Digital quantum simulation of spin models with circuit quantum electrodynamics

Systems of interacting quantum spins show a rich spectrum of quantum phases and display interesting many-body dynamics. Computing characteristics of even small systems on conventional computers poses significant challenges. A quantum simulator has the potential to outperform standard computers in calculating the evolution of complex quantum systems. Here, we perform a digital quantum simulation of the paradigmatic Heisenberg and Ising interacting spin models using a two transmon-qubit circuit quantum electrodynamics setup. We make use of the exchange interaction naturally present in the simulator to construct a digital decomposition of the model-specific evolution and extract its full dynamics. This approach is universal and efficient, employing only resources which are polynomial in the number of spins and indicates a path towards the controlled simulation of general spin dynamics in superconducting qubit platforms.Comment: 12 pages, 9 figure

Challenging local realism with human choices

A Bell test is a randomized trial that compares experimental observations against the philosophical worldview of local realism 1, 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 2,3 . Although technology can satisfy the first two of these requirements 4-7, 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 8 . 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 9 . 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 5,6, single atoms 7, atomic ensembles 10 and superconducting devices 11 . 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 bipartite and tripartite 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 13 ), the utilization of video-game methods 14 for rapid collection of human-generated randomness, and the use of networking techniques for global participation in experimental science

Challenging local realism with human choices

A Bell test is a randomized trial that compares experimental observations against the philosophical worldview of local realism. 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 bipartite and tripartite 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.Comment: This version includes minor changes resulting from reviewer and editorial input. Abstract shortened to fit within arXiv limit

Integrating conservation objectives into forest management: coppice management and forest habitats in Natura 2000 sites

Most forest habitats, as defined and listed for their nature conservation importance in the Habitats Directive of the European Union and in the Bern Convention, result from centuries of human intervention. This paper explores the scope for, and the attitudes towards coppicing in Natura 2000 sites in some of the EU28 countries where coppice was historically one of the most important traditional silvicultural systems. A questionnaire survey was circulated to experts involved with Natura 2000 sites and case studies were conducted in Belgium, the Czech Republic, Estonia, Germany, Italy and the United Kingdom, to investigate attitudes to coppice silviculture within the framework of Natura 2000 site management plans. A list of forest habitat types capable of being managed as coppices was compiled and populated with sites at national and regional levels. At the regional level, management plans for the relevant forest habitat types in Natura 2000 sites were critically scrutinised together with other statutory, administrative or contractual measures. The results show that approaches to integrate coppice management into conservation plans differ widely. Examples of disparities are given and the possible causes discussed. A case is made for coppicing to be continued, where appropriate, as an important strategy in site management plans that aim to conserve habitats and improve forest biodiversity

Integrating conservation objectives into forest management: coppice management and forest habitats in Natura 2000 sites

Most forest habitats, as defined and listed for their nature conservation importance in the Habitats Directive of the European Union and in the Bern Convention, result from centuries of human intervention. This paper explores the scope for, and the attitudes towards coppicing in Natura 2000 sites in some of the EU28 countries where coppice was historically one of the most important traditional silvicultural systems. A questionnaire survey was circulated to experts involved with Natura 2000 sites and case studies were conducted in Belgium, the Czech Republic, Estonia, Germany, Italy and the United Kingdom, to investigate attitudes to coppice silviculture within the framework of Natura 2000 site management plans. A list of forest habitat types capable of being managed as coppices was compiled and populated with sites at national and regional levels. At the regional level, management plans for the relevant forest habitat types in Natura 2000 sites were critically scrutinised together with other statutory, administrative or contractual measures. The results show that approaches to integrate coppice management into conservation plans differ widely. Examples of disparities are given and the possible causes discussed. A case is made for coppicing to be continued, where appropriate, as an important strategy in site management plans that aim to conserve habitats and improve forest biodiversity