  The physics of individual Q-balls and interactions between multiple Q-balls
are well-studied in classical numerical simulations. Interesting properties and
phenomena have been discovered, involving stability, forces, collisions and
swapping of charge between different components of multi-Q-ball systems. We
investigate these phenomena in quantum field theory, including quantum
corrections to leading order in a 2PI coupling expansion, the inhomogeneous
Hartree approximation. The presence of quantum modes and new decay channels
allows the mean-field Q-ball to exchange charge with the quantum modes, and
also alters the charge swapping frequencies of the composite Q-balls. It is
also observed that the periodic exchanges between the mean-field and quantum
modes tend to be quenched by collisions between Q-balls. We illustrate how the
classical limit arises through a scaling of the Q-ball potential, making
quantum corrections negligible for large-amplitude Q-balls.
