Coherent acceleration of Bose-Einstein condensates

We present a theoretical analysis of the coherent acceleration of atomic Bose-Einstein condensates. A first scheme relies on the ``conveyor belt'' provided by a frequency-chirped optical lattice. For potentials shallow enough that the condensate is not fragmented, the acceleration can be interpreted in terms of sequential Bragg scattering, with the atomic sample undergoing transitions to a succession of discrete momentum sidemodes. The narrow momentum width of these sidemodes offers the possibility to accelerate an ultracold atomic sample such as, e.g., a Bose-Einstein condensate without change in its momentum distribution. This is in contrast to classical point particles, for which this kind of acceleration leads to a substantial heating of the sample. A second scheme is based on the idea of a synchronous particle accelerator consisting of a spatial array of quadrupole traps. Pulsing the trapping potential creates a traveling trap that confines and accelerates the atomic system. We study this process using the concept of phase stability.