Articles de revues : « 3 photons »

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Xiu, Xiao-Ming, Li Dong, Hong-Zhi Shen, Ya-Jun Gao et X. X. Yi. « Two-party QPC with polarization-entangled Bell states and the coherent states ». Quantum Information and Computation 14, n^o 3&4 (mars 2014) : 236–54. http://dx.doi.org/10.26421/qic14.3-4-3.

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We propose a protocol of quantum privacy comparison with polarization-entangled Einstein-Podolsky-Rosen (Bell) states and the coherent states. One of two legitimate participants, Alice, prepares polarization-entangled Bell states and keeps one photon of each photon pair and sends the other photons to the third party, Charlie. Receiving the photons, Charlie performs single-photon transformation operations on them and then sends them to the other legitimate participant, Bob. Three participants adopt parity analysis method to check the distribution security of Bell states. Exploiting polarization beam splitters and nonlinear interactions mediated by the probe coherent states in Kerr media, Alice and Bob check the parities of their photons using the bases of $\{\ket H, \ket V\}$ or $\{\ket +, \ket -\}$. On the basis of the parity analysis outcomes and Charlie's publicized information, they can analyze the security of the distributed quantum channel. Confirming secure distribution of the shared Bell states, two participants perform respective parity measurements on the privacy photons and own photons of Bell states, and then send the results to Charlie. According to information provided by two legitimate participants and his single-qubit transformation operations, Charlie compares the privacy information of Alice and Bob and publicizes the conclusion.

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Pickford Scienti, Oliver L. P. Pickford, et Dimitra G. Darambara. « Demonstrating a Novel, Hidden Source of Spectral Distortion in X-ray Photon Counting Detectors and Assessing Novel Trigger Schemes Proposed to Avoid It ». Sensors 23, n^o 9 (1 mai 2023) : 4445. http://dx.doi.org/10.3390/s23094445.

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X-ray photon counting spectral imaging (x-CSI) determines a detected photon’s energy by comparing the charge it induces with several thresholds, counting how many times each is crossed (the standard method, STD). This paper is the first to demonstrate that this approach can unexpectedly delete counts from the recorded energy spectrum under some clinically relevant conditions: a process we call negative counting. Four alternative counting schemes are proposed and simulated for a wide range of sensor geometries (pixel pitch 100–600 µm, sensor thickness 1–3 mm), number of thresholds (3, 5, 8, 24 and 130) and medically relevant X-ray fluxes (106–109 photons mm−2 s−1). Spectral efficiency and counting efficiency are calculated for each simulation. Performance gains are explained mechanistically and correlated well with the improved suppression of “negative counting”. The best performing scheme (Shift Register, SR) entirely eliminates negative counting, remaining close to an ideal scheme at fluxes of up to 108 photons mm−2 s−1. At the highest fluxes considered, the deviation from ideal behaviour is reduced by 2/3 in SR compared with STD. The results have significant implications both for generally improving spectral fidelity and as a possible path toward the 109 photons mm−2 s−1 goal in photon-counting CT.

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MIKI, KENTARO. « AZIMUTHAL ANISOTROPY MEASUREMENT OF DIRECT PHOTON IN $\sqrt{^SNN} = 200\ {\rm GeV}$Au + Au COLLISIONS AT RHIC-PHENIX ». International Journal of Modern Physics E 16, n^o 07n08 (août 2007) : 2160–65. http://dx.doi.org/10.1142/s0218301307007623.

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Azimuthal anisotropy of direct photons is measured in [Formula: see text] Au + Au collisions by the PHENIX experiment at RHIC. Direct photons are one of the most effective probes to study properties of hot dense medium at initial state (also QGP state) of heavy ion collisions because photons do not interact strongly with medium once produced. They keep their conditions when they are created. Within statistical and systematic errors, the elliptic flow parameter (v2) of direct photons is consistent with zero. Direct photons v2 is measured by the hadron decay photon background v2 from inclusive photon v2 in intermediate to high transverse momentum (pT) region (0 to 10 GeV/c) for 3 centrality selections (20% steps) and minimum bias.

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Nikotin, Oleg P. « DIFFRACTION EXPERIMENTS WITH KOSSEL PHOTONS ». Bulletin of the Saint Petersburg State Institute of Technology (Technical University) 58 (2021) : 3–10. http://dx.doi.org/10.36807/1998-9849-2021-58-84-3-10.

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In the paper an attempt was made to obtain some information about the characteristics of photons as separate objects with the properties of localization in ordinary coordinate space. Experiments of various complexity with Kossel photons were carried out on a multiaxial diffractometer. A diffraction spectrometer with perfect calcite crystals was used to register the photons. The bidirectional angular measurements were carried out with sufficient angular and energy resolution to detect the influence of the coherent volume of the photons on the measurement results. The measurements showed some correlations that had not been paid enough attention before. Those effects were measured separately for Kα1 and Kα2 photons to allow their comparison. Such approach corresponds to the modern quantum mechanics of the photon; that mechanics showed the possibility of existence of wave functions of photons in their usual standard sense. Data on spatial parameters Kα1 and Kα2 of Kossel photons were obtained by comparing the effects of their diffraction scattering

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Rasulov, V. R., R. Ya Rasulov, I. Eshboltaev et M. X. Kuchkarov. « TO THE THEORY OF THE TWO AND THREE PHOTONIC LINEAR CIRCULAR DICHROISMS IN CUBIC SYMMETRY SEMICONDUCTORS ». SEMOCONDUCTOR PHYSICS AND MICROELECTRONICS 3, n^o 3 (30 juin 2021) : 51–55. http://dx.doi.org/10.37681/2181-1652-019-x-2021-3-9.

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The linear - circular dichroism of two and three photon absorption of light in semiconductors of cubic symmetry of hole conductivity is theoretically investigated. The matrix elements of two and three - photon optical transitions occurring between the subbands of the semiconductor valence band are calculated. In this case, transitions associated with both non - simultaneous absorption of individual photons and simultaneous absorption of two photons are taken into account, and the spectral and temperature dependences of the coefficient of two and three - photon absorption of polarized radiation are determined

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Peresunko, D. « Direct photon production in pp, p–Pb and Pb–Pb collisions measured with the ALICE experiment ». EPJ Web of Conferences 191 (2018) : 05001. http://dx.doi.org/10.1051/epjconf/201819105001.

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We review recent ALICE results on direct photon production in pp, p–Pb and Pb–Pb collisions at LHC energies. In light systems, pp and p–Pb, no signal of direct photons at low pT < 3-5 GeV/c is observed within uncertainties, while at high pT our measurements are consistent with NLO pQCD calculations. In central and mid-central Pb–Pb collisions a thermal photon contribution is observed at low pT < 3 - 4 GeV/c with slopes Teff = (304 ± 11stat ± 40syst) MeV and (407 ± 61stat ± 96syst) MeV respectively. A collective elliptic flow of direct photons is measured and appeared to be close to the decay photon flow.

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Hu, Huiqin, Xinyi Ren, Zhaoyang Wen, Xingtong Li, Yan Liang, Ming Yan et E. Wu. « Single-Pixel Photon-Counting Imaging Based on Dual-Comb Interferometry ». Nanomaterials 11, n^o 6 (24 mai 2021) : 1379. http://dx.doi.org/10.3390/nano11061379.

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We propose and experimentally demonstrate single-pixel photon counting imaging based on dual-comb interferometry at 1550 nm. Different from traditional dual-comb imaging, this approach enables imaging at the photon-counting regime by using single-photon detectors combined with a time-correlated single-photon counter to record the returning photons. The illumination power is as low as 14 pW, corresponding to 2.2 × 10−3 photons/pulse. The lateral resolution is about 50 μm. This technique paves the way for applying dual-comb in remote sensing and imaging.

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ZHANG, WENTAO, SIGUO XIAO, XIAOLIANG YANG et XIANGLIANG JIN. « BROADBAND QUANTUM CUTTING IN ZnO/Yb(Er)F3 OXY-FLUORIDE NANOCOMPOSITE PREPARED BY THERMAL OXIDATION METHOD ». Functional Materials Letters 06, n^o 01 (février 2013) : 1350002. http://dx.doi.org/10.1142/s1793604713500021.

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Yb(Er)F3 nanoparticles absorbed with ZnO sheet were prepared via two-step co-precipitation method followed with thermal oxidation. In the ZnO / Yb(Er)F3 composite phosphor, ZnO can efficiently absorb ultraviolet photons of 250–380 nm and transfer its absorbed photon energy to Er 3+ ions in fluoride particles. A followed quantum cutting between Er 3+- Yb 3+ couples in the fluoride takes place, down-converting an absorbed ultraviolet photon into two photons of 650 nm and 980 nm radiations. The composite phosphor combines the wide wavelength absorption range and high absorption cross-section of ZnO with high quantum cutting efficiency of Er 3+- Yb 3+ co-doped fluoride, showing potential application in the enhancement of Si solar cell efficiency.

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Yin, Bo, Pinshu Lv, Yanmin Yang et Leipeng Li. « Pr³⁺–Gd³⁺ co-doped Ba₂SiO₄ for multilevel anti-counterfeiting encryption ». Journal of Applied Physics 132, n^o 15 (21 octobre 2022) : 153104. http://dx.doi.org/10.1063/5.0119544.

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Developing anti-counterfeiting technology with a higher level of security is vital to boycott the fake commodities. Here, we report the detailed optical property of Ba2SiO4:Pr3+, Gd3+, and their potential applications in fluorescent anti-counterfeit. It has been confirmed that Pr3+ ions could emit the ultraviolet-C (UVC) photons upon excitation of a 450 nm laser, which originates from a two-photon upconverted mechanism. Moreover, the ultraviolet-B (UVB) light also appears simultaneously when co-doping Gd3+ into the host, due to the energy transfer from Pr3+ to Gd3+. Depending on the multimode emissions of Pr3+-Gd3+-codoped phosphors, including the routine magenta emission of Pr3+, as well as the UVC photons of Pr3+ and the UVB light of Gd3+, we successfully achieve multi-level anti-counterfeiting applications.

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Lin, Tao. « Deferred Optical Photon simulation for the JUNO experiment ». Journal of Physics : Conference Series 2438, n^o 1 (1 février 2023) : 012078. http://dx.doi.org/10.1088/1742-6596/2438/1/012078.

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Abstract The Jiangmen Underground Neutrino Observatory (JUNO) is designed to determine the neutrino mass ordering and precisely measure oscillation parameters. It is being built in South China at a depth of 700 m underground and comprises a central detector, water Cerenkov detector and top tracker. The central detector is designed to detect anti-neutrinos with an energy resolution of 3% at 1 MeV, using a 20 kt liquid scintillator target with 17,612 20-inch PMTs and 25,600 3-inch PMTs. The scintillator provides a light yield of approximately 10,000 photons per MeV. Monte Carlo simulation is a crucial tool for developing an understanding of detector performance, requiring the production of large samples of background processes with optical photons. Simulation of large numbers of optical photons with Geant4 is computationally challenging for both processing time and memory resources. In order to optimize resource usage, a deferred optical photon simulation workflow is proposed and implemented using Geant4 classes. The key idea is to simulate events initially without optical photons, only performing the optical photon simulation when user specified criteria are met. In this contribution, the design and the implementation of the deferred optical photon simulation will be presented. Optical simulation comprises generation of photons and propagation through the detector implementing optical physics processes including reflection, refraction, scattering and absorption. Instead of generating the optical photons at each step by Geant4 immediately, the necessary data to generate optical photons at each step are collected, which is termed GenStep. At the end of each event, user specified criteria determines if the optical photon simulation is performed using a class called G4OPSimulator. The class G4OPSimulator implements a customized simulation workflow, based on Geant4 internal classes including G4TrackingManager and G4StackManager. The simulator passes references to the collected GenStep objects to customized Scintillation and Cerenkov processes which generate the optical photons in G4Track objects. As a track could be absorbed and re-emitted, the secondaries will be retrieved from the G4TrackingManager and pushed to the G4StackManager. The performance of the simulator will be presented. The technique of deferred optical photon simulation can be applied to all event types and it is expected to be particularly beneficial with rare processes. Especially the events must be selected during the detector simulation at runtime, instead of the event generation. An application of the technique to the simulation of such events will be shown.

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Fahmi Mohd Yusof, Mohd, Nur Amirah Shariff, Nur Sajidah Muhammad Fauzi, Ahmad Bazlie Abdul Kadir et Noriza Mohd Isa. « Small beam dosimetry by using Al₂O₃ optically stimulated luminescent (OSL) dosimeters at high energy photons and electrons ». IOP Conference Series : Materials Science and Engineering 1231, n^o 1 (1 février 2022) : 012018. http://dx.doi.org/10.1088/1757-899x/1231/1/012018.

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Abstract The study focused on the measurements of depth dose for small beam in the high energy photons and electrons. The percentage depth dose (PDD) was measured in 6 and 10 MV photons and 9 and 12 MeV electrons at 3 × 3 cm field sizes by using the Al2O3 optically stimulated luminescent (OSL) dosimeters. The PDD in OSL dosimeters were compared to those in ionization chamber and Gafchromic EBT3 film dosimeter. The results showed that the PDD in OSL dosimeters in lower photon and electron energies were in good agreement within 4% to ionization chamber and film. The PDD in 10 MV photons however showed gradual increase of deviation up to 10% beyond the depth of maximum dose (dmax). The surface doses in OSL dosimeters were significantly higher compared to those in ionization chamber and film dosimeter. The overall results suggested the suitability of OSL dosimeters to be used as indirect dosimetry works in high energy photons and electrons.

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Walborn, S. P., M. P. Almeida, P. H. Souto Ribeiro et C. H. Monken. « Quantum information processing with hyperentangled photon states ». Quantum Information and Computation 6, n^o 4&5 (juillet 2006) : 336–50. http://dx.doi.org/10.26421/qic6.4-5-3.

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We discuss quantum information processing with hyperentangled photon states - states entangled in multiple degrees of freedom. Using an additional entangled degree of freedom as an ancilla space, it has been shown that it is possible to perform efficient Bell-state measurements. We briefly review these results and present a novel deterministic quantum key distribution protocol based on Bell-state measurements of hyperentangled photons. In addition, we propose a scheme for a probabilistic controlled-not gate which operates with a 50% success probability. We also show that despite its probabilistic nature, the controlled-not gate can be used for an efficient, nonlocal demonstration of the Deutsch algorithm using two separate photons.

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AKSENOV, A. G., R. RUFFINI, I. A. SIUTSOU et G. V. VERESHCHAGIN. « DYNAMICS AND EMISSION OF MILDLY RELATIVISTIC PLASMA ». International Journal of Modern Physics : Conference Series 12 (janvier 2012) : 1–9. http://dx.doi.org/10.1142/s2010194512006204.

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Initially optically thick (with τ = 3⋅107) spherically symmetric outflow consisting of electron-positron pairs and photons is considered. We do not assume thermal equilibrium, and include the two-body processes that occur in such plasma: Möller and Bhabha scattering of pairs, Compton scattering, two-photon pair annihilation, two-photon pair production, together with their radiative three-body variants: bremsstrahlung, double Compton scattering, and three-photon pair annihilation, with their inverse processes. We solve numerically the relativistic Boltzmann equations in spherically symmetric case for distribution functions of pairs and photons. Three epochs are considered in details: a) the thermalization, which brings initially nonequilibrium plasma to thermal equilibrium; b) the self-accelerated expansion, which we find in agreement with previous hydrodynamic studies and c) decoupling of photons from the expanding electron-positron plasma. Photon spectra are computed, and appear to be non thermal near the peak of the luminosity. In particular, the low energy part of the spectrum contain more power with respect to the black body one.

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Shi, Tingting, Yuanbin Fan, Zhengyu Yan, Lai Zhou, Yang Ji et Zhiliang Yuan. « GHz photon-number resolving detection with high detection efficiency and low noise by ultra-narrowband interference circuits ». Journal of Semiconductors 45, n^o 3 (1 mars 2024) : 032702. http://dx.doi.org/10.1088/1674-4926/45/3/032702.

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Abstract We demonstrate the photon-number resolution (PNR) capability of a 1.25 GHz gated InGaAs single-photon avalanche photodiode (APD) that is equipped with a simple, low-distortion ultra-narrowband interference circuit for the rejection of its background capacitive response. Through discriminating the avalanche current amplitude, we are able to resolve up to four detected photons in a single detection gate with a detection efficiency as high as 45%. The PNR capability is limited by the avalanche current saturation, and can be increased to five photons at a lower detection efficiency of 34%. The PNR capability, combined with high efficiency and low noise, will find applications in quantum information processing technique based on photonic qubits.

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Chef, Samuel, Chung Tah Chua et Chee Lip Gan. « Machine Learning for Time-Resolved Emission : Image Resolution Enhancement ». EDFA Technical Articles 23, n^o 3 (1 août 2021) : 24–31. http://dx.doi.org/10.31399/asm.edfa.2021-3.p024.

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Abstract This article describes a novel method for improving image resolution achieved using time-resolved photon emission techniques. Instead of directly generating images from photon counting, all detected photons are displayed as a point cloud in 3D space and a new higher-resolution image is generated based on probability density functions associated with photon distributions. Unsupervised learning algorithms identify photon distribution patterns as well as fainter emission sources.

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Neff, Ellen P. « 3 photons for rat research ». Lab Animal 49, n^o 7 (24 juin 2020) : 197. http://dx.doi.org/10.1038/s41684-020-0592-3.

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Rehrauer, Owen G., Vu C. Dinh, Bharat R. Mankani, Gregery T. Buzzard, Bradley J. Lucier et Dor Ben-Amotz. « Binary Complementary Filters for Compressive Raman Spectroscopy ». Applied Spectroscopy 72, n^o 1 (7 novembre 2017) : 69–78. http://dx.doi.org/10.1177/0003702817732324.

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The previously described optimized binary compressive detection (OB-CD) strategy enables fast hyperspectral Raman (and fluorescence) spectroscopic analysis of systems containing two or more chemical components. However, each OB-CD filter collects only a fraction of the scattered photons and the remainder of the photons are lost. Here, we present a refinement of OB-CD, the OB-CD2 strategy, in which all of the collected Raman photons are detected using a pair of complementary binary optical filters that direct photons of different colors to two photon counting detectors. The OB-CD2 filters are generated using a new optimization algorithm described in this work and implemented using a holographic volume diffraction grating and a digital micromirror device (DMD) whose mirrors are programed to selectively direct photons of different colors either to one or the other photon-counting detector. When applied to pairs of pure liquids or two-component solid powder mixtures, the resulting OB-CD2 strategy is shown to more accurately estimate Raman scattering rates of each chemical component, when compared to the original OB-CD, thus facilitating chemical classification at speeds as fast as 3 μs per measurement and the collection of Raman images in under a second.

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Feranchuk, Ilya D., Oleg D. Skoromnik et Quang San Nguyen. « Method of the equivalent photons for modulated electron beam ». Journal of the Belarusian State University. Physics, n^o 3 (7 octobre 2020) : 24–31. http://dx.doi.org/10.33581/2520-2243-2020-3-24-31.

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It is shown in this work that electromagnetic self-field of the periodically density modulated electron bunch can be considered as the beam of the equivalent photons (pseudo-photons), collimated along the electron velocity. Pseudo-photon spectrum includes both the incoherent contribution being proportional to number of electrons in the bunch and the coherent part with the sharp maximum corresponding the modulation frequency. Method of the equivalent photons can be applied for description of the interaction between the electron bunch and a crystal that leads to generation of the coherent parametric X-ray radiation by the modulated bunches exited from the undulator of the X-ray free electron laser. It provides the possibility to obtain the X-ray pulses directed at the large angle to the electron velocity where intensity of the background radiation essentially decreased. It is defined the conditions when the spectral and angular distributions of the coherent pseudo-photons can be compared with the analogous values for the pulses of the X-ray laser.

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DUMMERMUTH, ANGELIKA L., et CHRISTIAN WIENCKE. « Experimental investigation of seasonal development in six Antarctic red macroalgae ». Antarctic Science 15, n^o 4 (décembre 2003) : 449–57. http://dx.doi.org/10.1017/s095410200300155x.

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The phenology of six Antarctic red macroalgae, Delesseria salicifolia Reinsch, Gymnogongrus antarcticus Skottsberg, Gymnogongrus turquetii Hariot, Hymenocladiopsis crustigena Moe, Kallymenia antarctica Hariot and Phyllophora ahnfeltioides Skottsberg, was investigated in a two-year culture study under fluctuating daylengths imitating the conditions of King George Island, South Shetland Islands. The algae were cultured at 0°C in filtered, nutrient enriched seawater under photon fluence rates of 3, 10, 25, 50 μmol photons m−2 s−1. All species are classified as season anticipators, starting growth in late winter–spring and stopping growth before the summer solstice. Formation of new blades was observed from January/February onwards in most of the species. Carpospore formation was observed in K. antarctica in early summer. Growth was light saturated at photon fluence rates of 3 μmol photons m−2 s−1 in D. salicifolia and at 10 μmol photons m−2 s−1 in the other species, corresponding to an annual light dose of 31.4 and 157 mol photons m−2. The results show that this type of life strategy is typical for species from the Antarctic and give further evidence on the high degree of shade adaptation of Antarctic algae and predict a lower distribution limit for these species at 37 ± 15 m and 23 ± 10 m, respectively.

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Klinkhamer, F. R. « Lorentz-violating neutral-pion decays in isotropic modified Maxwell theory ». Modern Physics Letters A 33, n^o 18 (14 juin 2018) : 1850104. http://dx.doi.org/10.1142/s0217732318501043.

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We consider an extension of the Standard Model with isotropic non-birefringent Lorentz violation in the photon sector and restrict the discussion to the case of a “fast” photon with a phase velocity larger than the maximum attainable velocity of the quarks and leptons. With our conventions, this case corresponds to a negative Lorentz-violating parameter [Formula: see text] in the action. The decay rate of a neutral pion into two nonstandard photons is calculated as a function of the 3-momentum of the initial pion and the negative Lorentz-violating parameter [Formula: see text] of the final photons.

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White, John, Victoria Centonze, David Wokosin et William Mohler. « Using Multiphoton Microscopy for the Study of Embryogenesis ». Microscopy and Microanalysis 3, S2 (août 1997) : 307–8. http://dx.doi.org/10.1017/s1431927600008424.

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Multiphoton fluorescence excitation imaging is an optical sectioning technique for fluorescence microscopy. At very high photon densities, two or more photons may coordinately excite an energy transition in a fluorophore that corresponds to the sum of the energies of the individual photons. by this means, a fluorophore may be excited by a wavelength that is considerably longer than its single photon excitation wavelength. Ultra-fast pulsed (femtosecond) lasers can produce the peak power densities in the focal volume of an objective lens needed to provide sufficient 2- or 3- photon excitation events for imaging. The use of short-pulse lasers provides the high peak powers necessary for imaging yet with modest mean power levels that do not thermally damage biological specimens. Production of multiphoton events depends on the square of photon density for 2-photon excitation and the cube of photon density for 3-photon excitation. The power density therefore rapidly falls off away from the focal volume of an objective lens, thereby confining fluorescence excitation to the focal volume.

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Htoon, Han. « (Invited) Proximity Induced Chiral Quantum Light Generation in Strain-Engineered WSe₂/NiPS₃ Heterostructures ». ECS Meeting Abstracts MA2023-01, n^o 10 (28 août 2023) : 1173. http://dx.doi.org/10.1149/ma2023-01101173mtgabs.

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Quantum light emitters (QEs) capable of generating single photons of well-defined circular polarization could enable non-reciprocal single photon devices and deterministic spin-photon interfaces critical for realizing complex quantum networks. To date, emission of such chiral quantum light has been achieved via the application of intense external magnetic fields electrical/optical injection of spin polarized carriers/excitons, or coupling with complex photonic/meta-structures. Here we report free-space generation of highly chiral single photons from QEs created via nanoindentation of monolayer WSe2 - NiPS3 heterostructures at zero external magnetic field. These QEs emit in the 760-800 nm range with a degree of circular polarization and single photon purity as high as 0.89 and 80% respectively, independent of pump laser polarization. Scanning diamond nitrogen vacancy microscopy and temperature dependent magneto-photoluminescence studies reveal that the chiral quantum light emission arises from magnetic proximity interactions between localized excitons in the WSe2 monolayer and the out-of-plane magnetization of defects in antiferromagnetic (AFM) order of NiPS3, both of which are co-localized by the strain field associated with the nanoscale indentations.

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Tai, Yuping, Hanying Wang, Hui Wang et Jintao Bai. « Near-infrared down-conversion in Er3+–Yb3+ co-doped transparent nanostructured glass ceramics for crystalline silicon solar cells ». RSC Advances 6, n^o 5 (2016) : 4085–89. http://dx.doi.org/10.1039/c5ra25800f.

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A two-step energy transfer was achieved in Er³⁺–Yb³⁺ co-doped transparent glass ceramics containing CaF₂ nanocrystals, which involved down-conversion of an absorbed visible photon to two emitted near-infrared photons.

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Radjaroendee, Nattawat, Thammatorn Jamraschai et Ekapong Hirunsirisawat. « The photon trajectories around black hole with moving light source ». Journal of Physics : Conference Series 2653, n^o 1 (1 décembre 2023) : 012024. http://dx.doi.org/10.1088/1742-6596/2653/1/012024.

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Abstract The influence of curved spacetime around a black hole on photon trajectory has been widely studied recently. This study focuses on numerical simulations and some theoretical analysis to characterize the photons emitted from a moving light source around a Schwarzschild black hole. The results show that photon trajectories can be categorized based on the unique features of the light path caused by a variation in emitting angle (β). We propose three types of trajectories, including 1) the return angle (βret ): the photon from this angle orbits around the black hole and returns to the light source 2) the escaping angle (βesc ): the photon from this angle escapes to infinity parallel to the horizontal axis 3) the critical angle (βph ): the photon coming from this angle of initial condition enters a critical photon orbit. The escaped photons can be subclassified by computing the lensed ratio which is the difference between the angular position of the photon escaped to infinity and the initial emitting angle. This study reveals the characteristics of photons from light source moving around a black hole and can be further used to analyze the behavior of light from compact stars or other glowing objects in more complicated systems.

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Beck, Kristin M., Mahdi Hosseini, Yiheng Duan et Vladan Vuletić. « Large conditional single-photon cross-phase modulation ». Proceedings of the National Academy of Sciences 113, n^o 35 (12 août 2016) : 9740–44. http://dx.doi.org/10.1073/pnas.1524117113.

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Deterministic optical quantum logic requires a nonlinear quantum process that alters the phase of a quantum optical state by π through interaction with only one photon. Here, we demonstrate a large conditional cross-phase modulation between a signal field, stored inside an atomic quantum memory, and a control photon that traverses a high-finesse optical cavity containing the atomic memory. This approach avoids fundamental limitations associated with multimode effects for traveling optical photons. We measure a conditional cross-phase shift of π/6 (and up to π/3 by postselection on photons that remain in the system longer than average) between the retrieved signal and control photons, and confirm deterministic entanglement between the signal and control modes by extracting a positive concurrence. By upgrading to a state-of-the-art cavity, our system can reach a coherent phase shift of π at low loss, enabling deterministic and universal photonic quantum logic.

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Nomerotski, A., M. Chekhlov, D. Dolzhenko, R. Glazenborg, B. Farella, M. Keach, R. Mahon, D. Orlov et P. Svihra. « Intensified Tpx3Cam, a fast data-driven optical camera with nanosecond timing resolution for single photon detection in quantum applications ». Journal of Instrumentation 18, n^o 01 (1 janvier 2023) : C01023. http://dx.doi.org/10.1088/1748-0221/18/01/c01023.

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Abstract We describe a fast data-driven optical camera, Tpx3Cam, with nanosecond scale timing resolution and 80 Mpixel/sec throughput. After the addition of intensifier, the camera is single photon sensitive with quantum efficiency determined primarily by the intensifier photocathode. The single photon performance of the camera was characterized with results on the gain, timing resolution and afterpulsing reported here. The intensified camera was successfully used for measurements in a variety of applications including quantum applications. As an example of such application, which requires simultaneous detection of multiple photons, we describe registration of photon pairs from the spontaneous parametric down-conversion source in a spectrometer. We measured the photon wavelength and timing with respective precisions of 0.15 nm and 3 ns, and also demonstrated that the two photons are anti-correlated in energy.

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Klimanov, V. A., M. A. Kolyvanova et A. N. Moiseev. « Spatial Distributions of the Dose Created Phantom Pencil Beam of Mono-Energy and Bremsstrahlung Photons in a Water with Energies from 0.25 to 20 MeV ». MEDICAL RADIOLOGY AND RADIATION SAFETY 67, n^o 3 (juillet 2022) : 83–88. http://dx.doi.org/10.33266/1024-6177-2022-67-3-83-88.

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Purpose: Critical analysis of existing and obtaining more accurate data on the spatial dose distributions created in the water phantom by pencil beams (PB) of monoenergetic and bremsstrahlung photons with energies from 0.25 to 20.0 MeV, and approximation of these distributions for the purpose of calculating doses in radiation therapy. Material and Methods: Using the Monte Carlo method, the EGSnrc program and the MATLAB mathematical package, these distributions were calculated for monoenergetic photons in the energy range from 0.25 to 19.75 MeV in increments of 0.5 MeV, for bremsstrahlung photons with a maximum energy of 4.0, 6.0, 10.0, 15.0, 18.0 MeV and for the gamma-radiation spectrum of the therapeutic apparatus ROCUS. The calculation results are converted into the so-called dose kernel of photon pencil beam. The obtained dose kernel values are compared with previously published data and the observed discrepancies are discussed. Depths in water were studied from 1.0 to 40 cm in increments of 0,5 cm and along the radius from 0.02 to 46.0 cm with an uneven grid. For bremsstrahlung and photons with the spectrum of the Rocus apparatus, the possibility of approximating dose kernel values using approximation formulas convenient for calculating doses in radiation therapy has been investigated. Results: On the basis of the results obtained, a new version of the library of dose kernels of a pencil photon beam for water was created, which differs from previous versions by the use for calculating a better description and modeling of the physical processes of the interaction of photons and charged particles with matter, more adequate data on the interaction cross sections and significantly lower values of statistical uncertainties of the results. For bremsstrahlung and photons with the spectrum of the Rocus apparatus, a mathematical model of dose kernels of a pencil beam is proposed, which includes decomposition of the dose kernels into components of the primary and scattered doses, approximation formulas and empirical coefficients convenient for integration. The values of empirical coefficients are determined by fitting to the results of the calculation of dose kernels using a combination of the random search method and the nonlinear regression method. Conclusion: The results obtained in this work will improve the algorithms and increase the accuracy of dose calculation when planning remote therapy with photon beams.

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Dzhappuev, D. D., I. M. Dzaparova, E. A. Gorbacheva, I. S. Karpikov, M. M. Khadzhiev, N. F. Klimenko, A. U. Kudzhaev et al. « Search for astrophysical PeV gamma rays from point sources with Carpet-2 ». EPJ Web of Conferences 207 (2019) : 03004. http://dx.doi.org/10.1051/epjconf/201920703004.

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Early results of the search for Eγ > 1 PeV cosmic photons from point sources with the data of Carpet–2, an air-shower array equipped with a 175 m2 muon detector, are presented. They include 95% CL upper limits on PeV photon fluxes from stacked directions of high-energy IceCube neutrino events and from four predefined sources, Crab, Cyg X-3, Mrk 421 and Mrk 501. An insignificant excess of events from Mrk 421 will be further monitored. Prospects of the use of the upgraded installation, Carpet–3 (410 m2 muon detector), scheduled to start data taking in 2019, for searches of Eγ > 100 TeV photons, are briefly discussed.

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Dhobi, Saddam Husain, Kishori Yadav et Bhishma Karki. « Variation of Energy Density and Mass Density of Photon with Wavelength ». Indian Journal of Advanced Physics 1, n^o 2 (10 octobre 2021) : 1–5. http://dx.doi.org/10.54105/ijap.b1003.101221.

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The mass density and energy density of visible photon is calculated as 10-8 Kgm-3 and 109jm3 respectively. Moreover it is also observed that mass density and energy density of photon depend upon photons mass, wavelength, volume and energy. This is clear from figure 1, figure 2 and literatures. Therefore the mass density and energy density of photon varies with masses of photon, wavelength, volume, etc.

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U'Ren, A. B., K. Banaszek et I. A. Walmsley. « Photon engineering for quantum information processing ». Quantum Information and Computation 3, special (octobre 2003) : 480–502. http://dx.doi.org/10.26421/qic3.s-3.

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We study distinguishing information in the context of quantum interference involving more than one parametric downconversion (PDC) source and in the context of generating polarization-entangled photon pairs based on PDC. We arrive at specific design criteria for two-photon sources so that when used as part of complex optical systems, such as photon-based quantum information processing schemes, distinguishing information between the photons is eliminated guaranteeing high visibility interference. We propose practical techniques which lead to suitably engineered two-photon states that can be realistically implemented with available technology. Finally, we study an implementation of the nonlinear-sign shift (NS) logic gate with PDC sources and show the effect of distinguishing information on the performance of the gate.

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Vatarescu, Andre. « Instantaneous Quantum Description of Photonic Wavefronts and Applications ». Quantum Beam Science 6, n^o 4 (30 septembre 2022) : 29. http://dx.doi.org/10.3390/qubs6040029.

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Three physical elements are missing from the conventional formalism of quantum photonics: (1) the quantum Rayleigh spontaneous and stimulated emissions; (2) the unavoidable parametric amplification; and (3) the mixed time-frequency spectral structure of a photonic field which specifies its duration or spatial extent. As a single photon enters a dielectric medium, the quantum Rayleigh scattering prevents it from propagating in a straight-line, thereby destroying any possible entanglement. A pure dynamic and coherent state composed of two consecutive number states, delivers the correct expectation values for the number of photons carried by a photonic wave front, its complex optical field, and phase quadratures. The intrinsic longitudinal and lateral field profiles associated with a group of photons for any instantaneous number of photons are independent of the source. These photonic properties enable a step-by-step analysis of the correlation functions characterizing counting of coincident numbers of photons or intensities with unity visibility interference, spanning the classical and quantum optic regimes.

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F Crawford, David. « Photons in Curved Space?Time ». Australian Journal of Physics 40, n^o 3 (1987) : 449. http://dx.doi.org/10.1071/ph870449.

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Because photons are described by quantum mechanical wavefunctions that have a nonzero spatial extent it follows that they can be influenced by curved space-time. It is generally assumed that this tidal interaction is far too small to have a significant effect. This paper argues that there is a significant effect that results in an interaction between the photon and the material causing the curved space-time in which the photon loses energy to low energy secondary photons. The energy loss is a function of the space-time curvature and is proportional to distance. The only situation fully considered is that of a photon in curved space-time due to a uniform distribution of matter. Because the energy loss rate is very small it is difficult to observe in the laboratory and therefore its major applications are in astronomy. If the intergalactic density of matter is n hydrogen atoms m - 3, then the predicted value for the 'Hubble' constant (assuming no universal expansion) is 51�68 n1 /2 km s - 1 Mpc - 1. The theory can solve the virial mass discrepancy observed in clusters of galaxies and it makes a definite prediction about their relative magnitudes. Other astronomical applications are considered.

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Sun, Jia Yue, Yi Ning Sun, Ji Cheng Zhu, Jun Hui Zeng et Hai Yan Du. « Downconversion for Solar Cells in Sr₃Gd(PO₄)₃:Tb, Yb Phosphors ». Advanced Materials Research 502 (avril 2012) : 136–39. http://dx.doi.org/10.4028/www.scientific.net/amr.502.136.

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An efficient near-infrared (NIR) quantum cutting (QC) Tb3+ and Yb3+ co-doped phosphor Sr3Gd(PO4)3 has been synthesized by conventional high temperature solid technique. Upon excitation of Tb3+ with a visible photon at 485 nm, two NIR photons could be emitted by Yb3+ through cooperative energy transfer (CTE) from Tb3+ to two Yb3+ ions. Excitation and emission spectra as well as ﬂuorescence decay measurements have been carried out to examine the occurrence of cooperative energy transfer (CET ) from Tb3+ to Yb3+ ions. The result indicates Tb3+ and Yb3+ co-doped Sr3Gd(PO4)3 is potentially used as down-converter layer in silicon-based solar cell.

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Stetsenko, V. Y. « About the theory of relativity ». Litiyo i Metallurgiya (FOUNDRY PRODUCTION AND METALLURGY), n^o 3 (14 septembre 2023) : 112–15. http://dx.doi.org/10.21122/1683-6065-2023-3-112-115.

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It is shown that the Earth, the Sun and the stars are not inertial systems. The speed of movement of one inertial system relative to another does not affect the parameters of the moving system. Photons, electrons, protons, neutrons move in space in helical spirals. The equations of the special theory of relativity are not applicable to particles that have particle‑wave properties. It is shown that the fifth coordinate is needed for the curvature of the four‑dimensional space of general relativity. Therefore, gravity cannot be interpreted from the position of the curvature of a four‑dimensional space in a four‑dimensional space. In non‑inertial systems, the forces of inertia are not equivalent to the forces of gravity. Photons moving in space in helical spirals with huge rotational frequencies are stabilized in the direction of rectilinear motion. The gravitational field does not affect the energy of photons and the trajectory of their rectilinear motion. The deviation of the trajectory of stellar photons near the Sun is due to the effect of the atmospheric lens of the Sun. The atmospheres of stars absorb photon energy, which is recorded as a red shift in the radiation spectrum. The displacement of the perihelion of Mercury occurs due to the precession of the axis of Mercury’s orbit under the influence of the gravitational forces of the Sun.

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Wilke, R. N., J. Wallentin, M. Osterhoff, D. Pennicard, A. Zozulya, M. Sprung et T. Salditt. « High-flux ptychographic imaging using the new 55 µm-pixel detector `Lambda' based on the Medipix3 readout chip ». Acta Crystallographica Section A Foundations and Advances 70, n^o 6 (12 septembre 2014) : 552–62. http://dx.doi.org/10.1107/s2053273314014545.

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Suitable detection systems that are capable of recording high photon count rates with single-photon detection are instrumental for coherent X-ray imaging. The new single-photon-counting pixel detector `Lambda' has been tested in a ptychographic imaging experiment on solar-cell nanowires using Kirkpatrick–Baez-focused 13.8 keV X-rays. Taking advantage of the high count rate of the Lambda and dynamic range expansion by the semi-transparent central stop, a high-dynamic-range diffraction signal covering more than seven orders of magnitude has been recorded, which corresponds to a photon flux density of about 105 photons nm−2 s−1or a flux of ∼1010 photons s−1on the sample. By comparison with data taken without the semi-transparent central stop, an increase in resolution by a factor of 3–4 is determined: from about 125 nm to about 38 nm for the nanowire and from about 83 nm to about 21 nm for the illuminating wavefield.

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Rinkel, Jean, Debora Magalhães, Franz Wagner, Florian Meneau et Flavio Cesar Vicentin. « Detective quantum efficiency for photon-counting hybrid pixel detectors in the tender X-ray domain : application to Medipix3RX ». Journal of Synchrotron Radiation 23, n^o 1 (1 janvier 2016) : 206–13. http://dx.doi.org/10.1107/s1600577515020226.

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Synchrotron-radiation-based X-ray imaging techniques using tender X-rays are facing a growing demand, in particular to probe theKabsorption edges of low-Zelements. Here, a mathematical model has been developed for estimating the detective quantum efficiency (DQE) at zero spatial frequency in the tender X-ray energy range for photon-counting detectors by taking into account the influence of electronic noise. The experiments were carried out with a Medipix3RX ASIC bump-bonded to a 300 µm silicon sensor at the Soft X-ray Spectroscopy beamline (D04A-SXS) of the Brazilian Synchrotron Light Laboratory (LNLS, Campinas, Brazil). The results show that Medipix3RX can be used to develop new imaging modalities in the tender X-ray range for energies down to 2 keV. The efficiency and optimal DQE depend on the energy and flux of the photons. The optimal DQE values were found in the 7.9–8.6 keV photon energy range. The DQE deterioration for higher energies due to the lower absorption efficiency of the sensor and for lower energies due to the electronic noise has been quantified. The DQE for 3 keV photons and 1 × 104 photons pixel−1s−1is similar to that obtained with 19 keV photons. Based on our model, the use of Medipix3RX could be extended down to 2 keV which is crucial for coming applications in imaging techniques at modern synchrotron sources.

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Chandra, N., et R. Ghosh. « Generation of entanglement between spin of an electron and polarization of a photon ». Quantum Information and Computation 9, n^o 1&2 (janvier 2009) : 36–61. http://dx.doi.org/10.26421/qic9.1-2-3.

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This paper shows an electron and a photon, emitted in two consecutive steps from an atom following the absorption of a single photon, may be entangled in the presence of the spin-orbit interaction only. This entanglement strongly depends upon the polarization of the absorbed and of the radiated photons, kinematics of two emitted particles, and dynamics of photoionization; however, the photoemission dynamics plays no role in this entanglement. This hybrid entanglement can be used in teleporting a quantum state encoded in a flying/stationary material particle onto a light pulse, or vice versa. Such an electron-photon entanglement, in addition, will make it possible to learn about the polarization of a single photon or spin-polarization of a free electron without making any measurements on the corresponding particle itself.

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Albicocco, P., R. Assiro, F. Bossi, P. Branchini, B. Buonomo, V. Capirossi, E. Capitolo et al. « Commissioning of the PADME experiment with a positron beam ». Journal of Instrumentation 17, n^o 08 (1 août 2022) : P08032. http://dx.doi.org/10.1088/1748-0221/17/08/p08032.

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Abstract The PADME experiment is designed to search for a hypothetical dark photon A' produced in positron-electron annihilation using a bunched positron beam at the Beam Test Facility of the INFN Laboratori Nazionali di Frascati. The expected sensitivity to the A' -photon mixing parameter ϵ is 10-3, for A' mass ≤ 23.5 MeV/c 2 after collecting ∼ 1013 positrons-on-target. This paper presents the PADME detector status after commissioning in July 2019. In addition, the software algorithms employed to reconstruct physics objects, such as photons and charged particles, and the calibration procedures adopted are illustrated in detail. The results show that the experimental apparatus reaches the design performance, and is able to identify and measure standard electromagnetic processes, such as positron bremsstrahlung and electron-positron annihilation into two photons.

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Carvalho, A. M. G., D. H. C. Araújo, H. F. Canova, C. B. Rodella, D. H. Barrett, S. L. Cuffini, R. N. Costa et R. S. Nunes. « X-ray powder diffraction at the XRD1 beamline at LNLS ». Journal of Synchrotron Radiation 23, n^o 6 (6 octobre 2016) : 1501–6. http://dx.doi.org/10.1107/s1600577516012686.

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Various upgrades have been completed at the XRD1 beamline at the Brazilian synchrotron light source (LNLS). The upgrades are comprehensive, with changes to both hardware and software, now allowing users of the beamline to conduct X-ray powder diffraction experiments with faster data acquisition times and improved quality. The main beamline parameters and the results obtained for different standards are presented, showing the beamline ability of performing high-quality experiments in transmission geometry. XRD1 operates in the 5.5–14 keV range and has a photon flux of 7.8 × 109 photons s−1(with 100 mA) at 12 keV, which is one of the typical working energies. At 8 keV (the other typical working energy) the photon flux at the sample position is 3.4 × 1010 photons s−1and the energy resolution ΔE/E= 3 × 10−4.

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BERMAN, B. L. « PHOTOREACTIONS ON 3He AND 4He UP TO 1.6 GEV AT JEFFERSON LAB ». Modern Physics Letters A 18, n^o 02n06 (28 février 2003) : 225–34. http://dx.doi.org/10.1142/s0217732303010272.

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We have measured photoreactions on 3 He and 4 He in Hall B at Jefferson Lab, using real photons from the Photon Tagger and the CEBAF Large-Acceptance Spectrometer (CLAS). We obtained data over the full range of the Tagger — 0.33 to 1.56 GeV with an incident electron-beam energy of 1.645 GeV. Tagged, circularly polarized photons, produced by the 70% longitudinally polarized electrons, were incident on 1.2-g/cm2 liquid-helium targets positioned at the center of the CLAS. We were able to collect data at rates exceeding 3 kHz, and succeeded in collecting approximately 1.2 billion events for 3 He and 0.8 billion for 4 He . Over 5 Tb of data were obtained. The data show very good stability throughout the experimental run. Preliminary results from the analysis of several reaction channels are given here.

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von Stetten, David, Philippe Carpentier, David Flot, Antonia Beteva, Hugo Caserotto, Fabien Dobias, Matias Guijarro et al. « ID30A-3 (MASSIF-3) – a beamline for macromolecular crystallography at the ESRF with a small intense beam ». Journal of Synchrotron Radiation 27, n^o 3 (29 avril 2020) : 844–51. http://dx.doi.org/10.1107/s1600577520004002.

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ID30A-3 (or MASSIF-3) is a mini-focus (beam size 18 µm × 14 µm) highly intense (2.0 × 1013 photons s−1), fixed-energy (12.81 keV) beamline for macromolecular crystallography (MX) experiments at the European Synchrotron Radiation Facility (ESRF). MASSIF-3 is one of two fixed-energy beamlines sited on the first branch of the canted undulator setup on the ESRF ID30 port and is equipped with a MD2 micro-diffractometer, a Flex HCD sample changer, and an Eiger X 4M fast hybrid photon-counting detector. MASSIF-3 is recommended for collecting diffraction data from single small crystals (≤15 µm in one dimension) or for experiments using serial methods. The end-station has been in full user operation since December 2014, and here its current characteristics and capabilities are described.

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Zhou, Hou-Rong, Kun-Jie Cheng, Jie Ren, Li-Xing You, Li-Liang Ying, Xiao-Yan Yang, Hao Li et Zhen Wang. « Photon number resolvability of multi-pixel superconducting nanowire single photon detectors using a single flux quantum circuit ». Chinese Physics B 31, n^o 5 (1 avril 2022) : 057401. http://dx.doi.org/10.1088/1674-1056/ac398a.

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Superconducting nanowire single-photon detectors (SNSPDs) are typical switching devices capable of detecting single photons with almost 100% detection efficiency. However, they cannot determine the exact number of incident photons during a detection event. Multi-pixel SNSPDs employing multiple read-out channels can provide photon number resolvability (PNR), but they require increased cooling power and costly multi-channel electronic systems. In this work, a single-flux quantum (SFQ) circuit is employed, and PNR based on multi-pixel SNSPDs is successfully demonstrated. A multi-input magnetically coupled DC/SFQ converter (MMD2Q) circuit with a mutual inductance M is used to combine and record signals from a multi-pixel SNSPD device. The designed circuit is capable of discriminating the amplitude of the combined signals in accuracy of Φ 0/M with Φ 0 being a single magnetic flux quantum. By employing the MMD2Q circuit, the discrimination of up to 40 photons can be simulated. A 4-parallel-input MMD2Q circuit is fabricated, and a PNR of 3 is successfully demonstrated for an SNSPD array with one channel reserved for the functional verification. The results confirm that an MMD2Q circuit is an effective tool for implementing PNR with multi-pixel SNSPDs.

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Jucha, Paweł, et Mariola Kłusek-Gawenda. « The Role of Mesons in Light-by-Light Scattering at Low Transverse Momentum ». EPJ Web of Conferences 291 (2024) : 02012. http://dx.doi.org/10.1051/epjconf/202429102012.

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Abstract. Light-by-Light scattering involves the interaction of two strong elec tromagnetic fields, resulting in the emission of two photons. In the next years, the ALICE 3 experiment is going to measure photons in the transverse mo mentum range pt = 1 - 50 MeV and 100 - 5000 MeV, which have not been investigated so far. Moving to a lower range of pt imposes a consideration of low-energy meson resonances which decay into two-photon channel. Further more, experimental possibilities to investigate the VDM-Regge mechanism are discussed. The role of the vertical background in light-by-light scattering mea surements is also shown.

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Carcamo, D., J. Gamboa et M. Pino. « Higgs model coupled to dark photons ». Modern Physics Letters A 30, n^o 07 (26 février 2015) : 1550030. http://dx.doi.org/10.1142/s0217732315500303.

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A dark sector containing a Higgs field and a dark photon coupled to visible photons via a small kinetic mixing is considered. The mass of the dark gauge boson becomes rescaled by the parameter involved in the kinetic mixing. We also calculate the total annihilation cross-section for scalar Higgs interacting with an external field and show that exhibits Sommerfeld enhancement. The model can be extended to a SU(3) × SU(2) × U(1) dark sector. The mass of the dark Z boson increases due to the kinetic mixing.

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Faber, Manfried. « A Geometric Model in 3+1D Space-Time for Electrodynamic Phenomena ». Universe 8, n^o 2 (26 janvier 2022) : 73. http://dx.doi.org/10.3390/universe8020073.

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With the idea to find geometric formulations of particle physics we investigate the predictions of a three-dimensional generalization of the Sine-Gordon model, very close to the Skyrme model and to the Wu-Yang description of Dirac monopoles. With three rotational degrees of freedom of spatial Dreibeins, we formulate a Lagrangian and confront the predictions to electromagnetic phenomena. Stable solitonic excitations we compare with the lightest fundamental electric charges, electrons, and positrons. Two Goldstone bosons we relate to the properties of photons. These particles are characterized by three topological quantum numbers, which we compare to charge, spin, and photon numbers. Finally, we conjecture some ideas for further comparisons with experiments.

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Wu, Tong. « KL0→γ+darkphoton(γ¯) Search at the J-PARC KOTO Experiment ». Journal of Physics : Conference Series 2446, n^o 1 (1 février 2023) : 012054. http://dx.doi.org/10.1088/1742-6596/2446/1/012054.

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Abstract We present the study of massless dark photons in the decay of K L 0 → γ γ ¯ in the J-PARC KOTO experiment. The massless dark photon ( γ ¯ ) is different from the massive dark photon because it does not mix directly with ordinary photons, but it could interact with SM particles through direct coupling with quarks. In some theoretical predictions, the B R ( K L 0 → γ γ ¯ ) can be as large as 𝒪(10-3), which is well within the sensitivity of KOTO. Because of the lack of kinematic constraints, searching for K L 0 → γ γ ¯ could be challenging, but the hermetic veto system of KOTO provides a unique opportunity to probe for this decay. We used three techniques to suppress the neutron background, based on machine learning, Fourier analysis, and both-end readout. We will present the background suppression result based on data collected in 2020.

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Yamshchikov, V. M. « Influence of a Scattering Medium Consisting of Potassium Atoms on the Luminescent Signal Decay Time : Theoretical Investigation by Monte Carlo Method ». Herald of the Bauman Moscow State Technical University. Series Natural Sciences, n^o 3 (102) (juin 2022) : 69–85. http://dx.doi.org/10.18698/1812-3368-2022-3-69-85.

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The study solves the problem of the luminescent photons propagation in a resonantly absorbing medium consisting of atoms of the studied substance and a buffer inert gas. The Monte Carlo method was used in numerical experiments carried out to simulate real processes that occur in a chamber designed to determine the lifetime of an individual atom in an excited state by the method of measuring the luminescence intensity decay time. Findings of the research show that when luminescent photons are repeatedly scattered (scattering means the process of absorption and re-emission of a photon by an atom) in a medium, the luminescence decay time noticeably increases, reaching a value greater than the average lifetime of an individual atom in an excited state. The reflection of photons from the walls that make up the chamber can lead to errors in measuring the lifetime. The process of luminescence decay is studied theoretically for various detunings of the laser frequency from the resonant transition frequency. A three-level model of the atom and a model of complete frequency redistribution were applied. The study describes an algorithm based on the Monte Carlo method, which is used to model the three-level population kinetics, laser radiation transfer, radiation trapping, and frequency redistribution

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Johnstone, Graeme E., Johannes Herrnsdorf, Martin D. Dawson et Michael J. Strain. « Efficient Reconstruction of Low Photon Count Images from a High Speed Camera ». Photonics 10, n^o 1 (23 décembre 2022) : 10. http://dx.doi.org/10.3390/photonics10010010.

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Challenging imaging applications requiring ultra-short exposure times or imaging in photon-starved environments can acquire extremely low numbers of photons per pixel, (<1 photon per pixel). Such photon-sparse images can require post-processing techniques to improve the retrieved image quality as defined quantitatively by metrics including the Structural Similarity Index Measure (SSIM) and Mean Squared Error (MSE) with respect to the ground truth. Bayesian retrodiction methods have been shown to improve estimation of the number of photons detected and spatial distributions in single-photon imaging applications. In this work, we demonstrate that at high frame rates (>1 MHz) and low incident photon flux (<1 photon per pixel), image post processing can provide better grayscale information and spatial fidelity of reconstructed images than simple frame averaging, with improvements in SSIM up to a factor of 3. Various other image post-processing techniques are also explored and some of which result in a similar quality of image reconstruction to Bayesian retrodiction, with lower computational load. Image reconstructions using Bayesian Retrodiction or bilateral filtering are of comparable quality to frame averaging, as measured by the Structural Similarity Index Measure, when using less than 40% of the photon flux.

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Lu, Gang, et Yue Huang. « Fabrication of ZrO₂ :Er³⁺ Nanocrystals and the Researching of Emitting Mechanism ». Advanced Materials Research 616-618 (décembre 2012) : 1882–88. http://dx.doi.org/10.4028/www.scientific.net/amr.616-618.1882.

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Erbium doped ZrO2(ZrO2:Er3+) nanocrystals are fabricated by a butadinol low thermal crystallization method.The emitting mechanism of Er3+ is researched. Er3+ level of the stark split were calculated with the crystals field theory, and the two levels of the spectral lines have been further recognition. It can be indicated that 980nm stimulates Er3+ upconverting. One process is continuous absorption of two 980nm photons. Another is electronic transfer to metastability level after absorbing 980 nm photons, then reuptake 980 nm photons.

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Stick, Line Bjerregaard, Maria Fuglsang Jensen, Søren M. Bentzen, Claus Kamby, Anni Young Lundgaard, Maja Vestmø Maraldo, Birgitte Vrou Offersen, Jen Yu et Ivan Richter Vogelius. « Radiation-Induced Toxicity Risks in Photon Versus Proton Therapy for Synchronous Bilateral Breast Cancer ». International Journal of Particle Therapy 8, n^o 4 (11 novembre 2021) : 1–13. http://dx.doi.org/10.14338/ijpt-21-00023.1.

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Abstract Purpose This study compares photon and proton therapy plans for patients with synchronous bilateral early breast cancer and estimates risks of early and late radiation-induced toxicities. Materials and Methods Twenty-four patients with synchronous bilateral early breast cancer receiving adjuvant radiation therapy using photons, 3-dimensional conformal radiation therapy or volumetric modulated arc therapy, were included and competing pencil beam scanning proton therapy plans were created. Risks of dermatitis, pneumonitis, acute esophageal toxicity, lung and breast fibrosis, hypothyroidism, secondary lung and esophageal cancer and coronary artery events were estimated using published dose-response relationships and normal tissue complication probability (NTCP) models. Results The primary clinical target volume V95% and/or nodal clinical target volume V90% were less than 95% in 17 photon therapy plans and none of the proton plans. Median NTCP of radiation dermatitis ≥ grade 2 was 18.3% (range, 5.4-41.7) with photon therapy and 58.4% (range, 31.4-69.7) with proton therapy. Median excess absolute risk (EAR) of secondary lung cancer at age 80 for current and former smokers was 4.8% (range, 0.0-17.0) using photons and 2.7% (range, 0.0-13.6) using protons. Median EAR of coronary event at age 80, assuming all patients have preexisting cardiac risk factors, was 1.0% (range, 0.0-5.6) with photons and 0.2% (range, 0.0-1.3) with protons. Conclusion Proton therapy plans improved target coverage and reduced risk of coronary artery event and secondary lung cancer while increasing the risk of radiation dermatitis.

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