197 research outputs found

    Speech of Hon. John Lowndes McLaurin, of South Carolina, in the Senate of the United States, Monday, December 9, 1901

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    This document contains a speech by John L. McLaurin of South Carolina presented in the Senate of the United States. Sections of the speech include: sectionalism the cause, conditions in South Carolina, the federal administration in South Carolina, should not array class against class, freedom of thought and speech, the issues, under caucus dictation the Senate no longer a deliberative body, the beginning of the fight, matter of arraying class against class, freedom of thought and speech, and issues

    Design and test of optical payload for polarization encoded QKD for Nanosatellites

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    Satellite based Quantum Key Distribution (QKD) in Low Earth Orbit (LEO) is currently the only viable technology to span thousands of kilometres. Since the typical overhead pass of a satellite lasts for a few minutes, it is crucial to increase the the signal rate to maximise the secret key length. For the QUARC CubeSat mission due to be launched within two years, we are designing a dual wavelength, weak-coherent-pulse decoy-state Bennett-Brassard '84 (WCP DS BB84) QKD source. The optical payload is designed in a 12×9×5cm312{\times}9{\times}5 cm^3 bespoke aluminium casing. The Discrete Variable QKD Source consists of two symmetric sources operating at 785 nm and 808 nm. The laser diodes are fixed to produce Horizontal,Vertical, Diagonal, and Anti-diagonal (H,V,D,A) polarisation respectively, which are combined and attenuated to a mean photon number of 0.3 and 0.5 photons/pulse. We ensure that the source is secure against most side channel attacks by spatially mode filtering the output beam and characterising their spectral and temporal characterstics. The extinction ratio of the source contributes to the intrinsic Qubit Error Rate(QBER) with 0.817±0.001%0.817 \pm 0.001\%. This source operates at 200MHz, which is enough to provide secure key rates of a few kilo bits per second despite 40 dB of estimated loss in the free space channe

    On the de Haas-van Alphen effect in inhomogeneous alloys

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    We show that Landau level broadening in alloys occurs naturally as a consequence of random variations in the local quasiparticle density, without the need to consider a relaxation time. This approach predicts Lorentzian-broadened Landau levels similar to those derived by Dingle using the relaxation-time approximation. However, rather than being determined by a finite relaxation time τ\tau, the Landau-level widths instead depend directly on the rate at which the de Haas-van Alphen frequency changes with alloy composition. The results are in good agreement with recent data from three very different alloy systems.Comment: 5 pages, no figure

    Book Reviews

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    An Estate Planner\u27s Handbook By Mayo Adams Shattuck Boston: Little, Brown & Company, 1948. Pp. 575. 7.50reviewer:PhilipA.Hendrick================================EstatePlanningandEstateTaxSavingByEdwardN.PolisherPhiladelphia:GeorgeT.BiselCompany.SecondEdition,1948.2Volumes.Pp.xxxii,923.7.50 reviewer: Philip A. Hendrick ================================ Estate Planning and Estate Tax Saving By Edward N. Polisher Philadelphia: George T. Bisel Company. Second Edition, 1948. 2 Volumes. Pp. xxxii, 923. 20.00 reviewer: Charles L.B. Lowndes =============================== Federal Taxes--Corporations and Partnerships, 1948-49 By Robert H. Montgomery, Conrad B. Taylor and Mark E. Richardson Vol. I: Gross Income and Deductions Vol. II: Taxes, Returns and Administration New York: The Ronald Press Company, 1948. Pp. xiii, 1001; pp. iv, 881. 20.00FederalTaxesEstates,TrustsandGifts,194849ByRobertH.MontgomeryandJames0.WynnNewYork:TheRonaldPressCompany,1948.Pp.xi,1263.20.00 Federal Taxes--Estates, Trusts and Gifts, 1948-49 By Robert H. Montgomery and James 0. Wynn New York: The Ronald Press Company,1948. Pp. xi, 1263. 10.00 reviewer: Adrian W. DeWind ================================ Wills, Gifts and Estate Planning Under the 1948 Revenue Act By Seymour S. Mintz, Richard C. Flesch and Bernard Soman Washington: The Bureau of National Affairs, Inc., 1948. Pp. 328. 2.00reviewer:Chas.A.Morehead===============================FederalTaxationfortheLawyerByHoustinShockeyNewYork:PrenticeHall,Inc.,SecondEdition,1947.Pp.xiii,396.2.00 reviewer: Chas. A. Morehead =============================== Federal Taxation for the Lawyer By Houstin Shockey New York: Prentice-Hall, Inc., Second Edition, 1947. Pp. xiii, 396. 5.00 reviewer: John R. Stiver

    Modelling and experimental testing of an optical synchronisation beacon designed for high‐loss satellite quantum communication

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    Long‐distance free space quantum key distribution based on CubeSats can be used to establish global quantum secure communication networks, with potential commercial applications benefitting from the low cost of its design and launch. Detecting single‐photon level optical pulses sent from space requires highly accurate and robust timing systems to pick out signals from the noise. For such high‐loss applications, we envisage a low‐repetition (sub‐MHz) beacon laser emitting short (ns) high‐peak‐power pulses from which interpolated quantum signal arrival windows can be derived. We firstly study theoretically the effects of jitter on the efficiency of gating quantum signals including all important jitter sources, and then experimentally investigated it by changing the clock jitter, and the result shows that the greater jitter will reduce the gating rate of the signal. The experimental interpolation error is tested against loss under laboratory conditions giving results close to our model. We also found that the jitter introduced by the Doppler effect can be ignored with a repetition rate larger than 1 kHz. This model can be directly used for the performance analysis and optimisation of all quantum and non‐quantum systems using similar synchronisation schemes over terrestrial free space or fibre

    Payload Testing of a Weak Coherent Pulse Quantum Key Distribution Module for the Responsive Operations on Key Services (ROKS) Mission

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    Quantum Key Distribution (QKD) missions currently in development for space are expanding in number due to the increasing need for more secure means of encryption combined with the range limitations of terrestrial QKD. Most of these new missions are using smaller satellites to test their payloads. The ROKS (Responsive Operations for Key Services) mission is one such mission. It will utilize a 6U CubeSat bus and is set to launch in Q4 2022. A breadboard model of a 785nm weak coherent pulse quantum source module designed for ROKS, named JADE, was tested within a lab testbench environment with the mission’s systems represented by breadboard models with equivalent components. JADE’s optical module was miniaturized to be compatible with the limited payload volumes of these small classes of satellites. Lab-based testbench characterization of JADE’s ability to emit quantum pulses with four polarization states that propagate through the beam steering system for analysis by a receiver box was demonstrated. Future work will focus on further shrinking the JADE module down to less than 1/3U size, increasing the interoperability of the module with standard interfaces for both CubeSats and SmallSats, and adding further capabilities and full environmental testing qualification to JADE

    QUARC: Quantum Research Cubesat—A Constellation for Quantum Communication

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    Quantum key distribution (QKD) offers future proof security based on fundamental laws of physics. Long distance QKD spanning regions such as the United Kingdom (UK) may employ a constellation of satellites. Small satellites, CubeSats in particular, in low earth orbit (LEO) are a relatively low cost alternative to traditional, large platforms. They allow the deployment of a large number of spacecraft ensuring greater coverage and mitigating some of the risk associated with availability due to cloud cover. We present our mission analysis showing how a constellation of low cost 6U CubeSats can be used to form a secure communication backbone for ground based and metropolitan networks across the UK. We have estimated the monthly key rates at 43 sites across the UK incorporating local meteorological data, atmospheric channel modelling and orbital parameters. We have optimized the constellation topology for rapid revisit and thus low latency key distribution

    Design and test of optical payload for polarization encoded QKD for nanosatellites

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    Satellite based Quantum Key Distribution (QKD) in Low Earth Orbit (LEO) is currently the only viable technology to span thousands of kilometres. Since the typical overhead pass of a satellite lasts for a few minutes, it is crucial to increase the the signal rate to maximise the secret key length. For the QUARC CubeSat mission due to be launched within two years, we are designing a dual wavelength, weak-coherent-pulse decoy-state Bennett-Brassard '84 (WCP DS BB84) QKD source. The optical payload is designed in a 12×9×5cm312{\times}9{\times}5 cm^3 bespoke aluminium casing. The Discrete Variable QKD Source consists of two symmetric sources operating at 785 nm and 808 nm. The laser diodes are fixed to produce Horizontal,Vertical, Diagonal, and Anti-diagonal (H,V,D,A) polarisation respectively, which are combined and attenuated to a mean photon number of 0.3 and 0.5 photons/pulse. We ensure that the source is secure against most side channel attacks by spatially mode filtering the output beam and characterising their spectral and temporal characterstics. The extinction ratio of the source contributes to the intrinsic Qubit Error Rate(QBER) with 0.817±0.001%0.817 \pm 0.001\%. This source operates at 200MHz, which is enough to provide secure key rates of a few kilo bits per second despite 40 dB of estimated loss in the free space channe
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