9,797 research outputs found
Time-ordered data simulation and map-making for the PIXIE Fourier transform spectrometer
We develop a time-ordered data simulator and map-maker for the proposed PIXIE
Fourier transform spectrometer and use them to investigate the impact of
polarization leakage, imperfect collimation, elliptical beams, sub-pixel
effects, correlated noise and spectrometer mirror jitter on the PIXIE data
analysis. We find that PIXIE is robust to all of these effects, with the
exception of mirror jitter which could become the dominant source of noise in
the experiment if the jitter is not kept significantly below . Source code is available at https://github.com/amaurea/pixie.Comment: 27 pages, 15 figures. Accepted for publication in JCA
100 km secure differential phase shift quantum key distribution with low jitter up-conversion detectors
We present a quantum key distribution experiment in which keys that were
secure against all individual eavesdropping attacks allowed by quantum
mechanics were distributed over 100 km of optical fiber. We implemented the
differential phase shift quantum key distribution protocol and used low timing
jitter 1.55 um single-photon detectors based on frequency up-conversion in
periodically poled lithium niobate waveguides and silicon avalanche
photodiodes. Based on the security analysis of the protocol against general
individual attacks, we generated secure keys at a practical rate of 166 bit/s
over 100 km of fiber. The use of the low jitter detectors also increased the
sifted key generation rate to 2 Mbit/s over 10 km of fiber.Comment: 10 pages, 5 figure
Megabits secure key rate quantum key distribution
Quantum cryptography (QC) can provide unconditional secure communication
between two authorized parties based on the basic principles of quantum
mechanics. However, imperfect practical conditions limit its transmission
distance and communication speed. Here we implemented the differential phase
shift (DPS) quantum key distribution (QKD) with up-conversion assisted hybrid
photon detector (HPD) and achieved 1.3 M bits per second secure key rate over a
10-km fiber, which is tolerant against the photon number splitting (PNS)
attack, general collective attacks on individual photons, and any other known
sequential unambiguous state discrimination (USD) attacks.Comment: 14 pages, 4 figure
Spider Optimization: Probing the Systematics of a Large Scale B-Mode Experiment
Spider is a long-duration, balloon-borne polarimeter designed to measure
large scale Cosmic Microwave Background (CMB) polarization with very high
sensitivity and control of systematics. The instrument will map over half the
sky with degree angular resolution in I, Q and U Stokes parameters, in four
frequency bands from 96 to 275 GHz. Spider's ultimate goal is to detect the
primordial gravity wave signal imprinted on the CMB B-mode polarization. One of
the challenges in achieving this goal is the minimization of the contamination
of B-modes by systematic effects. This paper explores a number of instrument
systematics and observing strategies in order to optimize B-mode sensitivity.
This is done by injecting realistic-amplitude, time-varying systematics in a
set of simulated time-streams. Tests of the impact of detector noise
characteristics, pointing jitter, payload pendulations, polarization angle
offsets, beam systematics and receiver gain drifts are shown. Spider's default
observing strategy is to spin continuously in azimuth, with polarization
modulation achieved by either a rapidly spinning half-wave plate or a rapidly
spinning gondola and a slowly stepped half-wave plate. Although the latter is
more susceptible to systematics, results shown here indicate that either mode
of operation can be used by Spider.Comment: 15 pages, 12 figs, version with full resolution figs available here
http://www.astro.caltech.edu/~lgg/spider_front.ht
APOLLO: the Apache Point Observatory Lunar Laser-ranging Operation: Instrument Description and First Detections
A next-generation lunar laser ranging apparatus using the 3.5 m telescope at
the Apache Point Observatory in southern New Mexico has begun science
operation. APOLLO (the Apache Point Observatory Lunar Laser-ranging Operation)
has achieved one-millimeter range precision to the moon which should lead to
approximately one-order-of-magnitude improvements in the precision of several
tests of fundamental properties of gravity. We briefly motivate the scientific
goals, and then give a detailed discussion of the APOLLO instrumentation.Comment: 37 pages; 10 figures; 1 table: accepted for publication in PAS
Low Timing Jitter Detector for Gigahertz Quantum Key Distribution
A superconducting single-photon detector based on a niobium nitride nanowire
is demonstrated in an optical-fibre-based quantum key distribution test bed
operating at a clock rate of 3.3 GHz and a transmission wavelength of 850 nm.
The low jitter of the detector leads to significant reduction in the estimated
quantum bit error rate and a resultant improvement in the secrecy efficiency
compared to previous estimates made by use of silicon single-photon avalanche
detectors.Comment: 11 pages, including 2 figure
Hardware simulation of KU-band spacecraft receiver and bit synchronizer, phase 2, volume 1
The acquisition behavior of the PN subsystem of an automatically acquiring spacecraft receiver was studied. A symbol synchronizer subsystem was constructed and integrated into the composite simulation of the receiver. The overall performance of the receiver when subjected to anomalies such as signal fades was evaluated. Potential problems associated with PN/carrier sweep interactions were investigated
Quaternary pulse position modulation electronics for free-space laser communications
The development of a high data-rate communications electronic subsystem for future application in free-space, direct-detection laser communications is described. The dual channel subsystem uses quaternary pulse position modulation (QPPM) and operates at a throughput of 650 megabits per second. Transmitting functions described include source data multiplexing, channel data multiplexing, and QPPM symbol encoding. Implementation of a prototype version in discrete gallium arsenide logic, radiofrequency components, and microstrip circuitry is presented
Compact Frontend-Electronics and Bidirectional 3.3 Gbps Optical Datalink for Fast Proportional Chamber Readout
The 9600 channels of the multi-wire proportional chamber of the H1 experiment
at HERA have to be read out within 96 ns and made available to the trigger
system. The tight spatial conditions at the rear end flange require a compact
bidirectional readout electronics with minimal power consumption and dead
material.
A solution using 40 identical optical link modules, each transferring the
trigger information with a physical rate of 4 x 832 Mbps via optical fibers,
has been developed and commisioned. The analog pulses from the chamber can be
monitored and the synchronization to the global HERA clock signal is ensured.Comment: 13 pages, 10 figure
- …