09:00  09:45

Martin Zwierlein
(Massachusetts Institute of Technology)
Geometric Squeezing and Crystallization of Bosonic Quantum Hall States

09:45  10:15

Eric Bertok
(GeorgAugustUniversität Göttingen)
Splitting of topological charge pumping in an interacting twocomponent fermionic RiceMele Hubbard mode
A Thouless pump transports an integer amount of charge when pumping adiabatically around a singularity.
We study the splitting of such a critical point into two separate critical points by adding a Hubbard interaction. Furthermore, we consider extensions to a spinful RiceMele model, namely a staggered magnetic field or an Isingtype spin coupling, further reducing the spin symmetry.
The resulting models additionally allow for the transport of a single charge in a twocomponent system of spinful fermions, whereas in the absence of interactions, zero or two charges are pumped. In the SU(2)symmetric case, the ionic Hubbard model is visited once along pump cycles that enclose a single singularity. Adding a staggered magnetic field additionally transports an integer amount of spin while the Ising term realizes a pure charge pump.
We employ realtime simulations in finite and infinite systems to calculate the adiabatic charge and spin transport, complemented by the analysis of gaps and the manybody polarization to confirm the adiabatic nature of the pump. The resulting charge pumps are expected to be measurable in finitepumping speed experiments in ultracold atomic gases, for which the SU\((2)\) invariant version is the most promising path. We discuss the implications of our results for a related quantumgas experiment by Walter \textit{et al.} [arXiv:2204.06561].

10:15  10:45

coffee break

10:45  11:30

Nathan Goldman
(CenoliULB)
Chiral orbital order of ultracold bosons without higher bands
Interactions in higher Bloch bands provide a remarkable setting for realizing manybody states that spontaneously break timereversal symmetry.
Here, we show that the lowenergy physics of interacting bosons in a plaquette pierced by piflux shares feature of pband bosons, thus displaying condensates with chiral orbital order. We analyze the excitations of the condensate in terms of two orbitallike degrees of freedom and identify a gapped collective mode corresponding to the outofphase oscillations of the relative density and phase of the two orbitals. We further highlight the chiral nature of the ground state by revealing the cyclotronlike dynamics of the density upon quenching an impurity potential on a single site. This singleplaquette construction can be used as a building block for extended dimerized lattices with local orbital order, as we exemplify by using the BenalcazarBernevigHughes model. Our results provide a distinct direction to realize interacting orbitallike models with broken timereversal symmetry, without resorting to higher bands nor to external drives, with direct implications for cold gases and nonlinear photonics.

11:30  12:00

Luca Asteria
(Hamburg University)
Microscopy of ultracold atoms in optical lattice via quantum gas magnification
In this contribution we present results on quantum gas magnification as a microscopy
tool for ultracold atoms in optical lattices.
We developed a matter wave optics protocol which magnifies the atomic density
distribution by almost two orders of magnitude [1], allowing to image the magnified
cloud in a singleshot and with sublattice resolution by using standard optical
imaging techniques. This approach works with 3D systems
with many particles per lattice site, because it does not have the limitations of a small
depth of focus and of light induced collisions.
We demonstrate sublattice
resolution by observing the dynamics within the lattice sites after a
lattice potential quench, and we realize singlesite addressing using magnetic resonance techniques.
We report on a novel phenomenon that occurs in the regime of many particles
per lattice site when introducing a strong force into the system; this makes the correlated tunneling of
pairs of atoms the relevant dynamical process and causes the spontaneous formation of a density wave [2].
Quantum gas magnification opens the path for spatially resolved studies of new
quantum manybody regimes, like e.g. 3D systems, orbital lattices, and lattice
geometries with smaller lattice spacing.
We finally discuss the novel multifrequency scheme for optical lattices with dynamically tunable geometry and present experimental results and possible multifrequency realizations of tunable 3D lattices and quasicrystals [3].
References
[1] L. Asteria et al., Nature 599, 571575 (2021)
[2] H. P. Zahn et al., PRX 12, 021014 (2022)
[3] M. N. Kosch et al., https://arxiv.org/abs/2207.03811

12:00  13:00

Lunch

13:00  14:00

discussion

14:00  14:45

Jacqueline Bloch
(Centre National de la Recherche Scientifique (CNRS))
Nonlinear photonics in topological polariton lattices
I would like to send the abstract of my talk later.
Sorry for the inconvenience

14:45  15:30

Iacopo Carusotto
(NOCNR BEC Center)
Excitations and dynamics of fractional quantum Hall fluids of light and of atoms

15:30  16:00

Lukas Sieberer
(University of Innsbruck)
Relaxation to a paritytime symmetric generalized Gibbs ensemble after a quantum quench in a drivendissipative Kitaev chain
The construction of the generalized Gibbs ensemble, to which isolated integrable quantum manybody systems relax after a quantum quench, is based upon the principle of maximum entropy. In contrast, there are no universal and modelindependent laws that govern the relaxation dynamics and stationary states of open quantum systems, which are subjected to Markovian drive and dissipation. Yet, as we show, relaxation of drivendissipative systems after a quantum quench can, in fact, be determined by a maximum entropy ensemble, if the Liouvillian that generates the dynamics of the system has paritytime symmetry. Focusing on the specific example of a drivendissipative Kitaev chain, we show that, similarly to isolated integrable systems, the approach to a paritytime symmetric generalized Gibbs ensemble becomes manifest in the relaxation of local observables and the dynamics of subsystem entropies. In contrast, the directional pumping of fermion parity, which is induced by nontrivial nonHermitian topology of the Kitaev chain, represents a phenomenon that is unique to relaxation dynamics in drivendissipative systems. Upon increasing the strength of dissipation, paritytime symmetry is broken at a finite critical value, which thus constitutes a sharp dynamical transition that delimits the applicability of the principle of maximum entropy. While we focus here on the specific example of the Kitaev chain, our results generalize readily to all paritytime symmetric and integrable drivendissipative systems that are described by or can be mapped to noninteracting fermions.

16:00  16:45

coffee break

16:45  17:15

Hongzheng Zhao
(Max Planck Institute for the Physics of Complex Systems)
Making Trotterization adaptive for NISQ devices and beyond
The digital simulation of quantum manybody dynamics, one of the most promising applications of quantum computers, involves Trotterization as a key element. It is an outstanding challenge to formulate a quantum algorithm allowing adaptive Trotter time steps. This is particularly relevant for today's noisy intermediate scale quantum devices, where the minimization of the circuit depth is a central optimization task. Here, we introduce an adaptive Trotterization scheme providing a controlled solution of the quantum manybody dynamics of local observables. Our quantum algorithm outperforms conventional fixedtime step Trotterization schemes in a quantum quench and even allows for a controlled asymptotic longtime error, where Trotterized dynamics generically enter challenging regimes. This adaptive method can also be generalized to protect various other kinds of symmetries, which we illustrate by preserving the local Gauss's law in a lattice gauge theory. We discuss the requirements imposed by experimental resources, and point out that our adaptive Trotterization scheme can be of use also in numerical approaches based on Trotterization such as in timeevolving block decimation methods.

17:15  17:45

Youjiang Xu
(Johann Wolfgang GoetheUniversität Frankfurt)
Invisible flat bands on a topological chiral edge
We prove that invisible bands associated with zeros of the singleparticle Green's function exist ubiquitously at topological interfaces of 2D Chern insulators, dual to the chiral edge/domainwall modes. We verify this statement in a repulsive Hubbard model with a topological flat band, using realspace dynamical meanfield theory to study the domain walls of its ferromagnetic ground state. Moreover, our numerical results show that the chiral modes are split into branches due to the
interaction, and that the branches are connected by invisible flat bands. Our work provides deeper insight into interacting topological systems.

17:45  18:30

discussion

18:30  20:00

dinner at the restaurant Irodion Pallas (Greek restaurant)
Bienertstraße 55

20:00

Poster session (main building, 2nd floor)
