# Anomalous momentum diffusion in a dissipative many-body system

## TL;DR

This paper experimentally investigates how spontaneous emission causes anomalous sub-diffusive momentum spread in a strongly interacting bosonic gas, revealing universal slow decoherence dynamics due to many-body correlations.

## Contribution

It demonstrates the first observation of sub-diffusive momentum expansion in a dissipative many-body quantum system, highlighting the role of many-body states in decoherence.

## Key findings

- Observed algebraic decay of coherence with 1/√t behavior
- Identified sub-diffusive momentum expansion contrary to standard diffusion
- Supported experimental results with theoretical predictions

## Abstract

Decoherence is ubiquitous in quantum physics, from the conceptual foundations to quantum information processing or quantum technologies, where it is a threat that must be countered. While decoherence has been extensively studied for simple, well-isolated systems such as single atoms or ions, much less is known for many-body systems where inter-particle correlations and interactions can drastically alter the dissipative dynamics. Here we report an experimental study of how spontaneous emission destroys the spatial coherence of a gas of strongly interacting bosons in an optical lattice. Instead of the standard momentum diffusion expected for independent atoms, we observe an anomalous sub-diffusive expansion, associated with a universal slowing down $\propto 1/t^{1/2}$ of the decoherence dynamics. This algebraic decay reflects the emergence of slowly-relaxing many-body states, akin to sub-radiant states of many excited emitters. These results, supported by theoretical predictions, provide an important benchmark in the understanding of open many-body systems.