Quantum interference and slow light propagation in cold samples of open three-level atoms

We investigate theoretically the propagation of a probe laser pulse through a cold sample of three-level atoms in the presence of a strong coupling field. Our numerical analysis shows that the electromagnetically induced transparency phenomenon produces very small group velocities for the probe pulse even if the three-level atomic system is open, i.e. in the presence of decay channels to levels not excited by the laser radiation.