# Quantum Matter Seminar

Note: This event will be a virtual seminar please see the zoom link below:

https://caltech.zoom.us/j/7432388389

Well-controlled synthetic quantum systems, such as ultracold atoms in optical

lattices, offer intriguing possibilities to study complex many-body problems relevant

to a variety of research areas. In particular, out-of-equilibrium phenomena constitute

natural applications of quantum simulators, which have already successfully

demonstrated simulations in regimes that are beyond reach using state-of-the-art

numerical techniques. While generic models are expected to thermalize according to

the eigenstate thermalization hypothesis (ETH), violation of ETH is believed to occur

mainly in two types of systems: integrable models and many-body localized systems

(MBL). In between these two extreme limits there is, however, a whole range of

models that exhibit more complex dynamics.

The 1D tilted Fermi-Hubbard model has emerged as a versatile platform to study a

rich variety of weak ergodic-breaking phenomena in a clean system without disorder.

We have realized this model with fermionic K-atoms and observed a surprisingly

robust memory of the initial state over a wide range of parameters [1], which we

explain via emergent kinetic constraints. Our measurements were performed in

systems of about 290 lattice sites for up to 700 tunneling times - a regime that is

currently not accessible with state-of-the-art numerical techniques. We have used

these results to benchmark a novel more efficient numerical technique [2]. Moreover,

in the large-tilt regime the observed non-ergodic behavior is explained by an

emergent fragmentation of the many-body Hilbert space into an exponential number

of dynamically disconnected subspaces [3]. The experimental realization of this

regime paves the way for future studies at the interface of MBL and weak-ergodicity

breaking phenomena in one- and two-dimensions.

References:

[1] S. Scherg et al., Nat. Comm. 12, 4490 (2021).

[2] B. Hebbe Madhusudhana et al., arXiv:2105.06372, to appear in PRX Quantum.

[3] T. Kohlert et al., arXiv:2106.15586 (2021).