Heralded photon amplification for quantum communication

Heralded noiseless amplification based on single-photon sources and linear optics is ideally suited for long-distance quantum communication tasks based on discrete variables. We experimentally demonstrate such an amplifier, operating at telecommunication wavelengths. Coherent amplification is performed with a gain of G=1.98+/-0.2, for a state with a maximum expected gain G=2. We also demonstrate that there is no need for a stable phase reference between the initial signal state and the local auxiliary photons used by the amplifier. These results highlight the potential of heralded quantum amplifiers for long-distance quantum communication, and bring device-independent quantum key distribution one step closer.Comment: 5 pages, 4 figure

Confirming the least massive members of the Pleiades star cluster

We present optical photometry (i- and Z-band) and low-resolution spectroscopy (640-1015 nm) of very faint candidate members (J = 20.2-21.2 mag) of the Pleiades star cluster (120 Myr). The main goal is to address their cluster membership via photometric, astrometric, and spectroscopic studies, and to determine the properties of the least massive population of the cluster through the comparison of the data with younger and older spectral counterparts and state-of-the art model atmospheres. We confirm three bona-fide Pleiades members that have extremely red optical and infrared colors, effective temperatures of ~1150 K and ~1350 K, and masses in the interval 11-20 Mjup, and one additional likely member that shares the same motion as the cluster but does not appear to be as red as the other members with similar brightness. This latter object requires further near-infrared spectroscopy to fully address its membership in the Pleiades. The optical spectra of two bona-fide members were classified as L6-L7 and show features of KI, a tentative detection of CsI, hydrides and water vapor with an intensity similar to high-gravity dwarfs of related classification despite their young age. The properties of the Pleiades L6-L7 members clearly indicate that very red colors of L dwarfs are not a direct evidence of ages younger than ~100 Myr. We also report on the determination of the bolometric corrections for the coolest Pleiades members. These data can be used to interpret the observations of the atmospheres of exoplanets orbiting stars.Comment: Accepted for publication in MNRAS (17 pages

A New Pleiades Member at the Lithium Substellar Boundary

We present the discovery of an object in the Pleiades open cluster, named Teide 2, with optical and infrared photometry which place it on the cluster sequence slightly below the expected substellar mass limit. We have obtained low- and high-resolution spectra that allow us to determine its spectral type (M6), radial velocity and rotational broadening; and to detect H$_\alpha$ in emission and Li I 670.8 nm in absorption. All the observed properties strongly support the membership of Teide 2 into the Pleiades. This object has an important role in defining the reappearance of lithium below the substellar limit in the Pleiades. The age of the Pleiades very low-mass members based on their luminosities and absence or presence of lithium is constrained to be in the range 100--120 Myr.Comment: 17 pages, 3 figure

Approach to a classification of construction typologies of pig facilities: case study Antioquia – Colombia

Received: January 31th, 2021 ; Accepted: March 27th, 2021 ; Published: April 30th, 2021 ; Correspondence: [email protected] facilities foro confined production in tropical countries such as Colombia does not specify, in the present moment a typological classification that allows researchers to carry out evaluations related to animal comfort and environmental impacts according to the type of accommodation. To achieve the objective of this research were developed a survey to a panel of experts, a decision sensitivity analysis and the hierarchical analytical method AHP. Parameters that allowed to describe the concept of a technified pig farm were obteined, where the most relevant were: biosecurity measures, measurement of zootechnical parameters, training for workers and legal fulfilment. Additionally, ranges were defined to establish the production size in small, medium and large according to the number of animals. The results obtained per group were: 1) breeding small (50–200), medium (201–1,000) and large (1,001–5,000); 2) growth small (60–200), medium (201–800) and large (801–5000); and 3) finishing stage small (50–500), medium (501–1,000) and large (2,001–5,000). A total of 948 typological combinations were initially determined. Finally, the construction characteristics with the greatest technical and operational feasibility were prioritized for each group achieving 36 typologies that can represent the typological pig facilities not only in the state of Antioquia but also in many others states in Colombia

VLT X-shooter spectroscopy of the nearest brown dwarf binary

The aim of the project is to characterise both components of the nearest brown dwarf sytem to the Sun, WISE J104915.57-531906.1 (=Luhman16AB) at optical and near-infrared wavelengths. We obtained high signal-to-noise intermediate-resolution (R~6000-11000) optical (600-1000 nm) and near-infrared (1000-2480nm) spectra of each component of Luhman16AB, the closest brown dwarf binary to the Sun, with the X-Shooter instrument on the Very Large Telescope. We classify the primary and secondary of the Luhman16 system as L6-L7.5 and T0+/-1, respectively, in agreement with previous measurements published in the literature. We present measurements of the lithium pseudo-equivalent widths, which appears of similar strength on both components (8.2+/-1.0 Angstroms and 8.4+/-1.5 Angstroms for the L and T components, respectively). The presence of lithium (Lithium 7) in both components imply masses below 0.06 Msun while comparison with models suggests lower limits of 0.04 Msun. The detection of lithium in the T component is the first of its kind. Similarly, we assess the strength of other alkali lines (e.g. pseudo-equivalent widths of 6-7 Angstroms for RbI and 4-7 Angstroms for CsI) present in the optical and near-infrared regions and compare with estimates for L and T dwarfs. We also derive effective temperatures and luminosities of each component of the binary: -4.66+/-0.08 dex and 1305(+180)(-135) for the L dwarf and -4.68+/-0.13 dex and 1320(+185)(-135) for the T dwarf, respectively. Using our radial velocity determinations, the binary does not appear to belong to any of the well-known moving group. Our preliminary theoretical analysis of the optical and J-band spectra indicates that the L- and T-type spectra can be reproduced with a single temperature and gravity but different relative chemical abundances which impact strongly the spectral energy distribution of L/T transition objects.Comment: 12 pages, 9 figure, 3 tables, accepted to A&

New ultracool subdwarfs identified in large-scale surveys using Virtual Observatory tools: II. SDSS DR7 vs UKIDSS LAS DR6, SDSS DR7 vs UKIDSS LAS DR8, SDSS DR9 vs UKIDSS LAS DR10, and SDSS DR7 vs 2MASS

We aim at developing an efficient method to search for late-type subdwarfs (metal-depleted dwarfs with spectral types >M5) to improve the current statistics. Our objectives are: improve our knowledge of metal-poor low-mass dwarfs, bridge the gap between the late-M and L types, determine their surface density, and understand the impact of metallicity on the stellar and substellar mass function. We carried out a search cross-matching the SDSS, 2MASS, and UKIDSS using STILTS, Aladin, and Topcat. We considered different photometric and proper motion criteria for our selection. We identified 29 and 71 late-type subdwarf candidates in each cross-correlation over 8826 and 3679 square degrees, respectively. We obtained low-resolution optical spectra for 71 of our candidates with GTC, NOT, and VLT and retrieved spectra for 30 candidates from the SDSS spectroscopic database. We classified 92 candidates based on 101 optical spectra using two methods: spectral indices and comparison with templates of known subdwarfs. We confirmed 86% and 94% of the candidates as late-type subdwarfs from the SDSS vs 2MASS and SDSS vs UKIDSS cross-matches, respectively. These subdwarfs have spectral types ranging between M5 and L0.5 and SDSS magnitudes in the r=19.4-23.3 mag range. Our new late-type M discoveries include 49 subdwarfs, 25 extreme subdwarfs, six ultrasubdwarfs, one subdwarf/extreme subdwarf, and two dwarfs/subdwarfs. We derived a surface density of late-type subdwarfs of 0.040$^{+0.012}_{-0.007}$ per square degree in the SDSS DR7 vs UKIDSS LAS DR10 cross-match. We also checked the AllWISE photometry of known and new subdwarfs and found that mid-infrared colours of M subdwarfs do not appear to differ from their solar-metallicity counterparts of similar spectral types. However, the J-W2 and J-W1 colours are bluer for lower metallicity dwarfs. (abstract strongly abridged)Comment: 28 pages, 4 Tables, 10 figures, 1 appendix. Accepted to A&A. Photometry and spectra available in a dedicated archive on late-type subdwarfs at http://svo2.cab.inta-csic.es/vocats/ltsa

Dielectric screening in extended systems using the self-consistent Sternheimer equation and localized basis sets

We develop a first-principles computational method for investigating the dielectric screening in extended systems using the self-consistent Sternheimer equation and localized non-orthogonal basis sets. Our approach does not require the explicit calculation of unoccupied electronic states, only uses two-center integrals, and has a theoretical scaling of order O(N^3). We demonstrate this method by comparing our calculations for silicon, germanium, diamond, and LiCl with reference planewaves calculations. We show that accuracy comparable to planewaves calculations can be achieved via a systematic optimization of the basis set.Comment: 6 pages, 3 figure