Light-cone-like spreading of correlations in a quantum many-body system

TL;DR

This paper experimentally observes the light-cone-like spreading of correlations in a quantum many-body system, demonstrating finite velocity propagation of correlations after a quench in a 1D quantum gas.

Contribution

First experimental observation of light-cone-like correlation spreading in an interacting quantum many-body system using a quenched 1D quantum gas.

Findings

Correlations propagate with a finite velocity, forming an effective light cone.

Quasiparticle pairs transport correlations across the system.

Results have implications for quantum information and non-equilibrium dynamics.

Abstract

How fast can correlations spread in a quantum many-body system? Based on the seminal work by Lieb and Robinson, it has recently been shown that several interacting many-body systems exhibit an effective light cone that bounds the propagation speed of correlations. The existence of such a "speed of light" has profound implications for condensed matter physics and quantum information, but has never been observed experimentally. Here we report on the time-resolved detection of propagating correlations in an interacting quantum many-body system. By quenching a one-dimensional quantum gas in an optical lattice, we reveal how quasiparticle pairs transport correlations with a finite velocity across the system, resulting in an effective light cone for the quantum dynamics. Our results open important perspectives for understanding relaxation of closed quantum systems far from equilibrium as well as for engineering efficient quantum channels necessary for fast quantum computations.