Interplay of Soundcone and Supersonic Propagation in Lattice Models with Power Law Interactions

TL;DR

This paper investigates how correlations spread in quantum lattice models with power-law decaying interactions, revealing regimes of both soundcone and supersonic propagation relevant for experiments.

Contribution

It extends Lieb-Robinson bounds to strongly long-range interactions and characterizes the conditions for different propagation regimes in quantum systems.

Findings

Sharp bounds for correlation spreading including soundcone and supersonic regimes.

Faster-than-soundcone propagation occurs for decay exponents less than 2.

Both cone-like and supersonic features are observed depending on the interaction range.

Abstract

We study the spreading of correlations and other physical quantities in quantum lattice models with interactions or hopping decaying like $r^{-\alpha}$ with the distance $r$. Our focus is on exponents $\alpha$ between 0 and 6, where the interplay of long- and short-range features gives rise to a complex phenomenology and interesting physical effects, and which is also the relevant range for experimental realizations with cold atoms, ions, or molecules. We present analytical and numerical results, providing a comprehensive picture of spatio-temporal propagation. Lieb-Robinson-type bounds are extended to strongly long-range interactions where $\alpha$ is smaller than the lattice dimension, and we report particularly sharp bounds that are capable of reproducing regimes with soundcone as well as supersonic dynamics. Complementary lower bounds prove that faster-than-soundcone propagation occurs for $\alpha<2$ in any spatial dimension, although cone-like features are shown to also occur in that regime. Our results provide guidance for optimizing experimental efforts to harness long-range interactions in a variety of quantum information and signaling tasks.