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Oscillation instead of free fall – Science paper for Rudolf Mößbauer Tenure Track Professor Michael Knap

In the quantum world, our intuition for moving objects is strongly challenged and may sometimes even completely fail. An international team of physicists of the Universities of Innsbruck, Paris-Sud and Harvard as well as the Technical University of Munich (TUM), among them Rudolf Mößbauer Tenure Trak Professor Michael Knap, has found a quantum particle which shows an intriguing oscillatory back-and-forth motion in a one-dimensional atomic gas instead of moving uniformly. A ripe apple falling from a tree has inspired Sir Isaac Newton to formulate a theory that describes the motion of objects subject to a force. Newton’s equations of motion tell us that a moving body keeps on moving on a straight line unless any disturbing force may change its path. The impact of Newton’s laws is ubiquitous in our everyday experience, ranging from a skydiver falling in the earth’s gravitational field, over the inertia one feels in an accelerating airplane, to the earth orbiting around the sun. In the quantum world, however, our intuition for the motion of objects is strongly challenged and may sometimes even completely fail. In the current issue of “Science” an international team of physicists from Innsbruck, Munich, Paris and Cambridge (USA) describes a quantum particle that shows a completely unexpected behavior. In a quantum gas the particle does not move like the famous falling apple, but it oscillates. At the heart of this surprising behavior is what physicists call ‘quantum interference’, the fact that quantum mechanics allows particles to behave like waves, which can add up or cancel each other”

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