1,670 research outputs found
The Choice of Institutions: The Role of Risk and Risk-Aversion
Institutions can affect individual behavior both via their efficiency impact and via their risk reducing mechanisms. However there has been little study of the relative importance of these two channels in how individuals choose between simultaneously extant institutions. This paper presents a simple model of institutional choice in a labor market when there is a risk/reward trade-off, and tests the predictions of the theory. Using a novel empirical approach that adapts an ARCH-in-mean to cross-sectional survey data from China, we find that risk and risk aversion are strongly related to the choice of a labor market institution. Further, risk and risk aversion are quantitatively more important than the sectoral wage differential in explaining employment institution choices. Specifically, we find that wage risk has two orders of magnitude greater impact on labor market institutional choice than the wage difference, with a one standard deviation increase in earnings risk reducing the number of workers choosing jobs in the private (risky) sector by 22%.Institutions, Risk, Labor Market, Risk Aversion
Smoking status and subjective well-being
Background/aims: A debate is currently underway about the FDA's methods for evaluating anti-tobacco regulation. In particular, the US government requires a cost-benefit analysis for significant new regulations, which has led the FDA to consider potential lost subjective well-being (SWB) of ex-smokers as a cost of any proposed anti-tobacco policy. This practice, which significantly limits regulatory capacity, is premised on the assumption that there is in fact a loss in SWB among ex-smokers. Methods: We analyze the relationship between SWB and smoking status using a longitudinal internet survey of over 5000 Dutch adults across five years. We control for socio-economic, demographic and health characteristics, and in a contribution to the literature we additionally control for two potential confounding personality characteristics, habitual use of external substances and sensitivity to stress. In another contribution, we estimate panel fixed effects models that additionally control for unobservable time-invariant characteristics. Results: We find strong suggestive evidence that ex-smokers do not suffer a net loss in SWB. We also find no evidence that the change in SWB of those who quit smoking under stricter tobacco control policies is different from those who quit under a more relaxed regulatory environment. Furthermore, our cross-sectional estimates suggest that the increase in SWB from quitting smoking is not only statistically significant but also of a meaningful magnitude
Transport Dynamics of Broad Resonances
The propagation of short life time particles with consequently broad mass
width are discussed in the context of transport descriptions. In the first part
some known properties of finite life time particles such as resonances are
reviewed and discussed at the example of the -meson. Grave deficiencies
in some of the transport treatment of broad resonances are disclosed and
quantified. The second part addresses the derivation of transport equations
which permit to account for the damping width of the particles. Baym's
-derivable method is used to derive a self-consistent and conserving
scheme, which fulfils detailed balance relations even in the case of particles
with broad mass distributions. For this scheme a conserved energy-momentum
tensor can be constructed. Furthermore, a kinetic entropy can be derived which
besides the standard quasi-particle part also includes contributions from
fluctuations.Comment: Talk presented on the Erice School on Nuclear Physics, Erice, Italy,
Sept. 17 - 25, 1998 to be published in Progress in Particle and Nuclear
Physics, Vol. 42 (10 pages, 5 eps-figures
Generation of mechanical interference fringes by multi-photon counting
Exploring the quantum behaviour of macroscopic objects provides an intriguing
avenue to study the foundations of physics and to develop a suite of
quantum-enhanced technologies. One prominent path of study is provided by
quantum optomechanics which utilizes the tools of quantum optics to control the
motion of macroscopic mechanical resonators. Despite excellent recent progress,
the preparation of mechanical quantum superposition states remains outstanding
due to weak coupling and thermal decoherence. Here we present a novel
optomechanical scheme that significantly relaxes these requirements allowing
the preparation of quantum superposition states of motion of a mechanical
resonator by exploiting the nonlinearity of multi-photon quantum measurements.
Our method is capable of generating non-classical mechanical states without the
need for strong single photon coupling, is resilient against optical loss, and
offers more favourable scaling against initial mechanical thermal occupation
than existing schemes. Moreover, our approach allows the generation of larger
superposition states by projecting the optical field onto NOON states. We
experimentally demonstrate this multi-photon-counting technique on a mechanical
thermal state in the classical limit and observe interference fringes in the
mechanical position distribution that show phase superresolution. This opens a
feasible route to explore and exploit quantum phenomena at a macroscopic scale.Comment: 16 pages, 4 figures. v1: submitted for review on 28 Jan 2016. v2:
significantly revised manuscript. v3: some further revisions and some extra
results included. v3: new results added, extra author added, close to
published version, supplementary material available with published versio
Manipulating biphotonic qutrits
Quantum information carriers with higher dimension than the canonical qubit
offer significant advantages. However, manipulating such systems is extremely
difficult. We show how measurement induced non-linearities can be employed to
dramatically extend the range of possible transforms on biphotonic qutrits; the
three level quantum systems formed by the polarisation of two photons in the
same spatio-temporal mode. We fully characterise the biphoton-photon
entanglement that underpins our technique, thereby realising the first instance
of qubit-qutrit entanglement. We discuss an extension of our technique to
generate qutrit-qutrit entanglement and to manipulate any bosonic encoding of
quantum information.Comment: 4 pages, 4 figure
Demonstration of a simple entangling optical gate and its use in Bell-state analysis
We demonstrate a new architecture for an optical entangling gate that is
significantly simpler than previous realisations, using partially-polarising
beamsplitters so that only a single optical mode-matching condition is
required. We demonstrate operation of a controlled-Z gate in both
continuous-wave and pulsed regimes of operation, fully characterising it in
each case using quantum process tomography. We also demonstrate a
fully-resolving, nondeterministic optical Bell-state analyser based on this
controlled-Z gate. This new architecture is ideally suited to guided optics
implementations of optical gates.Comment: 4 pages, 3 figures. v2: additional author, improved data and figures
(low res), some other minor changes. Accepted for publication in PR
Experimental demonstration of Shor's algorithm with quantum entanglement
Shor's powerful quantum algorithm for factoring represents a major challenge
in quantum computation and its full realization will have a large impact on
modern cryptography. Here we implement a compiled version of Shor's algorithm
in a photonic system using single photons and employing the non-linearity
induced by measurement. For the first time we demonstrate the core processes,
coherent control, and resultant entangled states that are required in a
full-scale implementation of Shor's algorithm. Demonstration of these processes
is a necessary step on the path towards a full implementation of Shor's
algorithm and scalable quantum computing. Our results highlight that the
performance of a quantum algorithm is not the same as performance of the
underlying quantum circuit, and stress the importance of developing techniques
for characterising quantum algorithms.Comment: 4 pages, 5 figures + half-page additional online materia
Analysis of 1,000+ Type-Strain Genomes Substantially Improves Taxonomic Classification of Alphaproteobacteria.
The class Alphaproteobacteria is comprised of a diverse assemblage of Gram-negative bacteria that includes organisms of varying morphologies, physiologies and habitat preferences many of which are of clinical and ecological importance. Alphaproteobacteria classification has proved to be difficult, not least when taxonomic decisions rested heavily on a limited number of phenotypic features and interpretation of poorly resolved 16S rRNA gene trees. Despite progress in recent years regarding the classification of bacteria assigned to the class, there remains a need to further clarify taxonomic relationships. Here, draft genome sequences of a collection of genomes of more than 1000 Alphaproteobacteria and outgroup type strains were used to infer phylogenetic trees from genome-scale data using the principles drawn from phylogenetic systematics. The majority of taxa were found to be monophyletic but several orders, families and genera, including taxa recognized as problematic long ago but also quite recent taxa, as well as a few species were shown to be in need of revision. According proposals are made for the recognition of new orders, families and genera, as well as the transfer of a variety of species to other genera and of a variety of genera to other families. In addition, emended descriptions are given for many species mainly involving information on DNA G+C content and (approximate) genome size, both of which are confirmed as valuable taxonomic markers. Similarly, analysis of the gene content was shown to provide valuable taxonomic insights in the class. Significant incongruities between 16S rRNA gene and whole genome trees were not found in the class. The incongruities that became obvious when comparing the results of the present study with existing classifications appeared to be caused mainly by insufficiently resolved 16S rRNA gene trees or incomplete taxon sampling. Another probable cause of misclassifications in the past is the partially low overall fit of phenotypic characters to the sequence-based tree. Even though a significant degree of phylogenetic conservation was detected in all characters investigated, the overall fit to the tree varied considerably
Imaging of trapped ions with a microfabricated optic for quantum information processing
Trapped ions are a leading system for realizing quantum information processing (QIP). Most of the technologies required for implementing large-scale trapped-ion QIP have been demonstrated, with one key exception: a massively parallel ion-photon interconnect. Arrays of microfabricated phase Fresnel lenses (PFL) are a promising interconnect solution that is readily integrated with ion trap arrays for large-scale QIP. Here we show the first imaging of trapped ions with a microfabricated in-vacuum PFL, demonstrating performance suitable for scalable QIP. A single ion fluorescence collection efficiency of 4.2±1.5% was observed. The depth of focus for the imaging system was 19.4±2.4μm and the field of view was 140±20μm. Our approach also provides an integrated solution for high-efficiency optical coupling in neutral atom and solid-state QIP architectures
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