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TT: Fachverband Tiefe Temperaturen
TT 40: Focus Session: Quantum Sensing with Solid State Spin defects II (joint session TT/HL/MA)
TT 40.2: Vortrag
Mittwoch, 11. März 2026, 09:45–10:00, HSZ/0101
Topological Ambiguity in Stray Field Magnetometry — •Shirsopratim Chattopadhyay1,2 and Aparajita Singha1,2 — 1IFMP, TU Dresden, Germany — 2Würzburg-Dresden Cluster of Excellence (ct.qmat)
Inferring magnetic topology from stray field measurements is central to characterizing skyrmions, vortices, and other topological textures. Yet, the uniqueness of such reconstructions remains poorly characterized. We present a computational framework to systematically generate pairs of magnetization configurations with distinct topological charges (|ΔQ| = q, where q can be set by the user) that produce nearly identical stray fields (Normalized Root Mean Square Error ~ 0.8-4 percent). Our approach uses constrained optimization with a physics informed loss to jointly evolve magnetization pairs towards field degeneracy while preserving topological distinction. Across 200 randomized trials with varied initializations, we demonstrate rapid and reliable generation of adversarial pairs spanning skyrmions, merons, fractional defects and uniform domain textures. We theoretically analyse the relation between topological charge and stray field and construct an explicit example of near identical stray field from distinct topologies. Our adversarial dataset enables rigorous assessment of magnetization reconstruction algorithms and guides the design of measurement strategies capable of resolving topological ambiguity.
Keywords: Topological magnetism; Skyrmions; Magnetometry; Optimization; Topological degeneracy