  Indirect excitons in coupled quantum wells are long-living quasi-particles,
explored in the studies of collective quantum states. We demonstrate, that
despite the extremely low oscillator strength, their spin and population
dynamics can by addressed by time-resolved pump-probe spectroscopy. Our
experiments make it possible to unravel and compare spin dynamics of direct
excitons, indirect excitons and residual free electrons in coupled quantum
wells. Measured spin relaxation time of indirect excitons exceeds not only one
of direct excitons, but also one of free electrons by two orders of magnitude.
