176 research outputs found
Generating optimal states for a homodyne Bell test
Published versio
Fixed Points of Generalized Contractive Multi-valued Mappings
In a recent paper N. Mizoguchi and W. Takahashi gave a positive answer to the conjecture of S. Reich concerning the existence of fixed points of multi-valued mappings that satisfy a certain contractive condition. In this paper, we provide an alternative and somewhat more straightforward proof for the theorem of Mizoguchi and Takahashi. Also the problems associated with fixed points of weakly contractive multi-valued mappings are studied. Finally, we make a few comments that improve other results from their paper (J. Math. Anal. Appl. 141 (1989), 177-188)
A two-parameter control for contractive-like multivalued mappings
We propose a general approach to defining a contractive-like multivalued
mappings which avoids any use of the Hausdorff distance between the sets
and . Various fixed point theorems are proved under a
two-parameter control of the distance function between
a point and the value F(x) \ss X. Here, both parameters are
numerical functions. The first one \a\,:[0,+\i)\rightarrow [1,+\i) controls
the distance between and some appropriate point in comparison
with , whereas the second one \b\,:[0,+\i)\rightarrow [0,1)
estimates with respect to . It appears that the well
harmonized relations between \a and \b are sufficient for the existence of
fixed points of . Our results generalize several known fixed-point theorems
Long term changes in the upper stratospheric ozone at Syowa, Antarctica
第2回極域科学シンポジウム/第35回極域宙空圏シンポジウム 11月15日(火) 国立極地研究所 2階大会議
On a Conjecture of S. Reich
Simeon Reich (1974) proved that the fixed point theorem for single-valued mappings proved by Boyd and Wong can be generalized to multivalued mappings which map points into compact sets. He then asked (1983) whether his theorem can be extended to multivalued mappings whose range consists of bounded closed sets. In this note, we provide an affirmative answer for a certain subclass of Boyd-Wong contractive mappings
Jet and Tropopause Products for Analysis and Characterization (JETPAC)
This suite of IDL programs provides identification and comprehensive characterization of the dynamical features of the jet streams in the upper troposphere, the lower stratospheric polar night jet, and the tropopause. The output of this software not only provides comprehensive information on the jets and tropopause, but also gives this information in a form that facilitates studies of observations in relation to the jets and tropopauses
Quantum-circuit guide to optical and atomic interferometry
Atomic (qubit) and optical or microwave (modal) phase-estimation protocols
are placed on the same footing in terms of quantum-circuit diagrams. Circuit
equivalences are used to demonstrate the equivalence of protocols that achieve
the Heisenberg limit by employing entangled superpositions of Fock states, such
as N00N states. The key equivalences are those that disentangle a circuit so
that phase information is written exclusively on a mode or modes or on a qubit.
The Fock-state-superposition phase-estimation circuits are converted to use
entangled coherent-state superpositions; the resulting protocols are more
amenable to realization in the lab, particularly in a qubit/cavity setting at
microwave frequencies.Comment: To appear in Optics Communications special issue in memory of
Krzysztof Wodkiewic
Bloch Equations and Completely Positive Maps
The phenomenological dissipation of the Bloch equations is reexamined in the
context of completely positive maps. Such maps occur if the dissipation arises
from a reduction of a unitary evolution of a system coupled to a reservoir. In
such a case the reduced dynamics for the system alone will always yield
completely positive maps of the density operator. We show that, for Markovian
Bloch maps, the requirement of complete positivity imposes some Bloch
inequalities on the phenomenological damping constants. For non-Markovian Bloch
maps some kind of Bloch inequalities involving eigenvalues of the damping basis
can be established as well. As an illustration of these general properties we
use the depolarizing channel with white and colored stochastic noise.Comment: Talk given at the Conference "Quantum Challenges", Falenty, Poland,
September 4-7, 2003. 21 pages, 3 figure
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