Phase-locked indistinguishable photons with synthesized waveforms from a solid-state source

Resonance fluorescence in the Heitler regime provides access to single photons with coherence well beyond the Fourier transform limit of the transition, and holds the promise to circumvent environment-induced dephasing common to all solid-state systems. Here we demonstrate that the coherently generated single photons from a single self-assembled InAs quantum dot display mutual coherence with the excitation laser on a timescale exceeding 3 seconds. Exploiting this degree of mutual coherence we synthesize near-arbitrary coherent photon waveforms by shaping the excitation laser field. In contrast to post-emission filtering, our technique avoids both photon loss and degradation of the single photon nature for all synthesized waveforms. By engineering pulsed waveforms of single photons, we further demonstrate that separate photons generated coherently by the same laser field are fundamentally indistinguishable, lending themselves to creation of distant entanglement through quantum interference.Comment: Additional data and analysis in PDF format is available for download at the publications section of our website: http://www.amop.phy.cam.ac.uk/amop-ma

Inventory and quantitative assessment of geosites and geodiversity sites: a review

"Published online: 15 January 2015"The inventory and quantitative assessment of the most valuable occurrences of geodiversity are essential steps in any geoconservation strategy and in the establishment of priorities in site management. Despite the existence of many site inventories applied to different scales (countries, municipalities, parks, etc.), the criteria used for their selection are often unclear and poorly defined. This paper proposes a new approach to the concepts of geosite and geodiversity site and reviews the procedures used in the development of a systematic site inventory applied to different scales and values. Procedures to achieve a numerical evaluation of the value and degradation risk of sites are reviewed and new criteria are proposed. Finally, guidelines are presented, bearing in mind the preparation of effective geodiversity inventories, to support geoparks’ strategies. This paper aims to contribute to a better understanding and use of the above-mentioned concepts, which are essential for the implementation of geoconservation actions worldwide.The author thanks Diamantino Pereira, Flavia Lima, and Paulo Pereira for fruitful discussions and insights; Teresa Mota for the English revision; and the reviewers for significant improvements of the first submitted version. This paper results of the research done at the University of Minho and at the Geology Centre of the University of Porto, partially founded by the Foundation for Science and Technology (Portugal), strategic project with reference PEst-OE/CTE/UI0039/2014

Micron-scale mapping of megagauss magnetic fields using optical polarimetry to probe hot electron transport in petawatt-class laser-solid interactions

The transport of hot, relativistic electrons produced by the interaction of an intense petawatt laser pulse with a solid has garnered interest due to its potential application in the development of innovative x-ray sources and ion-acceleration schemes. We report on spatially and temporally resolved measurements of megagauss magnetic fields at the rear of a 50-μm thick plastic target, irradiated by a multi-picosecond petawatt laser pulse at an incident intensity of ~1020 W/cm2. The pump-probe polarimetric measurements with micron-scale spatial resolution reveal the dynamics of the magnetic fields generated by the hot electron distribution at the target rear. An annular magnetic field profile was observed ~5 ps after the interaction, indicating a relatively smooth hot electron distribution at the rear-side of the plastic target. This is contrary to previous time-integrated measurements, which infer that such targets will produce highly structured hot electron transport. We measured large-scale filamentation of the hot electron distribution at the target rear only at later time-scales of ~10 ps, resulting in a commensurate large-scale filamentation of the magnetic field profile. Three-dimensional hybrid simulations corroborate our experimental observations and demonstrate a beam-like hot electron transport at initial time-scales that may be attributed to the local resistivity profile at the target rear

Proliferation and aneusomy predict survival of young patients with astrocytoma grade II

The clinical course of astrocytoma grade II (AII) is highly variable and not reflected by histological characteristics. As one of the best prognostic factors, higher age identifies rapid progressive A II. For patients over 35 years of age, an aggressive treatment is normally propagated. For patients under 35 years, there is no clear guidance for treatment choices, and therefore also the necessity of histopathological diagnosis is often questioned. We studied the additional prognostic value of the proliferation index and the detection of genetic aberrations for patients with A II. The tumour samples were obtained by stereotactic biopsy or tumour resection and divided into two age groups, that is 18–34 years (n=19) and 35 years (n=28). Factors tested included the proliferation (Ki-67) index, and numerical aberrations for chromosomes 1, 7, and 10, as detected by in situ hybridisation (ISH). The results show that age is a prognostic indicator when studied in the total patient group, with patients above 35 years showing a relatively poor prognosis. Increased proliferation index in the presence of aneusomy appears to identify a subgroup of patients with poor prognosis more accurately than predicted by proliferation index alone. We conclude that histologically classified cases of A II comprise a heterogeneous group of tumours with different biological and genetic constitution, which exhibit a highly variable clinical course. Immunostaining for Ki-67 in combination with the detection of aneusomy by ISH allows the identification of a subgroup of patients with rapidly progressive A II. This is an extra argument not to defer stereotactic biopsy in young patients with radiological suspicion of A II

Genetic and proteomic analysis of the MHC class I repertoire from four ovine haplotypes

Immunity to livestock diseases can be studied directly in the target animal, but its elucidation is often constrained by the lack of major histocompatibility complex (MHC)-defined animals. To address this issue, we have established an MHC-defined sheep resource flock generated around four diverse MHC haplotypes. Initial characterisation of the repertoire of transcribed MHC class I genes identified three class I transcripts associated with each haplotype. Nucleotide sequence, transcript abundance and phylogenetic analysis indicated that they represent alleles at up to four polymorphic loci that vary in number between the different haplotypes. The functional significance of each of these genes is evaluated here using complementary molecular genetic and proteomic approaches. We determine which genes give rise to proteins that localise to the surface of transfected cells. In addition, we provide data to support the generation of expressed products, based on immunoprecipitation of class I products from animals homozygous for each of the four MHC haplotypes followed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. This provides a clearer picture of the number of MHC class I loci in sheep and allows more rational prediction of their classical (class Ia) or non-classical (class Ib) nature. On the basis of the cellular localisation, phylogenetic and transcriptional analyses, we propose that the ovine MHC comprises a minimum of eight class I loci, with considerable variation between haplotypes