646 research outputs found
Measurement-induced disturbances and nonclassical correlations of Gaussian states
We study quantum correlations beyond entanglement in two-mode Gaussian states of continuous-variable systems by means of the measurement-induced disturbance (MID) and its ameliorated version (AMID). In analogy with the recent studies of the Gaussian quantum discord, we define a Gaussian AMID by constraining the optimization to all bi-local Gaussian positive operator valued measurements. We solve the optimization explicitly for relevant families of states, including squeezed thermal states. Remarkably, we find that there is a finite subset of two-mode Gaussian states comprising pure states where non-Gaussian measurements such as photon counting are globally optimal for the AMID and realize a strictly smaller state disturbance compared to the best Gaussian measurements. However, for the majority of two-mode Gaussian states the unoptimized MID provides a loose overestimation of the actual content of quantum correlations, as evidenced by its comparison with Gaussian discord. This feature displays strong similarity with the case of two qubits. Upper and lower bounds for the Gaussian AMID at fixed Gaussian discord are identified. We further present a comparison between Gaussian AMID and Gaussian entanglement of formation, and classify families of two-mode states in terms of their Gaussian AMID, Gaussian discord, and Gaussian entanglement of formation. Our findings provide a further confirmation of the genuinely quantum nature of general Gaussian states, yet they reveal that non-Gaussian measurements can play a crucial role for the optimized extraction and potential exploitation of classical and nonclassical correlations in Gaussian states. © 2011 American Physical Society
Measuring Gaussian quantum information and correlations using the Renyi entropy of order 2
We demonstrate that the Renyi-2 entropy provides a natural measure of
information for any multimode Gaussian state of quantum harmonic systems,
operationally linked to the phase-space Shannon sampling entropy of the Wigner
distribution of the state. We prove that, in the Gaussian scenario, such an
entropy satisfies the strong subadditivity inequality, a key requirement for
quantum information theory. This allows us to define and analyze measures of
Gaussian entanglement and more general quantum correlations based on such an
entropy, which are shown to satisfy relevant properties such as monogamy.Comment: 6+5 pages, published in PRL. Typo in Eq. (1) correcte
Measurement-induced disturbances and nonclassical correlations of Gaussian states
We study quantum correlations beyond entanglement in two-mode Gaussian states
of continuous variable systems, by means of the measurement-induced disturbance
(MID) and its ameliorated version (AMID). In analogy with the recent studies of
the Gaussian quantum discord, we define a Gaussian AMID by constraining the
optimization to all bi-local Gaussian positive operator valued measurements. We
solve the optimization explicitly for relevant families of states, including
squeezed thermal states. Remarkably, we find that there is a finite subset of
two-mode Gaussian states, comprising pure states, where non-Gaussian
measurements such as photon counting are globally optimal for the AMID and
realize a strictly smaller state disturbance compared to the best Gaussian
measurements. However, for the majority of two--mode Gaussian states the
unoptimized MID provides a loose overestimation of the actual content of
quantum correlations, as evidenced by its comparison with Gaussian discord.
This feature displays strong similarity with the case of two qubits. Upper and
lower bounds for the Gaussian AMID at fixed Gaussian discord are identified. We
further present a comparison between Gaussian AMID and Gaussian entanglement of
formation, and classify families of two-mode states in terms of their Gaussian
AMID, Gaussian discord, and Gaussian entanglement of formation. Our findings
provide a further confirmation of the genuinely quantum nature of general
Gaussian states, yet they reveal that non-Gaussian measurements can play a
crucial role for the optimized extraction and potential exploitation of
classical and nonclassical correlations in Gaussian states.Comment: 16 pages, 5 figures; new results added; to appear in Phys. Rev.
The GRAAL high resolution BGO calorimeter and its energy calibration and monitoring system
We describe the electromagnetic calorimeter built for the GRAAL apparatus at
the ESRF. Its monitoring system is presented in detail. Results from tests and
the performance obtained during the first GRAAL experiments are given. The
energy calibration accuracy and stability reached is a small fraction of the
intrinsic detector resolution.Comment: 19 pages, 14 figures, submitted to Nuclear Instruments and Method
Concomitant Campylobacteriosis in a Puppy and in Its Caregiver: A One Health Perspective Paradigm in Human-Pet Relationship
Semi-supervised prediction of protein interaction sentences exploiting semantically encoded metrics
Protein-protein interaction (PPI) identification is an integral component of many biomedical research and database curation tools. Automation of this task through classification is one of the key goals of text mining (TM). However, labelled PPI corpora required to train classifiers are generally small. In order to overcome this sparsity in the training data, we propose a novel method of integrating corpora that do not contain relevance judgements. Our approach uses a semantic language model to gather word similarity from a large unlabelled corpus. This additional information is integrated into the sentence classification process using kernel transformations and has a re-weighting effect on the training features that leads to an 8% improvement in F-score over the baseline results. Furthermore, we discover that some words which are generally considered indicative of interactions are actually neutralised by this process
Polarization Asymmetry In The Photodisintegration Of The Deuteron
The reaction ²(γ,p)n has been studied using a monochromatic and polarized gamma ray beam at energies E(γ)=19.8, 29.0, 38.6, and 60.8 MeV. The beam of an intensity ∼4×10⁵ γ/sec was obtained by Compton back scattering of mode-locked laser light off electron bunches in the Adone storage ring. Photoneutron yields were measured at nine neutron angles thetan≃15, 30, 45, 60, 90, 120, 135, 150, and 165 deg in the center of mass (c.m.) for E(γ)=19.8, 29.0, and 38.6 MeV, and at thetan≃30, 60, 90, 120, and 150 deg c.m. for E(γ)=60.8 MeV. The polarization independent component Iₒ(theta) of the differential cross section and the polarization dependent component PI₁(theta) were deduced and the angular distribution of the azimuthal asymmetry factor Σ(theta)=I₁(theta)/Iₒ(theta) was obtained. An extensive comparison with theory has been carried out and the inclusion of corrections due to meson exchange currents and to Δ-isobar configurations have been shown to be mandatory at energies E(γ)≳40 MeV. Theoretical and experimental implications of intermediate energy deuteron photo- disintegration studies are discussed in some detail
Entanglement distribution and quantum discord
Establishing entanglement between distant parties is one of the most
important problems of quantum technology, since long-distance entanglement is
an essential part of such fundamental tasks as quantum cryptography or quantum
teleportation. In this lecture we review basic properties of entanglement and
quantum discord, and discuss recent results on entanglement distribution and
the role of quantum discord therein. We also review entanglement distribution
with separable states, and discuss important problems which still remain open.
One such open problem is a possible advantage of indirect entanglement
distribution, when compared to direct distribution protocols.Comment: 7 pages, 2 figures, contribution to "Lectures on general quantum
correlations and their applications", edited by Felipe Fanchini, Diogo
Soares-Pinto, and Gerardo Adess
Accurate prediction of BRCA1 and BRCA2 heterozygous genotypes using expression profiling of lymphocytes after irradiation-induced DNA damage
Using differential reinforcement of high rates of behavior to improve work productivity : a replication and extension
Background: Due to deficits in adaptive and cognitive functioning, productivity may pose challenges for individuals with intellectual disability in the workplace.Method: Using a changing‐criterion embedded in a multiple baseline across partici‐pants design, we examined the effects of differential reinforcement of high rates of behaviour (DRH) on the rate of data entry (i.e., productivity) in four adults with intel‐lectual disability.Results: Although the DRH procedure increased the rate of correct data entry in all four participants, none of the participants achieved the criterion that we set with novice undergraduate students.Conclusions: Our results indicate that DRH is an effective intervention to increase rate of correct responding in individuals with intellectual disability, but that achiev‐ing the same productivity as workers without disability may not always be possible
- …