2,126 research outputs found
Robust Unconditionally Secure Quantum Key Distribution with Two Nonorthogonal and Uninformative States
We introduce a novel form of decoy-state technique to make the single-photon
Bennett 1992 protocol robust against losses and noise of a communication
channel. Two uninformative states are prepared by the transmitter in order to
prevent the unambiguous state discrimination attack and improve the phase-error
rate estimation. The presented method does not require strong reference pulses,
additional electronics or extra detectors for its implementation.Comment: 7 pages, 2 figure
Deformed Maxwell Algebras and their Realizations
We study all possible deformations of the Maxwell algebra. In D=d+1\neq 3
dimensions there is only one-parameter deformation. The deformed algebra is
isomorphic to so(d+1,1)\oplus so(d,1) or to so(d,2)\oplus so(d,1) depending on
the signs of the deformation parameter. We construct in the dS (AdS) space a
model of massive particle interacting with Abelian vector field via non-local
Lorentz force. In D=2+1 the deformations depend on two parameters b and k. We
construct a phase diagram, with two parts of the (b,k) plane with so(3,1)\oplus
so(2,1) and so(2,2)\oplus so(2,1) algebras separated by a critical curve along
which the algebra is isomorphic to Iso(2,1)\oplus so(2,1). We introduce in
D=2+1 the Volkov-Akulov type model for a Abelian Goldstone-Nambu vector field
described by a non-linear action containing as its bilinear term the free
Chern-Simons Lagrangean.Comment: 10 pages, Talk based on [1] in the XXV-th Max Born Symposium "Planck
Scale", held in Wroclaw 29.06-3.07.200
Unconditionally Secure Key Distribution Based on Two Nonorthogonal States
We prove the unconditional security of the Bennett 1992 protocol, by using a
reduction to an entanglement distillation protocol initiated by a local
filtering process. The bit errors and the phase errors are correlated after the
filtering, and we can bound the amount of phase errors from the observed bit
errors by an estimation method involving nonorthogonal measurements. The angle
between the two states shows a trade-off between accuracy of the estimation and
robustness to noises.Comment: 5 pages, 1 figur
Quantum circuit for security proof of quantum key distribution without encryption of error syndrome and noisy processing
One of the simplest security proofs of quantum key distribution is based on
the so-called complementarity scenario, which involves the complementarity
control of an actual protocol and a virtual protocol [M. Koashi, e-print
arXiv:0704.3661 (2007)]. The existing virtual protocol has a limitation in
classical postprocessing, i.e., the syndrome for the error-correction step has
to be encrypted. In this paper, we remove this limitation by constructing a
quantum circuit for the virtual protocol. Moreover, our circuit with a shield
system gives an intuitive proof of why adding noise to the sifted key increases
the bit error rate threshold in the general case in which one of the parties
does not possess a qubit. Thus, our circuit bridges the simple proof and the
use of wider classes of classical postprocessing.Comment: 8 pages, 2 figures. Typo correcte
Unconditional Security of Single-Photon Differential Phase Shift Quantum Key Distribution
In this Letter, we prove the unconditional security of single-photon
differential phase shift quantum key distribution (DPS-QKD) protocol, based on
the conversion to an equivalent entanglement-based protocol. We estimate the
upper bound of the phase error rate from the bit error rate, and show that
DPS-QKD can generate unconditionally secure key when the bit error rate is not
greater than 4.12%. This proof is the first step to the unconditional security
proof of coherent state DPS-QKD.Comment: 5 pages, 2 figures; shorten the length, improve clarity, and correct
typos; accepted for publication in Physical Review Letter
Unconditional security of the Bennett 1992 quantum key-distribution scheme with strong reference pulse
We prove the unconditional security of the original Bennett 1992 protocol
with strong reference pulse. We show that we may place a projection onto
suitably defined qubit spaces before the receiver, which makes the analysis as
simple as qubit-based protocols. Unlike the single-photon-based qubits, the
qubits identified in this scheme are almost surely detected by the receiver
even after a lossy channel. This leads to the key generation rate that is
proportional to the channel transmission rate for proper choices of
experimental parameters.Comment: More detailed presentation and a bit modified security proo
Strength and Ductility of Reinforced High Strength Concrete Beams
Complete stress-strain curves for different concrete strengths up to 920 ㎏/㎠ were measured, and the coefficients of stress block were calculated. Meanwhile, a total number of 1 14 reinforced concrete beams, made with normal or high strength concrete, were tested in shear and flexure. It is shown that though high strength concrete is less ductile than normal strength concrete, reinforced concrete beams made with high strength concrete can show more ductility than might be expected from the ductility of concrete itself. Also, the influences of different factors such as shear span to depth ratio, reinforcement ratio and cross-section on the strength of singly reinforced high strength concrete beams are discussed
Algorithms for FFT Beamforming Radio Interferometers
Radio interferometers consisting of identical antennas arranged on a regular
lattice permit fast Fourier transform beamforming, which reduces the
correlation cost from in the number of antennas to
. We develop a formalism for describing this process and
apply this formalism to derive a number of algorithms with a range of
observational applications. These include algorithms for forming arbitrarily
pointed tied-array beams from the regularly spaced Fourier-transform formed
beams, sculpting the beams to suppress sidelobes while only losing
percent-level sensitivity, and optimally estimating the position of a detected
source from its observed brightness in the set of beams. We also discuss the
effect that correlations in the visibility-space noise, due to cross-talk and
sky contributions, have on the optimality of Fourier transform beamforming,
showing that it does not strictly preserve the sky information of the
correlation, even for an idealized array. Our results have applications to a
number of upcoming interferometers, in particular the Canadian Hydrogen
Intensity Mapping Experiment--Fast Radio Burst (CHIME/FRB) project.Comment: 17 pages, 4 figures, accepted to Ap
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On quantifying agricultural and water management practices from low spatial resolution RS data using genetic algorithms: A numerical study for mixed-pixel environment
In this paper, we present a genetic algorithm-based methodology to quantify agricultural and water management practices from remote sensing (RS) data in a mixed-pixel environment. First, we formulated a linear mixture model for low spatial resolution RS data where we considered three agricultural land uses as dominant inside the pixel—rainfed, irrigated with two, and three croppings a year; the mixing parameters we considered were the sowing dates, area fractions of agricultural land uses in the pixel, and their corresponding water management practices. Then, we carried out numerical experiments to evaluate the feasibility of the proposed approach. In the process, the mixing parameters were parameterized by data assimilation using evapotranspiration and leaf area index as conditioning criteria. The soil–water–atmosphere–plant system model SWAP was used to simulate the dynamics of these two biophysical variables in the pixel. The results of our numerical experiments showed that it is possible to derive some sub-pixel information from low spatial resolution data e.g. the existing agricultural and water management practices in a region, which are relevant for regional agricultural monitoring programs
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