  We evaluate self-interaction effects on the quantum correlations of field
modes of opposite momenta for scalar $\lambda \phi^4$ theory in a
two-dimensional asymptotically flat Robertson-Walker spacetime. Such
correlations are encoded both in the von-Neumann entropy defined through the
reduced density matrix in one of the modes and in the covariance expressed in
terms of the expectation value of the number operators for each mode in the
evolved state. The entanglement between field modes carries information about
the underlying spacetime evolution.
