LMU
MPQ
Quantum Optics Group (LMU) - Quantum Many Body Systems Division (MPQ)

QUANTUM

Welcome! We are carrying out research in the field of quantum optics and quantum many-body systems using ultracold atomic and molecular quantum gases at the Max Planck Institute of Quantum Optics and the Ludwig Maximilians University. Furthermore, our group is part of the Munich Quantum Center.

We are always looking for Master students, PhD students and Postdocs. For more information click here! 

Thomas Kohlert received the Best Poster Prize at the 669. International WE-Heraeus-Seminar on Quantum Gases and Quantum Coherence.

The poster title is “Single-Particle Mobility Edge and Many-Body Localized Phase in a 1D Quasiperiodic Optical Lattice with Ultracold Atoms”.

Click here to view the poster.

 

A single-particle mobility edge (SPME) marks a critical energy separating extended from localized statesin a quantum system. In one-dimensional systems with uncorrelated disorder, a SPME cannot exist, since all single-particle states localize for arbitrarily weak disorder strengths. However, in a quasiperiodic system, the localization transition can occur at a finite detuning strength and SPMEs become possible. In this work, we find experimental evidence for the existence of such a SPME in a one-dimensional quasi-periodic optical lattice. Specifically, we find a regime where extended and localized single-particle states coexist, in good agreement with theoretical simulations, which predict a SPME in this regime.

Phys. Rev. Lett. 120, 160404 (2018)

 

Using fermionic ytterbium in a state-dependent optical lattice, we extend the capabilities of quantum simulators towards Kondo-type materials which exhibit spin-exchange interactions of mobile particles with localized magnetic impurities. The selective lattice potential only pins a fraction of the atoms, serving as immobile magnetic impurities. The emerging spin-exchange dynamics between the mobile atoms and impurities are directly observed, and in addition, an experimental tuning mechanism for the spin coupling is presented. This provides the framework for the future realization of a broad range of systems with spin impurity or two-orbital physics, including Kondo compounds, transition-metal oxides, heavy-fermion or colossal magnetoresistive materials.

Phys. Rev. Lett. 120, 143601 (2018) 

Dan Stamper-Kurn is Professor of Physics at the University of California and a Faculty Scientist at the Lawrence Berkeley National Laboratory, both in California, USA. He is an experimentalist who uses ultracold atomic gases to explore fundamental phenomena in condensed-matter physics, atomic physics, and quantum optics. Prof. Stamper-Kurn also chairs the Science Definition Team of the Bose-Einstein Condensation Cold Atom Laboratory (BECCAL), a joint mission of the German (DLR) and American (NASA) space agencies that aims to operate a quantum gas experiment aboard the International Space Station. Prof. Stamper-Kurn arrived in Munich in January 2018, where he is pleased to be hosted by the Bloch group and is honored to be a Distinguished Fellow of the Max Planck Institute of Quantum Optics.

The quantum Hall effect - a prominent example for topological states of matter in 2D - can be generalized to 4D systems. In 4D, a novel quantized Hall response appears, which is nonlinear and described by a 4D topological invariant -  the second Chern number. We realize a dynamical version of the 4D quantum Hall effect by implementing a 2D topological charge pump for ultracold bosonic atoms in an angled optical superlattice. We observe a bulk response with intrinsic 4D topology and demonstrate its quantization by measuring the associated second Chern number.

Nature 553, 55 (2018)

Press release: English (.pdf), Deutsch (.pdf)

Many-body localization (MBL) is relatively well understood in one-dimensional systems. However, in two or more dimensions, its  nature is largely unknown and is strongly debated. In this experiment, we probe local relaxation in a two-dimensional quasi-periodic system and find that it becomes exceedingly large, hinting towards a 2D MBL phase. Our experiment provides access to regimes where controlled theoretical approaches are scarce and opens routes for stabilizing exotic phases of matter in two dimensions.

Phys. Rev. X 7, 041047

Shaken lattice systems have become a versatile tool to create novel band structures that exhibit topological properties and artificial magnetic fields for neutral atoms. However, especially interacting bosonic systems often suffer from strong heating. We have systematically studied the loss rates of an interacting BEC in a driven one-dimensional optical lattice and have identified the most dominant heating channels. Our findings suggest that heating might be strongly reduced in shaken three-dimensional lattice structures.

Phys. Rev. Lett. 119, 200402 (2017)

Science highlights research on ultracold matter in a special issue! We contributed a review on quantum simulations based on neutral atoms in optical lattice:

Science 357, 995 (2017) (DOI: 10.1126/science.aal3837)

SEMINARS

Group Seminar at LMU: Multimode Optomechanics with Membrane-in-the-middle system

Tuesday, April 17, 2018 at 09:15, LMU seminar room H107 Sameer Sonar, University of Leiden in the...

Group Seminar at MPQ: Synthetic Lorentz force, frequency comb cooling, and precondensation of classical waves

Tuesday, April 10, 2018, MPQ temporary lecture hall B 0.32 Neven Santic, Institute of Physics in...

Group Seminar at MPQ: Typicality and unconventional stationary states of an embedded quantum system

Monday, March 26, 2018, at MPQ in B 032 Gregoire Ithier, theory collaboration G. Ithier, S....

Group Seminar at LMU: Constructing a heralded ion source and building lasers for MOGlabs in Melbourne, Australia

Monday, March 26, 2018, at LMU Bloch group seminar room Stephan Wissenberg, Internship Rob...

NEWS

Open Lab Day - 4 July 2017

You are a Master student and considering doing your research thesis in experimental quantum physics?

From Laser Spectroscopy to Quantum Science

Symposium in Honor of the 75th birthday of Ted Hänsch