  We study theoretically the time-resolved four-wave mixing (FWM) response of
an ensemble of pairs of quantum dots undergoing radiative recombination. At
short (picosecond) delay times, the response signal shows beats that may be
dominated by the subensemble of resonant pairs, which gives access to the
information on the interdot coupling. At longer delay times, the decay of the
FWM signal is governed by two rates which result from the collective
interaction between the two dots and the radiation modes. The two rates
correspond to the subradiant and super-radiant components in the radiative
decay. Coupling between the dots enhances the collective effects and makes them
observable even when the average energy mismatch between the dots is relatively
large.
