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Q: Fachverband Quantenoptik und Photonik

Q 50: Matter Wave Interferometry and Metrology II

Q 50.1: Talk

Thursday, March 5, 2026, 11:00–11:15, P 11

Quantum Metrology of Spin Sensing with Free Space Electrons — Santiago Beltran Romero¹, •Michael Gaida², Philipp Haslinger¹, Dennis Rätzel¹, and Stefan Nimmrichter³ — ¹Atominstitut, Technische Universität Wien, Stadionallee 2, 1020 Vienna, Austria — ²Institute for Complex Quantum Systems and Center for Integrated Quantum Science and Technology, Ulm University, Albert-Einstein-Allee 11, 89069 Ulm, Germany — ³Naturwissenschaftlich-Technische Fakultät, Universität Siegen, Walter-Flex-Str. 3, 57068 Siegen, Germany

Advances in transmission electron microscopy (TEM) are bringing single-spin-sensitive spin-resonance spectroscopy within reach. We analyze the quantum precision limits for sensing magnetic moments with free-electron probes using a scattering model of an electron wavepacket interacting with a localized spin. We study two tasks: estimating the magnitude of a magnetic moment and detecting the presence of a spin. For estimation, we compare the classical Fisher information for typical measurements with the quantum limit and find that standard TEM imaging can saturate this bound when probe backaction is negligible. When backaction is significant, measuring the electron`s orbital angular momentum can offer higher sensitivity. Our results establish the quantum limits of spin sensing in TEM and guide the design of experiments targeting individual electron spins or nanoscale nuclear-spin ensembles.

Keywords: Free electron quantum optics; Fisher information; Electron microscopes; Sensing