1,042 research outputs found
Direct measurement of finite-time disentanglement induced by a reservoir
We propose a method for directly probing the dynamics of disentanglement of
an initial two-qubit entangled state, under the action of a reservoir. We show
that it is possible to detect disentanglement, for experimentally realizable
examples of decaying systems, through the measurement of a single observable,
which is invariant throughout the decay. The systems under consideration may
lead to either finite-time or asymptotic disentanglement. A general
prescription for measuring this observable, which yields an operational meaning
to entanglement measures, is proposed, and exemplified for cavity quantum
electrodynamics and trapped ions.Comment: 4 pages, 2 figure
Rate of parity violation from measure concentration
We present a geometric argument determining the kinematic (phase-space)
factor contributing to the relative rate at which degrees of freedom of one
chirality come to dominate over degrees of freedom of opposite chirality, in
models with parity violation. We rely on the measure concentration of a subset
of a Euclidean cube which is controlled by an isoperimetric inequality. We
provide an interpretation of this result in terms of ideas of Statistical
Mechanics.Comment: 10 pages, no figure
Dvoretzky type theorems for multivariate polynomials and sections of convex bodies
In this paper we prove the Gromov--Milman conjecture (the Dvoretzky type
theorem) for homogeneous polynomials on , and improve bounds on
the number in the analogous conjecture for odd degrees (this case
is known as the Birch theorem) and complex polynomials. We also consider a
stronger conjecture on the homogeneous polynomial fields in the canonical
bundle over real and complex Grassmannians. This conjecture is much stronger
and false in general, but it is proved in the cases of (for 's of
certain type), odd , and the complex Grassmannian (for odd and even and
any ). Corollaries for the John ellipsoid of projections or sections of a
convex body are deduced from the case of the polynomial field conjecture
Transference Principles for Log-Sobolev and Spectral-Gap with Applications to Conservative Spin Systems
We obtain new principles for transferring log-Sobolev and Spectral-Gap
inequalities from a source metric-measure space to a target one, when the
curvature of the target space is bounded from below. As our main application,
we obtain explicit estimates for the log-Sobolev and Spectral-Gap constants of
various conservative spin system models, consisting of non-interacting and
weakly-interacting particles, constrained to conserve the mean-spin. When the
self-interaction is a perturbation of a strongly convex potential, this
partially recovers and partially extends previous results of Caputo,
Chafa\"{\i}, Grunewald, Landim, Lu, Menz, Otto, Panizo, Villani, Westdickenberg
and Yau. When the self-interaction is only assumed to be (non-strongly) convex,
as in the case of the two-sided exponential measure, we obtain sharp estimates
on the system's spectral-gap as a function of the mean-spin, independently of
the size of the system.Comment: 57 page
Topological phase for spin-orbit transformations on a laser beam
We investigate the topological phase associated with the double connectedness
of the SO(3) representation in terms of maximally entangled states. An
experimental demonstration is provided in the context of polarization and
spatial mode transformations of a laser beam carrying orbital angular momentum.
The topological phase is evidenced through interferometric measurements and a
quantitative relationship between the concurrence and the fringes visibility is
derived. Both the quantum and the classical regimes were investigated.Comment: 4 pages, 4 figure
Hardware and software installation for the research of luminescent processes in the temperature range 4-500 K
In paper the description of the apparatus and software complex intended for researches radiation and thermally stimulated of processes in solids at 4-500 К is resulted. Hardware-software complex is applicable for laboratory works at the rate of solid state physics, as well as for scientific research. Working capacity of a complex is illustrated by the data of measurements of spectra thermoluminescence (TL), energized X-ray or an ultraviolet radiation at 8 К and phototransfered luminescence (PTTL) crystals an anion-defective corundum. The gained results in comparison with the literary data have shown working capacity of a complex and possibility of reception with its help of new resultВ статье описан аппаратурно-программный комплекс для исследования радиационно- и термостимулированных люминесцентных явлений в диапазоне температур 4-500К. Данный комплекс применяется для проведения лабораторных работ по курсу физики твердого тела и проведения научных исследований магистрантами и аспирантами. На базе комплекса возможно проведение учебных работ по созданию автоматизированных систем научных исследований и систем автоматического управления технологическими процессами. Для апробации установки проведены исследования анион-дефектного корунда. Полученные результаты в сравнении с литературными данными показали работоспособность комплекса и возможность получения с его помощью новых данны
On Hastings' counterexamples to the minimum output entropy additivity conjecture
Hastings recently reported a randomized construction of channels violating
the minimum output entropy additivity conjecture. Here we revisit his argument,
presenting a simplified proof. In particular, we do not resort to the exact
probability distribution of the Schmidt coefficients of a random bipartite pure
state, as in the original proof, but rather derive the necessary large
deviation bounds by a concentration of measure argument. Furthermore, we prove
non-additivity for the overwhelming majority of channels consisting of a Haar
random isometry followed by partial trace over the environment, for an
environment dimension much bigger than the output dimension. This makes
Hastings' original reasoning clearer and extends the class of channels for
which additivity can be shown to be violated.Comment: 17 pages + 1 lin
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