Stimulated Raman adiabatic passage from an atomic to a molecular Bose-Einstein condensate

Summary form only given. Coherent conversion of an atomic to a molecular Bose-Einstein condensate (BEC) is a first step towards ´superchemistry´, which is the atom optics analog of frequency conversion in nonlinear optics. A number of studies of this have shown that direct conversion via Raman photo-association appears feasible, based on stimulated free-bound and bound-bound transitions in the presence of two laser fields E/sup (1)/=E/sub 0//sup (1)/ cos(/spl omega//sup (1)/t) and E/sup (2)/=E/sub 0//sup (2)/ cos(/spl omega//sup (2)/t). Here pairs of atoms from the two-atom continuum are transferred-via an excited bound molecular state-to a bound molecular state of lower energy. Raman photo-association allows coupling to a single molecular state, which can be selected by the Raman laser frequencies /spl omega//sup (1)/ and /spl omega//sup (2)/. However, practical calculations using available lasers and transitions indicate that coherent transfer is often limited by spontaneous emission from the intermediate molecular excited electronic state. A possible route towards minimizing losses and decoherence from spontaneous emission is to use the stimulated Raman adiabatic passage (STIRAP) method (Drummond et al, Phys. Rev. Lett. vol. 81, p. 3055, 1998) in which a counter-intuitive pulse sequence is used where the first input pulse couples the molecular levels, even when there are no molecules present.