Quasiparticle engineering and entanglement propagation in a quantum many-body system

Abstract

The key to explaining and controlling a range of quantum phenom-ena is to study how information propagates around many-body sys-tems. Quantum dynamics can be described by particle-like carriers ofinformation that emerge in the collective behaviour of the underlyingsystem, the so-called quasiparticles¹. These elementary excitationsare predicted to distribute quantum information in a fashion deter-mined by the system’s interactions². Here we report quasiparticledynamics observed in a quantum many-body system of trapped atomicions^3,4. First, we observe the entanglement distributed by quasiparticlesas they trace out light-cone-like wavefronts^5–11. Second, using theability to tune the interaction range in our system, we observe informa-tion propagation in an experimental regime where the effective-light-cone picture does not apply^7,12. Our results will enable experimentalstudies of a range of quantum phenomena, including transport^13,14, thermalization¹⁵, localization¹⁶ and entanglement growth¹⁷, and represent a first step towards a new quantum-optic regime of engineeredquasiparticles with tunable nonlinear interactions.