Quantum simulation of fracton dynamics

Applying constraints to a familiar system can give rise to new effects. This idea underlies the interest in realizing and probing fractonic systems. In these systems, kinetic constraints restrict the motion of the constituent particles, while these particles can pair up to form mobile composite particles known as fractons. A strongly-tilted optical lattice places such a constraint on particle motion, as it forces the system dynamics to conserve the position of its center of mass. Practically, this implies that single particle tunneling is suppressed, but atom pairs are still able to undergo correlated motion, where two atoms move simultaneously in opposite directions.

In this work, we explore the dynamics of such a system using a rubidium-87 quantum gas microscope. Using a digital micromirror device, we initialize a set number of particle-hole pairs on top of a tilted chain with unity filling, and allow these fractons to expand in the lattice. For a single fracton, the resulting density profile shows dynamics similar to a single-particle quantum walk despite its many-body nature. We also prepare two fractons a few sites away from each other and demonstrate effective hard-core interactions between them. This experiment serves as a proof of concept for preparing such fracton excitations as probes of the underlying many-body state.