04 July 2013 Generating Laughlin states with atomic systems

The ultracold atomic sample is tightly confined above a metallic surface as explained in detail in the Methods section.

Collaboration between the University of Barcelona and ICFO published in Nature Communications. Since the discovery over a decade ago of a new type of quantum fluid with fractional charge excitations known as Laughlin state, the production of this quantum state, which explains the behavior of electrons in two-dimensional metallic plaques when they are exposed to intense magnetic fields, has been one of the most popular research topics on ultracold and Bose-Einstein condensed atoms.

Now, theoretical research developed by researchers from the University of Barcelona and ICFO published on Nature Communications proposes a method to generate this kind of states in two-dimensional systems of ultracold atoms, with possible applications in quantum computers.

The research combines several modern ideas such as the generation of artificial magnetic fields, which enable the study of phenomena such as fractional quantum Hall states (which gives rise to Laughlin states) in systems composed by neutral atoms and the use of nanoplasmonic planar traps (a type of collective oscillations of the conduction electrons in a metal at quantum level) to confine the system in a two-dimensional region”, remarks Bruno Juliá, researcher from the University of Barcelona.

According to numerical simulations, ultracold atoms would be suspended over a metallic surface by the action of a nanoplasmonic field. Once atoms are arranged like that, they would be lit by a laser that would enable the generation of an artificial magnetic field which atoms would be able to detect, as happens with electrons on a metallic plaque. “It is innovative research because we were able to combine nanotechnology basics with ultracold atoms physics”, explains Maciej Lewenstein, ICREA Professor at ICFO.

To achieve interactions between atoms, which at first is prohibited by Pauli principle, the quantum mechanical principle that states that no two identical fermions may occupy the same quantum state simultaneously, and a similar behavior to electrons’ charges repulsion, virtual excitation of each atom is used to produce an interatomic force and its intensity can be regulated in an experimental way.