Atom cooling with an atom-optical diode on a ring
  We propose a method to cool atoms on a ring by combining an atom diode -a laser valve for one-way atomic motion which induces robust internal state excitation- and a trap. We demonstrate numerically that the atom is efficiently slowed down at each diode crossing, and it is finally trapped when its velocity is below the trap threshold. 
A. Ruschhaupt, J. G. Muga