays fundamental roles in quantum computation advantage. Here, we demonstrate for the first time quantum contextuality in an integrated photonic chip. The chip implements different combinations of measurements on a single photon delocalized on four distinct spatial modes, showing violations of a Clauser-Horne-Shimony-Holt (CHSH)-like noncontextuality inequality. This paves the way to compact and portable devices for contextuality-based quantum-powered protocols.

6.
Sci Rep ; 7(1): 13265, 2017 10 16.
Artículo en Inglés | MEDLINE | ID: mdl-29038486

RESUMEN

Greenberger-Horne-Zeilinger (GHZ) states and their mixtures exhibit fascinating properties. A complete basis of GHZ states can be constructed by properly choosing local basis rotations. We demonstrate this experimentally for the Hilbert space [Formula: see text] by entangling two photons in polarization and orbital angular momentum. Mixing GHZ states unmasks different entanglement features based on their particular local geometrical connectedness. In particular, a specific GHZ state in a complete orthonormal basis has a "twin" GHZ state for which equally mixing leads to full separability in opposition to any other basis-state. Exploiting these local geometrical relations provides a toolbox for generating specific types of multipartite entanglement, each providing different benefits in outperforming classical devices. Our experiment investigates these GHZ's properties exploiting the HMGH framework which allows us to study the geometry for the different depths of entanglement in our system and showing a good stability and fidelity thus admitting a scaling in degrees of freedom and advanced operational manipulations.

7.
Opt Express ; 24(15): 16390-5, 2016 Jul 25.
Artículo en Inglés | MEDLINE | ID: mdl-27464091

RESUMEN

When a phase singularity is suddenly imprinted on the axis of an ordinary Gaussian beam, an optical vortex appears and starts to grow radially, by effect of diffraction. This radial growth and the subsequent evolution of the optical vortex under focusing or imaging can be well described in general within the recently introduced theory of circular beams, which generalize the hypergeometric-Gaussian beams and which obey novel kinds of ABCD rules. Here, we investigate experimentally these vortex propagation phenomena and test the validity of circular-beam theory. Moreover, we analyze the difference in radial structure between the newly generated optical vortex and the vortex obtained in the image plane, where perfect imaging would lead to complete closure of the vortex core.

8.
Nat Commun ; 6: 7706, 2015 Jul 13.
Artículo en Inglés | MEDLINE | ID: mdl-26166257

RESUMEN

The full structuration of light in the transverse plane, including intensity, phase and polarization, holds the promise of unprecedented capabilities for applications in classical optics as well as in quantum optics and information sciences. Harnessing special topologies can lead to enhanced focusing, data multiplexing or advanced sensing and metrology. Here we experimentally demonstrate the storage of such spatio-polarization-patterned beams into an optical memory. A set of vectorial vortex modes is generated via liquid crystal cell with topological charge in the optic axis distribution, and preservation of the phase and polarization singularities is demonstrated after retrieval, at the single-photon level. The realized multiple-degree-of-freedom memory can find applications in classical data processing but also in quantum network scenarios where structured states have been shown to provide promising attributes, such as rotational invariance.

9.
Sci Rep ; 5: 8424, 2015 Feb 12.
Artículo en Inglés | MEDLINE | ID: mdl-25672667

RESUMEN

Recent schemes to encode quantum information into the total angular momentum of light, defining rotation-invariant hybrid qubits composed of the polarization and orbital angular momentum degrees of freedom, present interesting applications for quantum information technology. However, there remains the question as to how detrimental effects such as random spatial perturbations affect these encodings. Here, we demonstrate that alignment-free quantum communication through a turbulent channel based on hybrid qubits can be achieved with unit transmission fidelity. In our experiment, alignment-free qubits are produced with q-plates and sent through a homemade turbulence chamber. The decoding procedure, also realized with q-plates, relies on both degrees of freedom and renders an intrinsic error-filtering mechanism that maps errors into losses.

10.
Sci Rep ; 5: 7840, 2015 Jan 19.
Artículo en Inglés | MEDLINE | ID: mdl-25598018

RESUMEN

Vectorial vortex light beams, also referred to as spirally polarized beams, are of particular interest since they can be exploited in several applications ranging from quantum communication to spectroscopy and microscopy. In particular, symmetric pairs of vector beams define two-dimensional spaces which are described as "hybrid Poincaré spheres" (HPS). While generation of vortex beams has been demonstrated by various techniques, their manipulation, in particular in order to obtain transformations describing curves entirely contained on a given HPS, is quite challenging, as it requires a simultaneous action on both polarization and orbital angular momentum degrees of freedom. Here, we demonstrate experimentally this kind of manipulation by exploiting electrically-tuned q-plates: an arbitrary transformation on the HPS can be obtained, by controlling two parameters of the q-plate, namely the initial optic axis orientation α0 and the uniform birefringent phase retardation δ. Upon varying such parameters, one can determine both the rotation axis and the rotation angle on the HPS, obtaining the desired state manipulation with high fidelity.

11.
Phys Rev Lett ; 113(6): 060503, 2014 Aug 08.
Artículo en Inglés | MEDLINE | ID: mdl-25148310

RESUMEN

"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 m. 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, 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 2 orders of magnitude in the link scale, providing an important step forward in achieving the vision of a worldwide quantum network.

12.
Phys Rev Lett ; 112(14): 140501, 2014 Apr 11.
Artículo en Inglés | MEDLINE | ID: mdl-24765931

RESUMEN

In quantum mechanics, observing is not a passive act. Consider a system of two quantum particles A and B: if a measurement apparatus M is used to make an observation on B, the overall state of the system AB will typically be altered. When this happens, no matter which local measurement is performed, the two objects A and B are revealed to possess peculiar correlations known as quantum discord. Here, we demonstrate experimentally that the very act of local observation gives rise to an activation protocol which converts discord into distillable entanglement, a stronger and more useful form of quantum correlations, between the apparatus M and the composite system AB. We adopt a flexible two-photon setup to realize a three-qubit system (A, B, M) with programmable degrees of initial correlations, measurement interaction, and characterization processes. Our experiment demonstrates the fundamental mechanism underpinning the ubiquitous act of observing the quantum world and establishes the potential of discord in entanglement generation.

13.
Phys Rev Lett ; 112(14): 140503, 2014 Apr 11.
Artículo en Inglés | MEDLINE | ID: mdl-24765933

RESUMEN

An important problem in quantum information processing is the certification of the dimension of quantum systems without making assumptions about the devices used to prepare and measure them, that is, in a device-independent manner. A crucial question is whether such certification is experimentally feasible for high-dimensional quantum systems. Here we experimentally witness in a device-independent manner the generation of six-dimensional quantum systems encoded in the orbital angular momentum of single photons and show that the same method can be scaled, at least, up to dimension 13.

14.
Nat Commun ; 4: 2432, 2013.
Artículo en Inglés | MEDLINE | ID: mdl-24045270

RESUMEN

Quantum metrology bears a great promise in enhancing measurement precision, but is unlikely to become practical in the near future. Its concepts can nevertheless inspire classical or hybrid methods of immediate value. Here we demonstrate NOON-like photonic states of m quanta of angular momentum up to m=100, in a setup that acts as a 'photonic gear', converting, for each photon, a mechanical rotation of an angle θ into an amplified rotation of the optical polarization by mθ, corresponding to a 'super-resolving' Malus' law. We show that this effect leads to single-photon angular measurements with the same precision of polarization-only quantum strategies with m photons, but robust to photon losses. Moreover, we combine the gear effect with the quantum enhancement due to entanglement, thus exploiting the advantages of both approaches. The high 'gear ratio' m boosts the current state of the art of optical non-contact angular measurements by almost two orders of magnitude.

15.
Sci Rep ; 3: 2726, 2013 Sep 25.
Artículo en Inglés | MEDLINE | ID: mdl-24067548

RESUMEN

In quantum information, complementarity of quantum mechanical observables plays a key role. The eigenstates of two complementary observables form a pair of mutually unbiased bases (MUBs). More generally, a set of MUBs consists of bases that are all pairwise unbiased. Except for specific dimensions of the Hilbert space, the maximal sets of MUBs are unknown in general. Even for a dimension as low as six, the identification of a maximal set of MUBs remains an open problem, although there is strong numerical evidence that no more than three simultaneous MUBs do exist. Here, by exploiting a newly developed holographic technique, we implement and test different sets of three MUBs for a single photon six-dimensional quantum state (a "qusix"), encoded exploiting polarization and orbital angular momentum of photons. A close agreement is observed between theory and experiments. Our results can find applications in state tomography, quantitative wave-particle duality, quantum key distribution.

16.
Lung Cancer ; 80(1): 50-4, 2013 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-23294502

RESUMEN

BACKGROUND: The effectiveness of screening for lung cancer (LC) in smokers on a population level, as distinct from the special circumstances that may apply in a randomized trial of selected volunteers, has not been thoroughly investigated. Here we evaluate by the standardized mortality ratio (SMR) indicator the impact of a chest X-ray (CXR) screening programme carried out at community level on LC mortality in smokers. METHODS: All smokers of >10 pack-years, of both genders, ages 45-75 years, resident in 50 communities of the Province of Varese, Italy, screening-eligible, in 1997 were invited by their National Health Service (NHS) general practitioner physicians to a nonrandomized programme of five annual CXR screenings. The entire invitation-to-screen cohort (n=5815 subjects) received NHS usual care, with the addition of CXR exams in volunteer participants (21% of invitees), and was observed through December 2006. To overcome participants' selection bias of LC mortality assessment, for the entire invitation-to-screen cohort we estimated the LC-specific SMR, based on the local reference population receiving the NHS usual care. RESULTS: Over the 8-year period 1999-2006, a total of 172 cumulative LC deaths were observed in the invitation-to-screen cohort; 210 were expected based on the reference population. Each year in the invited cohort the observed LC deaths were fewer than expected. The cumulative LC SMR was 0.82 (95% CI, 0.67-0.99; p=0.048), suggesting that LC mortality was reduced by 18% with CXR screening. CONCLUSION: Implementation of a CXR screening programme at community level was associated with a significant reduction of LC mortality in smokers.


Asunto(s)
Neoplasias Pulmonares/diagnóstico , Pulmón/diagnóstico por imagen , Radiografías Pulmonares Masivas/métodos , Fumar , Anciano , Estudios de Cohortes , Femenino , Humanos , Italia/epidemiología , Pulmón/patología , Neoplasias Pulmonares/mortalidad , Masculino , Persona de Mediana Edad , Vigilancia de la Población/métodos , Factores de Riesgo , Tasa de Supervivencia/tendencias
17.
Opt Lett ; 37(2): 172-4, 2012 Jan 15.
Artículo en Inglés | MEDLINE | ID: mdl-22854457

RESUMEN

In this work we experimentally implement a deterministic transfer of a generic qubit initially encoded in the orbital angular momentum of a single-photon to its polarization. Such a transfer of quantum information, which is completely reversible, has been implemented adopting an electrically tunable q-plate device and a Sagnac interferometer with a Dove prism. The adopted scheme exhibits high fidelity and low losses.

18.
Nat Commun ; 3: 961, 2012 Jul 17.
Artículo en Inglés | MEDLINE | ID: mdl-22805568

RESUMEN

Quantum communication employs the counter-intuitive features of quantum physics for tasks that are impossible in the classical world. It is crucial for testing the foundations of quantum theory and promises to revolutionize information and communication technologies. However, to execute even the simplest quantum transmission, one must establish, and maintain, a shared reference frame. This introduces a considerable overhead in resources, particularly if the parties are in motion or rotating relative to each other. Here we experimentally show how to circumvent this problem with the transmission of quantum information encoded in rotationally invariant states of single photons. By developing a complete toolbox for the efficient encoding and decoding of quantum information in such photonic qubits, we demonstrate the feasibility of alignment-free quantum key-distribution, and perform proof-of-principle demonstrations of alignment-free entanglement distribution and Bell-inequality violation. The scheme should find applications in fundamental tests of quantum mechanics and satellite-based quantum communication.

19.
Sci Rep ; 2: 443, 2012.
Artículo en Inglés | MEDLINE | ID: mdl-22720131

RESUMEN

The extraction of information from a quantum system unavoidably implies a modification of the measured system itself. In this framework partial measurements can be carried out in order to extract only a portion of the information encoded in a quantum system, at the cost of inducing a limited amount of disturbance. Here we analyze experimentally the dynamics of sequential partial measurements carried out on a quantum system, focusing on the trade-off between the maximal information extractable and the disturbance. In particular we implement two sequential measurements observing that, by exploiting an adaptive strategy, is possible to find an optimal trade-off between the two quantities.


Asunto(s)
Algoritmos , Modelos Teóricos , Teoría Cuántica , Fenómenos Químicos , Fotones
20.
Phys Rev Lett ; 108(9): 090501, 2012 Mar 02.
Artículo en Inglés | MEDLINE | ID: mdl-22463620

RESUMEN

Quantum resources outperform classical ones for certain communication and computational tasks. Remarkably, in some cases, the quantum advantage cannot be improved using hypothetical postquantum resources. A class of tasks with this property can be singled out using graph theory. Here we report the experimental observation of an impossible-to-beat quantum advantage on a four-dimensional quantum system defined by the polarization and orbital angular momentum of a single photon. The results show pristine evidence of the quantum advantage and are compatible with the maximum advantage allowed using postquantum resources.

SELECCIÓN DE REFERENCIAS
DETALLE DE LA BÚSQUEDA
...