332 research outputs found
Complexity Measures from Interaction Structures
We evaluate new complexity measures on the symbolic dynamics of coupled tent
maps and cellular automata. These measures quantify complexity in terms of
-th order statistical dependencies that cannot be reduced to interactions
between units. We demonstrate that these measures are able to identify
complex dynamical regimes.Comment: 11 pages, figures improved, minor changes to the tex
Security of Quantum Key Distribution with entangled quNits
We consider a generalisation of Ekert's entanglement-based quantum
cryptographic protocol where qubits are replaced by quits (i.e.,
N-dimensional systems). In order to study its robustness against optimal
incoherent attacks, we derive the information gained by a potential
eavesdropper during a cloning-based individual attack. In doing so, we
generalize Cerf's formalism for cloning machines and establish the form of the
most general cloning machine that respects all the symmetries of the problem.
We obtain an upper bound on the error rate that guarantees the confidentiality
of quNit generalisations of the Ekert's protocol for qubits.Comment: 15 pages, equation 15 and conclusions corrected the 14th of April
2003, new results adde
Two-parameter deformations of logarithm, exponential, and entropy: A consistent framework for generalized statistical mechanics
A consistent generalization of statistical mechanics is obtained by applying
the maximum entropy principle to a trace-form entropy and by requiring that
physically motivated mathematical properties are preserved. The emerging
differential-functional equation yields a two-parameter class of generalized
logarithms, from which entropies and power-law distributions follow: these
distributions could be relevant in many anomalous systems. Within the specified
range of parameters, these entropies possess positivity, continuity, symmetry,
expansibility, decisivity, maximality, concavity, and are Lesche stable. The
Boltzmann-Shannon entropy and some one parameter generalized entropies already
known belong to this class. These entropies and their distribution functions
are compared, and the corresponding deformed algebras are discussed.Comment: Version to appear in PRE: about 20% shorter, references updated, 13
PRE pages, 3 figure
Controlling orbital moment and spin orientation in CoO layers by strain
We have observed that CoO films grown on different substrates show dramatic
differences in their magnetic properties. Using polarization dependent x-ray
absorption spectroscopy at the Co L edges, we revealed that the
magnitude and orientation of the magnetic moments strongly depend on the strain
in the films induced by the substrate. We presented a quantitative model to
explain how strain together with the spin-orbit interaction determine the 3d
orbital occupation, the magnetic anisotropy, as well as the spin and orbital
contributions to the magnetic moments. Control over the sign and direction of
the strain may therefore open new opportunities for applications in the field
of exchange bias in multilayered magnetic films
A Bivariate Measure of Redundant Information
We define a measure of redundant information based on projections in the
space of probability distributions. Redundant information between random
variables is information that is shared between those variables. But in
contrast to mutual information, redundant information denotes information that
is shared about the outcome of a third variable. Formalizing this concept, and
being able to measure it, is required for the non-negative decomposition of
mutual information into redundant and synergistic information. Previous
attempts to formalize redundant or synergistic information struggle to capture
some desired properties. We introduce a new formalism for redundant information
and prove that it satisfies all the properties necessary outlined in earlier
work, as well as an additional criterion that we propose to be necessary to
capture redundancy. We also demonstrate the behaviour of this new measure for
several examples, compare it to previous measures and apply it to the
decomposition of transfer entropy.Comment: 16 pages, 15 figures, 1 table, added citation to Griffith et al 2012,
Maurer et al 199
Universal Quantum Information Compression
Suppose that a quantum source is known to have von Neumann entropy less than
or equal to S but is otherwise completely unspecified. We describe a method of
universal quantum data compression which will faithfully compress the quantum
information of any such source to S qubits per signal (in the limit of large
block lengths).Comment: RevTex 4 page
Experimental implementation of time-coding quantum key distribution
We have implemented an experimental set-up in order to demonstrate the
feasibility of time-coding protocols for quantum key distribution. Alice
produces coherent 20 ns faint pulses of light at 853 nm. They are sent to Bob
with delay 0 ns (encoding bit 0) or 10 ns (encoding bit 1). Bob directs at
random the received pulses to two different arms. In the first one, a 300 ps
resolution Si photon-counter allows Bob to precisely measure the detection
times of each photon in order to establish the key. Comparing them with the
emission times of the pulses sent by Alice allows to evaluate the quantum bit
error rate (QBER). The minimum obtained QBER is 1.62 %. The possible loss of
coherence in the set-up can be exploited by Eve to eavesdrop the line.
Therefore, the second arm of Bob set-up is a Mach-Zender interferometer with a
10 ns propagation delay between the two path. Contrast measurement of the
output beams allows to measure the autocorrelation function of the received
pulses that characterizes their average coherence. In the case of an ideal
set-up, the value expected with the pulses sent by Alice is 0.576. The
experimental value of the pulses autocorrelation function is found to be 0.541.
Knowing the resulting loss of coherence and the measured QBER, one can evaluate
the mutual information between Alice and Eve and the mutual information between
Alice and Bob, in the case of intercept-resend attacks and in the case of
attacks with intrication. With our values, Bob has an advantage on Eve of 0.43
bit per pulse. The maximum possible QBER corresponding to equal informations
for Bob and Eve is 5.8 %. With the usual attenuation of fibres at 850 nm, it
shows that secure key distribution is possible up to a distance of 2.75 km,
which is sufficient for local links.Comment: 27 pages, 6 figure
HyspIRI High-Temperature Saturation Study
As part of the precursor activities for the HyspIRI mission, a small team was assembled to determine the optimum saturation level for the mid-infrared (4-?m) channel, which is dedicated to the measurement of hot targets. Examples of hot targets include wildland fires and active lava flows. This determination took into account both the temperature expected for the natural phenomena and the expected performance of the mid-infrared channel as well as its overlap with the other channels in the thermal infrared (7.5-12 ?m) designed to measure the temperature of lower temperature targets. Based on this work, the hot target saturation group recommends a saturation temperature of 1200 K for the mid-infrared channel. The saturation temperature of 1200 K represents a good compromise between the prevention of saturation and sensitivity to ambient temperature
Strengthened Lindblad inequality: applications in non equilibrium thermodynamics and quantum information theory
A strengthened Lindblad inequality has been proved. We have applied this
result for proving a generalized -theorem in non equilibrium thermodynamics.
Information processing also can be considered as some thermodynamic process.
From this point of view we have proved a strengthened data processing
inequality in quantum information theory.Comment: 7 pages, revte
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