WW-Colloquium: Dr. Vincenzo Grillo – Quantum Tomography in Electron Microscopy

Dr. Vincenzo Grillo
Centro S3, CNR - Istituto di Nanoscienze, 41125 Modena, Italy
Quantum Tomography in Electron Microscopy

The physical properties of a quantum system, whether pure or mixed, are fully described by its density matrix. Recovering the density matrix through projective measurements—known as quantum state tomography—is a cornerstone of quantum optics and metrology. However, applying this technique to electron microscopy, particularly for characterising electron beams after inelastic scattering, has hitherto remained a longstanding challenge due to the complexity of scanning high-dimensional phase spaces, where the number of required measurements grows quadratically with space dimensionality. Here, we introduce a simplified approach by restricting tomography to the electron orbital angular momentum (OAM) subspace. Using an electron optics device known as an OAM sorter, we discretise the phase space into a finite set of measurable states, thus significantly reducing the experimental and computational burden. Although the set of measurements is incomplete, it suffices to probe essential features of inelastic scattering. We demonstrate this technique by investigating the inelastic scattering of a structured electron probe exciting volume plasmons in a carbon film. Combining structured beams with OAM-resolved quantum tomography reveals symmetry-breaking effects and offers insights into the coherence and evolution of the scattered quantum states. Analysis of the diagonalised density matrices further reveals the nature of the induced state transitions, paving the way for future developments in quantum tomography of electron scattering.