Experimental Quantum Networking Protocols via Four-Qubit Hyperentangled Dicke States

We report the experimental demonstration of two quantum networking protocols, namely quantum 1 -> 3 telecloning and open-destination teleportation, implemented using a four-qubit register whose state is encoded in a high-quality two-photon hyperentangled Dicke state. The state resource is characterized using criteria based on multipartite entanglement witnesses. We explore the characteristic entanglement-sharing structure of a Dicke state by implementing high-fidelity projections of the four-qubit resource onto lower-dimensional states. Our work demonstrates for the first time the usefulness of Dicke states for quantum information processing.

Liouville-space R-matrix-Floquet description of atomic radiative processes involving autoionizing states in the presence of intense electromagnetic fields

A reduced-density-operator description is developed for coherent optical phenomena in many-electron atomic systems, utilizing a Liouville-space, multiple-mode Floquet–Fourier representation. The Liouville-space formulation provides a natural generalization of the ordinary Hilbert-space (Hamiltonian) R-matrix-Floquet method, which has been developed for multi-photon transitions and laser-assisted electron–atom collision processes. In these applications, the R-matrix-Floquet method has been demonstrated to be capable of providing an accurate representation of the complex, multi-level structure of many-electron atomic systems in bound, continuum, and autoionizing states. The ordinary Hilbert-space (Hamiltonian) formulation of the R-matrix-Floquet method has been implemented in highly developed computer programs, which can provide a non-perturbative treatment of the interaction of a classical, multiple-mode electromagnetic field with a quantum system. This quantum system may correspond to a many-electron, bound atomic system and a single continuum electron. However, including pseudo-states in the expansion of the many-electron atomic wave function can provide a representation of multiple continuum electrons. The 'dressed' many-electron atomic states thereby obtained can be used in a realistic non-perturbative evaluation of the transition probabilities for an extensive class of atomic collision and radiation processes in the presence of intense electromagnetic fields. In order to incorporate environmental relaxation and decoherence phenomena, we propose to utilize the ordinary Hilbert-space (Hamiltonian) R-matrix-Floquet method as a starting-point for a Liouville-space (reduced-density-operator) formulation. To illustrate how the Liouville-space R-matrix-Floquet formulation can be implemented for coherent atomic radiative processes, we discuss applications to electromagnetically induced transparency, as well as to related pump–probe optical phenomena, and also to the unified description of radiative and dielectronic recombination in electron–ion beam interactions and high-temperature plasmas.

Macroscopic bound entanglement in thermal graph states

We address the presence of bound entanglement in strongly interacting spin systems at thermal equilibrium. In particular, we consider thermal graph states composed of an arbitrary number of particles. We show that for a certain range of temperatures no entanglement can be extracted by means of local operations and classical communication, even though the system is still entangled. This is found by harnessing the independence of the entanglement in some bipartitions of such states with the system's size. Specific examples for one- and two-dimensional systems are given. Our results thus prove the existence of thermal bound entanglement in an arbitrary large spin system with finite-range local interactions.

Area laws and entanglement distillability of thermal states

We study the entanglement distillability properties of thermal states of many-body systems Following the ideas presented in [6, A Ferraro et al., Phys. Rev Lett 100, 080502 (2008)], we first discuss the appearance of bound entanglement in those systems satisfying an entanglement area law Then, we extend these results to other topologies, not necessarily satisfying an entanglement area law We also study whether bound entanglement survives in the macroscopic limit of an infinite number of particles.

Gaussian States in Quantum Information

These notes originated out of a set of lectures in Quantum Optics and Quantum Information given by one of us (MGAP) at the University of Napoli and the University of Milano. A quite broad set of issues are covered, ranging from elementary concepts to current research topics, and from fundamental concepts to applications. A special emphasis has been given to the phase space analysis of quantum dynamics and to the role of Gaussian states in continuous variable quantum information.

A Note on Race, Ethnicity and Nativity Differences in Remarriage in the United States

The objectives of this study are to produce up-to-date estimates of race/ethnic/nativity differentials for remarriage and repartnership among women in the United States and to see if these differences are due to across-group differences in demographic characteristics. First, we produce lifetable estimates of remarriage and repartnering for white, black, U.S. born Latina and foreign born Latina women. Next, we estimate race/ethnic/nativity differentials for remarriage and repartnership using event-history analysis with and without controls for demographic characteristics. The results suggest a continued overall decline in remarriage rates, while many women repartner by cohabitating. Whites are more likely than blacks or Latinas to remarry and they are also more likely to repartner. Race/ethnic/nativity differentials remain even after accounting for variations in demographic characteristics. This suggests that race/ethnic/nativity differentials in remarriage and repartnering rates, rather than ameliorating disadvantages associated with divorce, reinforce these differentials.

A multiconfigurational time-dependent Hartree-Fock method for excited electronic states. II. Coulomb interaction effects in single conjugated polymer chains

Conjugated polymers have attracted considerable attention in the last few decades due to their potential for optoelectronic applications. A key step that needs optimisation is charge carrier separation following photoexcitation. To understand better the dynamics of the exciton prior to charge separation, we have performed simulations of the formation and dynamics of localised excitations in single conjugated polymer strands. We use a nonadiabatic molecular dynamics method which allows for the coupled evolution of the nuclear degrees of freedom and of multiconfigurational electronic wavefunctions. We show the relaxation of electron-hole pairs to form excitons and oppositely charged polaron pairs and discuss the modifications to the relaxation process predicted by the inclusion of the Coulomb interaction between the carriers. The issue of charge photogeneration in conjugated polymers in dilute solution is also addressed. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3600404]

Vitamin D and mortality: meta-analysis of individual participant data from a large consortium of cohort studies from Europe and the United States

Objective: To investigate the association between serum 25-hydroxyvitamin D concentrations (25(OH)D) and mortality in a large consortium of cohort studies paying particular attention to potential age, sex, season, and country differences.

Design: Meta-analysis of individual participant data of eight prospective cohort studies from Europe and the US.

Setting: General population.

Participants: 26 018 men and women aged 50-79 years

Main outcome measures: All-cause, cardiovascular, and cancer mortality.

Results: 25(OH)D concentrations varied strongly by season (higher in summer), country (higher in US and northern Europe) and sex (higher in men), but no consistent trend with age was observed. During follow-up, 6695 study participants died, among whom 2624 died of cardiovascular diseases and 2227 died of cancer. For each cohort and analysis, 25(OH)D quintiles were defined with cohort and subgroup specific cut-off values. Comparing bottom versus top quintiles resulted in a pooled risk ratio of 1.57 (95% CI 1.36 to 1.81) for all-cause mortality. Risk ratios for cardiovascular mortality were similar in magnitude to that for all-cause mortality in subjects both with and without a history of cardiovascular disease at baseline. With respect to cancer mortality, an association was only observed among subjects with a history of cancer (risk ratio, 1.70 (1.00 to 2.88)). Analyses using all quintiles suggest curvilinear, inverse, dose-response curves for the aforementioned relationships. No strong age, sex, season, or country specific differences were detected. Heterogeneity was low in most meta-analyses.

Conclusions: Despite levels of 25(OH)D strongly varying with country, sex, and season, the association between 25(OH)D level and all-cause and cause-specific mortality was remarkably consistent. Results from a long term randomised controlled trial addressing longevity are being awaited before vitamin D supplementation can be recommended in most individuals with low 25(OH)D levels.

Population trapping in bound states during IR-assisted ultrafast photoionization of Ne+

We have investigated the photoionization of Ne+ in the combined field of a short infrared laser pulse and a delayed ultrashort pulse of the infrared laser's 23rd harmonic. We observe an ionization yield compatible with a picture in which one electron gets excited into Rydberg states by the harmonic laser field and is subsequently removed by the infrared laser field. Modulations are seen in the ionization yield as a function of time delay. These modulations originate from the trapping of population in low members of the Rydberg series with different states being populated at different ranges of delay times. The calculations further demonstrate that single-threshold calculations cannot reproduce the Ne+ photoionization yields obtained in multithreshold calculations.

Political Posturing or Real Powers: Control of Genetically Modified Crops by the Member States and their Regions

The cultivation of genetically modified (GM) crops in the EU is highly harmonised, involving a central authorisation procedure that aims to ensure a high level of environmental and human health protection. However conflicts over authority persist and the Commission has responded to a combination of internal and external pressures with a more flexible approach to coexistence, a proposed opt-out clause and recently a promise by the head of the Commission to review the existing EU GM legislative regime, providing an opportunity to consider and suggest paths of development. In light of the significance of multilevel governance and subsidiarity for GM cultivation, this paper considers the policy-making powers of the Member States and subnational regions in this regime, focussing upon post-authorisation options in particular. A number of core mechanisms exist, including voluntary measures, safeguard clauses, coexistence measures, a proposed express opt-out and Article 4(2) TEU on ‘national identity. These mechanisms are examined in light of the goals and challenges of multilevel governance, in order to consider whether the relevant powers are located at the appropriate level. Overall, it is apparent that the developments occurring at the EU level are strengthening multilevel governance, but with significant opportunities to improve it further through focussing on the supporting roles and the regional levels in particular.

Sovereignty, Article 4(2) TEU and the Respect of National Identities: Swinging the Balance of Power in Favour of the Member States?

The question of whether and to what extent sovereignty has been transferred to the European Union (EU) from its Member States remains a central debate within the EU and is interlinked with issues such as Kompetenz-Kompetenz, direct effect and primacy. Central to any claim to sovereignty is the principle of primacy, which requires that Member States uphold EU law over national law where there is a conflict. However, limitations to primacy can traditionally be found in national jurisprudence and the Maastricht Treaty introduced a possible EU limitation with the requirement that the EU respect national identities of Member States. The Lisbon Treaty provided only minimal further support to the principle of primacy whilst simultaneously developing the provision on national identities, now found within Article 4(2) TEU. There are indications from the literature, national constitutional courts and the Court of Justice of the EU that the provision is gathering strength as a legal tool and is likely to have a wider scope than the text might indicate. In its new role, Article 4(2) TEU bolsters the Member States’ claim to sovereignty and the possibility to uphold aspects crucial to them in conflict with EU law and the principle of primacy. Consequently, it is central to the relationship between the constitutional courts of the Member States and the CJEU, and where the final elements of control remain in ‘hard cases’. However, it does so as part of EU law, thereby facilitating the evasion of direct fundamental conflicts and reflecting the concept of constitutional pluralism.

The continued salience of religious voting in the United States, Germany, and Great Britain

Conventional wisdom on party systems in advanced industrial democracies holds that modern electorates are dealigned and that social cleavages no longer structure party politics. Recent work on class cleavages has challenged this stylized fact. The analysis performed here extends this criticism to the religious-secular cleavage. Using path analysis and comparing the current electorates of the United States, Germany, and Great Britain with the early 1960s, this paper demonstrates that the religious-secular cleavage remains or has become a significant predictor of conservative vote choice. While the effects of the religious-secular cleavage on vote choice have become largely indirect, the total of the direct and indirect effects is substantial and equivalent to the effects of class and status.