Continuous Variable Approach Research Articles

Practical approach to extending baselines of telescopes using continuous-variable quantum information

Abstract Interferometric telescopes are instrumental for the imaging of distant astronomical bodies, but optical loss heavily restricts how far telescopes in an array can be placed from one another, leading to a bottleneck in the resolution that can be achieved. An entanglement-assisted approach to this problem has been proposed by (Gottesman et al 2011 Phys. Rev. Lett. 109 070503), as a possible solution to the issue of optical loss if the entangled state can be distributed across long distances by employing a quantum repeater network. In this paper, we propose an alternative entanglement-assisted scheme that interferes a two-mode squeezed vacuum state with the astronomical state and then measures the resulting state by means of homodyne detection. We use a continuous-variable approach and compute the Fisher information with respect to the mutual coherence of the astronomical source. We show that when the Fisher information is observed cumulatively at the rate at which successful measurements can be performed, our proposed scheme does not outperform the traditional direct detection approach or the entanglement-assisted approach of GJC12.

Spectrally shaped and pulse-by-pulse multiplexed multimode squeezed states of light

Spectral- and time-multiplexing are currently explored to generate large multipartite quantum states of light for quantum technologies. In the continuous variable approach, the deterministic generation of scalable entangled states requires the generation of a scalable number of squeezed modes. Here, we demonstrate the simultaneous generation of 21 squeezed spectral modes at the repetition rate of our laser, i.e., 156 MHz. We exploit the full repetition rate and the pulse shaping of a femtosecond light source to combine, for the first time, frequency- and time-multiplexing in multimode squeezing. This paves the way for the implementation of multipartite entangled states that are both scalable and fully reconfigurable.

Kelly Betting with Quantum Payoff: a continuous variable approach

The main purpose of this study is to introduce a semi-classical model describing betting scenarios in which, at variance with conventional approaches, the payoff of the gambler is encoded into the internal degrees of freedom of a quantum memory element. In our scheme, we assume that the invested capital is explicitly associated with the quantum analog of the free-energy (i.e. ergotropy functional by Allahverdyan, Balian, and Nieuwenhuizen) of a single mode of the electromagnetic radiation which, depending on the outcome of the betting, experiences attenuation or amplification processes which model losses and winning events. The resulting stochastic evolution of the quantum memory resembles the dynamics of random lasing which we characterize within the theoretical setting of Bosonic Gaussian channels. As in the classical Kelly Criterion for optimal betting, we define the asymptotic doubling rate of the model and identify the optimal gambling strategy for fixed odds and probabilities of winning. The performance of the model are hence studied as a function of the input capital state under the assumption that the latter belongs to the set of Gaussian density matrices (i.e. displaced, squeezed thermal Gibbs states) revealing that the best option for the gambler is to devote all their initial resources into coherent state amplitude.

Clustering and variable selection in the presence of mixed variable types and missing data.

We consider the problem of model-based clustering in the presence of many correlated, mixed continuous, and discrete variables, some of which may have missing values. Discrete variables are treated with a latent continuous variable approach, and the Dirichlet process is used to construct a mixture model with an unknown number of components. Variable selection is also performed to identify the variables that are most influential for determining cluster membership. The work is motivated by the need to cluster patients thought to potentially have autism spectrum disorder on the basis of many cognitive and/or behavioral test scores. There are a modest number of patients (486) in the data set along with many (55) test score variables (many of which are discrete valued and/or missing). The goal of the work is to (1) cluster these patients into similar groups to help identify those with similar clinical presentation and (2) identify a sparse subset of tests that inform the clusters in order to eliminate unnecessary testing. The proposed approach compares very favorably with other methods via simulation of problems of this type. The results of the autism spectrum disorder analysis suggested 3 clusters to be most likely, while only 4 test scores had high (>0.5) posterior probability of being informative. This will result in much more efficient and informative testing. The need to cluster observations on the basis of many correlated, continuous/discrete variables with missing values is a common problem in the health sciences as well as in many other disciplines.

Multilevel Modeling of Cognitive Diagnostic Assessment: The Multilevel DINA Example.

Many multilevel linear and item response theory models have been developed to account for multilevel data structures. However, most existing cognitive diagnostic models (CDMs) are unilevel in nature and become inapplicable when data have a multilevel structure. In this study, using the log-linear CDM as the item-level model, multilevel CDMs were developed based on the latent continuous variable approach and the multivariate Bernoulli distribution approach. In a series of simulations, the newly developed multilevel deterministic input, noisy, and gate (DINA) model was used as an example to evaluate the parameter recovery and consequences of ignoring the multilevel structures. The results indicated that all parameters in the new multilevel DINA were recovered fairly well by using the freeware Just Another Gibbs Sampler (JAGS) and that ignoring multilevel structures by fitting the standard unilevel DINA model resulted in poor estimates for the student-level covariates and underestimated standard errors, as well as led to poor recovery for the latent attribute profiles for individuals. An empirical example using the 2003 Trends in International Mathematics and Science Study eighth-grade mathematical test was provided.

Quantum Nondemolition Measurement Enables Macroscopic Leggett-Garg Tests.

We show how a test of macroscopic realism based on Leggett-Garg inequalities (LGIs) can be performed in a macroscopic system. Using a continuous-variable approach, we consider quantum nondemolition (QND) measurements applied to atomic ensembles undergoing magnetically driven coherent oscillation. We identify measurement schemes requiring only Gaussian states as inputs and giving a significant LGI violation with realistic experimental parameters and imperfections. The predicted violation is shown to be due to true quantum effects rather than to a classical invasivity of the measurement. Using QND measurements to tighten the "clumsiness loophole" forces the stubborn macrorealist to recreate quantum backaction in his or her account of measurement.

Mapping the geogenic radon potential: methodology and spatial analysis for central Hungary

A detailed geogenic radon potential (GRP) mapping based on field soil gas radon and soil gas permeability measurements was carried out in this study. A conventional continuous variable approach was used in this study for GRP determination and to test its applicability to the selected area of Hungary. Spatial pattern of soil gas radon concentration, soil permeability and GRP and the relationship between geological formations and these parameters were studied by performing detailed spatial analysis.Exploratory data analysis revealed that higher soil gas radon activity concentration and GRP characterizes the mountains and hills than the plains. The highest values were found in the proluvial–deluvial sediments, rock debris on the downhill slopes eroded from hills. Among the Quaternary sediments, which characterize the study area, the fluvial sediment has the highest values, which are also located in the hilly areas. The lowest values were found in the plain areas covered by drift sand, fluvioeolic sand, fluvial sand and loess. As a conclusion, radon is related to the sediment cycle in the study area.A geogenic radon risk map was created, which assists human health risk assessment and risk reduction since it indicates the potential of the source of indoor radon. The map shows that low and medium geogenic radon potential characterizes the study area in central Hungary. High risk occurs only locally. The results reveal that Quaternary sediments are inhomogeneous from a radon point of view, fluvial sediment has medium GRP, whereas the other rock formations such as drift sand, fluioeolic sand, fluvial sand and loess, found in the study area, have low GRP.

Continuous variable approach to identifying points of interest [in the subthalamic nucleus (STN)

Continuous variable approach to identifying points of interest [in the subthalamic nucleus (STN)

Intimate Partner Violence and Child Custody Evaluation, Part I: Theoretical Framework, Forensic Model, and Assessment Issues

An integrative conceptual framework and forensic evaluation model are presented for custody evaluators when the issue of Intimate Partner Violence is salient in a child custody case (IPV-CC). A revised typology of IPV combines previously proposed categories with a violence risk assessment approach to reflect both the descriptive and predictive functions for evaluators. It is a research-based forensic model. Continuous and categorical variable approaches to the analysis of IPV in custody cases are presented and contrasted. Ten behavioral dimensions of IPV-CC are described to serve as a multidimensional behavioral grid approach to the assessment of IPV. The integrated framework and perspective allows for greater behavioral specificity in the analysis. It avoids problems inherent in forensic assessment by subtype labeling. The court will be better informed by a multidimensional and continuous variable approach that provides behavioral versus categorical differentiation. This approach allows for more accurate and efficient risk communications to the court and translation to parenting plan recommendations. Issues involved with the forensic assessment of IPV in the custody context and making predictions/ recommendations about future parenting, co-parenting, and child adjustment are discussed.

Double-Λmicroscopic model for entangled light generation by four-wave mixing

Motivated by recent experiments, we study four-wave-mixing in an atomic double-{\Lambda} system driven by a far-detuned pump. Using the Heisenberg-Langevin formalism, and based on the microscopic properties of the medium, we calculate the classical and quantum properties of seed and conju- gate beams beyond the linear amplifier approximation. A continuous variable approach gives us access to relative-intensity noise spectra that can be directly compared to experiments. Restricting ourselves to the cold-atom regime, we predict the generation of quantum-correlated beams with a relative-intensity noise spectrum well below the standard quantum limit (down to -6 dB). Moreover entanglement between seed and conjugate beams measured by an inseparability down to 0.25 is expected. This work opens the way to the generation of entangled beams by four-wave mixing in a cold atomic sample.

Confidential Direct Communications: A Quantum Approach Using Continuous Variables

We consider the problem of privacy in direct communications, showing how quantum mechanics can be useful to guarantee a certain level of confidentiality. In particular, we review a continuous variable approach recently proposed by us [S. Pirandola et al., Europhys. Lett. 84, 20013 (2008)]. Here, we analyze the degree of privacy of this technique against a broader class of attacks, which includes non-Gaussian eavesdropping.

Relative occupancy, endemism, taxonomic distinctiveness and vulnerability: prioritizing regional conservation actions

A method is presented whereby regional species are scored and ranked in order of regional conservation importance according to a number of different but complementary 'rarity' criteria. Approaches for determining regional occupancy (RO), relative taxonomic distinctiveness (RTD), relative endemism (RE) and relative vulnerability (RV) rankings for regional faunas are proposed. The continuous variable approach and resultant positively skewed 'rarity' scores suggest easy identification of regional priority species. These methods are collectively applied to a regional mammalian fauna in order to prioritize species for conservation action using a regional priority score (RPS). The proposed method is a comparative relational approach aimed at determining which species require the establishment of viable populations within a regional context. The two species afforded highest RPSs for the Transvaal region, South Africa, are Gunning's golden mole Amblysomus gunningi and Juliana's golden mole A. julianae. These two species are true endemics, with geographic ranges completely restricted to the region. Also of high regional conservation importance are the four-toed elephant shrew Petrodromus tetradactylus, pangolin Manis temminckii and aardvark Orycteropus afer. Although these species have low RE scores, they have high RTD and RV scores. The equal weightings given to the four components of 'rarity' ensures that species achieving a high score in any of these categories will be considered for regional priority listing. This approach is simple, explicit and repeatable, circumventing problems of scale.

The dimensionality of the urban functional system

This paper suggests that the formulation and testing of hypotheses relating the functional role of cities in a society to other urban structure and process variables might be facilitated by substituting a continous variable approach to the functional system for the prevailing discrete typologies. Using variables indexing the scope of economic activities in U.S. communities at two points in time, we elaborate a technique for identifying the dimensions underlying an existing typology, and the 56 largest SMSA's are ranked along these dimensions.