Here at the Greiner Lab, we study ultracold gases that are put into artificial crystals of light called optical lattices. The atoms in the optical lattice end up behaving like electrons in a solid. That means we can use these atoms to simulate models from condensed matter physics in a highly controlled environment.

We have developed a microscopy technique that lets us image atoms in optical lattices with submicron optical resolution, so we can see and manipulate individual atoms. This technique gives us unprecedented understanding of the quantum states we create, and lets us perform experiments with remarkable levels of control and accuracy.

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Publications (View All)

Probing entanglement in a many-body-localized system
07/2018
arXiv:1805.09819
An interacting quantum system that is subject to disorder may cease to thermalize due to localization of its constituents, thereby marking the breakdown of thermodynamics. The key to our understanding of this phenomenon lies in the system’s entanglement, which is experimentally challenging to measure. We realize such a many-body-localized system in a disordered Bose-Hubbard chain and characterize its entanglement properties through particle fluctuations and correlations. We observe that the particles become localized, suppressing transport and preventing the thermalization of subsystems. Notably, we measure the development of non-local correlations, whose evolution is consistent with a logarithmic growth of entanglement entropy - the hallmark of many-body localization. Our work experimentally establishes many-body localization as a qualitatively distinct phenomenon from localization in non-interacting, disordered systems.
Quantum state engineering of a Hubbard system with ultracold fermions
06/2018
Phys. Rev. Lett. 120, 243201 (2018) arXiv:1712.07114
Accessing new regimes in quantum simulation requires the development of new techniques for quantum state preparation. We demonstrate the quantum state engineering of a strongly correlated many-body state of the two-component repulsive Fermi-Hubbard model on a square lattice. Our scheme makes use of an ultralow entropy doublon band insulator created through entropy redistribution. After isolating the band insulator, we change the underlying potential to expand it into a half-filled system. The final many-body state realized shows strong antiferromagnetic correlations and a temperature below the exchange energy. We observe an increase in entropy, which we find is likely caused by the many-body physics in the last step of the scheme. This technique is promising for low-temperature studies of cold-atom-based lattice models.
Microscopy of the interacting Harper-Hofstadter model in the two-body limit
06/2017
Nature 546, 519-523 (2017) arXiv:1612.05631v1
The interplay between magnetic fields and interacting particles can lead to exotic phases of matter that exhibit topological order and high degrees of spatial entanglement. Although these phases were discovered in a solid-state setting, recent innovations in systems of ultracold neutral atoms - uncharged atoms that do not naturally experience a Lorentz force - allow the synthesis of artificial magnetic, or gauge, fields. This experimental platform holds promise for exploring exotic physics in fractional quantum Hall systems, owing to the microscopic control and precision that is achievable in cold-atom systems. However, so far these experiments have mostly explored the regime of weak interactions, which precludes access to correlated many-body states. Here, through microscopic atomic control and detection, we demonstrate the controlled incorporation of strong interactions into a two-body system with a chiral band structure.
A cold-atom Fermi-Hubbard antiferromagnet
05/2017
Nature 545, 462-466 (2017) arXiv:1612.08436v1
A. Mazurenko, C. S. Chiu, G. Ji, M. F. Parsons, M. Kanasz-Nagy, R. Schmidt, F. Grusdt, E. Demler, D. Greif, M. Greiner
Many exotic phenomena in strongly correlated electron systems emerge from the interplay between spin ordering and motional degrees of freedom. For example, doping an antiferromagnet is expected to give rise to interesting phases including pseudogap states, stripe-ordering and incommensurate spin order. Ultracold fermions in optical lattices offer the potential to answer open questions on the low-temperature regime of the doped Hubbard model, which is thought to capture essential aspects of the cuprate superconductor phase diagram but is numerically intractable in that parameter regime.

News

Justus joins Lithium lab
09/2018
Master’s student Justus Brüggenjürgen has joined the Lithium lab. Welcome, Justus!
Geoffrey wins best talk award
07/2018
Congratulations to graduate student Geoffrey Ji for winning the award for best contributed talk at the Quantum Transport with Cold Atoms conference!
Joyce joins Rubidium lab
07/2018
Graduate student Joyce Kwan has joined the Rubidium lab. Welcome, Joyce!
Sooshin Kim receives NSF fellowship!
06/2018
Congratulations to Sooshin Kim who was awarded a 2018 NSF Graduate Research Fellowship!
Quantum Chill Documentary
05/2018
Thanks to Ying Gao, Anzet du Plessis, Frankie Schembri, and Professor Thomas Levenson for this short documentary on our lab and the field of Ultracold Atoms!
Greiner Lab members take home multiple awards at the 2016 ICAP Poster Session!
07/2016
Anton and Matthew win awards for their posters on Probing Antiferromagnetic Ordering and Dynamics with the Fermi Gas Microscope and Quantum Thermalization in an isolated many-body system, respectively.