Quantum ratchet using a delta kicked accelerator

A Quantum ratchet is a directed transport of particles in a spatially periodic system arising from the asymmetry between the initial distribution and the spatially periodic potential. A quantum $\delta$-kicked rotor has already been utilized to realize a ratchet [1]. When a quantum $\delta$-kicked accelerator is used instead of a kicked rotor, the ratchet acceleration is found to be generally suppressed [2]. Furthermore the ratchet arises only for special values of the acceleration. We use accelerated standing wave pulses on an atomic state prepared with a Bragg pulse on a BEC to realize the $\delta$-kicked accelerator and to study the ratchet. [1]I. Dana et. al., Phys. Rev. Lett. 100, 024103 (2008). [2]I. Dana et. al., Phys. Rev. E 76, 015201(R) (2007)