17,458 research outputs found
Two quantum analogues of Fisher information from a large deviation viewpoint of quantum estimation
We discuss two quantum analogues of Fisher information, symmetric logarithmic
derivative (SLD) Fisher information and Kubo-Mori-Bogoljubov (KMB) Fisher
information from a large deviation viewpoint of quantum estimation and prove
that the former gives the true bound and the latter gives the bound of
consistent superefficient estimators. In another comparison, it is shown that
the difference between them is characterized by the change of the order of
limits.Comment: LaTeX with iopart.cls, iopart12.clo, iopams.st
Asymptotics of Quantum Relative Entropy From Representation Theoretical Viewpoint
In this paper it was proved that the quantum relative entropy can be asymptotically attained by Kullback Leibler divergences of
probabilities given by a certain sequence of POVMs. The sequence of POVMs
depends on , but is independent of the choice of .Comment: LaTeX2e. 8 pages. The title was changed from "Asymptotic Attainment
for Quantum Relative Entropy
Geometrically Frustrated Crystals: Elastic Theory and Dislocations
Elastic theory of ring-(or cylinder-)shaped crystals is constructed and the
generation of edge dislocations due to geometrical frustration caused by the
bending is studied. The analogy to superconducting (or superfluid) vortex state
is pointed out and the phase diagram of the ring-crystal, which depends on
radius and thickness, is discussed.Comment: 4 pages, 3 figure
Poincar\'{e} gauge theory of gravity
A Poincar\'{e} gauge theory of (2+1)-dimensional gravity is developed.
Fundamental gravitational field variables are dreibein fields and Lorentz gauge
potentials, and the theory is underlain with the Riemann-Cartan space-time. The
most general gravitational Lagrangian density, which is at most quadratic in
curvature and torsion tensors and invariant under local Lorentz transformations
and under general coordinate transformations, is given. Gravitational field
equations are studied in detail, and solutions of the equations for weak
gravitational fields are examined for the case with a static, \lq \lq spin"less
point like source. We find, among other things, the following: (1)Solutions of
the vacuum Einstein equation satisfy gravitational field equations in the
vacuum in this theory. (2)For a class of the parameters in the gravitational
Lagrangian density, the torsion is \lq \lq frozen" at the place where \lq \lq
spin" density of the source field is not vanishing. In this case, the field
equation actually agrees with the Einstein equation, when the source field is
\lq \lq spin"less. (3)A teleparallel theory developed in a previous paper is
\lq \lq included as a solution" in a limiting case. (4)A Newtonian limit is
obtainable, if the parameters in the Lagrangian density satisfy certain
conditions.Comment: 27pages, RevTeX, OCU-PHYS-15
Adaptive experimental design for one-qubit state estimation with finite data based on a statistical update criterion
We consider 1-qubit mixed quantum state estimation by adaptively updating
measurements according to previously obtained outcomes and measurement
settings. Updates are determined by the average-variance-optimality
(A-optimality) criterion, known in the classical theory of experimental design
and applied here to quantum state estimation. In general, A-optimization is a
nonlinear minimization problem; however, we find an analytic solution for
1-qubit state estimation using projective measurements, reducing computational
effort. We compare numerically two adaptive and two nonadaptive schemes for
finite data sets and show that the A-optimality criterion gives more precise
estimates than standard quantum tomography.Comment: 15 pages, 7 figure
Analytical Formulation of the Local Density of States around a Vortex Core in Unconventional Superconductors
On the basis of the quasiclassical theory of superconductivity, we obtain a
formula for the local density of states (LDOS) around a vortex core of
superconductors with anisotropic pair-potential and Fermi surface in arbitrary
directions of magnetic fields. Earlier results on the LDOS of d-wave
superconductors and NbSe are naturally interpreted within our theory
geometrically; the region with high intensity of the LDOS observed in numerical
calculations turns out to the enveloping curve of the trajectory of Andreev
bound states. We discuss experimental results on YNiBC within the
quasiclassical theory of superconductivity.Comment: 13 pages, 16 figure
Lazy states: sufficient and necessary condition for zero quantum entropy rates under any coupling to the environment
We find the necessary and sufficient conditions for the entropy rate of the
system to be zero under any system-environment Hamiltonian interaction. We call
the class of system-environment states that satisfy this condition lazy states.
They are a generalization of classically correlated states defined by quantum
discord, but based on projective measurements of any rank. The concept of lazy
states permits the construction of a protocol for detecting global quantum
correlations using only local dynamical information. We show how quantum
correlations to the environment provide bounds to the entropy rate, and how to
estimate dissipation rates for general non-Markovian open quantum systems.Comment: 4 page
Cell adhesion and cortex contractility determine cell patterning in the Drosophila retina
Hayashi and Carthew (Nature 431 [2004], 647) have shown that the packing of
cone cells in the Drosophila retina resembles soap bubble packing, and that
changing E- and N-cadherin expression can change this packing, as well as cell
shape.
The analogy with bubbles suggests that cell packing is driven by surface
minimization. We find that this assumption is insufficient to model the
experimentally observed shapes and packing of the cells based on their cadherin
expression. We then consider a model in which adhesion leads to a surface
increase, balanced by cell cortex contraction. Using the experimentally
observed distributions of E- and N-cadherin, we simulate the packing and cell
shapes in the wildtype eye. Furthermore, by changing only the corresponding
parameters, this model can describe the mutants with different numbers of
cells, or changes in cadherin expression.Comment: revised manuscript; 8 pages, 6 figures; supplementary information not
include
CIRCULAR DICHROISM OF LIGHT-HARVESTING COMPLEXES FROM PURPLE PHOTOSYNTHETIC BACTERIA
The CD spectra of a range of antenna complexes from several different species of purple photosynthetic bacteria were recorded in the wavelength range of 190 to 930 nm. Analysis of the far UV CD (190 to 250 nm) showed that in each case except for the B800-850 from Chr. vinosum the secondary structure of the light-harvesting complexes contains a large amount of α-helix (50%) and very little 0-pleated sheet. This confirms the predictions of the group of Zuber of a high a-helical content based upon consideration of the primary structures of several antenna apoproteins. The CD spectra from the carotenoids and the bacteriochlorophylls show considerable variations depending upon the type of antenna complex. The different amplitude ratios in the CD spectrum for the bacteriochlorophyll Qy, Qx and Soret bands indicate not only different degrees of exciton coupling, but also a strong and variable hyperchromism (Scherz and Parson, 1984a, b)
Low-lying Quasiparticle Excitations around a Vortex Core in Quantum Limit
Focusing on a quantum-limit behavior, we study a single vortex in a clean
s-wave type-II superconductor by self-consistently solving the Bogoliubov-de
Gennes equation. The discrete energy levels of the vortex bound states in the
quantum limit is discussed. The vortex core radius shrinks monotonically up to
an atomic-scale length on lowering the temperature T, and the shrinkage stops
to saturate at a lower T. The pair potential, supercurrent, and local density
of states around the vortex exhibit Friedel-like oscillations. The local
density of states has particle-hole asymmetry induced by the vortex. These are
potentially observed directly by STM.Comment: 4 pages, 6 figure
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