A quantum resonance model is prepared by periodically kicking cold atoms exposed to an optical ratchet potential in the direction of the gravitational field. Within tailored parameters, intriguing phenomena emerge including absolute negative mobility, in which the atom surprisingly moves against the bias (gravity). In its upward motion, the particle current can be less or greater than or equal to the zero-gravity case, for which current reversal may prevail. Contrary to its associated zero-gravity case, the particle can be fully trapped or can slowly move downward. These phenomena occur when the classical counterpart is chaotic. With the present-day optical-lattice setup, it will be interesting to observe all these phenomena and, in particular, to see how the atom flies uphill.

• Received 25 February 2021
• Accepted 16 September 2021

DOI:https://doi.org/10.1103/PhysRevA.104.033321