Many people will recall the traditional definition of momentum from high-school physics as being the product of the mass of an object and the velocity at which it is travelling. In quantum theory an object is represented by a wave function and its position cannot be determined unless the wave function is 'collapsed' into a single state. This is the essence of measurement in quantum mechanics.
Classical momentum can be obtained simply by measuring the time an object takes to pass between two stationary detectors ('time-of-flight'), finding the velocity and multiplying by the mass. Di Pumpo and Freyberger have developed a model of the quantum equivalent of this experiment in which the roles...
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Drove my Ford to the fjord, but the fjord was dry. . .