26,295 research outputs found
First experimental demonstration of temporal hypertelescope operation with a laboratory prototype
In this paper, we report the first experimental demonstration of a Temporal
HyperTelescope (THT). Our breadboard including 8 telescopes is firstly tested
in a manual cophasing configuration on a 1D object. The Point Spread Function
(PSF) is measured and exhibits a dynamics in the range of 300. A quantitative
analysis of the potential biases demonstrates that this limitation is related
to the residual phase fluctuation on each interferometric arm. Secondly, an
unbalanced binary star is imaged demonstrating the imaging capability of THT.
In addition, 2D PSF is recorded even if the telescope array is not optimized
for this purpose.Comment: Accepted for publication in MNRAS. 11 pages, 25 figure
Quantum information processing with space-division multiplexing optical fibres
The optical fibre is an essential tool for our communication infrastructure
since it is the main transmission channel for optical communications. The
latest major advance in optical fibre technology is spatial division
multiplexing (SDM), where new fibre designs and components establish multiple
co-existing data channels based on light propagation over distinct transverse
optical modes. Simultaneously, there have been many recent developments in the
field of quantum information processing (QIP), with novel protocols and devices
in areas such as computing, communication and metrology. Here, we review recent
works implementing QIP protocols with SDM optical fibres, and discuss new
possibilities for manipulating quantum systems based on this technology.Comment: Originally submitted version. Please see published version for
improved layout, new tables and updated references following review proces
Studies of Single-Molecule Dynamics in Microorganisms
Fluorescence microscopy is one of the most extensively used techniques in the life sciences. Considering the non-invasive sample preparation, enabling live-cell compliant imaging, and the specific fluorescence labeling, allowing for a specific visualization of virtually any cellular compound, it is possible to localize even a single molecule in living cells. This makes modern fluorescence microscopy a powerful toolbox.
In the recent decades, the development of new, "super-resolution" fluorescence microscopy techniques, which surpass the diffraction limit, revolutionized the field. Single-Molecule Localization Microscopy (SMLM) is a class of super-resolution microscopy methods and it enables resolution of down to tens of nanometers. SMLM methods like Photoactivated Localization Microscopy (PALM), (direct) Stochastic Optical Reconstruction Microscopy ((d)STORM), Ground-State Depletion followed by Individual Molecule Return (GSDIM) and Point Accumulation for Imaging in Nanoscale Topography (PAINT) have allowed to investigate both, the intracellular spatial organization of proteins and to observe their real-time dynamics at the single-molecule level in live cells.
The focus of this thesis was the development of novel tools and strategies for live-cell SingleParticle Tracking PALM (sptPALM) imaging and implementing them for biological research. In the first part of this thesis, I describe the development of new Photoconvertible Fluorescent Proteins (pcFPs) which are optimized for sptPALM lowering the phototoxic damage caused by the imaging procedure. Furthermore, we show that we can utilize them together with Photoactivatable Fluorescent Proteins (paFPs) to enable multi-target labeling and read-out in a single color channel, which significantly simplifies the sample preparation and imaging routines as well as data analysis of multi-color PALM imaging of live cells.
In parallel to developing new fluorescent proteins, I developed a high throughput data analysis pipeline. I have implemented this pipeline in my second project, described in the second part of this thesis, where I have investigated the protein organization and dynamics of the CRISPR-Cas antiviral defense mechanism of bacteria in vivo at a high spatiotemporal level with the sptPALM approach. I was successful to show the differences in the target search dynamics of the CRISPR effector complexes as well as of single Cas proteins for different target complementarities. I have also first data describing longer-lasting bound-times between effector complex and their potential targets in vivo, for which only in vitro data has been available till today.
In summary, this thesis is a significant contribution for both, the advances of current sptPALM imaging methods, as well as for the understanding of the native behavior of CRISPR-Cas systems in vivo
High coherence photon pair source for quantum communication
This paper reports a novel single mode source of narrow-band entangled photon
pairs at telecom wavelengths under continuous wave excitation, based on
parametric down conversion. For only 7 mW of pump power it has a created
spectral radiance of 0.08 pairs per coherence length and a bandwidth of 10 pm
(1.2 GHz). The effectively emitted spectral brightness reaches 3.9*10^5 pairs
/(s pm). Furthermore, when combined with low jitter single photon detectors,
such sources allow for the implementation of quantum communication protocols
without any active synchronization or path length stabilization. A HOM-Dip with
photons from two autonomous CW sources has been realized demonstrating the
setup's stability and performance.Comment: 12 pages, 4 figure
Experimental Validation and Proof-of-concept of 5G Dense Small Cells Networks in Indoor Environments
Multi-purpose SLM-light-sheet microscope
By integrating a phase-only Spatial Light Modulator (SLM) into the
illumination arm of a cylindrical-lens-based Selective Plane Illumination
Microscope (SPIM), we have created a versatile system able to deliver high
quality images by operating in a wide variety of different imaging modalities.
When placed in a Fourier plane, the SLM permits modulation of the microscope's
light-sheet to implement imaging techniques such as structured illumination,
tiling, pivoting, autofocusing and pencil beam scanning. Previous publications
on dedicated microscope setups have shown how these techniques can deliver
improved image quality by rejecting out-offocus light (structured illumination
and pencil beam scanning), reducing shadowing (light-sheet pivoting), and
obtaining a more uniform illumination by moving the highest-resolution region
of the light-sheet across the imaging Field of View (tiling). Our SLM-SPIM
configuration is easy to build and use, and has been designed to allow all of
these techniques to be employed on one optical setup compatible with the
OpenSPIM design. It also offers the possibility to choose between three
different light-sheets, in thickness and height, which can be selected
according to the characteristics of the sample and the imaging technique to be
applied. We demonstrate the flexibility and performance of the system with
results obtained by applying a variety of different imaging techniques on
samples of fluorescent beads, Zebrafish embryos, and optically cleared whole
mouse brain samples. Thus our approach allows easy implementation of advanced
imaging techniques while retaining the simplicity of a cylindrical-lens-based
light-sheet microscope
Experimental evaluation of flexible duplexing in multi-tier MIMO networks
In this paper, we present an experimental evaluation of the performance benefits provided by flexible duplexing, an access technique that allows uplink and downlink cells to coexist within the same time-frequency resource blocks. In order to replicate a wireless multi-tier network composed of 1 macro-cell and 2 small cells, a measurement campaign has been conducted using an indoor wireless testbed comprised of a total of 6 multiple-input multiple-output (MIMO) software-defined radio (SDR) devices. Since each cell has a single active user, each uplink/downlink configuration can be identified with a different interference channel, over which interference alignment (IA) is used as an inter-cell interference management technique and compared to other existing methods. The obtained results show that flexible duplexing clearly outperforms the conventional time-division duplex (TDD) access approach, where all cells operate synchronized either in uplink or dowlink mode. Additionally, interference alignment consistently provides better results in most of the interference regimes when compared to minimum means quare error (MMSE)-based schemes. The impact of channel estimate quality on the different communication strategies is also studied. It is worth highlighting that the presented over-the-air (OTA) experiments represent the first implementation of IA with real-time precoding and decoding.The work of Jacobo Fanjul, Jesús Ibáñez and Ignacio Santamaria has been supported by the Ministerio de Economía, Industria y Competitividad (MINECO) of Spain, and AEI/FEDER funds of the E.U., under grant TEC2016-75067-C4-4-R (CARMEN), grant PID2019-104958RB-C43 (ADELE), and FPI grant BES-2014-069786. The work of José A. García-Naya has been funded by the Xunta de Galicia (ED431G2019/01), the Agencia Estatal de Investigación of Spain (TEC2016-75067-C4-1-R, RED2018-102668-T), and ERDF funds of the E.U. (AEI/FEDER, UE)
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