1,985 research outputs found
Universal entanglement concentration
We propose a new protocol of \textit{universal} entanglement concentration,
which converts many copies of an \textit{unknown} pure state to an \textit{%
exact} maximally entangled state. The yield of the protocol, which is outputted
as a classical information, is probabilistic, and achives the entropy rate with
high probability, just as non-universal entanglement concentration protocols
do.
Our protocol is optimal among all similar protocols in terms of wide
varieties of measures either up to higher orders or non-asymptotically,
depending on the choice of the measure. The key of the proof of optimality is
the following fact, which is a consequence of the symmetry-based construction
of the protocol: For any invariant measures, optimal protocols are found out in
modifications of the protocol only in its classical output, or the claim on the
product.
We also observe that the classical part of the output of the protocol gives a
natural estimate of the entropy of entanglement, and prove that that estimate
achieves the better asymptotic performance than any other (potentially global)
measurements.Comment: Revised a lot, especially proofs, though no change in theorems,
lemmas itself. Very long, but essential part is from Sec.I to Sec IV-C. Some
of the appendces are almost independent of the main bod
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
Asymptotic estimation theory for a finite dimensional pure state model
The optimization of measurement for n samples of pure sates are studied. The
error of the optimal measurement for n samples is asymptotically compared with
the one of the maximum likelihood estimators from n data given by the optimal
measurement for one sample.Comment: LaTeX, 23 pages, Doctoral Thesi
Why do we live in 3+1 dimensions?
In the context of string theory we argue that higher dimensional Dp-branes
unwind and evaporate so that we are left with D3-branes embedded in a
(9+1)-dimensional bulk. One of these D3-branes plays the role of our Universe.
Within this picture, the evaporation of the higher dimensional Dp-branes
provides the entropy of our Universe.Comment: 9 pages, 4 figures. Citations added, text and figures updated to
match version accepted for publicatio
Electron Beam Dynamics in the 50 MeV ThomX Compact Storage Ring
International audienceThomX is a high flux compact X-ray source based on Compton back scattering between a relativistic electron beam and an intense laser pulse. To increase the repetition rate, the electron beam is stored in a ring. The main drawback of such a scheme is the low energy of the electrons regarding collective effects and intrabeam scattering. These effects tend to enlarge or even disrupt the stored bunch and they limit its charge, especially in a system where damping plays a negligible role. Thus such collective effects reduce the maximum X-ray flux and it is important to investigate them to predict the performance of this type of X-ray source. In addition, the Compton back scattering acts on the electron beam by increasing its energy spread. This presentation will show firstly the impact of collective effects on the electron beam, essentially during the first turns when they are the most harmful. Then, the reduction of the X-ray flux due to Compton back scattering and intrabeam scattering will be investigated on a longer time scale
Kondo Effect and Surface-State Electrons
We have used low temperature scanning tunneling spectroscopy and atomic
manipulation to study the role of surface-state electrons in the Kondo effect
of an isolated cobalt atom adsorbed on Ag(111). We show that the observed Kondo
signature remains unchanged in close proximity of a monoatomic step, where the
local density of states of the surface-state electrons is strongly perturbed.
This result indicates a minor role for surface-state electrons in the Kondo
effect of cobalt, compared to bulk electrons. A possible explanation for our
findings is presented.Comment: 4 pages, 4 figures, ACSIN-7 proceeding
Fontes de nitrogĂȘnio e tĂ©cnicas de propagação de mudas atuam na produtividade de erva-mate.
Avaliou-se a influĂȘncia de fontes de nitrogĂȘnio e tĂ©cnicas de propagação na produtividade de erva-mate. Em plantio realizado em 2005 em SĂŁo Mateus do Sul-PR (SMS), no espaçamento 1,2 x 3,0 m com mudas propagadas: por semente (procedĂȘncia SMS) e por miniestaquia (procedĂȘncias Bituruna, Cruz Machado e SMS). Em 2010, apĂłs a segunda colheita aplicou-se 130 kg ha-1 de nitrogĂȘnio na forma de nitrato de amĂŽnio, sulfato de amĂŽnio e ureia. Na colheita de 2012, com intervalo de 18 meses, quantificou-se a produtividade de erva-mate comercial, galho fino e galho grosso. A produtividade de todos os componentes avaliados foi influenciada pela interação entre fontes de N e procedĂȘncias. Conclui-se que a preferĂȘncia da erva-mate pela fonte de nitrogĂȘnio Ă© dependente do local de origem da cultura; a miniestaquia Ă© uma tĂ©cnica eficiente na propagação de erva-mate, recomendada para melhorar a produtividade da cultura
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
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