Measurement in control and discrimination of entangled pairs under self-distortion

Quantum correlations and entanglement are fundamental resources for quantum information and quantum communication processes. Developments in these fields normally assume these resources stable and not susceptible of distortion. That is not always the case, Heisenberg interactions between qubits can produce distortion on entangled pairs generated for engineering purposes (e. g. for quantum computation or quantum cryptography). Experimental work shows how to produce entangled spin qubits in quantum dots and electron gases, so its identification and control are crucial for later applications. The presence of parasite magnetic fields modifies the expected properties and behavior for which the pair was intended. Quantum measurement and control help to discriminate the original state in order to correct it or, just to try of reconstruct it using some procedures which do not alter their quantum nature. Two different kinds of quantum entangled pairs driven by a Heisenberg Hamiltonian with an additional inhomogeneous magnetic field which becoming self-distorted, can be reconstructed without previous discrimination by adding an external magnetic field, with fidelity close to 1 (with respect to the original state, but without discrimination). After, each state can be more efficiently discriminated. The aim of this work is to show how combining both processes, first reconstruction without discrimination and after discrimination with adequate non-local measurements, it's possible a) improve the discrimination, and b) reprepare faithfully the original states. The complete process gives fidelities better than 0.9. In the meanwhile, some results about a class of equivalence for the required measurements were found. This property lets us select the adequate measurement in order to ease the repreparation after of discrimination, without loss of entanglement.Comment: 6 figure

The Unhiggs

We examine a scenario where the Higgs is part of an approximate conformal field theory, and has a scaling dimension greater than one. Such an unparticle Higgs (or Unhiggs) can still break electroweak symmetry and unitarize WW scattering, but its gauge couplings are suppressed. An Unhiggs model has a reduced sensitivity of the weak scale to the cutoff, and can thus provide a solution to the little hierarchy problem.Comment: 21 pages, 9 figures; v2: further discussion, references added, version published in JHE

Count data models with variance of unknown form: an application to a hedonic model of worker absenteeism

We examine an econometric model of counts of worker absences due to illness in a sluggishly adjusting hedonic labor market. We compare three estimators that parameterize the conditional variance?least squares, Poisson, and negative binomial pseudo maximum likelihood?to generalized least squares (GLS) using nonparametric estimates of the conditional variance. Our data support the hedonic absenteeism model. Semiparametric GLS coefficients are similar in sign, magnitude, and statistical significance to coefficients where the mean and variance of the errors are specified ex ante. In our data, coefficient estimates are sensitive to a regressor list but not to the econometric technique, including correcting for possible heteroskedasticity of unknown form.Publicad

Count data models with variance of unknown form: an application to a hedonic model of worker absenteeism

We examined an econometric model of counts of worker absences due to illness. The underlying theoretical model is of a sluggishly adjusting hedonic labor market. We compared results fromı three parametric estimators, nonlinear least squares plus Poissonand negative binomial pseudo maximum likelihood, to generalized least squares using nonparametric estimates of the conditional variance. Our data support the hedonic model of worker absenteeism. Semiparametric generalized least squares coefficients are similar in sign, magnitude, and statistical significance to their econometric analogs where the mean and variance of the errors were specified ex ante. Overdispersion test reject the Poisson specification. Robustness checks confirm that in our dataı parameter estimates are sensitive to regressor list but are not sensitive to econometric technique, including how we corrected for possible heteroskedasticity of unknown form

Exploring singlet deflection of gauge mediation

We embed the Next-to Minimal Supersymmetric Standard Model into gauge mediation of supersymmetry breaking and study the phenomenology of scenarios where the gauge-mediation contributions to soft parameters are deflected by superpotential interactions of the gauge singlet with the messenger fields and the Higgs doublets. This kind of models provide a satisfactory solution to the mu-b_mu problem of gauge mediation, compatible with the adequate pattern of electroweak symmetry breaking and a realistic spectrum with supersymmetric partners at the TeV scale without requiring a significant fine tuning.Comment: Latex 18 pages, 4 eps figures. Minor corrections, version published in Phys. Rev.

Analysis of the stellar population in the central area of the HII region Sh 2-284

There is a lack of state-of-the-art information on very young open clusters, with implications for determining the structure of the Galaxy. Our main objective is to study the timing and location of the star formation processes which yielded the generation of the giant HII region Sh 2-284. The analysis is based on UBVRcIc CCD measurements and JHKs photometry in the central part of the HII region, where the cluster Dolidze 25 is located.The determination of cluster distance, reddening and age is carried out through comparison with ZAMS, post-MS and PMS isochrones. Reference lines for metallicity Z=0.004 are used, in agreement with spectroscopic metallicity determination published for several cluster members. The results are: E(B-V)=0.78+-0.02, M=12.8+-0.2, LogAge(yr)=6.51+-0.07. A PMS member sequence is proposed, coeval within the errors with the post-MS cluster age (LogAge(yr)=6.7+-0.2). The mass function for this PMS population in the mass range above 1.3-3.5 Msun is well fitted by a Salpeter mass function.The presence of a different star generation in the cluster with a distinctly older age, around 40 Myr, is suggested. The NIR results indicate a large number of sources with H-Ks excess, practically distinct from the optical PMS candidate members. The distance determined for the cluster is distinctly lower than previously published values. This result originates in the consistent use of low metallicity models for ZAMS fitting, applying published metallicity values for the cluster.Comment: gzipped tar file: 1 aa.cls, 1 tex file, 1 bbl file, 13 figures. Accepted in Astronomy & Astrophysics (9.11.2009