A diode laser stabilization scheme for 40Ca+ single ion spectroscopy

We present a scheme for stabilizing multiple lasers at wavelengths between 795 and 866 nm to the same atomic reference line. A reference laser at 852 nm is stabilized to the Cs D2 line using a Doppler-free frequency modulation technique. Through transfer cavities, four lasers are stabilized to the relevant atomic transitions in 40Ca+. The rms linewidth of a transfer-locked laser is measured to be 123 kHz with respect to an independent atomic reference, the Rb D1 line. This stability is confirmed by the comparison of an excitation spectrum of a single 40Ca+ ion to an eight-level Bloch equation model. The measured Allan variance of 10^(-22) at 10 s demonstrates a high degree of stability for time scales up to 100 s.Comment: 8 pages, 11 figure

Byung-Chul Han y el problema de la transparencia

The standardization of the display of intimacy implies that transparency is normalized in the information society. Social practices are bringing the idea of emancipation to the technological field. This carries significant but unquestioned socio-political expectations that are associated with powerful cybercompanies. Byung-Chul Han treats these issues in his political texts. He argues that transparency is a neoliberal device which does not help solve the problems of citizenship, and it even involves a “depoliticization”. My intention is to carry out a critical review of his texts, and highlight their convergences with other authors dedicated to the philosophy of technology.La normalización de la exhibición de la intimidad hace que la transparencia sea algo cotidiano en la sociedad de la información. Las prácticas sociales están llevando la idea de emancipación al ámbito tecnológico. Hay grandes e incuestionadas expectativas sociopolíticas asociadas a potentes ciberempresas. Los textos políticos de Byung-Chul Han se centran en estas temáticas. Presentan la transparencia como un dispositivo neoliberal, que no ayuda a resolver los problemas de la ciudadanía, e incluso conduce a una despolitización. Mi intención es realizar un análisis crítico de sus textos y destacar sus convergencias con otros autores dedicados a la filosofía de la tecnología

Conocimiento e infoxicación en la pandemia de la COVID-19

The emergence and spread of the SARS-CoV-2 pandemic has shown that the techno-scientific system of research, development, innovation and dissemination presents problems of predictability and risk management and a high level of uncertainty. This paper analyses the process of production, management and dissemination of knowledge, focusing on the techno-scientific and social media and the modes of scientific information and communication regarding COVID-19. First, we analyse the deficiencies in the techno-scientific model of knowledge production and management during the COVID-19 crisis. Second, we explore the treatment and dissemination of information in the new modes of information and social communication, where a situation of infoxication has been created. Third, the aim is to assess the effectiveness of communication and discussion among scientific communities. To do this, we used the Web of Science database to perform a bibliometric study on research publications related to the virus, its disease and its treatment as of 2020.La aparición y difusión pandémica del virus SARS-CoV-2 ha evidenciado que el sistema tecnocientífico de investigación, desarrollo, innovación y difusión presenta problemas de previsibilidad, de gestión de riesgos y un alto nivel de incertidumbre. Este trabajo analiza el proceso de producción, gestión y difusión del conocimiento centrándose en los modos y medios tecnocientíficos y sociales de información y comunicación científica sobre la COVID-19. Para ello, en primer lugar, se ha realizado un análisis de los déficits del modelo tecnocientífico de producción y gestión del conocimiento durante la crisis de la COVID-19. En segundo lugar, se ha estudiado el tratamiento y difusión de información en los nuevos modos de información y comunicación social donde se ha generado una circunstancia de infoxicación. En tercer lugar, para evaluar si está teniendo lugar una efectiva comunicación y discusión entre las comunidades científicas, se ha realizado un estudio bibliométrico a partir de los datos de la Web of Science sobre la publicación de resultados de investigación desde 2020 en relación con el virus, su enfermedad y tratamiento

Quantum interference from remotely trapped ions

We observe quantum interference of photons emitted by two continuously laser-excited single ions, independently trapped in distinct vacuum vessels. High contrast two-photon interference is observed in two experiments with different ion species, calcium and barium. Our experimental findings are quantitatively reproduced by Bloch equation calculations. In particular, we show that the coherence of the individual resonance fluorescence light field is determined from the observed interference

The first spectroscopically confirmed brown dwarfs in NGC 2264

Support from STFC through grant number ST/R000824/1. K.M. acknowledges funding by the Science and Technology Foundation of Portugal (FCT), grants No. IF/00194/2015, PTDC/FISAST/28731/2017 and UIDB/00099/2020.We present spectroscopic follow-up observations of 68 red, faint candidates from our multi-epoch, multi-wavelength, previously published survey of NGC 2264. Using near-infrared spectra from VLT/KMOS, we measure spectral types and extinction for 32 young low-mass sources. We confirm 13 as brown dwarfs in NGC 2264, with spectral types between M6 and M8, corresponding to masses between 0.02 and 0.08 M⊙. These are the first spectroscopically confirmed brown dwarfs in this benchmark cluster. 19 more objects are found to be young M-type stars of NGC 2264 with masses of 0.08 to 0.3 M⊙. 7 of the confirmed brown dwarfs as well as 15 of the M-stars have IR excess caused by a disc. Comparing with isochrones, the typical age of the confirmed brown dwarfs is <0.5 to 5 Myr. More than half of the newly identified brown dwarfs and very low mass stars have ages <0.5 Myr, significantly younger than the bulk of the known cluster population. Based on the success rate of our spectroscopic follow-up, we estimate that NGC 2264 hosts 200-600 brown dwarfs in total (in the given mass range). This would correspond to a star-to-brown dwarf ratio between 2.5:1 and 7.5:1. We determine the slope of the substellar mass function as α=0.43+0.41−0.56⁠, these values are consistent with those measured for other young clusters. This points to a uniform substellar mass function across all star forming environments.Publisher PDFPeer reviewe

Tecno-Estados, infoesfera y tecnopolítica ¿Cómo hackear las nubes?

Our way of life is going through a process of informatization that redefines practices and power relations. In this transformation, the State and traditional activism have lost their capacity to act and, thus, their power. To realize this situation, and to be able to develop new modes of resistance, it is necessary to understand how power relations are being configured: what politics is and how it is done today.Luciano Floridi's philosophy of information offers a good conceptual framework to characterize this new way of life. But he considers the process of computerization as an ontological issue, which leads to an informational ecosystem vision as neutral environment. This hinders the critical capacity in a way of life whose logic is symbiotic and compromises freedom. Our intention is to complete his analysis from an axiological and political perspective, in order to characterize a set of conditions for the development of effective political resistance in the informational age.Nuestra forma de vida está sufriendo un proceso de informatización que redefine las prácticas y relaciones de poder. En esta transformación, el Estado y el activismo tradicional han perdido capacidad de actuación y con ello poder. Para comprender esta pérdida y desarrollar nuevos modos de resistencia, es necesario entender el modo en que están configuradas las relaciones de poder: qué es y cómo se hace la política en la actualidad.La filosofía de la información de Luciano Floridi ofrece un buen marco conceptual para caracterizar esta nueva forma de vida, pero considera el proceso de informatización como una cuestión ontológica que conduce a una visión del ecosistema informacional como un entorno neutral. Esto obstaculiza la capacidad crítica de una forma de vida cuya lógica simbiótica pone en jaque la libertad. Nuestra intención es completar sus análisis desde una perspectiva axiológica y política, con el fin de caracterizar un conjunto de condiciones para el desarrollo de resistencia política efectiva en la era informacional

Highlights from the 2018 European Respiratory Society International Congress: sleep and clinical physiology.

The 2018 European Respiratory Society (ERS) International Congress held in Paris, France, served as a platform to discover the latest research on respiratory diseases, the improvement in their treatments and patient care. Specifically, the scientific sessions organised by ERS Assembly 4 provided novel insights into sleep disordered breathing and fresh knowledge in respiratory physiology, stressing its importance to understanding and treating respiratory diseases. This article, divided by session, will summarise the most relevant studies presented at the ERS International Congress. Each session has been written by early career members specialised in the different fields of this interdisciplinary assembly

Throughflow Velocity Crossing the Dome of Erupting Bubbles in 2-D Fluidized Beds

A new non-intrusive method for measuring the throughflow velocity crossing the dome of erupting bubbles in freely bubbling 2-D fluidized beds is presented. Using a high speed video-camera, the dome acceleration, drag force and throughflow velocity profiles are obtained for different experiments, varying the superficial gas velocity. The acceleration profiles show greater values in the dome zone where the gravity component is negligible. The drag force and the throughflow velocity profiles show a uniform value in the central region of the dome (40 deg \u3c \u3c 140 deg) and the total throughflow increases with the superficial gas velocity

Heralded single photon absorption by a single atom

The emission and absorption of single photons by single atomic particles is a fundamental limit of matter-light interaction, manifesting its quantum mechanical nature. At the same time, as a controlled process it is a key enabling tool for quantum technologies, such as quantum optical information technology [1, 2] and quantum metrology [3, 4, 5, 6]. Controlling both emission and absorption will allow implementing quantum networking scenarios [1, 7, 8, 9], where photonic communication of quantum information is interfaced with its local processing in atoms. In studies of single-photon emission, recent progress includes control of the shape, bandwidth, frequency, and polarization of single-photon sources [10, 11, 12, 13, 14, 15, 16, 17], and the demonstration of atom-photon entanglement [18, 19, 20]. Controlled absorption of a single photon by a single atom is much less investigated; proposals exist but only very preliminary steps have been taken experimentally such as detecting the attenuation and phase shift of a weak laser beam by a single atom [21, 22], and designing an optical system that covers a large fraction of the full solid angle [23, 24, 25]. Here we report the interaction of single heralded photons with a single trapped atom. We find strong correlations of the detection of a heralding photon with a change in the quantum state of the atom marking absorption of the quantum-correlated heralded photon. In coupling a single absorber with a quantum light source, our experiment demonstrates previously unexplored matter-light interaction, while opening up new avenues towards photon-atom entanglement conversion in quantum technology.Comment: 10 pages, 4 figure

Hydrodynamic Characteristics of a Fluidized Bed with Rotating Distributor

The performance of a novel rotating distributor fluidized bed is presented. The pressure drop and the standard deviation of pressure fluctuations, σp, were used to find the minimum fluidization velocity, Umf, and to characterize the quality of fluidization at different rotational speeds of the distributor plate. Experiments were conducted in the freely bubbling regime in a 0.19 m i.d. fluidized bed, operating with Group B particles according to Geldart’s classification. A decrease in Umf is observed when the rotational speed increases. Frequency analysis of pressure fluctuations shows that fluidization can be controlled by the adjustable rotational speed, at several excess gas velocities