Witnessing effective entanglement in a continuous variable prepare&measure setup and application to a QKD scheme using postselection

We report an experimental demonstration of effective entanglement in a prepare&measure type of quantum key distribution protocol. Coherent polarization states and heterodyne measurement to characterize the transmitted quantum states are used, thus enabling us to reconstruct directly their Q-function. By evaluating the excess noise of the states, we experimentally demonstrate that they fulfill a non-separability criterion previously presented by Rigas et al. [J. Rigas, O. G\"uhne, N. L\"utkenhaus, Phys. Rev. A 73, 012341 (2006)]. For a restricted eavesdropping scenario we predict key rates using postselection of the heterodyne measurement results.Comment: 12 pages, 12 figures, 2 table

Electron-phonon coupling in the conventional superconductor YNi2_2B2_2C at high phonon energies studied by time-of-flight neutron spectroscopy

We report an inelastic neutron scattering investigation of phonons with energies up to 159 meV in the conventional superconductor YNi$_2$B$_2$C. Using the SWEEP mode, a newly developed time-of-flight technique involving the continuous rotation of a single crystal specimen, allowed us to measure a four dimensional volume in (Q,E) space and, thus, determine the dispersion surface and linewidths of the $A_{1g}$ (~ 102 meV) and $A_u$ (~ 159 meV) type phonon modes for the whole Brillouin zone. Despite of having linewidths of $\Gamma = 10 meV$, $A_{1g}$ modes do not strongly contribute to the total electron-phonon coupling constant $\lambda$. However, experimental linewidths show a remarkable agreement with ab-initio calculations over the complete phonon energy range demonstrating the accuracy of such calculations in a rare comparison to a comprehensive experimental data set.Comment: accepted for publication in PR

Linear Response Calculations of Lattice Dynamics in Strongly Correlated Systems

We introduce a new linear response method to study the lattice dynamics of materials with strong correlations. It is based on a combination of dynamical mean field theory of strongly correlated electrons and the local density functional theory of electronic structure of solids. We apply the method to study the phonon dispersions of a prototype Mott insulator NiO. Our results show overall much better agreement with experiment than the corresponding local density predictions.Comment: 4 pages, 2 figure

Efficiency of coherent state quantum cryptography in the presence of loss: Influence of realistic error correction

We investigate the performance of continuous variable quantum key distribution scheme in a practical setting. More specifically, we take non-ideal error reconciliation procedure into account. The quantum channel connecting the two honest parties is assumed to be lossy but noiseless. Secret key rates are given for the case that the measurement outcomes are postselected or a reverse reconciliation scheme is applied. The reverse reconciliation scheme loses its initial advantage in the practical setting. If one combines postselection with reverse reconciliation however, much of this advantage can be recovered.Comment: 7 pages, 2 figure

Relationship tensions and mood: Adult children’s daily experience of aging parents’ stubbornness

This study examined middle‐aged individuals’ reports of parents’ behaviors commonly attributed to stubbornness. Middle‐aged adults (N = 192) completed a 7‐day diary reporting their mood and how often they felt their parents (N = 254) engaged in behaviors often described as “stubbornness” (insistent or risky). Thirty‐one percent of middle‐aged children reported insistent behaviors, and 17% reported risky behaviors by their parent(s). Daily reports of parent behaviors attributed to stubbornness were positively associated with parent–child relationship quality, parent functional limitations, and child neuroticism. Reports of perceived parent insistent behaviors were also associated with greater daily negative mood among adult children. Findings highlight the impact of adult children’s daily perceptions of parent behaviors commonly attributed to stubbornness on the individual and relationship.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/142899/1/pere12229_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/142899/2/pere12229.pd