Abstract
Interference of more and more massive objects provides a spectacular confirmation of quantum theory. It is usually regarded as support for “wave–particle duality” and in an extension of this duality even as support for “complementarity”. We first give an outline of the historical development of these notions. Already here it becomes evident that they are hard to define rigorously, i.e. have mainly a heuristic function. Then we discuss recent interference experiments of large and complex molecules which seem to support this heuristic function of “duality”. However, we show that in these experiments the diffraction of a delocalized center-of-mass wave function depends on the interaction of the localized structure of the molecule with the diffraction element. Thus, the molecules display “dual features” at the same time, which contradicts the usual understanding of wave–particle duality. We conclude that the notion of “wave–particle duality” deserves no place in modern quantum physics.
Highlights
In 2002 the journal Physics World asked its readers to vote for the most beautiful physics experiment
It is curious to note that these most advanced experiments in quantum-interferometry and nanotechnology are still discussed in terms of “complementarity” or “wave–particle duality”—notions that have fallen from grace in other quarters of quantum theory and are otherwise discussed in introductory textbooks only
Gehrenbeck [26] notes that the matter wave experiments of Davisson and Germer gained immediate acceptance
Summary
In 2002 the journal Physics World asked its readers to vote for the most beautiful physics experiment. A majority choose the “double-slit experiment with electrons” [1]. Richard Feynman called this experiment the “only mystery” of quantum physics in his lectures [2]. The Feynman lectures go on to state:
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