# Atom Optics Group

## Prof. Dr. Andreas Hemmerich

What we do in short:

We use samples of atoms cooled to ultralow temperatures below hundred nanokelvin, such that their motion is governed by quantum mechanics, in order to either prepare minimal models of natural electronic many-body systems or to form entirely new types of many-body scenarios, which do not exist in electronic matter. Both strategies are motivated by the desire to increase our understanding of quantum many-body physics. Our present research covers topics such as optical lattices with orbital degrees of freedom, topological optical lattices, ultracold atoms in optical high finesse cavities. We also employ cold atomic samples to explore new concepts for quantum metrology such as superradiant lasing as a means to read out optical atomic clocks.

And in a few more words:

The essence of quantum many-body physics is nicely captured by the punch line "More is Different". In fact, it is a fascinating intellectual and technically relevant venture to understand how collections of seemingly simple elementary constituents, under the reign of physical principles such as degeneracies, interactions, and symmetries, collude to bring about the often unexpected collective phenomena of condensed matter.This is all the more true, when we consider the dynamics of such systems.

The vast complexity of natural many-body systems often leads us to seek ab initio tractable minimal quantum models, which can capture a few isolated phenomena of interest, while excluding the superimposed jungle of secondary structure that would impede a clear understanding. This is where quantum gases come into play. Quantum gas systems have synthetic model character, in the sense that they follow a bottom-up philosophy, where elementary ingredients are strategically combined to find the minimal input required to produce a specific physical mechanism conjectured to explain a specific feature of a natural electronic many-body system.

Alternatively, quantum gas systems allow one to form entirely new types of many-body scenarios, which do not exist in electronic matter but nevertheless can be extremely helpful to increase our intuition and knowledge of many-body physics in general. A typical example of a quantum gas system is what one calls an optical lattice, where neutral atoms at temperatures of few ten nanokelvin are confined in periodic potentials created by the interference of several laser beams, thus forming crystals of atoms bound by light.

Our special focus is to explore the interaction of quantum gas systems with light often in a dynamical regime far from thermal equilibrium. Our present research covers topics such as optical lattices with orbital degrees of freedom, topological optical lattices, ultracold atoms in optical high finesse cavities, and superradiant lasing in optical atomic clocks.

Students interested in Bachelor, Master or PhD thesis work are welcome at any time. If you want to participate in current research and are not yet at a stage to begin with your thesis you can nevertheless join our group and gain some practical experience. Why not participate for a few weeks in between semesters and get hands-on experience in electronics, optics, or laser technology? For students, who can already provide some kind of expertise, e.g. in electronics, we frequently offer paid short term project works.

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