Bonn 2025 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe
QI: Fachverband Quanteninformation
QI 33: Quantum Materials and Many-Body Systems
QI 33.7: Vortrag
Donnerstag, 13. März 2025, 16:00–16:15, HS VIII
Post-measurement Quantum Monte Carlo — •Kriti Baweja1, David Luitz1, and Samuel Garratt2 — 1Institute of Physics, University of Bonn, Nußallee 12, 53115 Bonn, Germany — 2Department of Physics, University of California, Berkeley, CA 94720, USA
We study the effects of extensive measurements on many-body quantum ground and thermal states using Quantum Monte Carlo (QMC). Measurements generate density matrices composed of products of local non-unitary operators, which we expand into operator strings via a generalised stochastic series expansion (SSE). This `post-measurement SSE' employs importance sampling of operator strings contributing to a measured thermal density matrix. Our algorithm is applied to the spin-1/2 Heisenberg antiferromagnet on a square lattice. Thermal states of this system exhibit SU(2) symmetry, which is preserved through SU(2)-symmetric measurements. We identify two classes of post-measurement states: one where correlations can be efficiently computed using deterministic loop updates, and another where SU(2)-symmetric measurements induce a QMC sign problem in any site-local basis. Using this approach, we demonstrate measurement-induced phenomena, including the creation of long-range Bell pairs, symmetry-protected topological order, and enhanced antiferromagnetic correlations. This method offers a scalable way to simulate measurement-induced collective effects, providing numerical insights to complement experimental studies. Our work opens the door to exploring how measurements influence many-body quantum systems, enabling deeper understanding of their dynamics. [1] arXiv:2410.13844
Keywords: Quantum Monte Carlo; Measurement; Entanglement; Strongly correlated system; Quantum many-body system