Effective preparation and collisional decay of atomic condensates in excited bands of an optical lattice

We present a method for the effective preparation of a Bose-Einstein condensate (BEC) into the excited bands of an optical lattice via a standing-wave pulse sequence. With our method, the BEC can be prepared in either a single Bloch state in an excited band or a coherent superposition of states in different bands. Our scheme is experimentally demonstrated by preparing a Rb-87 BEC into the d band and the superposition of s- and d-band states of a one-dimensional optical lattice, within a few tens of microseconds. We further measure the decay of the BEC in the d-band state and carry an analytical calculation for the collisional decay of atoms in the excited-band states. Our theoretical and experimental results agree well.