Wave–particle duality of C60 molecules

Abstract

Quantum superposition lies at the heart of quantum mechanics and gives rise to many of its paradoxes. Superposition of de Broglie matter waves¹ has been observed for massive particles such as electrons², atoms and dimers³, small van der Waals clusters⁴, and neutrons⁵. But matter wave interferometry with larger objects has remained experimentally challenging, despite the development of powerful atom interferometric techniques for experiments in fundamental quantum mechanics, metrology and lithography⁶. Here we report the observation of de Broglie wave interference of C₆₀ molecules by diffraction at a material absorption grating. This molecule is the most massive and complex object in which wave behaviour has been observed. Of particular interest is the fact that C₆₀ is almost a classical body, because of its many excited internal degrees of freedom and their possible couplings to the environment. Such couplings are essential for the appearance of decoherence^7,8, suggesting that interference experiments with large molecules should facilitate detailed studies of this process.