A Quantum Pump for Ultracold Atoms

Quantum Pump
An example of periodic modulation: Archimedes‘ screw. Continuous rotation of the screw pumps water from the lower-lying reservoir into the upper one. Munich physicists have now demonstrated a quantum mechanical equivalent of such a system. Graphics: MPQ, Quantum Many-Body Systems Division

A group of researchers led by LMU-Professor Immanuel Bloch has, for the first time, succeeded in experimentally realizing a dynamic version of the quantum Hall effect in optical superlattices.

The transport of particles is usually induced by applying an external gradient to a system. Water, for example, flows downslope and electric current is generated by applying a voltage. But even in ancient times, people were aware of a different way of generating directional drive: by periodic modulation of a system. A famous example of this principle is Archimedes’ screw, in which water in a pipe is transported upslope by rotating the helical thread of a screw. More than 30 years ago, the Scottish physicist David Thouless predicted that a similar phenomenon should also occur in quantum mechanical systems, which he called topological pumping. A group of researchers based at LMU and the Max Planck Institute of Quantum Optics and led by Professor Immanuel Bloch, in collaboration with theoretical physicist Oded Zilberberg (ETH Zürich), has now, for the first time, successfully implemented such a topological charge pump in a model system consisting of ultracold atoms distributed in an optical lattice formed by interacting laser beams. (MPQ/LMU)
Nature Physics 2015