Uncertainty reconciles complementarity with joint measurability

The fundamental principles of complementarity and uncertainty are shown to be related to the possibility of joint unsharp measurements of pairs of noncommuting quantum observables. A new joint measurement scheme for complementary observables is proposed. The measured observables are represented as positive operator valued measures (POVMs), whose intrinsic fuzziness parameters are found to satisfy an intriguing pay-off relation reflecting the complementarity. At the same time, this relation represents an instance of a Heisenberg uncertainty relation for measurement imprecisions. A model-independent consideration show that this uncertainty relation is logically connected with the joint measurability of the POVMs in question.Comment: 4 pages, RevTeX. Title of previous version: "Complementarity and uncertainty - entangled in joint path-interference measurements". This new version focuses on the "measurement uncertainty relation" and its role, disentangling this issue from the special context of path interference duality. See also http://www.vjquantuminfo.org (October 2003

Theoretical Uncertainties in Red Giant Branch Evolution: The Red Giant Branch Bump

A Monte Carlo simulation exploring uncertainties in standard stellar evolution theory on the red giant branch of metal-poor globular clusters has been conducted. Confidence limits are derived on the absolute V-band magnitude of the bump in the red giant branch luminosity function (M_v,b) and the excess number of stars in thebump, R_b. The analysis takes into account uncertainties in the primordial helium abundance, abundance of alpha-capture elements, radiative and conductive opacities, nuclear reaction rates, neutrino energy losses, the treatments of diffusion and convection, the surface boundary conditions, and color transformations. The uncertainty in theoretical values for the red giant bump magnitude varies with metallicity between +0.13/-0.12 mag at [Fe/H] = -2.4 and +0.23/-0.21 mag at [Fe/H] = -1.0$. The dominant sources of uncertainty are the abundance of the alpha-capture elements, the mixing length, and the low-temperature opacities. The theoretical values of M_v,b are in good agreement with observations. The uncertainty in the theoretical value of R_b is +/-0.01 at all metallicities studied. The dominant sources of uncertainty are the abundance of the alpha-capture elements, the mixing length, and the high-temperature opacities. The median value of R_b varies from 0.44 at [Fe/H] = -2.4$ to 0.50 at [Fe/H] = -1.0. These theoretical values for R_b are in agreement with observations.Comment: 30 pages, 6 figures. To appear in Ap

Doppler-free two-photon spectrum of the 000 band of the Ã1B1←X1A1 transition in difluorodiazirine, F2CN2

The Doppler-free two-photon excitation spectrum of the vibrationless Ã1B1←Image 1A1 transition of difluorodiazirine (F2CN2) has been recorded with a resolution of 15 MHz using a cw single-mode dye laser coupled to an external concentric resonator. The asymmetric rotor spectrum has been analysed and more than 350 lines randomly selected from all five branches were assigned in order to fit the ground- and excited-state rotational and quartic centrifugal distortion constants. From the rotational constants the rNN and rFF distances in the ground Image 1A1 and excited Ã1B1 state were determined. The geometry change upon excitation is found to be ΔrNN = 3.89(2) pm and ΔrFF = −4.09(2) pm. No perturbation in the rotational structure of the 000 band has been found. This points to a small singlet-triplet coupling matrix element in the small molecule limit

Beta contamination monitor energy response

Beta contamination is monitored at Los Alamos National Laboratory (LANL) with portable handheld probes and their associated counters, smear counters, air-breathing continuous air monitors (CAM), personnel contamination monitors (PCM), and hand and foot monitors (HFM). The response of these monitors was measured using a set of anodized-aluminum beta sources for the five isotopes: Carbon-14, Technetium-99, Cesium-137, Chlorine-36 and Strontium/Yttrium-90. The surface emission rates of the sources are traceable to the National Institute of Standards and Technology (NIST) with a precision of one relative standard deviation equal to 1.7%. All measurements were made in reproducible geometry, mostly using aluminum source holders. All counts, significantly above background, were collected to a precision of 1% or better. The study of the hand-held probes included measurements of six air gaps from 0.76 to 26.2 mm. The energy response of the detectors is well-parameterized as a function of the average beta energy of the isotopes (C14=50 keV, Tc99=85, Cs137=188, C136=246, and Sr/Y90=934). The authors conclude that Chlorine-36 is a suitable beta emitter for routine calibration. They recommend that a pancake Geiger-Mueller (GM) or gas-proportional counter be used for primarily beta contamination surveys with an air gap not to exceed 6 mm. Energy response varies about 30% from Tc99 to Sr/Y90 for the pancake GM detector. Dual alpha/beta probes have poor to negligible efficiency for low-energy betas. The rugged anodized sources represent partially imbedded contamination found in the field and they are provided with precise, NIST-traceable, emission rates for reliable calibration

STM fingerprint of molecule–adatom interactions in a self-assembled metal–organic surface coordination network on Cu(111)

7 páginas, 5 figuras, 3 tablas.-- El pdf del artículo es la versión pre-print.A novel approach of identifying metal atoms within a metal–organic surface coordination network using scanning tunnelling microscopy (STM) is presented. The Cu adatoms coordinated in the porous surface network of 1,3,8,10-tetraazaperopyrene (TAPP) molecules on a Cu(111) surface give rise to a characteristic electronic resonance in STM experiments. Using density functional theory calculations, we provide strong evidence that this resonance is a fingerprint of the interaction between the molecules and the Cu adatoms. We also show that the bonding of the Cu adatoms to the organic exodentate ligands is characterised by both the mixing of the nitrogen lone-pair orbitals of TAPP with states on the Cu adatoms and the partial filling of the lowest unoccupied molecular orbital (LUMO) of the TAPP molecule. Furthermore, the key interactions determining the surface unit cell of the network are discussed.This work was financially supported by the European Union through the Marie Curie Research Training Network PRAIRIES (MRTN-CT-2006-035810). Support from the Swiss National Science Foundation, the National Center of Competence in Research (NCCR) ‘‘Nanoscale Science’’ and the Wolfermann Naegeli Stiftung is also acknowledged. MP is also grateful for support from the Swedish Research Council (VR).Peer reviewe

GaAs:Mn nanowires grown by molecular beam epitaxy of (Ga,Mn)As at MnAs segregation conditions

GaAs:Mn nanowires were obtained on GaAs(001) and GaAs(111)B substrates by molecular beam epitaxial growth of (Ga,Mn)As at conditions leading to MnAs phase separation. Their density is proportional to the density of catalyzing MnAs nanoislands, which can be controlled by the Mn flux and/or the substrate temperature. Being rooted in the ferromagnetic semiconductor (Ga,Mn)As, the nanowires combine one-dimensional properties with the magnetic properties of (Ga,Mn)As and provide natural, self assembled structures for nanospintronics.Comment: 13 pages, 6 figure