Experimental high-dimensional two-photon entanglement and violations of generalised Bell inequalities

Quantum entanglement plays a vital role in many quantum information and communication tasks. Entangled states of higher dimensional systems are of great interest due to the extended possibilities they provide. For example, they allow the realisation of new types of quantum information schemes that can offer higher information-density coding and greater resilience to errors than can be achieved with entangled two-dimensional systems. Closing the detection loophole in Bell test experiments is also more experimentally feasible when higher dimensional entangled systems are used. We have measured previously untested correlations between two photons to experimentally demonstrate high-dimensional entangled states. We obtain violations of Bell-type inequalities generalised to d-dimensional systems with up to d = 12. Furthermore, the violations are strong enough to indicate genuine 11-dimensional entanglement. Our experiments use photons entangled in orbital angular momentum (OAM), generated through spontaneous parametric down-conversion (SPDC), and manipulated using computer controlled holograms

A Positive-Weight Next-to-Leading-Order Monte Carlo for e+e- Annihilation to Hadrons

We apply the positive-weight Monte Carlo method of Nason for simulating QCD processes accurate to Next-To-Leading Order to the case of e+e- annihilation to hadrons. The method entails the generation of the hardest gluon emission first and then subsequently adding a `truncated' shower before the emission. We have interfaced our result to the Herwig++ shower Monte Carlo program and obtained better results than those obtained with Herwig++ at leading order with a matrix element correction.Comment: 21 pages, 11 figures, 2 tables Reason for replacement: minor corrections, typos and 1 changed referenc

A positive-weight next-to-leading-order Monte Carlo for e⁺e ^- annihilation to hadrons

We apply the positive-weight Monte Carlo method of Nason for simulating QCD processes accurate to Next-To-Leading Order to the case of e+e- annihilation to hadrons. The method entails the generation of the hardest gluon emission first and then subsequently adding a `truncated' shower before the emission. We have interfaced our result to the Herwig++ shower Monte Carlo program and obtained better results than those obtained with Herwig++ at leading order with a matrix element correction

A Positive-Weight Next-to-Leading-Order Monte Carlo for Heavy Flavour Hadroproduction

We present a next-to-leading order calculation of heavy flavour production in hadronic collisions that can be interfaced to shower Monte Carlo programs. The calculation is performed in the context of the POWHEG method. It is suitable for the computation of charm, bottom and top hadroproduction. In the case of top production, spin correlations in the decay products are taken into account.Comment: 18 pages, 12 figures. Few misprints corrected, references updated, final remarks adde

Coherent Parton Showers with Local Recoils

We outline a new formalism for dipole-type parton showers which maintain exact energy-momentum conservation at each step of the evolution. Particular emphasis is put on the coherence properties, the level at which recoil effects do enter and the role of transverse momentum generation from initial state radiation. The formulated algorithm is shown to correctly incorporate coherence for soft gluon radiation. Furthermore, it is well suited for easing matching to next-to-leading order calculations.Comment: 24 pages, 3 figure

Codeine misuse and dependence in South Africa – learning from substance abuse treatment admissions

Background. Misuse of prescription and over-the-counter codeine-containing products is a global public health issue. Objectives. To investigate the extent of treatment demand related to the misuse of codeine or codeine dependence in South Africa (SA) and the profile of patients seeking treatment, so as to understand the nature and extent of the problem. Method. Data were collected from centres participating in the South African Community Epidemiology Network on Drug Use in 2014. A total of 17 260 admissions were recorded. Results. There were 435 recorded treatment admissions for codeine misuse or dependence as a primary or secondary substance of abuse (2.5% of all admissions). Of treatment admissions, 137 (0.8%) involved codeine as the primary substance of abuse; 74.9% of patients were males, with an even spread across population groups. Ages ranged from 11 to 70 years, with the highest proportion aged 20 - 29 years; > 40% were referred by self, family and/or friends, and 26.7% by health professionals; and 36.8% had received treatment previously. The majority reported misuse of tablets/capsules, with 17.6% reporting misuse of syrups. Oral use comprised 96.6% and daily use 63.1%. Conclusions. Data from treatment admissions related to codeine misuse and dependence are informative, but provide an incomplete picture of the nature and extent of codeine-related problems in SA. Other data sources must be considered before further regulatory/policy changes regarding codeine are implemented. © 2015, South African Medical Association. All rights reserved

Quantum measurements of atoms using cavity QED

Generalized quantum measurements are an important extension of projective or von Neumann measurements, in that they can be used to describe any measurement that can be implemented on a quantum system. We describe how to realize two non-standard quantum measurements using cavity quantum electrodynamics (QED). The first measurement optimally and unabmiguously distinguishes between two non-orthogonal quantum states. The second example is a measurement that demonstrates superadditive quantum coding gain. The experimental tools used are single-atom unitary operations effected by Ramsey pulses and two-atom Tavis-Cummings interactions. We show how the superadditive quantum coding gain is affected by errors in the field-ionisation detection of atoms, and that even with rather high levels of experimental imperfections, a reasonable amount of superadditivity can still be seen. To date, these types of measurement have only been realized on photons. It would be of great interest to have realizations using other physical systems. This is for fundamental reasons, but also since quantum coding gain in general increases with code word length, and a realization using atoms could be more easily scaled than existing realizations using photons.Comment: 10 pages, 5 figure