University of St Andrews

About: University of St Andrews is a education organization based out in St Andrews, Fife, United Kingdom. It is known for research contribution in the topics: Population & Laser. The organization has 16260 authors who have published 43364 publications receiving 1636072 citations. The organization is also known as: St Andrews University & University of St. Andrews.

Boson Sampling with 20 Input Photons and a 60-Mode Interferometer in a 10^{14}-Dimensional Hilbert Space.

Abstract: Quantum computing experiments are moving into a new realm of increasing size and complexity, with the short-term goal of demonstrating an advantage over classical computers. Boson sampling is a promising platform for such a goal; however, the number of detected single photons is up to five so far, limiting these small-scale implementations to a proof-of-principle stage. Here, we develop solid-state sources of highly efficient, pure, and indistinguishable single photons and 3D integration of ultralow-loss optical circuits. We perform experiments with 20 pure single photons fed into a 60-mode interferometer. In the output, we detect up to 14 photons and sample over Hilbert spaces with a size up to 3.7×10^{14}, over 10 orders of magnitude larger than all previous experiments, which for the first time enters into a genuine sampling regime where it becomes impossible to exhaust all possible output combinations. The results are validated against distinguishable samplers and uniform samplers with a confidence level of 99.9%.

Explaining enduring empowerment: A comparative study of collective action and psychological outcomes

Abstract: An ethnographic study of two crowd events was carried out in order to develop a hypothesis about the experience of empowerment in collective action. Qualitative comparison of an anti-roads occupation and a mass eviction suggests that empowerment as an outcome of collective action is a function of the extent to which oneb

Two or four Neoproterozoic glaciations

Abstract: A thick Neoproterozoic carbonate and glaciogenic succession of the southern Congo craton has yielded δ 13 C and 87 Sr/ 86 Sr records through the later Cryogenian (ca. 750–600 Ma) and earlier part of the Terminal Proterozoic (ca. 600–570 Ma). Sizeable negative δ 13 C excursions (to less than–5‰) occur above each of two glacial intervals and the 87 Sr/ 86 Sr values of marine carbonates shift from ∼0.7072 to ∼0.7079 at the upper glacial level. These geochemical constraints provide a Marinoan (younger Varanger) age for the upper glacial interval, previously regarded as a second phase of the Sturtian glaciation. The δ 13 C record from the Congo craton is therefore incompatible with recent global δ 13 C syntheses that have identified four or more separate ice ages during the Neoproterozoic. A cladistic analysis of geologic and geochemical characters of 12 Neoproterozoic glacial deposits identifies two distinct groups that are found in a consistent stratigraphic order whenever two glacial units occur within a single succession. We use δ 13 C and 87 Sr/ 86 Sr records from the Congo craton and other key successions to test the null hypothesis that there were only two global glaciations (Sturtian and Marinoan) during the Neoproterozoic. Placing the GSSP (global stratotype section and point) for the base of the Terminal Proterozoic within or just above a cap carbonate of the younger (Marinoan) glaciogenic succession would confine all known Neoproterozoic glaciations to the Cryogenian. The rapid shift in marine 87 Sr/ 86 Sr to more radiogenic values during the Marinoan glaciation is opposite that predicted by the snowball Earth scenario which calls for continental runoff to cease during glaciation, resulting in a shift to less radiogenic values.

Chapter 28 Visual pathways to perception and action

Abstract: Publisher Summary There appears to be important integrative areas within the superior temporal sulcus in the monkey where a great deal of the necessary interaction to ensure behavioral and perceptual unity. Indeed there are many polysensory neurons in these areas, such that not only visual but also cross-modal perceptual integration may be enabled by these networks. Despite the crosstalk between the dorsal and ventral streams, the chapter discusses that each stream uses visual information in different ways. Both streams process information about orientation and shape, and probably about spatial relationships, including depth; and both are subject to the modulatory influences of an animal's shifting spatial attention. The ventral stream provide object-centered coding, while the dorsal provide entirely viewer-centered information: the former would enable a monkey to identify an object as being of an edible type, the latter to guide its actions in picking it up. Although there will be differences in the ways that visual information is processed in the two systems, these differences are not a reflection of some biologically arbitrary separation of inputs, but rather a consequence of the special transformations required for perception and action, respectively.