2,313 research outputs found
Passive decoy state quantum key distribution: Closing the gap to perfect sources
We propose a quantum key distribution scheme which closely matches the
performance of a perfect single photon source. It nearly attains the physical
upper bound in terms of key generation rate and maximally achievable distance.
Our scheme relies on a practical setup based on a parametric downconversion
source and present-day, non-ideal photon-number detection. Arbitrary
experimental imperfections which lead to bit errors are included. We select
decoy states by classical post-processing. This allows to improve the effective
signal statistics and achievable distance.Comment: 4 pages, 3 figures. State preparation correcte
Interpolation of Hilbert and Sobolev Spaces: Quantitative Estimates and Counterexamples
This paper provides an overview of interpolation of Banach and Hilbert
spaces, with a focus on establishing when equivalence of norms is in fact
equality of norms in the key results of the theory. (In brief, our conclusion
for the Hilbert space case is that, with the right normalisations, all the key
results hold with equality of norms.) In the final section we apply the Hilbert
space results to the Sobolev spaces and
, for and an open . We exhibit examples in one and two dimensions of sets
for which these scales of Sobolev spaces are not interpolation scales. In the
cases when they are interpolation scales (in particular, if is
Lipschitz) we exhibit examples that show that, in general, the interpolation
norm does not coincide with the intrinsic Sobolev norm and, in fact, the ratio
of these two norms can be arbitrarily large
Modeling the Daily Variations of the Coronal X-ray Spectral Irradiance with Two Temperatures and Two Emission Measures
The Miniature X-ray Solar Spectrometer (MinXSS-1) CubeSat observed solar
X-rays between 0.5 and 10 keV. A two-temperature, two-emission measure model is
fit to each daily averaged spectrum. These daily average temperatures and
emission measures are plotted against the corresponding daily solar 10.7 cm
radio flux (F10.7) value and a linear correlation is found between each that we
call the Schwab Woods Mason (SWM) model. The linear trends show that one can
estimate the solar spectrum between 0.5 keV and 10 keV based on the F10.7
measurement alone. The cooler temperature component of this model represents
the quiescent sun contribution to the spectra and is essentially independent of
solar activity, meaning the daily average quiescent sun is accurately described
by a single temperature (1.70 MK) regardless of solar intensity and only the
emission measure corresponding to this temperature needs to be adjusted for
higher or lower solar intensity. The warmer temperature component is shown to
represent active region contributions to the spectra and varies between 5 MK to
6 MK. GOES XRS-B data between 1-8 Angstroms is used to validate this model and
it is found that the ratio between the SWM model irradiance and the GOES XRS-B
irradiance is close to unity on average. MinXSS-1 spectra during quiescent
solar conditions have very low counts beyond around 3 keV. The SWM model can
generate MinXSS-1 or DAXSS spectra at very high spectral resolution and with
extended energy ranges to fill in gaps between measurements and extend
predictions back to 1947
Quantum Cryptography Based on the Time--Energy Uncertainty Relation
A new cryptosystem based on the fundamental time--energy uncertainty relation
is proposed. Such a cryptosystem can be implemented with both correlated photon
pairs and single photon states.Comment: 5 pages, LaTex, no figure
Quasiparticle Resonances in the BCS Approach
We present a simple method for calculating the energies and the widths of
quasiparticle resonant states. The method is based on BCS equations solved in
the Berggren representation. In this representation the quasiparticle
resonances are associated to the Gamow states of the mean field. The method is
illustrated for the case of neutron-rich nuclei O and Ni. It
is shown that the contribution of the continuum coupling to the pairing
correlations is small and largely dominated by a few resonant states close to
the continuum threshold.Comment: 14 pages, 2 figure
Using of small-scale quantum computers in cryptography with many-qubit entangled states
We propose a new cryptographic protocol. It is suggested to encode
information in ordinary binary form into many-qubit entangled states with the
help of a quantum computer. A state of qubits (realized, e.g., with photons) is
transmitted through a quantum channel to the addressee, who applies a quantum
computer tuned to realize the inverse unitary transformation decoding of the
message. Different ways of eavesdropping are considered, and an estimate of the
time needed for determining the secret unitary transformation is given. It is
shown that using even small quantum computers can serve as a basis for very
efficient cryptographic protocols. For a suggested cryptographic protocol, the
time scale on which communication can be considered secure is exponential in
the number of qubits in the entangled states and in the number of gates used to
construct the quantum network
Current Models of Investor State Dispute Settlement Are Bad for Health: The European Union Could Offer an Alternative Comment on "The Trans-Pacific Partnership: Is It Everything We Feared for Health?"
In this commentary, we endorse concerns about the health impact of the trans-pacific partnership (TPP), paying particular attention to its mechanisms for investor state dispute settlement. We then describe the different, judge-led approach being advocated by the European Commission team negotiating the Trans-Atlantic Trade and Investment Partnership, arguing that, while not perfect, it offers significant advantages
Entangled photon pairs produced by a quantum dot strongly coupled to a microcavity
We show theoretically that entangled photon pairs can be produced on demand
through the biexciton decay of a quantum dot strongly coupled to the modes of a
photonic crystal. The strong coupling allows to tune the energy of the mixed
exciton-photon (polariton) eigenmodes, and to overcome the natural splitting
existing between the exciton states coupled with different linear polarizations
of light. Polariton states are moreover well protected against dephasing due to
their lifetime ten to hundred times shorter than that of a bare exciton. Our
analysis shows that the scheme proposed can be achievable with the present
technology
A MEMORY EFFICIENT HARDWARE BASED PATTERN MATCHING AND PROTEIN ALIGNMENT SCHEMES FOR HIGHLY COMPLEX DATABASES
Protein sequence alignment to find correlation between different species, or genetic mutations etc. is the most computational intensive task when performing protein comparison. To speed-up the alignment, Systolic Arrays (SAs) have been used. In order to avoid the internal-loop problem which reduces the performance, pipeline interleaving strategy has been presented. This strategy is applied to an SA for Smith Waterman (SW) algorithm which is an alignment algorithm to locally align two proteins. In the proposed system, the above methodology has been extended to implement a memory efficient FPGA-hardware based Network Intrusion Detection System (NIDS) to speed up network processing. The pattern matching in Intrusion Detection Systems (IDS) is done using SNORT to find the pattern of intrusions. A Finite State Machine (FSM) based Processing Elements (PE) unit to achieve minimum number of states for pattern matching and bit wise early intrusion detection to increase the throughput by pipelining is presented
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