Wave-particle duality of C-60 molecules

Quantum superposition lies at the heart of quantum mechanics and gives rise to many of its paradoxes. Superposition of de Broglie matter waves(1) has been observed for massive particles such as electrons(2), atoms and dimers( 3), small van der Waals clusters(4), and neutrons(5). But matter wave inter ferometry with larger objects has remained experimentally challenging, desp ite the development of powerful atom interferometric techniques for experim ents in fundamental quantum mechanics, metrology and lithography(6). Here w e report the observation of de Broglie wave interference of C-60 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 pa rticular interest is the fact that C-60 is almost a classical body, because of its many excited internal degrees of freedom and their possible couplin gs to the environment. Such couplings are essential for the appearance of d ecoherence(7,8), suggesting that interference experiments with large molecu les should facilitate detailed studies of this process.