Bonn 2025 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe
QI: Fachverband Quanteninformation
QI 29: Quantum Information: Concepts and Methods I
QI 29.1: Hauptvortrag
Donnerstag, 13. März 2025, 11:00–11:30, HS IV
Measurement-induced entanglement and complexity in shallow 2D quantum circuits — •Max McGinley1, Wen Wei Ho2, and Daniel Malz3 — 1Cambridge University, UK — 2NUS, Singapore — 3University of Copenhagen, Denmark
There has been a great deal of recent interest in understanding how measurements can influence the dynamics of entanglement in many-body systems. In this talk, I will elucidate how long-ranged entanglement can be generated by measuring states prepared by constant-depth 2D quantum circuits, and discuss implications for the complexity of random circuit sampling. We introduce a new theoretical technique, based on ideas from multi-user quantum Shannon theory, which allows us to establish a rigorous lower bound on the amount of entanglement generated by measurements in this setting. Our method avoids the so-called replica approach—the main tool employed for studying such problems so far—which gives concrete results only in the simplest of scenarios. Using this technique, we prove a recent conjecture about generic (random) 2D shallow circuits followed by measurements: Namely, that above some O(1) critical depth, extensive long-ranged measurement-induced entanglement is produced, even though the pre-measurement state is strictly short-ranged entangled. As a consequence of this result, we establish strong evidence that sampling from generic shallow-depth quantum circuits yields a quantum advantage, and analogously that contracting random 2D tensor networks is classically hard above a constant critical bond dimension.
Keywords: Measurement-induced dynamics; Circuit sampling; Multi-user information theory; Random quantum circuits; Tensor network contraction