Blar i NTNU Open på forfatter "Skaar, Johannes"

Viser treff 1-20 av 36

    • After-gate attack on a quantum cryptosystem 

      Wiechers, Carlos; Lydersen, Lars Vincent Van de Wiel; Wittmann, Christoffer; Elser, Dominique; Skaar, Johannes; Marquardt, Christoph; Makarov, Vadim; Leuchs, Gerd (Journal article; Peer reviewed, 2011)
      We present a method to control the detection events in quantum key distribution systems that use gated single-photon detectors. We employ bright pulses as faked states, timed to arrive at the avalanche photodiodes outside ...

    • Ambient RF-energy harvesting at 900 MHz 

      Brynhildsvoll, Fredrik S (Master thesis, 2016)
      In this thesis a RF-energy harvesting system able to harvest ambient power at 900MHz(GSM band) is simulated. Especially the efficiency at low power is of interest (-19 to -23 dBm rectifier input). A rectifier and a boost ...

    • Analysis of active and passive metamaterials 

      Hågenvik, Hans Olaf (Doctoral theses at NTNU;2019:158, Doctoral thesis, 2019)
      Metamaterials are composite materials acting as effectively continuous media, which are capable of realizing entirely new phenomena such as negative refraction and transformation optics. This class of new materials may ...

    • Behandling av inkontinens med magneter 

      Landro, Harald (Master thesis, 2013)
      I fattige land hender det at kvinner mister all kontroll over urinblæra etter kompliserte fødsler. Denne oppgaven har undersøkt et mulig hjelpemiddel for disse kvinnene basert på å ha en plugg i urinblæra som styres av en ...

    • Boundary Conditions and Fresnel Equations for Weakly Spatially Dispersive Media 

      Jansen, Erlend Grøndahl (Master thesis, 2017)
      Although usually negligible for natural materials for optical and lower frequencies, spatial dispersion is a significant effect for metamaterials. In this thesis the electromagnetics of such media are investigated using a ...

    • Comparison of Principal Component Analysis and Spectral Angle Mapping for Identification of Materials in Terahertz Transmission Measurements 

      Nystad, Helle Emilia (Master thesis, 2015)
      The terahertz range of the electromagnetic spectrum ranges from 0.1 to 10 THz, and has some unique properties which make it interesting for security applications. The identification of a range of dangerous substances is ...

    • Controlled Laser Damage of Single-Photon Avalanche Photodiodes 

      Bugge, Audun Nystad (Master thesis, 2012)
      Quantum cryptography has been developed from being a theoretical proposal to having real world applications, with companies developing and selling quantum key distribution (QKD) instruments commercially. Although laws of ...

    • Controlling a superconducting nanowire single-photon detector using tailored bright illumination 

      Lydersen, Lars Vincent Van de Wiel; Akhlaghi, Mohsen K.; Majedi, A. Hamed; Skaar, Johannes; Makarov, Vadim (Journal article; Peer reviewed, 2011)
      We experimentally demonstrate that a superconducting nanowire single-photon detector is deterministically controllable by bright illumination. We found that bright light can temporarily make a large fraction of the nanowire ...

    • Controlling an actively-quenched single photon detector with bright light 

      Sauge, Sebastien; Lydersen, Lars Vincent Van de Wiel; Anisimov, Andrey; Skaar, Johannes; Makarov, Vadim (Journal article; Peer reviewed, 2011)
      We control using bright light an actively-quenched avalanche single-photon detector. Actively-quenched detectors are commonly used for quantum key distribution (QKD) in the visible and near-infrared range. This study shows ...

    • Development of a new algorithm for measurement of fatigue and stress in steel 

      Avdal, Jørgen (Master thesis, 2009)
      A study is done on the transient phase of a voltage signal resulting from a current regulated four point probe measurement on steel plates. Some electromagnetic theory is developed, including a study of the effects of ...

    • Diamagnetism and the dispersion of the magnetic permeability 

      Dirdal, Christopher Andrew; Skaar, Johannes (Journal article; Peer reviewed, 2018)
      It is well known that the usual Kramers–Kronig relations for the relative permeability function μ(ω) are not compatible with diamagnetism (μ(0) < 1) and a positive imaginary part (Im μ(ω) > 0 for ω > 0). We demonstrate ...

    • Dielectric media considered as vacuum with sources 

      Hågenvik, Hans Olaf; Bløtekjær, Kjell; Skaar, Johannes (Journal article; Peer reviewed, 2017)
      Conventional textbook treatments on electromagnetic wave propagation consider the induced charge and current densities as “bound” and therefore absorb them into a refractive index. In principle, it must also be possible ...

    • FDTD simulations of novel gain media 

      Hågenvik, Hans Olaf (Master thesis, 2014)
      Fourier-Laplace analysis of gain media predicts the existence of novel types of media. In particular it predicts the existence of media refracting positively and negatively at the same time, so-called simultaneous refraction. ...

    • Four definitions of magnetic permeability for periodic metamaterials 

      Skaar, Johannes; Hågenvik, Hans Olaf; Dirdal, Christopher Andrew (Journal article; Peer reviewed, 2019)
      We state and compare four different definitions of magnetic permeability for periodic, artificial media, or metamaterials. The connections among them, and properties in general, are discussed in detail, including causality, ...

    • Full-field implementation of a perfect eavesdropper on a quantum cryptography system 

      Gerhardt, Ilja; Liu, Qin; Lamas-linares, Antia; Skaar, Johannes; Kurtsiefer, Christian; Makarov, Vadim (Journal article; Peer reviewed, 2011)
      Quantum key distribution (QKD) allows two remote parties to grow a shared secret key. Its security is founded on the principles of quantum mechanics, but in reality it significantly relies on the physical implementation. ...

    • Higher order multipoles in metamaterial homogenization 

      Dirdal, Christopher Andrew; Hågenvik, Hans Olaf; Haave, Haakon Aamodt; Skaar, Johannes (Journal article; Peer reviewed, 2018)
      The higher order multipoles above the electric quadrupole are commonly neglected in metamaterial homogenization. We show that they nevertheless can be significant when the second-order spatial dispersive effects, such as ...

    • Hilberttransformpar og negativ brytning 

      Lind-Johansen, Øyvind (Master thesis, 2006)
      I løpet av de siste årene har det blitt mulig å lage medier som har permittivitet $epsilon_r=chi_e+1$ og permeabilitet $mu_r=chi_m+1$ med simultant negative realdeler. I slike medier vil man få negativ brytning og dette ...

    • Homogenizing metamaterials by the plane wave expansion method 

      Haave, Haakon Aamot (Master thesis, 2017)
      Increasingly complex metamaterial structures has revitalized the interest in homogenization and effective medium theories, with the intention of finding better ways to model and understand their electromagnetic complexity. ...

    • Kalibrering av optisk effekt ved hjelp av temperatursensor 

      Fjermeros, Bastian (Master thesis, 2014)
      Rapporten inneholder et design på et system som bruker elektrisk effekt til å kalibrere optisk effekt. Resultatene ble gode; en innkommende laserstråle be kalibrert til å være 10.6986 mW.

    • Kommersialisering av metamaterialer: Fremtidens teknologi 

      Jacobsen, Nina Westgaard (Master thesis, 2007)
      Metamaterialer har blitt betraktet som et kontroversielt tema siden de ble presentert som en teoretisk mulighet av Viktor Veselago i 1969. I den senere tid har det blitt verifisert at flere fundamentale prinsipper i fysikken ...