QM Research Seminar: When Can Long-Range Entanglement Be Ignored? Insights from the Information Lattice

Speaker: Thomas Klein Kvorning (​KTH Royal Institute of Technology). 

Abstract: 
​​​​​​​Simulating quantum many-body systems is fundamentally challenging because quantum states encode correlations that cannot be decomposed into local parts, leading to an exponential growth of required resources with system size. Yet physical observables are typically local: they are fully determined by density matrices of small subsystems. This raises a central question: can local density matrices be time-evolved without explicitly tracking long-range correlations? In this talk, I address this question using the framework of the information lattice, a scale-resolved decomposition of the information content of a quantum state. This construction provides a precise notion of where information resides in a quantum system, both in space and across length scales, and thereby offers a diagnostic of how correlations build up dynamically. I will show how this perspective reveals regimes in which local degrees of freedom are exactly decoupled from long-range entanglement, as well as how it can guide the development of approximate numerical methods for ab initio simulation of condensed matter systems.