8,843 research outputs found

    Coupled-channel pseudo-potential description of the Feshbach resonance in two dimensions

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    We derive pseudo-potentials that describe the scattering between two particles in two spatial dimensions for any partial wave m, whose scattering strength is parameterized in terms of the m-dependent phase shift. Using our m=0 pseudo-potential, we develop a coupled channel model with 2D zero-range interactions, which describes the two-body physics across a Feshbach resonance. Our model predicts the scattering length, the binding energy and the "closed channel molecular fraction" of two particles; these observables can be measured in experiments on ultracold quasi-2D atomic Bose and Fermi gases with present-day technology.Comment: 4 pages, 3 figure

    Quantum data gathering

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    Measurement of a quantum system – the process by which an observer gathers information about it – provides a link between the quantum and classical worlds. The nature of this process is the central issue for attempts to reconcile quantum and classical descriptions of physical processes. Here, we show that the conventional paradigm of quantum measurement is directly responsible for a well-known disparity between the resources required to extract information from quantum and classical systems. We introduce a simple form of quantum data gathering, “coherent measurement”, that eliminates this disparity and restores a pleasing symmetry between classical and quantum statistical inference. To illustrate the power of quantum data gathering, we demonstrate that coherent measurements are optimal and strictly more powerful than conventional one-at-a-time measurements for the task of discriminating quantum states, including certain entangled many-body states (e.g., matrix product states)

    Learning Strategic Sophistication

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    We experimentally investigate coordination games in which cognition plays an important role, i.e. where outcomes are affected by the agents level of understanding of the game and the beliefs they form about each others understanding.We ask whether and when repeated exposure permits agents to learn to improve cognition in a strategic setting.We find evidence for strategic sophistication being learned, generalized and promoted.Agents acquire strategic sophistication in simple settings.They may fail to do so in similar but more demanding settings.Given the opportunity, they transfer learning from the simple to the more demanding task.There is heterogeneity in sophistication.We find some evidence for sophisticated agents trying to spread sophistication early in the game, provided there is a long enough time horizon.noncooperative games;laboratory group behavior

    Cognition in Spatial Dispersion Games

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    In common-interest spatial-dispersion games the agents common goal is to choose distinct locations.We experimentally investigate the role of cognition in such games and compare it with the role of cognition in spatial matching games. In our setup cognition matters because agents may be differentially aware of the dispersion opportunities that are created by the history of the game.We ask whether cognitive constraints limit the agents ability to achieve dispersion and, if there is dispersion, whether these constraints affect the mode by which agents achieve dispersion.Our main finding is that strategic interaction magnifies the role of cognitive constraints.Specifically, with cognitive constraints, pairs of agents fail to solve a dispersion problem that poses little or no problem for individual agents playing against themselves.When we remove the cognitive constraints in our design, pairs of agents solve the same problem just as well as individuals do.In addition, we find that when playing against themselves agents do not change the mode by which they solve the dispersion problem when our design removes the cognitive constraints.noncooperative games;laboratory group behavior