Dresden 2026 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 53: Nonequilibrium Quantum Systems II (joint session TT/DY)

TT 53.6: Talk

Wednesday, March 11, 2026, 16:30–16:45, HSZ/0105

Conditioning Subsystem Magnetization into the Large-Deviation Regime in Quantum Spin Chains — •Kriti Baweja¹, Samuel Garratt², David Luitz¹, Ali Zahra^3,4, and Jérôme Dubail^3,5 — ¹Institute of Physics, University of Bonn, Germany — ²Department of Physics, Princeton University, USA — ³Laboratoire de Physique et Chimie Théoriques, University of Lorraine, France — ⁴Centro de Análise Matemática, Departamento de Matemática, Universidade de Lisboa, Portugal — ⁵Centre Européen de Sciences Quantiques and ISIS, University of Strasbourg, France

We investigate the ground-state and finite-temperature properties of free-fermion and XXZ spin systems when a contiguous spatial region of the chain is conditioned to have a fixed value of its total S^z. We analyze how this conditioning operation reshapes the local magnetization profile and longitudinal spin-spin correlations both within the constrained region and in its surrounding environment. To access regimes beyond analytically tractable limits, we extend an existing post-measurement Quantum Monte Carlo (QMC) framework by introducing new update rules that enable efficient sampling of states with arbitrary subsystem magnetization. Using this post-measurement QMC approach, we probe the finite-temperature properties of these conditioned states and characterize how magnetization constraints modify local structure in both interacting and non-interacting spin models. Our results provide a computational tool for exploring measurement-induced constraints and conditioned ensembles in quantum many-body systems.

Keywords: Quantum Monte Carlo; Strongly correlated system; Low Temperature Physics; Quantum Many body system; Statistical Physics