  Cosmic inflation is commonly assumed to be driven by quantum fields. Quantum
mechanics predicts phenomena such as quantum fluctuations and tunneling of the
field. Here we show an example of a quantum interference effect which goes
beyond the semi-classical treatment and which may be of relevance in the early
universe. We study the quantum coherent dynamics for a tilted, periodic
potential, which results in genuine quantum oscillations of the inflaton field,
analogous to Bloch oscillations in condensed matter and atomic systems. Our
results show that quantum interference phenomena may be of relevance in
cosmology.
