Theory colloquium Luitz: Quantum Information Spreading

Quantum Information Spreading

 Nonrelativistic quantum systems with short range interactions have an emergent "speed limit" known as the Lieb-Robinson bound, which limits how fast information in the system can spread up to exponentially small "leakage" outside of the emergent light cone. I will show that while maximally ergodic systems saturate this bound, in the presence of disorder the spreading of information is actually much slower than expected by the bound even though the system remains ergodic.

 On the other hand, systems with long range interactions, can exhibit faster information spreading. Nevertheless, numerically exact calculations show that also in these systems a causal space-time region emerges, precluding infintely fast communication.