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- Abellán, C., et al.
(författare)
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Challenging Local Realism with Human Choices
- 2018
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Ingår i: Nature. - : Nature Publishing Group. - 0028-0836 .- 1476-4687. ; 557, s. 212-216
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Tidskriftsartikel (refereegranskat)abstract
- A Bell test is a randomized trial that compares experimental observations against the philosophical worldview of local realism , in which the properties of the physical world are independent of our observation of them and no signal travels faster than light. A Bell test requires spatially distributed entanglement, fast and high-efficiency detection and unpredictable measurement settings. Although technology can satisfy the first two of these requirements, the use of physical devices to choose settings in a Bell test involves making assumptions about the physics that one aims to test. Bell himself noted this weakness in using physical setting choices and argued that human 'free will' could be used rigorously to ensure unpredictability in Bell tests. Here we report a set of local-realism tests using human choices, which avoids assumptions about predictability in physics. We recruited about 100,000 human participants to play an online video game that incentivizes fast, sustained input of unpredictable selections and illustrates Bell-test methodology. The participants generated 97,347,490 binary choices, which were directed via a scalable web platform to 12 laboratories on five continents, where 13 experiments tested local realism using photons, single atoms, atomic ensembles and superconducting devices. Over a 12-hour period on 30 November 2016, participants worldwide provided a sustained data flow of over 1,000 bits per second to the experiments, which used different human-generated data to choose each measurement setting. The observed correlations strongly contradict local realism and other realistic positions in bi-partite and tri-partite 12 scenarios. Project outcomes include closing the 'freedom-of-choice loophole' (the possibility that the setting choices are influenced by 'hidden variables' to correlate with the particle properties), the utilization of video-game methods for rapid collection of human-generated randomness, and the use of networking techniques for global participation in experimental science.
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- Myrberg, T, et al.
(författare)
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Structural properties of relaxed Ge buffer layers on Si(001) : effect of layer thickness and low temperature Si initial buffer
- 2004
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Ingår i: Journal of materials science. Materials in electronics. - : Springer Science Business Media. - 0957-4522 .- 1573-482X. ; 15:7, s. 411-417
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Tidskriftsartikel (refereegranskat)abstract
- We have used the strain sensitive tool two-dimensional reciprocal space mapping (2D-RSM) and high resolution rocking curves (HR-RC) to assess the effect of the layer thickness and the influence of low temperature Si buffer on the properties of fully relaxed Ge on Si (0 0 1). The samples were grown by chemical vapor deposition in an ASM commercial reactor. As complementary measurements we have employed secondary ion mass spectrometry (SIMS) for chemical analysis, cross sectional transmission electron microscopy for quality assessment, and finally atomic force microscopy (AFM) for investigating the surface roughness. The investigated samples have a thickness ranging from 0.25 to 5.0 mum. In addition and for a 5.0 mum thick Ge layer, an initial low temperature Si (LT-Si) template was grown before the Ge epitaxy. The results indicate that high quality fully relaxed Ge layers have been achieved using the adopted growth procedure. Most of the improvement in crystalline quality was observed for Ge layers with thickness up to 1.5 mum. Above this thickness the observed crystalline quality improvement was negligible. The LT-Si buffer observed to be disadvantageous for pure relaxed Ge growth.
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