1,721,171 research outputs found
Breaking the weak Heisenberg limit
Get PDF©2017 American Physical Society
I thank Dr. Angel Rivas and Dr. Jesus Rubio for enlightening discussions and acknowledge support from Spanish MINECO Grant no. FIS2012-35583 and CAM research consortium QUITEMAD+ Grant No. S2013/ICE-2801.We provide a very simple case showing that the weak form of the Heisenberg limit can be beaten while the prior information is improved without bias.Ministerio de Economía y Competitividad (MINECO)Comunidad de MadridDepto. de ÓpticaFac. de Ciencias FísicasTRUEpu
Nonclassical light revealed by the joint statistics of simultaneous measurements
Get PDF© 2016 Optical Society of America.
Funding. Ministerio de Economía y Competitividad (MINECO) (FIS2012-35583); Comunidad de Madrid (QUITEMAD+S2013/ICE-2801).Nonclassicality cannot be a single-observable property, since the statistics of any quantum observable is compatible with classical physics. We develop a general procedure to reveal nonclassical behavior of light states from the joint statistics arising in the practical measurement of multiple observables. Beside embracing previous approaches, this protocol can disclose nonclassical features for standard examples of classical-like behavior, such as SU(2) and Glauber coherent states. When combined with other criteria, this would imply that every light state is nonclassical.Ministerio de Economía y Competitividad (MINECO), EspañaComunidad Autónoma de Madrid (CAM)Información y Tecnología Cuánticas en la Comunidad de Madrid (QUITEMAD+), CAMDepto. de ÓpticaFac. de Ciencias FísicasTRUEpu
Alternative measures of uncertainty in quantum metrology: contradictions and limits
Get PDF©2013 American Physical Society.
A.L. acknowledges support from Projects No. FIS2012-35583 of the Spanish Ministerio de Economia y Competitividad, and No. QUITEMAD S2009-ESP-1594 of the Comunidad de Madrid.We examine a family of intrinsic performance measures in terms of probability distributions that generalize Hellinger distance and Fisher information. They are applied to quantum metrology to assess the uncertainty in the detection of minute changes of physical quantities. We show that different measures lead to contradictory conclusions, including the possibility of arbitrarily small uncertainty for fixed resources. These intrinsic performances are compared with the averaged error in the corresponding estimation problem after single-shot measurements.Ministerio de Economia y Competitividad (MINECO), EspañaComunidad de MadridDepto. de ÓpticaFac. de Ciencias FísicasTRUEpu
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Zeno inhibition of polarization rotation in an optically active medium
No full text© 2015 IOP Publishing Ltd. We acknowledge support from Projects of the Spanish Ministerio de Economi a y Competitividad No. MTM2012-39101-C02-01 (MAP), No. FIS2013-41709-P (MAP), No. FIS2013-41709-P (IG), and No. FIS2012-35583 (AL).We describe an experiment in which the rotation of the polarization of light propagating in an optically active water solution of D-fructose tends to be inhibited by frequent monitoring whether the polarization remains unchanged. This is an example of the Zeno effect that has remarkable pedagogical interest because of its conceptual simplicity, easy implementation, low cost, and because the same the Zeno effect holds at classical and quantum levels. An added value is the demonstration of the Zeno effect beyond typical idealized assumptions in a practical setting with real polarizers.Ministerio de Economía y Competitividad (MINECO), EspañaDepto. de ÓpticaFac. de Ciencias FísicasTRUEpu
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Nonlinear Michelson interferometer for improved quantum metrology
Get PDF©2015 American Physical Society. We acknowledge financial support from Spanish Ministerio de Economia y Competitividad Projects No. FIS2012-33152 and No. FIS2012-35583 and from the Comunidad Autonoma de Madrid research consortium QUITEMAD+ Grant No. S2013/ICE-2801.We examine quantum detection via a Michelson interferometer embedded in a gas with Kerr nonlinearity. This nonlinear interferometer is illuminated by pulses of classical light. This strategy combines the robustness against practical imperfections of classical light with the improvement provided by nonlinear processes. Regarding ultimate quantum limits, we stress that, as a difference with linear schemes, the nonlinearity introduces pulse duration as a new variable into play along with the energy resources.Ministerio de Economia y Competitividad (MINECO), EspañaComunidad Autonoma de MadridDepto. de ÓpticaFac. de Ciencias FísicasTRUEpu
Quantum Zeno effect for a free-moving particle
Get PDF©2014 American Physical Society. We acknowledge support from Projects of the Spanish Ministerio de Economía y Competitividad No. MTM2012- 39101-C02-01 (M.A.P.), No. FIS2013-41709-P (M.A.P.), No. FIS2013-41709-P (I.G.), and No. FIS2012-35583 (A. L.).Although the quantum Zeno effect takes its name from Zeno’s arrow paradox, the effect of frequently observing the position of a freely moving particle on its motion has not been analyzed in detail in the frame of standard quantum mechanics. We study the evolution of a moving free particle while monitoring whether it lingers in a given region of space, and explain the dependence of the lingering probability on the frequency of the measurements and the initial momentum of the particle. Stopping the particle entails the emergence of Schrödinger cat states during the observed evolution, closely connected to the high-order diffraction modes in Fabry-Pérot optical resonators.Spanish Ministerio de Economía y CompetitividadDepto. de ÓpticaFac. de Ciencias FísicasTRUEpu
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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