3,893 research outputs found
0.5 Petabyte Simulation of a 45-Qubit Quantum Circuit
Near-term quantum computers will soon reach sizes that are challenging to
directly simulate, even when employing the most powerful supercomputers. Yet,
the ability to simulate these early devices using classical computers is
crucial for calibration, validation, and benchmarking. In order to make use of
the full potential of systems featuring multi- and many-core processors, we use
automatic code generation and optimization of compute kernels, which also
enables performance portability. We apply a scheduling algorithm to quantum
supremacy circuits in order to reduce the required communication and simulate a
45-qubit circuit on the Cori II supercomputer using 8,192 nodes and 0.5
petabytes of memory. To our knowledge, this constitutes the largest quantum
circuit simulation to this date. Our highly-tuned kernels in combination with
the reduced communication requirements allow an improvement in time-to-solution
over state-of-the-art simulations by more than an order of magnitude at every
scale
Personality traits in resident and migratory warbler species.
Animals are often confronted with environmental challenges and the way in which they cope with these challenges can have important fitness consequences. There is increasing evidence that individuals differ consistently in their reaction to the environment (personality traits). However, little is known about whether different life-styles (e.g., resident or migratory) influence personality traits and if so, in what manner. We compared neophobic and exploratory behaviours, both of which play an important role in personality traits, between two closely related species, the resident Sardinian warblers and the migratory garden warblers, at two different times during the year. Neophobia was tested by placing a novel object, a mop, beside the feeding dish and measuring the latency to feed (neophobia score). Exploration was tested by offering another novel object, a tube, attached to a perch at a neutral location and measuring latency to approach and investigate the tube (exploration score). Both tests were carried out at the end of the breeding season and repeated ten months later in spring. The Sardinian warblers showed consistent behavioural reactions over time. Furthermore, neophobia and exploration scores were negatively related. The garden warblers neither behaved consistently over time nor was there a correlation between neophobia and exploration. Overall, Sardinian warblers were less neophobic and more explorative than garden warblers. The different reactivity may be due to a different frequency distribution of the individuals of the two species along a reactivity axis. It can be concluded that the Sardinian warblers have personality traits. The situation is less clear in the garden warblers. Possibly, different life-styles require different organisation of behaviours
Sub-nanometer free electrons with topological charge
The holographic mask technique is used to create freely moving electrons with
quantized angular momentum. With electron optical elements they can be focused
to vortices with diameters below the nanometer range. The understanding of
these vortex beams is important for many applications. Here we present a theory
of focused free electron vortices. The agreement with experimental data is
excellent. As an immediate application, fundamental experimental parameters
like spherical aberration and partial coherence are determined.Comment: 4 pages, 5 figure
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